Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity

The general step reduction and enlargement (GeneSteR + E) method and the general forging die design (GeneDie) method can exhaustively generate forging processes and dies for non-axisymmetric forged products. However, the variation of generated plans are limited, potentially excluding optimal solutions. This paper proposes an optimization support method that generates alternative design plans for non-axisymmetric forged products. The proposed method generates various die design plans according to various shapes of a workpiece and relative positions of the forged product and workpiece to dies. The shape of an initial work material is generated by resizing the shape in an original process plan while keeping the same volume as planned, and the parting lines of dies are defined by rotating the forged product around its center of gravity. The positions of the workpiece are generated by distributing the workpiece around its center of gravity. The shape of a forged product is modified so that undercut constraints are satisfied on the premise of subsequent blanking or punching processes. A large number of design candidates are evaluated by a finite element method analysis tool using a robotic process automation (RPA) tool. An experimental design knowledge base and RPA workflows were developed and applied to the forging dies of automotive parts. The experimental results show that the proposed method can generate alternative forging dies including those nearly equivalent those designed by an experienced engineer but in less time.

In order to investigate the relationship between ultrasonic energy and thermal energy in micro-forming processes, as well as the effects of the resulting heat on the surface deformation. A novel ultrasonic-assisted micro-forging test system is designed, which can offer 60 kHz frequency to the pure copper specimens, face-centered cubic, and proper melting point under amplitude from 0–3.5 μm. A piezoelectric transducer was also used to provide vertical vibration at a lower frequency of about 21 kHz and 1 kHz under the same amplitude for comparison. Furthermore, a technique for directly measuring the surface temperature of the specimen was proposed. A thermoelectric couple with a diameter of 0.1 mm was put into the machined dimple in the specimen surface with a depth of 0.2 mm and width of 1 mm. The entire process was monitored by a high-sensitivity dynamic force sensing system to ensure correct frequency and to distinguish between acoustic softening and impact effects. The experimental results indicate that the increase in surface temperature caused by acoustic softening is very limited, even at high frequencies. The significant increase in temperature is mainly due to the impact effect, which results in high deformation rates. However, as the amplitude continues to increase, the thermal expansion effect caused by the continuous increase in surface temperature will enhance the surface deformation resistance, but this indirectly enhances the impact effect, resulting in more reduction of surface roughness.

To reduce barreling of hollow cylinder in upsetting, circumferential one-way torsion with twist/compression speed of 0–12°/mm was combined with axial compression in upsetting. Due to combination of compression and torsion, the plastic flow of the workpiece was enhanced in the outer radial direction on the die–workpiece interface. Barreling was reduced by combining compression and torsion with lower than 5°/mm, whereas hourglass deformation occurred by combining compression and torsion with higher than 6°/mm. The workpiece was successfully deformed without barreling and hourglass deformation (0.97 < fraction of diameters of height center/end face < 1.01) by interrupting the die rotation in upsetting with reduction in height of lower than 50%.

The development of new materials or material systems is always accompanied by the development of processing technologies suitable for the material. The reduction of process steps, the saving of material and the optimization of material properties are aims of forming processes. The basis for this is the comprehensive characterisation of the thermos-physical and thermos-mechanical technologically relevant material behaviour, taking into account the real process conditions. In the present work, the material-specific process limits were determined by means of experimental simulation and used in the numerical simulation in order, on the one hand, to identify the forming steps for optimizing the manufacturing conditions and, on the other hand, to be able to set the final material properties. It was essential to homogenize the casting microstructure for the forming processes and to adjust it to globulitical grains by solution annealing. The previously limited forming behaviour of the cast AlSi9Mg alloy with 20 vol.-% SiC could be increased thus to forging-relevant plastic strains without occurring damages. Based on the comprehensive temperature-dependent material data, a one-step and resource-efficient manufacturing process for AMC materials by hot forming could be developed with the help of the FE software Simufact Forming and validated in reality under near-industrial conditions.

To reduce the processing load and improve the filling ratio of the tooth part of spur gear, combining divided flow forging and pulse slide motion using liquid lubricant was studied. The test materials were A1070 and A5056 aluminum alloy. The diameter of relief area (relief axis method) was 6 mm and the effect of relief axis height: δ and a viscosity of lubricant were investigated. The die pressure in A1070 aluminum divided flow forging with viscosity 56 cSt decreased from 850 MPa to 795 MPa for closed forging and be reduced to 750 MPa by applying pulse slide motion. However, in A5056, the load reduction due to the pulse slide motion was small, but the filling ratio increased with the number of vibrations. Controlled divided flow forging of A5056 that with back pressure resulted in lower load and higher filling ratio than conventional divided flow forging during processing at relief axis height δ = 1.5 mm and 2 mm.

The features of shear forging for a pure aluminum A1100, aluminum alloy A5052 and pure copper C1100 were investigated using the simulations and experiments. Shear forging is a process of cold forging to form a H-shaped double cup from a bottomed cup using the material flow in cutting. One of the critical defects of shear forging is folding defect. The critical conditions of folding generation for each material are investigated using the simulations based on finite element method changing the ratio of the depth of cut to the bottom thickness of the cup and the corner radius of the counter punch. The shear forging experiments are conducted using a servo press. Products of all materials are formed without folding defects using the successful condition in the simulations. The surface textures of the forged products were measured by a scanning electron microscope and a grooved texture by cutting was observed. In addition the surface rubbed with the punch corner have small surface roughness.

The non-heat-treated steel for a cold forging does not require post-heat-treatment to meet mechanical requirements of product. This steel is very cost-effective due to the elimination of quenching-tempering heat treatment. In this study, the developed non-heat-treated-steel which is a Fe-Mn-Si-C-based multi-phase steel was used to manufacture the automotive part, pillow ball. Non-heat-treated steel was prepared and subjected to a two-step heat treatment process. The microstructure, phase composition, and mechanical properties of the non-heat-treated steel were investigated before and after the two-step continuous heat treatment. Subsequently, a pillow ball was manufactured using the developed non-heat-treated steel through a multi-stage cold forging process. The hardness analysis of the forged part was conducted and compared with that of a forged part made of conventional steel subjected to quenching-tempering heat treatment. Result showed that developed non-heat-treated steel meets the mechanical requirements of pillow ball without post-heat-treatment.

Deformation characteristics during high-frequency (1200 strokes /min) radial forging of AA7075-O bar and tube at room temperature were investigated using A GFM SKK-10/R radial forging machine. A comprehensive process model taking account of complex process kinematics, and elastoplastic material behaviour was developed in DEFORM (version 12.1) to investigate the material flow, temperature, and strain evolution during the radial forging process. To verify the simulation results, a novel experimental approach has been used to reveal the material flow behaviour during the radial forging process, in which copper wires were embedded into an AA7075-0 blank prior to the radial forging process and the whole radial forged part was scanned using a Nikon XT H 225 LC X-ray computed tomography system after radial forging. The experimental results provide quantitative characterizations of the material flow in 3D. The experimental and numerical results shed light on the mechanism of fishtail and crack formation during the high-frequency radial forging of AA7075-O and provide guidance to minimise these defects.

The influence of the combinations of the materials of plate and die on the deformation behavior during unloading in compression of a plate with a high ratio between the diameter and the thickness is investigated by simulations. A plate becomes thicker by elastic recovery during unloading in plate compression for a small ratio of thickness reduction in loading. On the other hand, a plate becomes thinner by the additional compression caused by the elastic recovery of die during unloading for a large ratio of thickness reduction in loading. The turning points by the ratio of thickness reduction from thicker to thinner during unloading depend on the combination of the materials of plate and die. The amount of thickness reduction during unloading is evaluated using the increase in plate diameter during unloading. Increase in plate diameter is large for the conditions that the friction hill in loading is large. Deformation behaviors of a plate using crown dies which are designed to obtain a uniform thickness plate are also investigated. The additional reduction of the thickness during unloading contributes the flatness of the plate.

Producing complex forging parts requires multiple operations depending on the initial billet shape, the desired final forging shape, and the material’s deformability. The intermediate preforming impressions are used to achieve a complete finish die fill with minimal flash and reduced forming load while avoiding flow defects such as laps and flow-through. Practically effective preform design should also minimise the die wear by reducing metal sliding over the tool surface during impressions. In this paper we present a practical implementation of the approach to developing a preform shape that involves a potential flow approximation and utilising equipotential surfaces as a preliminary guess. This study continues the author’s previous work [1], which has been expanded to a broader range of product shapes. To make this approach applicable in the industry, a specialised CAD program was developed and tested in real production conditions that have proven its efficiency.

This study examines the effects of applying lateral oscillation during compression. A circular cylindrical aluminum bar inserted in an upper and a lower die with fitting bores was radially extruded, and lateral oscillation was applied to the lower die. The finite element analysis predicted that the relative oscillating speed against the compressing speed can affect the load reduction. Experiments were conducted based on the numerical results, demonstrating a maximum load reduction of 35% compared with the case without oscillation. From the relevant measurement of the workpiece, the compressed region was reported to be slightly elongated in the oscillating direction.

This article highlights a case-based reasoning method combined with expert knowledge in the design of multi-pass hot forging process for hub bearings, as well as the outcomes of our research on the representation and revise of forging design knowledge. Forging design knowledge acquired from manuals and the experience of technologists was refined and then framed in the form of an “IF-Then” variety of production rules, including the selection of the shape complexity factor and the machining allowance, etc. A forging similarity measure based on part sizes of the hub bearing was proposed to retrieve cases. After the dimensional input of the new hub bearing, the synthesis weight was determined using the objective weight calculated from historical cases and the subjective weight recorded in the expert knowledge. Based on the global similarity calculated by the synthesis weight, the two most similar historical cases would be then searched for use as templates in the design of the new forging process. Size ranges of the new forging and dies were established in detail based on design values of two similar cases combined with expert knowledge, including the machining allowance and the fillet, etc. The above system was coded in Visual C#, and its user interface was developed using WinForm, AutoCAD, and UG software. The newly designed dies were imported into Deform 3D for the finite element simulation, and the results demonstrated that the hub bearing forging was adequately filled, proving that CBR would assist technologists in achieving the goal of rapid design.

Nowadays, new Continuous Cooling Bainitic Steels are being developed to decrease the manufacturing steps and energy consumption in the forging industry. However, there is still a lack of knowledge concerning their application. Control of stress state, plastic deformation, strain rate, and temperature directly affect the workability of forged products. One way to determine the best processing window during hot forging is by creating 3D process maps. This work aimed to develop and implement a virtual process map in finite element software. Forgeability tests were carried out on a wedge workpiece. The results of the three-dimensional forging simulation, such as austenitic grain size, energy dissipation, and Instability, showed a good agreement with the experimental results. The Finite Element Analysis reveals that the geometric complexity of the wedge test showed different energy dissipation and instability levels along of the plastic deformation, caused by the transient regime of temperature and strain rate.

The use of accurate preform dies and billets in forging can improve quality, conserve material, reduce manufacturing costs, and eliminate rehabilitative processes. This paper presents a Finite Element (FE) simulation-based preform die design method that might require a few iterations to find an optimal preform shape. The preforms are iteratively searched by backward tracing of material points in the FE models. The proposed scheme for establishing preform geometries for flash-less forging exploits the ability of FE software packages to track material points at any given process time and location. In this methodology, “flash” is considered a defect—one that can easily be induced by using a slightly larger volume of a preform shape than the exact volume that results is flash-less forging. Since the materials under plastic deformation seek the path of least resistance, other defects are bound to occur. Several case studies on preform designs of 3D forgings are presented. The viability of the methodology is assessed based on strain distribution patterns and forging loads. The methodology was also used on a few example parts which are currently forged with flash. The preform designs with this methodology resulted in a substantial reduction in the flash. Besides aiding in the development of new progression sequences for flash-less die forging, the method could be used to modify preforms in a production line to minimize material waste due to flash. The method can also be used to probe preform shapes that occasionally result in defects caused by variability emanating from interface friction, die temperature fluctuation or other factors.

As the main structure of launch vehicles, the forming of cylindrical parts with reinforcing ribs still follows the manufacture mode of milling, rolling and welding in the middle of last century, which has the problems of long manufacturing cycle and low material utilization. In this paper, an innovative rolling method is proposed for manufacturing cylindrical parts with external cross ribs of high performance, high efficiency and low cost. Firstly, the forming principles of the rolling method are presented. Secondly, the experimental samples of cylindrical parts are formed by rolling method. Finally, the forming defects are analyzed and optimized, and the ideal cylindrical parts with external cross ribs are formed, which proves the feasibility of the rolling method.

Rolled metal wires and rods often exhibit tilting, the material is rotated around the pass line. When material is rolled with tilt at the entry side, torsion of the cross section occurs due to asymmetric deformation during rolling. Torsion may result in reduced shape accuracy and surface defects. In previous research, by comparing the tilt angle of specific points on the surface of the material (e.g., the corner point of a square cross section) at the entry(θs) with that at the exit(θe), tilting was evaluated as either restoration (θs > θe) or overturning (θs < θe). This revealed the influence of tilting by pass sequence (e.g., diamond-square, oval-round, square-oval), or rolling conditions (e.g., roll diameter, friction coefficient). On the other hand, it is known that metal rolled with tilting rotates after rolling. This is important because this rotation becomes the tilt angle at the entry to the next rolling. In this work, the rotation at the delivery side by metal rolled with tilting was investigated by both experiment and FE simulation and was considered in relation to asymmetric deformation behavior of the roll bite.

On the roll bite during rolling, the normal and shear stresses acting between the material and the roll surface are the key variables in the rolling model. If these stresses can be directly measured, the interaction between the roll and the material can be understood. In this paper, we propose a new method to estimate the stress on the roll surface by measured strain distribution from multiple strain gauges inside the work roll.In this method, the measured strain distributions are Fourier expanded to determine the coefficients of the general solution of equilibrium of forces in the cylindrical coordinate system, but it is difficult to determine the coefficients of the general solution with higher order Fourier coefficients. So we developed a way to make it possible to determine higher-order coefficients by imposing constraints between them. Using this technique, the measurement results of rolling stress distribution during the rolling of aluminum sheet are introduced.

It is increasingly important to improve dimensional control techniques for pipe rolling to meet stringent requirement for dimensional accuracy. Sizing mill, which is the final process for seamless steel pipes, is an important mill that determines outer diameter accuracy and roundness. Outer diameter accuracy and roundness of seamless steel pipe is usually controlled by fill in seamless steel pipe into caliber roll, which’s shape is a perfect circle of the final stand. However, depending on size of product, caliber roll’s shape of the final stand became elliptical, making it difficult to achieve both high precision control of outer diameter accuracy and roundness. Therefore, in this study, we proposed to divide the role of stand for controlling outer diameter accuracy and roundness in order not to be affected by caliber roll’s shape of the final stand. Outer diameter was determined by controlling circumference length at the penultimate stand. And roundness was controlled at the final stand. As a result of the actual test, it was confirmed that the seamless steel pipe can be controlled by the new rolling control technology considering the roll wear aiming at the outside diameter accuracy and roundness. The newly proposed dimensional control technique enabled to obtain outer diameter and roundness of seamless steel pipe with high accuracy by means of several size of caliber rolls.

Flexible Skew Rolling (FSR) is a novel near-net-forming process for forming bars and shaft parts. This work relates to forming the GH4169 bars with FSR technology. Firstly, the finite element (FE) model was established to analyze the metal deformation characteristics in the FSR process. Furthermore, the rolling experiments was carried out. The initial microstructures of GH4169 alloy bars with and without δ-phase were obtained by Solution Treatment (ST) and Aging Treatment (AT), respectively, and the δ-phase effect on microstructure evolution of GH4169 alloy bars during FSR process was studied. The FE simulation results show that the metal spiral moves forward under the action of the rolls, completing the radial compression and axial extension. The experimental results show that the δ-phase has an important influence on the microstructure evolution of GH4169 bar. It was found that for ST workpieces and AT workpieces, the dynamic recrystallization (DRX) fraction in the middle is greater than that in the surface. This is because the surface temperature of workpiece is lower than the middle, which is not conducive to DRX. Comparing the middle part of ST and AT workpieces, it can be found that the $$\delta$$ δ phase accelerates the DRX process. DRX has been completed in the middle part of ST workpiece, and the grain size is refined from 87 μm to about 5 μm. In addition, $$\delta$$ δ phase also has a significant effect on the morphology of core defects. The bars obtained have good accuracy, and the diameter deviation is within ± 0.04 mm.

Welding with an electric arc is mainly used as a joining technology, where a high energy input is required locally for the joining process. Due to the heat input, the welded bead is characterized by a heat affected zone, that consists of an inhomogeneous microstructure of different phases and grain sizes. This leads to non-optimal mechanical properties.One way to improve the microstructure is to induce plastic deformation (e.g. by rolling), which can enable recrystallization mechanisms, that homogenize the microstructure and therefore can optimize the material properties. Yet, the recrystallization mechanisms require a minimum temperature to be activated. On one hand, the in-situ heat input during welding can be used for this in a process combination of welding and rolling but might not be enough, to reach or hold this recrystallization temperature during rolling. An excessive heat input on the other hand leads to too high temperatures, causing significant grain growth, that also negatively affect the mechanical properties. In any case, a certain temperature range over time has to be maintained.The temperature can be controlled by burners for pre-heating and post-heating, and the heating power can be controlled separately. In this numerical study, burner heat models are used to simulate the temperature-controlled process combination of welding one single bead with a subsequent rolling step for the mild steel St37/S235JR. The influence of the pre- and post-heating could be numerically proven and suitable heating combinations were found, that allow a full recrystallization with a nearly homogenous grain size distribution.

The lateral deformation in hot rolling has been investigated with finite element method for different geometries of billets, temperature gradients over the cross section and alloys. The maximal lateral spread is evaluated with different billets geometries and temperature gradients, and compared between isotropic and anisotropic deformation. The cross section of billets is exemplarily compared between the flat and curvy surface at the entry zone, and at different roll speeds in continuous rolling and reduction sequences. The lateral spread increases with increasing the billet size and decreasing the temperature gradient. It can be enhanced by the anisotropic deformation. The profiles of the cross section are varied with its contour at the entry zone and reduction sequences. They are sensitive to changing the roll speed in the continuous hot rolling.

The finite element (FE) method is a powerful tool for simulating industrial metal forming processes such as metal rolling. FE allows users to estimate the stress distribution in the metal sheet during the rolling process. However, FE simulations do not allow for real-time online process control due to model complexity and computational time. This paper forms part of a large-scale research project aimed at designing a simple-but-accurate mathematical model that provides sufficiently precise results (compared to FE simulations) with faster computational timescales allowing for real-time process control. To validate the asympotics-based mathematical model, an accurate FE model is required. In this paper, we give a detailed description of a quasi-static Abaqus/Explicit FE model and show how this is optimised to represent the rolling process. We report new insights gained from the FE simulations which can guide the development of simpler, faster mathematical models.

In this work, a new mathematical model for cold rolling processes is presented. Starting from the governing equations and assuming only a narrow roll gap aspect ratio (in effect, large rolls on a thin strip), we find a solution by introducing two length scales inherent to the problem. The solution consists of a large scale, along with small (next order) correction at a small scale. The leading-order solution depends on the large length scale and matches with slab theory. The next-order correction depends on both the large and small length scales, and reveals rapid stress and strain oscillation. These oscillations are also seen in preliminary FE simulations. The oscillations resemble the slip-line fields, and the FE simulations suggest a strong connection between these oscillations and the residual stress in the resulting strip. The modelling approach used here has potential applications for modelling many metal forming processes, just as the slip-line theory itself did, but with the distinct advantage of simplicity and quick computation.

Hot rolling tools composed mainly of Fe, such as plugs for seamless pipe rolling, is generally used with iron oxide scale on the outer surface of the toolThis is to inform you that corresponding author has been identified as per the information available in the Copyright form.. Oxide scale affects the tool life as a protection from seizure to the rolled material and the heat flux caused the tool’s deformation. Therefore, the tool life depends on the remained the oxide scale against wear and peeled off, and the improvement of the wear resistance of the scale is needed.The wear resistance of the scale varies greatly depending on the tool’s composition, oxygen concentration, water vapor content during heat treatment and heat treatment pattern. In this report, we focused on the most influential chemical composition of the tool. The amount of Cr affected the generation of oxidation, so the effects of Cr concentration and scale composition on the wear resistance were investigated. As the results, the Magnetite composition ratio of the oxide scale depended on the Cr concentration and that was strongly affected the tool life.

To implement SFR (Schedule-free Rolling) is an effective way to organize production flexibly and maximize production efficiency in hot rolling. In order to meet the increasingly stringent requirements of PCFC (Profile Contour and Flatness Control) of multiple-width electrical steel strips in hot rolling, the innovative ASR (asymmetry self-compensating rolling) technology is developed that has crown control, edge drop control, and wear control abilities simultaneously. Based on the ASR principle for multiple-width electrical steel, the ASR work rolls, the ASR shifting strategy, and the arranged SFR plan with a width group scheme are developed for SFR of multiple-width electrical steel strips. A comparative study on the strip profile and flatness control performance of CVC, K-WRS, and ASR technologies with work roll wear contours variation within the entire rolling campaign is carried out. The ASR technology of multiple-width electrical steel strips has been industrially tested and applied on the production hot strip mills with the high-quality crown hit rate increased and work roll wear contours improved significantly, which provides an innovative way to new generation high-tech PAI (PCFC All-in-one Integrated, “π” briefly) hot strip mills.

The magnitude of residual stresses in hot-rolled profiles influences the quality of the final product. Cooling conditions after rolling are the main factor affecting the residual stresses. Beyond the thermal expansion, dilatation due to phase transformations is of particular importance. The prediction of residual stresses is usually associated with the three-dimensional coupled thermomechanical problem solved by the finite element method (FEM). In some cases, this is unacceptable due to the high costs of calculation. The paper proposes an alternative approach based on simplifying the description of the stress state in the profile. The model is based on the representation of the profile as a system of bars connected at the ends. Thus, only longitudinal stresses in the profile are taken into account. An elastic-plastic model of the material, which takes into account both the active load and the unloading when the temperature is equalized over the profile section is used. The thermal problem is solved for the cross-section of the profile using the FEM. To create a model of phase transformations, an approach based on a modified Leblond equation was used, which also significantly accelerates the calculation of the kinetics of phase transformations. All models were calibrated for 20MnCr5 steel based on appropriate mechanical and dilatometric tests on a range of steels. The last part of the work is devoted to the validation of the obtained model by comparing the calculation results with the measured residual stresses in the profiles. Simulation of the cooling process of the profiles under production conditions recapitulates the work.

The ring rolling process offers the possibility of producing seamless rings. For certain applications, it would be advantageous for cost reasons to produce rings with different materials at the area of the inner and outer circumference. Composite ring rolling, the combination of ring rolling and roll bonding, enables the production of such rings. In this study, a composite ring made of stainless steel (inside) and quenched and tempered steel (outside) is investigated to reduce the proportion of expensive stainless steel in the overall component. The ratio of wall thicknesses of the rings sOR (outer ring)/sIR (inner ring) was varied in simulations. The simulation shows permanent contact between ring sections for a wall thickness ratio of sOR/sIR > 3, which is a pre-condition for a successful bonding. When these ratios are applied, a given absolute reduction leads to higher relative wall thickness reductions of the inner ring, since the given absolute reduction meets a smaller wall thickness of the inner ring at the roll gap entrance. The higher relative reductions of the inner ring then lead to a faster diameter growth of the inner ring during rolling. According to the simulation, the most promising wall thickness ratio was then investigated in the experiment. In addition, the effect of axial rolling was reproduced in the simulation and investigated in the experiment. The results show that a successful composite ring rolling process is supported by a high wall thickness ratio in combination with a low or without an axial reduction.

Casting metal products are characterized by porosity due to shrinkage occurring during solidification of the molten material. However, final products such as bars must comply with internal soundness requirements, usually assessed by ultrasonic testing. In this view hot metal forming processes such as rolling or forging could mechanically ensure void closure and therefore the desired product soundness. Based on literature and previous experience, a study of the void closure during hot rolling of austenitic stainless-steel bars coming from ingot has been carried out. The effects of hot rolling main parameters on void closure have been first investigated by FE analysis and then experimental trails on rolling mill have been designed. Material coming from experimental tests was then analyzed both with destructive and non destructive tests (i.e., ultrasonic analysis, micro and macro etches) so to validate process design and optimization. Experimental results allowed the validation of FE analysis and also showed an effective improvement in terms of void closure.

Lightweight design efforts are generally limited by highly stressed areas. In the case of shafts with cross bore the cross bore forms a notch. Due to geometry and position, those notches lead under cyclic torsional loading to stress peaks in the component, which appear as highly stressed areas. In order to counteract tensile stress peaks, compressive residual stresses may be induced into the surface layer by means of surface treatments such as deep rolling. The induction of compressive residual stresses may delay crack initiation and growth. When deep rolled components are subsequently subjected to cyclic loading, the induced residual stresses are redistributed until a stable residual stress state is established, which is decisive in the assessment of the fatigue strength. The influence of deep rolling on the surface properties of cross bores in shafts made of GJS700 and the redistribution behavior of the induced residual stresses under subsequent cyclic torsional loading is mostly unknown. The objective of this work was therefore to identify the cause-effect relationships between the deep rolling parameters (pressure, overlap) as well as the cyclic loading and the resulting surface properties. Therefore, experimental investigations of deep rolling and of the subsequent cyclic torsional loading were carried out. Subsequently, the process sequence was modeled numerically consisting of a deep rolling and a torsion model. The experimental tests were used to validate the models. Finally, the cause-effect relationships between the deep rolling parameters on the residual stresses and the redistribution due to cyclic torsional loading were investigated.

In the presented study, a combination of physical experiments and the finite element method numerical simulations of the micro-extrusion mechanism in solid-state bonding of an aluminum alloy, during cold rolling has been investigated. For better monitoring of the metal flow during deformation and especially for tracking fractured alumina fragments a thick colored oxide layer was deliberately created on the surface of AA3xxx aluminum strips before rolling through the anodizing process. A progressive reduction per pass from 2% to 65% has been implemented in consecutive experiments at constant rolling speeds for corresponding deformation zone geometry its fracture as well as a different range of metal micro-extrusion through the created cracks within the oxide layer. The evolution of the oxide fracture as a function of deformation per pass was systematically evaluated by scanning electron microscopy for each sample. A numerical model of the metal flow called the micro-extrusion has been developed utilizing DEFORM-2DTM software allowing to calculation of the height of the micro-extrusions for given rolling conditions. Depending on the geometry of the crack the local deformation and friction conditions dictated various responses from the metal flowing through the distance between the oxide fragments.

Due to several physical causes, high-amplitude, undesirable mechanical vibrations, called chatter, can be experienced during hot and cold rolling processes. To study this instability phenomenon, several authors have distinguished third octave and fifth octave chatter based on the vibration frequency. While fifth octave chatter mainly causes quality issues on the products, third octave chatter is much more problematic. This vibration can provoke strip break and, therefore, cause severe damage to the mill. Previous studies have shown that third octave chatter is linked to a regeneration effect due to stand coupling. It has also been demonstrated that there exists a critical speed above which the vibration becomes unstable. Therefore, the main actuator used to control third octave chatter is a speed reduction, resulting in a loss of productivity.In the presented work, a numerical model was designed to study third octave chatter with low computational costs. The model was developed using MATLAB/Simulink, and each stand is represented by mass-spring-damper systems, which link the different elements of the stand. The mechanical behavior of the strip in the roll bite is non-linear and generally requires a more complex model. In the proposed model, this behavior is linearized around the working point. Additionally, consecutive stands are coupled by variations in the strip tension and thickness transportation.The proposed model was utilized to calculate the stability of various operating points. It is possible to compute the critical speed for each set of parameters, which includes working points, reduction, mass, stiffness, damping of various elements, and friction coefficients. Sensitivity studies were conducted to determine the impact of each parameter on the critical speed. In the second step, the model can be employed to evaluate different actuators with the aim of controlling third octave chatter.

The new method of asperity forming using plastic film with fine pattern produced by laser printer as a tool was proposed in the previous report. This new method can easily form micro-surface-shape on the metal workpiece. In this research, this method is applied to rolling for forming micro-surface-shape on the large area. The forming length of this method depends on the film length rather than the roll circumference. Therefore, the micro-surface-shape can be formed on large area without repeating by roll circumference. The influence of conditions in rolling on the forming accuracy of micro asperity are investigated. The workpiece material is pure aluminum sheet A1050-O. The soft material tools are laser-printed PET (polyethylene terephthalate) film. The experimental result showed that the pattern of asperities is expanded in the rolling direction. When the large-diameter roll (d = 80 mm) is used, uniform asperity can be formed with uniform workpiece thickness. However, when the small diameter roll (d = 40 mm) is used, the workpiece has the thickness distribution in the width direction.

This paper presents on-going efforts made to develop a unified template for smart manufacturing (SM) use cases. As the modern manufacturing system getting more and more complex and “smarter”, the Use case methodology becomes useful for system requirements management and specifying standards to support the system level functions. It has been used to identify the challenges of the AI and big data application [1, 2], but also the realization of smart gird projects [3]. The starting point is to set up a template in order to gather and analysis use cases in a consistent manner. Thus, this paper presents: 1) analysis of the use cases collected by standardization organizations such as ISO/JTC 1, IEC/TC 65 etc.; 2) comparison of the use case templates to reveal the mapping rules; 3) a unified template is proposed to facilitate comparison and analysis of SM use cases; The unified template could be the basis for the future SM use cases repository, thereby facilitating the development of standards and realization of SM applications.

When manufacturing bars with multi-specification and small-batch production, the traditional longitudinal bar rolling process brings a high tooling cost due to the complex and long process production line. In previous studies, authors have proposed a flexible skew rolling (FSR) process. This process has the advantages of universal mold, low production cost and suitable for small batch parts production. The author successfully rolled different shapes of shafts by this process. In this study, the flexible skew rolling process was used to produce bar, and a physical investigation corresponding was undertaken with a $$\varnothing $$ ∅ 60 LZ50 steel billet. It can be concluded that, the main defects of FSR formed bar mainly have the defects of concavity and surface spiral marks. The depth of concavity is reduced by 27.56 mm when using 40° cone angle billet, and the height of surface threads is reduced by 0.26 mm when using 15° unloading circular chamfer.

ERW (Electric Resistant Welded) pipes are generally used in the industries, such as the petrochemical pipes, the transportation, the construction and the mechanical structures. The most important advantage of the ERW pipes is high strength weight ratio. The production of ERW pipes were generally made using the cold roll forming (CRF) process. The CRF production line is designed using the break down forming, the cage roll forming, the fin pass finishing, the squeeze welding, and the sizing and straightening passes. In this paper, three fin-pass profile designs were proposed by using the single-arc (design 1), the bi-arc, (design 2) and the three-arc (design 3) composition for the top roll, the side roll, and the bottom roll, respectively. FEM simulations were carried out the predict the contact pressure distributions of the fin-pass rolls and the circumferential strain distributions of the blank at the fin-pas 1, 2, and 3. The single arc fin-pass roll profile design had shown more even contact points and contact pressure distributions. The three-arc fin-pass profile design had shown the possibility of using only two fin-pass roll stand to form the tube perfectly.

Hot rolling on a reversing mill is the first stage of the transformation route for producing aluminium plates and coils. Optimizing the recovery and reducing cracks occurrences are major objectives of our operational excellence program. Among the six faces of a plate, two of them are constrained by the rolls and the others are trimmed at the end. The understanding of the deformation of these free edges is required prior to any metal loss optimization. For this purpose, two FEM models were developed to assess final shape and strain field. A steady-state 3D approach is used to evaluate the effects of rolling parameters, including the use of vertical rolls, on the edge deformation. Concerning the ends, a 2D plane-strain modelling is chosen to be able to predict the ‘crocodiling effect’ and study the impact of initial shape and rolling parameters. In both models, a remeshing procedure had to be implemented in order to follow the high level of deformation that takes place during this multi-pass process. In combination with the tracking of the surface deformation and in order to address the issue of edge cracking, a Hosford-Coulomb empirical damage model is implemented and validated with lab trials.

Wide-thin aluminium components have a wide range of applications in rib-reinforced structures in aircraft, floor and body panels for trains/underground/buses and battery trays for electric cars. Extrusion is an effective manufacturing method for producing such kind of components, but the main issue is that the extrusion ratio is very high and thus requires extra-large extrusion machines, which is not economical. This research introduces a new extrusion method, which has multiple extrusion containers, for producing wide-thin aluminium components with significant reduction of extrusion ratios and thus reducing extrusion forces. The technology is known as multi-container extrusion technique, and the principle is to use several small extrusion containers to replace the traditional single large extrusion cylinder to decrease the extrusion ratio, and therefore enables the manufacturing of wide-thin profiles with significant reduction of extrusion forces. Experimental and numerical studies have been carried out to testify the feasibility of this method. A three-container extrusion system has been established and used to produce different aluminium components and case studies are presented.

In this work, a hot extrusion process was proposed to manufacture the 18Ni (250) maraging steel large fan shaft for aero engines. To reduce the wear of the hot extrusion punch and extend its service life, a wear model of the hot extrusion punch for the large fan shaft was established based on the Archard theoretical model, and the wear distribution of the punch and the effects of the geometric structure parameters of the punch, such as draft angle and draft height, on the wear of the punch were studied. The results show that the wear of the punch after extrusion forming was mainly concentrated in the bottom transition fillet and working bevel areas. With the increase of the punch draft angle, the maximum wear depth at the punch fillet increased linearly and significantly. With the increase of the draft height, the wear depth of the punch increased gradually. After 35 times of continuous extrusion production, the accumulative wear depth of the round corner area at the bottom of the punch was about 10 mm, with an error of 18.5% from the prediction result, which proved the correctness of the FE simulation and the accuracy of the prediction model of the accumulated wear depth of the extrusion punch.

Hot extrusion materials produced by rapidly solidified Al-Fe alloy powder are a promising solution to replace copper-based electrical conductors because they exhibit good heat resistance and relatively high electrical conductivity. However, the in-situ temperature of the billet in extrusion dies tends to increase, which can affect the mechanical properties of the extruded material. The present work investigated the effect of the temperature change during hot extrusion on the mechanical property. Then the influence of the billet composition gradient control was studied. An air-jet atomized aluminum alloy powder containing a 2.3% iron by mass was pre-sintered into a cylindrical billet and then hot extruded. The in-situ temperature changed from a minimum of 656 K to a maximum of 700 K. The hardness of the extruded material varied from 66 HV to 54 HV when increasing the in-situ temperature. The grain size of the extruded material became coarse as the in-situ temperature increased, which caused the decrease in hardness. The billet's iron content was graded by mixing a different aluminum alloy powder containing 5% iron by mass to improve the hardness variation. As a result, the decrease in hardness of the extruded composition-graded material was suppressed. Fine Al-Fe intermetallic compounds increased due to the composition gradient, which can account for the improvement in the mechanical property variation.

Pin structures extruded from the sheet metal plane have numerous industrial applications. For instance, they can be used in bulk microforming to solve handling difficulties or in joining technology to connect dissimilar materials. Due to the absence of material flow restrictions in the direction of the sheet metal plane, pin extrusion is affected by numerous process-, workpiece- and tool-related parameters, which have a huge impact on the material utilization and the obtainable pin geometry. Within the scope of this study, a combined numerical-experimental research approach is used to analyze the influence of the material and its condition on the achievable pin height and the occurrence of the mostly undesired funnel formation at high punch penetration depths. For this purpose, elastic-ideal plastic and elastic-real hardening model materials are first investigated numerically, which are subsequently validated and verified in experiments by using the materials Cu-OFE, AA6016, DC04 on a laboratory scale. Based on the results, recommendations for the material selection and its properties are derived in order to maximize the material utilization.

The Friction Stir Extrusion process is increasingly proving to be a good answer to the growing demand for metal products obtained by limiting the consumption of both energy and raw materials. Indeed, with this technological process, it is possible to obtain axisymmetric extruded components starting directly from metal scraps, which are typically the traditional processing scraps by chip removal. In this work, the feasibility and effects of different process configurations (direct or inverse extrusion) and of different manufactured objects (filled rods or pipes) on the response parameters (stress analysis and global bonding conditions) were investigated. To do this, a finite element simulation model was developed with which it was possible to carry out the thermo-mechanical analysis of the entire process. The results obtained allowed to highlight the potential of Friction Stir Extrusion in both its declinations of direct and inverse extrusion and in the possibility of correctly extruding both full rods and pipes. Furthermore, the technological windows able to determine the optimal combinations of process parameters, according to the achievement of the global bonding conditions, were also identified.

To establish a designing method of drawing schedule of the wire with an elliptic cross-section, the influence of the cross-sectional shape and the reduction in cross-sectional area on underfilling and drawing limit has been investigated by experiments and numerical analyses. It is found that under the conditions where the axis ratio (major length / minor length) is less than 1.3, the underfilling is suppressed when the reduction is greater than 20%. However, the wire fractures if the reduction is higher than 50%. It is confirmed that the lateral spread by the drawing is very small, about 2 to 3%, and not sensitive to the reduction. Based on the above results, it is concluded that the wire diameter before the drawing should be designed larger than the major length of the die. Furthermore, by considering underfilling, drawing limit and die seizure, a method to find the designable window of the reduction in cross-sectional area and the axis ratio of the cross section for single-pass wire drawing will be presented.

Extruded aluminum supply chains are materially inefficient with around 40% of the billet likely to be scrapped before the profile is embedded in a product. One of the largest sources of scrap is the removal due to weld integrity concerns of the tongue-shaped transverse weld(s) that forms between consecutively extruded billets. Process setting and die geometry optimization can decrease the weld length (and hence scrapped material) by modest amounts. We explore a process for significant scrap savings using profiled dummy blocks to generate shorter welds by compensating for the differential metal flow velocities across the billet cross-section as it flows through the die ports. We develop a design process for defining the profiled dummy block shape. For a given part and press, we first define an ideal dummy block shape by extracting the velocity field from finite element simulations of the conventional process and assuming perfectly rigid tooling. Next, we rationalize the tool shape using stress and deflection limits (preventing plastic deformation and interference with the container wall) and ductile damage limits for the billet to prevent cracking. We then simulate the likely effect of the rationalized dummy block design on back-end defect removal. The methodology is demonstrated for four profiles of increasing complexity. The process’ potential is evaluated experimentally using billets machined to match the ideal dummy block shape. The results show that profiled billets can achieve weld length reductions >50% for simple shapes. We demonstrate that multi-profile tooling can deliver scrap savings across a family of similar profiles.

Friction extrusion (FE) is a solid-state processing technique based on heat and shear introduction via friction at the die-feedstock interface. FE can be used to process feedstock of different forms, such as solid billets, chips or powder as well as being applicable to a variety of Al-, Mg- and Cu-alloys. The relative rotation between die and feedstock makes preheating obsolete and the induced plastic deformation has the potential of not only energy-efficient consolidation but also grain refinement for improved extrudate properties.In this study, the processability of Mg-Gd powder via FE is investigated. Mg-Gd alloys have their main use in aerospace as well as being promising candidates for biomedical applications. In these fields the homogeneity in terms of mechanical and chemical properties, respectively, is a critical factor.Consequently, the application of FE in this study aims to provide insight on a new possible processing route for Mg-Gd alloys by investigating the mechanical properties of the extruded, fully consolidated wires, i.e. hardness and compressive properties, as well as the microstructural features of the feedstock during processing, i.e. void volume, grain structure and morphology changes.

With increasing climate concerns and the urgent need to reduce carbon emissions, hydrogen as a clean and renewable energy source for vehicles has attracted rising interest. A major challenge is the on-board storage of flammable hydrogen gas, which restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper investigates the advantages and limitations of the existing backward extrusion techniques in producing the aluminium liners of the Type III tanks. Backward extrusion is a simple and efficient method that can manufacture near net-shape cylindrical liners in one step without the requirement of welding. However, this process requires high extrusion force, which makes the production of large tanks difficult and leads to high manufacturing cost. In the recent decades, several advanced tool designs have been proposed to reduce the extrusion force, and the merits and limitations of these designs are reviewed and analysed in this paper. Furthermore, the feasibility of these designs in processing aluminium alloys is assessed using the finite element analysis (FEA). The simulation results show that these designs are effective in reducing the extrusion load as compared to the conventional method, but the product size is restricted. Further improvements are required to make these designs suitable for producing large and long tanks for practical applications.

Continuous hot extrusion enables a constant profile velocity throughout all stages of the process, including the dead cycle time when reloading a billet. The processes direct and indirect hot extrusion are combined with a stationary or a movable valve. Both variants have different influences on the process and the profile properties. The movable and the stationary valve are directly compared with numerical and experimental methods. Continuous extrusion experiments are conducted using the method of similarity with a model material. The results show that a movable valve secures the functionality safely and a stationary valve reduces the length of the machine, the required ram forces and the amount of weld seams. The stationary valve also leads to a reduced profile temperature, which allows enhanced profile speeds and increases the productivity of the continuous extrusion process.

Aluminum-polymer profiles offer various benefits for lightweight design and multifunctional parts, whereby the aluminum provides the required stiffness and strength and the polymer contributes functionality or decreases weight. In a new intrinsic co-extrusion process, aluminum hot extrusion and polymer extrusion is combined. The polymer melt is injected into the material flow of the aluminum at the weld chamber of a modified porthole die. Regarding pressure and weld chamber length of the polymer, the process windows of aluminum and polymer extrusion vary significantly. These process parameters are investigated numerically with the objective to enable a stable co-extrusion process. Slight changes in these parameters can lead to different profile geometries. With the chosen material combination of AA6060 and polyethersulfone (PESU), co-extrusion experiments are performed successfully and continuous hybrid profiles with a polymer core and aluminum shell are produced.

Aluminium extrusions are used in more and more applications in different industrial fields, due to their properties and productivity. However, in-process scrap produced in aluminium extrusions needs to be reduced to increase material yield, process efficiency and sustainability. An important source of in-process scrap is the charge weld created in billet-to-billet extrusion, which is an inevitable transition zone occurring in the extruded product due to the transition between successive aluminium billets. Therefore, understanding how to reduce and control the charge weld in extrusion is crucial to the carbon footprint of the extrusion process while reducing the risk of failures of the extruded product in service and use. This paper aims to provide preliminary insights into the formation of charge welds and how to minimize their impact on in-process scrap in extrusion, with a primary focus on the role of die design and process parameters. First, four typical types of extrusion die structures were designed: spreader, feeder, flat and pyramid die. Second, a finite element (FE) model of aluminium extrusion was developed based on QForm. The simulations were validated by representative industrial extrusion experiments. Based on the FE model, the processing formation history of charge welds with different die types was investigated, with a particular focus on the effect of material flow behaviour and dead-metal zones on the charge weld. Finally, a sensitivity study on the effect of ram speed and billet temperature was performed.

The influence of the dieless wire drawing process parameters on the forming zone of magnesium- and zinc-based wires are investigated. For this purpose, a numerical thermo-mechanical finite element model of the dieless wire drawing process is developed. For the validation of the numerical model and for experimental investigation of the forming zone, experiments are carried out using a flexible wire drawing setup with the same process parameters as for the numerical model for selected magnesium- and zinc-based alloys. The results show that reduction in cross-sectional area of up to 30% is possible for magnesium-based wires. Furthermore, a localization of the forming zone is essential for feasible parameter settings and high diameter reductions in one drawing pass. In addition, the length of the forming zone itself can be influenced not only by the material and the process temperature, but also by the process speeds.

Multi-material design is often used to improve performance of products and components. The authors proposed the multi-property design, where a material having desired properties is fabricated on demand, for further optimization. In the multi-property design, after dimensions of the component are fixed, properties required are determined. Then, a component having the desired properties is fabricated. In the previous study, multi-filament cold extrusion was proposed as a process to realize the multi-property design of composite rods. Al, Fe and Cu filaments and a Cu sheath were used to constitute a billet. By changing numbers of filaments of each material, three properties (density, yield strength, electrical resistivity) of extruded rods were controlled. The measured properties were found to be close to the predictions by the mixture rule. However, it was not shown that the process can really produce the rod having the prescribed properties. In this study, a different material combination of Mg/Ti/Ag is used to achieve the same properties as the Al/Fe/Cu rods. By selecting number of filaments of each material, Mg/Ti/Ag composite rods show similar properties as the Al/Fe/Cu rods.

Due to the process-specific high material utilization and the associated high energy and resource efficiency, cold forming processes represent an important technology in the processing of steel. To increase wear resistance and fatigue strength, cold formed workpieces are often case hardened. However, case hardening is an energy- and cost-intensive process step. As a complement, the finishing may be realized by means of mechanical surface treatments, like deep rolling, machine hammer peening or shot peening. These treatments improve the surface layer condition of the component by inducing favorable residual compressive stresses, strain hardening, grain refinement and surface smoothing to increase wear resistance and fatigue strength.For the design of the surface treatment process of an impact extruded component, there is a considerable deficit in scientific knowledge about the concrete cause-effect relations between process parameters and surface integrity as well as component performance. To make these interactions explainable, knowledge about internal stress and temperature distributions during process execution is necessary. These can only be determined numerically. For this reason, the finite element method is a suitable tool for an overall investigation of the processes.In the present work, a manufacturing process consisting of full forward extrusion and deep rolling is implemented as finite element model. The focus of this model is a fully coupled thermal-stress analysis.The investigations are carried out for the material 16MnCr5. This case-hardening steel is used to produce workpieces via cold forming, which are used in both hardened and unhardened condition. The experimental performance of the simulations performed here has already been carried out for this material.

A parametric study was carried out on the direct extrusion of magnesium flat products made of AZ31 and ZN10, in which the extrusion speed and the die geometry were varied. This leads to a change in recrystallization behavior (process temperature), material flow and strain path. The resulted microstructure and texture development were investigated using EBSD measurements. Additionally, a finite element model for AZ31 was developed based on the parametric study and later used helping to understand the material flow and strain path during the extrusion. The obtained knowledge is essential to optimize the die geometry and process parameters and allows a more controlled development of microstructure and texture during extrusion of magnesium.

Backward cup extrusion occurs high pressure, high temperature, and a large surface expansion ratio during forming. Thus, this forming provides the severe tribological conditions because lubricant film between the punch and the specimen is broken. This study investigates the influence of the material flow on forming conditions using the FEM analysis data and the previous experimental data in the cold backward cup extrusion at the extrusion ratio of 2.8. Additionally, suitable punch nose shape is also verified to keep good lubricant condition between the punch and the specimen during the forming. The friction between the punch and the specimen of the punch with corner radius is lower than that with nose angle.

Lightweight automotive extrusions are increasingly complex, thin-walled, multi-hollow profiles made from high-strength, quench-sensitive aluminum alloys such as AA6082. These alloys require rapid quenching as the profile leaves the press to prevent the precipitation of undesired phases, to create a supersaturated solid solution, and to prepare them for subsequent age-hardening treatments; e.g., for the T6 temper. However, rapid quenching can cause profile distortion, which leads to high scrap reject rates, increasing costs, environmental impacts, and production lead time. This study tests two hypotheses: (1) That the different cooling rates set-up across the profile section during quenching induces not only distortion but also varying mechanical properties across the section; and (2) That this temperature differential can be minimized by combining (conventional) external quenching with internal quenching supplied by through-die cooling channels. The first hypothesis is tested experimentally by taking tensile specimens from different locations of an AA6082 multi-hollow profile, showing a significant decrease in the ductility and ultimate tensile strength of samples extracted from internal webs. The second hypothesis is tested by performing thermo-mechanical finite element simulations that compare the thermal history, stresses, and strains of simultaneous internal and external quenching in contrast with conventional quenching (external only). The combined quenching approach results in a significant reduction in the residual stress and plastic deformation. This implies lower scrap reject rates, improved internal wall mechanical properties (giving scope for further light-weighting), and a wider profile design space by enabling the extrusion of more challenging profile shapes.

In bending processes with generic tools (e.g., three-roll push bending), the part geometry is a result of the free tool kinematics. In contrast, processes with geometry-specific tools (e.g., rotary draw bending) require a specialized tool geometry to form a dedicated part geometry. To make them more flexible while maintaining their advantages of dimensional accuracy and process controllability, adjustable tools are needed. Inspired by multi forming techniques, one possible approach is to segment the conventionally closed tool surfaces and adjust them in-process. For the design of the segmentation in terms of segment geometry and size, as well as in terms of tolerable spaces, a deep understanding of the deformation mechanisms of the workpiece in contact with segmented surfaces is crucial. As a first step toward this goal, this work presents lateral indentation tests of circular and square steel and aluminum tubes by segments and segmented surfaces. Based on these tests, finite element (FE) models are validated and show a good correlation with the experimental tests in terms of force-displacement curves and part geometries. Finally, the FE-model is used to perform a parameter study to investigate the deformation behavior of tubes subjected to lateral loading by segmented surfaces in dependency of different tube wall thicknesses as well as of different segment spacings. It is outlined, that the segmentation of forming tools is generally possible with negligible impact on the process when choosing a suitable surface topology.

To produce tubular components with high-strength and high-stiffness but without length restriction, a new process based on a combination of press hardening and granular media-based tube forming is presented. Compared to conventional tube hydroforming using liquid media or gas, the use of granular forming media offers the advantages of being stable at relatively high temperatures and avoiding leakage problems. The previously developed granular media-based tube press hardening, where the forming force is directly induced through the granular medium, is severely limited in the length of the tubes. The proposed solution is a passive granular media-based tube press hardening process. Granular material is used as a passive forming medium inside the tube, while the forming force is applied on the tube’s circumference by a rigid punch. The tube material is 22MnB5. Process defects for press hardening of tubes without forming media are discussed and the process chain for a passive granular media-based tube press hardening is presented. The impact of various levels of granulate filling is investigated with FEM simulations showing friction causes asymmetric deformation, which can be avoided by a double-acting process. A lower limit is analytically derived for the filling factor. An analytical approach to predict the punch force underestimates the required forces, as the inhomogeneous cap hardening, and the complex stress state of the granulate are not considered.

Cold roll forming is traditionally widely used to incrementally manufacture cost-effective welded tubes, where the metal strip is progressively deformed by multiple rollers to the final round cross-section following the so-called flower pattern. However, different flower patterns may allow obtaining the same final round cross-section with a variable number of forming steps and intermediate geometries.The deformation steps are obtained by combining vertical and horizontal rollers, with specific geometrical features, but, in the case of inappropriate design, a non-homogeneous distribution of the mechanical properties along the tube cross-section may result and affect the tube behavior in subsequent processes (i.e. bending) or even in its service-life.The paper aims at proposing reliable quality indices to evaluate the homogeneity of the mechanical properties as a function of the flower pattern design and of the main process parameters. To this purpose, a numerical model of the tube roll forming was developed in LS-Dyna and validated on an industrial case for welded tubes. Then, the validated model was used to investigate the effects of three different flower patterns, named respectively W-shaped, P-shaped and C-shaped, on the introduced indices. The results show the influence of the patterns on the strain distribution and workpiece final characteristics.

Classic forming technologies can make a difference to a climate-neutral economy. This also applies to the production of innovative hydrogen coolers (recuperators). To improve the efficiency of hydrogen coolers, heat transfer and heat flux can be increased by tube structures made by pressing spherical elements on their surface. Hydrogen is passed through the tubes of the recuperators and the cooling medium flows across it (Fig. 1a). The tube serves as an atmosphere separator. Structured tubes can increase the power density with the same dimensions. Figure 1b shows a process for introducing the structure into the pipe using radially and symmetrically arranged tools. Sheet metal forming usually involves pressing with structural tools, bending into a tube, and longitudinally welding. However, producing small tube diameters in the range of one inch presents a technical challenge. The challenge considered in this paper is to develop a new structuring process while maintaining the structural integrity and wall thickness of the tubes. This study aims to determine the feasibility of a multi-stage vault structuring process for recuperator tubes using heat-resistant semi-finished products.

This paper explores the application of incremental sheet-bulk forming by means of a tube boss forming process that is capable to reduce and locally pile-up material in thin-walled tubes. Local thickening of the tube wall thickness allows creating three-dimensional functional features for subsequent forming and assembly operations. The presentation is focused on the development of a flexible laboratory tool system capable of performing boss forming of thin-walled tubes in unit cells made from various materials and geometries. Special emphasis is placed on the design of the tool system taking into consideration the process formability limits. Information on the mechanical and formability characterization of the tube material gives support to the work.

Conventional tube drawing methods have the disadvantages that thickness reduction in one pass is small. This paper proposes a tube drawing method for overcoming this disadvantage and the method expands the diameter while drawing. At first, the tube is flared by pushing the plug into the tube end. Then, the plug is drawn by chucking the flared end, and the entire tube is expanded. Tensile circumferential and axial stress reduce the tube thickness effectively during the plug drawing. In this study, the influence of the material on the forming characteristics, such as thickness reduction and strain state, was investigated by experiments and finite element analysis. The results show that the forming limit is larger when the elongation to initiating the necking and the R-value of the material are large. Materials with large n values and large friction coefficients undergo a deformation close to biaxial stretching to realize high thickness reduction.

The objective of this paper is to present experimental investigations for the analysis of flow-forming of hybrid components. For this purpose, experiments were first carried out in which a heated hybrid tube made of plastic and aluminum is formed by flow-forming. Initial temperature, roller feed rate and thickness reduction ratio were varied for the investigations. During the process, the temperature and forces were measured. This was followed by measurement of the geometry of the produced components.It has been established, that there is a strong local increase in temperature due to the forming, which is decisive for the process result.

An investigation was made on the application of expansion drawing for processing a circular parent tube to a square tube with high dimensional accuracy in this study. Influences of the dimensional parameters on thickness distribution and dimensional accuracy of the drawn tube were evaluated using finite element analysis. The parameters were plug width, plug half-angle, and plug corner shape. The material of the parent tube was aluminum alloy 1070. When the plug width was large, local thinning occurred on the corner of the drawn tube. When the plug width was small, a discrepancy in dimension occurred between the plug and the inner surface of the drawn tube. This discrepancy can be suppressed by using a plug with a small half angle. In addition, the local thinning was suppressed by using the plug which the cross-sectional shape was changed from a circle to a square in the taper portion. The results of experiments that followed the analyses were successfully in good agreement with the results of the analyses.

Tube hydroforming (THF) is an assessed production process for the fabrication of tubular components. Its main advantages are the enhancement of the material strength and the shortening of the production chain. Moreover, THF allows to obtain complex geometries all in one so reducing the number of production steps, assembly time and production costs. For these reasons, THF finds applications in many industrial fields. The design of the production process is typically done in two subsequent steps, using Finite Element Models (FEM) and, then, experiments. FEM allows to outline the process curves globally (punch strokes and pressures) and to estimate the loads (punch and die closing forces), while experiments validate the FEM and perform the final tuning of the process. To reduce the efforts in the experimental phase, a reliable FEM software is necessary. The available commercial software can be divided into two main groups depending on the solving algorithms: explicit and implicit. Explicit software is faster but less reliable, the opposite for implicit one. Moreover, in the case of thin-walled parts (such as tubes or sheets), also the type of mesh adopted can be grouped into two: shell and solid meshes. The main differences are the same as the solver, faster but less precise the first and the opposite for the second. Given these countertrends in computation, this paper aims at comparing two software for THF: an explicit with shell elements (PamStamp) and an implicit with solid elements (DeForm). The comparison will highlight the pro and cons of the two solutions and, finally, a trade-off will be proposed.

The material-efficient and also locally-adapted manufacture of semi-finished products is a highly aspired goal of modern manufacturing processes. Internal Flow-Turning [1] is a forming process that is capable of producing wall-thickness-contoured tubes without material loss and hence contributing to material savings and an area-adapted lightweight design of semi-finished parts. Internal flow-turning can also be used for manufacturing secondary design elements, like local reinforcements or defined external ribs in addition to the main wall thickness contour [2].In this paper, a modular tool setup is presented that makes it possible to use internal flow-turning on conventional CNC machines. The machine requirement for this is that the CNC machine has two linear axes and a rotary drive. In addition to presenting the process capabilities of this tool setup, new material flow findings are set out for the internal flow-turning process of local wall thickness reduction and the forming of external longitudinal ribs.

Tube hydroforming is an advanced technology for manufacturing thin-walled tubular components with irregular cross-sections. However, a real-time measurement and quantitative research on the friction effect in hydroforming process has never been involved. In this paper, the unloading theoretical condition for tube blank after contacting with die during corner filling process was derived based on ideal rigid plastic assumption. It is predicted that the tube blank would unload quickly once it contacts with the die due to friction. Furthermore, an experimental setup was firstly developed for visual measurement of corner filling deformation in tube hydroforming process. Based on 3D full-field strain measurement technology (3D-DIC), this setup can be used to realize a real-time measurement of strain field on the tube blank during corner filling process. Then the effects of friction and tube properties on deformation behavior were investigated by pure lead (approximately ideal plastic model) and aluminum alloy (hardening model). It is shown that the friction causes pure lead tube blank to unload after a very small deformation of less than 0.02 in contact with the die, which basically verifies theoretical analysis results. For aluminum alloy tube blank with strong hardening ability, it continues to deform after sticking on the die surface. There is little effect on improving the uniform deformation of pure lead tube by reducing friction with lubricants, but it is very effective to improve the uniform deformation of aluminum alloy tube.

The residual stress of submarine pipeline pipe directly affects its service safety, and the collapse resistance of submarine pipelines can be improved by controlling the residual stress, which is great significance for the long-term service of submarine pipeline pipe. In this paper, ABAQUS software was used to simulate the whole process forming of JCO-welding-compression calibration of submarine pipeline pipe. The influence of multi-directional compression calibration process parameters (number of petal molds, compression ratio and friction coefficient) on the residual stress was discussed, and the evolution law of residual stress of pipeline pipe under different forming processes was analyzed. The simulation results show that the residual stress of the calibrate pipeline pipe using the 4-petal and 8-petal molds is smaller than that of the2-petal molds; The friction coefficient has less effect on the residual stress; The average von Mises residual stress of the compression calibration pipeline pipe is 120 ± 20 MPa, which is reduced by 79% and 30% in the welded and non-welded areas, respectively, the maximum circumferential residual stress on the inner and outer surfaces is 20 MPa and −18 MPa, and the ovality of the pipeline pipe is 0.05%. The research results provide a foundation for the forming process strategy of submarine pipeline pipe.

Spinning processes are incremental forming processes whose numerical modeling involves several difficulties related to the high rotational speed of the workpiece and very localized roller-workpiece contact area. Based on a shear spinning model, some major modeling options in Abaqus® finite element software are investigated, after a prior comparison of the simulation results from Abaqus® and Forge®. Conclusions are drawn regarding results accuracy and computational cost. The relevance of the tested options is thereafter discussed.

Beads are typical offset features used in sheet metal parts for increased out-of-plane bending stiffness. Incrementally forming beads using common tools presents a new paradigm for manufacturing versatility and geometrical flexibility in part design while bringing significant cost benefits for low volume applications in automotive and other industries. However, the production applications of incremental beading can be limited due to beading induced distortion and subsequent dimensional quality concerns. In this study, distortion reduction solutions are sought after based on a combined approach of virtual simulations and physical testing. Numerical models, through Finite Element Analysis, are developed to virtually describe the incremental beading process and predict the resultant distortion with the goal of improving model accuracy and reducing computational cost. The developed FEM models are validated against experimental data to serve as the basis for future virtual process optimization. Experimental approaches to effectively reduce distortion are identified during model validations. Effects of process variables are discussed.

Pillow plate heat exchangers (PPHE) represent a promising alternative to conventional heat exchangers. The manufacturing process of the heat exchangers often consists of two processes. In the first step, two plane sheets are positioned and spot-welded over the entirety of their surface. The edges are sealed, such as by roll seam welding. In the second step, the inner channels are formed by hydroforming. This construction method does, however, offer enormous potential for optimization. According to [2], a secondary-structured surface, in which the sheets are dimpled, leads to an improvement in heat transfer. This is because the fluid mechanics are positively influenced by these dimples. This sheet modification also leads to an increase in surface area and stiffness. One approach to manufacturing this secondary structure is by using a new electrohydraulic incremental forming process (EHIF) [3]. The topic of this research is the development of a numerical model that can predict the manufacturing process using EHIF. The model is developed in two steps. In this paper, the free forming process using a drawing ring is modeled and validated. Based on the validation tests, it can be stated that the simulation model represents the electrohydraulic forming process in a good way. Both the drawing depths and the displacement-time curves of the free forming showed a high level of agreement for the charging energy of 1.5 to 4.5 kJ. In future work, the simulation model will be adapted in such a way that incremental structuring of a sheet metal can be carried out.

The application of forming operations instead of conventional cutting processes is a practical approach to increase material efficiency and functional integration, thus addressing lightweight design. In this context, the innovative process class of Sheet-Bulk Metal Forming is presented, which combines the advantage of bulk and sheet metal forming. One of the assigned processes for the manufacturing of functional components with different form elements is orbital forming. Within previous investigations, the major challenge could be identified as a control of the material flow. Since process parameters, like an increased forming force, are not sufficient to avoid process failures in form of wrinkles, other measures have to be taken into account. Especially when applying precipitation hardenable aluminum alloys, one possibility is the application of a local short-term heat treatment. By locally reversing the hardening effect of the precipitation clusters, the interaction between softened and still hard areas can be used to attain the desired material flow. Although this procedure is established for conventional sheet metal forming processes and was furthermore investigated for the orbital forming of components from the aluminum alloy EN AW-6016, the influence on the forming of high-strength aluminum from the 7xxx-series is still content of current research. Especially due to a reduced formability at room temperature, this alloy is predominantly formed at elevated temperatures. By introducing the established method of a local short-term heat treatment on 7xxx alloys, a contribution towards a possible forming at room temperature is made. Therefore, this work focuses on the development of a tailored heat treatment strategy to control the material flow during orbital forming. Specimens out of the high-strength aluminum alloy EN AW-7075 with a thickness of 2.0 mm in condition T6 are heat-treated and consequently cold formed. The results are quantified by a geometry-based analysis. The resulting strain distribution is used to verify the material flow proportions.

Single point incremental forming (SPIF) and Double-sided incremental forming (DSIF) are two main variants of incremental sheet forming (ISF) processes. Tension under cyclic bending (TCB) have been developed as a means for experimental evaluation and validation of the SPIF process and further extended to DSIF process by adding a compression force (TCBC) in recent years.In this study, an analytical model is proposed to capture the localised deformation and stress evolutions due to bending, reverse-bending and additional compression in TCB and TCBC tests as a simplification of SPIF and DSIF processes. The results show the through-thickness stress variation has determinative influence on fracture initiation. The effects of test parameters and their interactions on formability were evaluated. Although the surface contact deformation and material thinning are simplified in the analytical model, the results obtained are comparable to experimental testing and finite element (FE) simulations. This work shows that the analytical model can be used as an effective means to decouple the complex deformation modes and local stress evolutions of TCB and TCBC and to provide a new insight into SPIF and DSIF processes.

This paper presents the extension, analysis and modelling of the deformation in the combined friction-spinning and flow-forming process using the example of the manufacture of flange contours, which is dominated by shear and tensile stresses in the tangential direction and by bending-like forming in the radial direction. With the aim of influencing these characteristic deformation mechanisms, the existing tool system was extended by an improved tool drive. The fundamental investigations on the influence of the increased tool rotation speed on the deformation were carried out using visio-plastic measurements. The key finding is that the velocity and direction of friction between the tool and the workpiece in interaction with the length of the path of friction is the major predictor of the twist angle and thus has a significant influence on shearing. It is shown that the twist angle can be adjusted by at least 105° using optimized parameters for the new tool system. Furthermore, enabling the defined adjustment of the twist angle a model has been built up and successfully validated. As a result, this enables a significant increase in the controllability of the deformation in this forming process and thus of the component properties, which lays the foundation for a significant expansion of the scope for defined residual stress adjustment in the friction-spinning process.

Forming-induced residual stresses can be used to increase the fatigue strength of formed components. By adjusting the process parameters of the incremental sheet metal forming process (ISF), the forming mechanisms can be adjusted and thus the resulting residual stress can be targetedly set, to meet specific component requirements. Within the scope of this work, experimental results show that superposed compressive stresses using a flexible polymer die during ISF, near-to-surface compressive residual stresses can be induced on both sides of aluminum alloy 5083 truncated cones. The resulting residual stress state is measured by means of X-ray diffraction (XRD). In addition, the amount of near-to-surface residual stress can be adjusted by varying the degree of hardness of the elastomeric die material. These findings can be used to set tailored properties of formed components by forming-induced residual stresses, to extend the operating time of the component until failure.

Deformation-induced martensite has been observed in the incremental sheet forming of metastable austenitic stainless steels (MASS). The presence of martensite improves the characteristics of the springs. Martensite transformation usually occurs at low temperatures (<70 ℃). Depending on the tool speed, incremental forming of disk springs requires between 3 to 5 min. The forming time needs to be short to increase the process output in industrial settings. However, accelerating the process leads to high temperatures above the martensite transformation temperature that suppress martensite formation, necessitating temperature control during forming. It is suggested to enhance the martensite content of the blank by cooling during the forming operation. In this contribution, two-point incremental sheet forming is conducted to determine the influence of process temperature on the phase content of MASS disk springs. A temperature-dependent phase change material model that includes the strain rate effect is implemented in finite element (FE) simulations to predict the martensite content. FE simulations are performed to investigate the convection coefficients and cooling time leading to process temperatures below 70 ℃. The framework can be used to control and speed up the incremental forming of disk springs while maintaining a high martensite content.

The Invar 36 alloy is widely used in aerospace and precision instruments for its extremely low coefficient of thermal expansion below Curie temperature (230 ℃). The conventional method of manufacturing Invar moulds is hot-pressing forming, which requires two dies and causes high cost, slow efficiency, and challenges in forming intricate surfaces. To resolve these issues, an electrically-assisted incremental forming (ESIF) process is used for Invar 36 sheet metal forming. In this process, the forming step size, temperature, and tool diameter are the key factors affecting the final forming quality. Through an orthogonal array, the influence of these parameters on the thickness and contour deviation of ESIF was studied in this study using a finite element (FE) simulation model. The study reveals that the minimum thickness and RMSE of contour deviation are primarily influenced by the tool diameter and temperature, respectively. The optimum process parameters to form the part were determined to be: a step size of 1.0 mm, a forming temperature of 600 ℃, and a tool diameter of 12 mm.

As a die-less manufacturing technique, the incremental sheet forming (ISF) is a flexible and potentially cost-effective process for producing small-batch or customised sheet products with complex geometries. However, some important limitations of the ISF have prevented this flexible sheet forming process to be utilised for industrial applications. These limitations include low surface finishing, unacceptable springback and inability to process hard-to-form materials at room temperature. To overcome these limitations, a new rotational vibration-assisted ISF (RV-ISF) by creating a novel rosette tool concept has been developed in the University of Sheffield. In this study, RV-ISF tests using new tools are conducted to create straight grooves and rectangular pyramids to evaluate surface quality of the parts formed by the RV-ISF process. Friction conditions between the RV-ISF tool and the deforming sheet, as well as part surface roughness and surface texture are measured and evaluated. The results provide an insight into the effect of new tool design and key parameters on the interfacial friction condition and surface quality of the new RV-ISF process.

Shear spinning is a bulk forming technique used to produce hollow, rotationally symmetric parts used in automotive, aerospace, nuclear and defence industry. The process has been invented about 60 years ago and is used widely in the industry. However, the literature and the understanding of process mechanics is limited. This paper investigates the process mechanics through a numerical model and a series of physical trials using commercially pure copper. The model is developed using commercial Finite Element software with input from tests to determine friction coefficient and material properties. It is then validated against physical trials comparing both part geometry and strain distribution in shear-spun parts. Validated model is then used to investigate mechanics of the process in terms of maximum equivalent plastic strain on the plate surface for different stages of the process and through thickness in three different sections. Also, another numerical model which has different kinematics has been developed to increase computation efficiency.

Metallic components with large-area functional surface microtextures like microgrooves and dimples have special functions such as drag reduction and energy efficiency enhancement. Existing forming processes are not suitable for small batch production of functional surface microtextures over large areas due to the following disadvantages: low flexibility, time consuming and high production cost. Therefore, we proposed a hybrid incremental sheet forming process which combines the excellent flexibility of incremental sheet forming process with the characteristic of high forming quality of microgrooves in rolling process to manufacture both the macroscopic geometric shape and surface microtextures on curved metal components, simultaneously. An experimental platform for the hybrid incremental sheet forming process was firstly developed and curved microgroove arrays were successfully fabricated on the surface of AA2024-T6 sheet. Then, the effect of different press-in depth (h) and different step size (∆z) on the formation of microgrooves of the formed parts were investigated. It can be found that the depth of the fabricated microgrooves shows a nonlinear growth in relation to the press-in depth (h) due to the spring-back effect. Meanwhile, increasing the step size (∆z) is conducive to improving the formation of the microgroove. Furthermore, the surface roughness (Ra) and the surface morphology of the formed parts were analyzed. This work provides an effective approach to realize low-cost and high-quality processing of functional surface microtextures over large areas on metal sheets.

The development of a preformed cylinder made by wire and arc additively manufacturing (WAAM) from 316L stainless steel (SS316L) and extended to a thin tube via flow-forming operation was introduced in previous work. It was shown that the material can tolerate high plastic deformation in the as-received condition and did not require any heat treatment (HT) before the flow-forming operation. However, the flow-forming’s high reduction in tube thickness and length increase generates large amounts of residual stresses that might affect the final product. For most engineering applications these residual stresses must be reduced or eliminated by appropriate HT. In this work, different HT on the final tube were investigated. The stress-relief heat treatments were conducted in air and vacuum environments, within the temperature range of 400–800 °C. The representative test samples were rings made of the above flow-formed tube. In an attempt to minimize the variation in the mechanical properties of the produced tube, a typical high reduction flow-formed tube was sliced into rings. Part of the rings were sectioned to evaluate the residual stresses left after each HT. Other rings were tested via the ring expansion technique to evaluate the impact of each HT on the ultimate strength of the material. It is shown that the variation in the HT temperatures directly influenced the residual stresses, the thermal treatments reduced the material’s ultimate strength by about 20% with respect to the post deformation state. It was shown that even further strengthening can be gained by the HT up to 600 °C while the residual stress decreases. Full stress relief is achieved in 800 °C with some strength reduction.

This work focuses on the robotic incremental forming process. The general objective of this study is to provide an instrumented device dedicated to the qualifying of the forming of typical cases. The manufacturing cell is equipped to evaluate in situ the characteristics of the process as a function of: (i) the tool diameter; (ii) the feed rate; (iii) the rotational speed i and (iv) the step size. In a first approach, the influence of these operating parameters on the quality of the part is studied by forming spherical shapes. The material is an AA5754-H11 aluminum sheet whose behavior is characterized by tensile tests at room temperature.The robot movements are analyzed by laser scanning to highlight the dispersions induced by the joint stiffness and the deformations of its structure. The observed deviations will be used in future work to improve the control of the robot trajectories. The tool/material interaction and the behavior of the shaped sheet are studied by image analysis based on the experimental results. A preliminary numerical model of the process is proposed, to analyze the evolution of the forming forces and the equivalent plastic strain. The predictions correlate well with experiments and several future development paths are derived from the comparison.