60 Excellent Inventions in Metal Forming

Two simple experiments for probing the plastic response of thin-walled tubes under pure hoop tension and combined tension and shear are described. They both use ring-like specimens with test-sections machined on them. The specimens are placed over two D-shaped mandrels that are parted in a universal testing machine. The first experiment is the Ring Hoop Tension Test, which can be used to obtain the uniaxial hoop response of the tube. The second is the recently proposed Ring Plane-Strain Tension experiment, which can impose stress-states with an arbitrary combination of tension and shear. It is shown that the results of these experiments can be used to probe the yield locus of the tube material and calibrate suitable anisotropic yield functions. The experiments are proposed as complementary to the established tension-internal pressure loading of thin-walled tubes, but can also be used independently, in the absence of the specialized equipment that the latter experiment requires.

A new procedure for the experimental determination of the FLCs has been proposed. The procedure is based on the hydraulic bulging of two specimens. The upper blank has a pair of holes pierced in symmetric positions with respect to the center, while the lower blank acts both as a carrier and a deformable punch. By modifying the dimensions and reciprocal position of the holes, it is possible to investigate the formability in different strain combinations. The most important advantages of the method are the capability of investigating the entire deformation domain specific to sheet metal forming processes, simplicity of the equipment, and reduction of the parasitic effects induced by the friction, as well as the occurrence of the necking in the polar region. The comparison between the FLCs determined using the new procedure and the Nakazima test shows minor differences.

The numerical analysis of springback in sheet metal forming is used to increase the accuracy of shape and the design of tools and processes. The more precise the material used for modeling is described, the more accurate the prediction ability of simulations is. For that reason, mixed isotropic-kinematic hardening models are used whose parameters are described by cyclic flow curves. The in-plane torsion test is used for the determination of cyclic flow curves. The optical strain measurement allows the simultaneous determination of cyclic flow curves with different pre-strain on a single sample. A modified twin bridge specimen is used to test anisotropic material behavior and a specimen with circular groove is used to characterize failure prediction under ideal shear load.

A methodology to characterize friction according to the severe conditions of contact encountered in metal forming is presented. The main peculiarity of the proposed method is to use specimens and contactor made of industrial tool and workpiece surface in laboratory bench tests in order to ensure their representativeness regarding to the real process. Four steps are then required to identify friction: measurement/computation of mechanical loading on the process to be simulated in the lab (sliding velocities, contact pressures, plastic strains…), machining of specimens and contactors, adjustment of the friction test to simulate the target loading, analyzes of the results in terms of friction and lubricant efficiency. Examples are presented to exhibit the reliability and flexibility of the methodology.

For practical determination of flow stress curve under forming conditions, i.e. at large strains, high strain rates and at elevated temperatures, a method is proposed based on the upsetting test with grooved platens. The procedure of the method is to measure the load and stroke during upsetting test, and transform them to average flow stress and average equivalent strain. This method was proved to be applied up to 700°C with measuring error within ±5% for various metals, and was employed as a standard material testing method for cold forging steels in Japan.

Many sheet metal forming industries dealing with tribologically difficult materials e. g. stainless steel, aluminum and titanium alloys are searching for new, environmentally benign tribo-systems [3]. This is due to increasing demands as regards environmental issues dictated by legislation in Europe [4], Japan [5]. Industry is, however, reluctant to carry out production tests of new tribo-systems without any prior knowledge about the possible performance, since these tests are costly due to production stops, which may take even longer than anticipated, if the new system turns out to have poor performance and the tools therefore have to be dismounted and repolished.

The development of yield functions for anisotropic materials is presented in a concise manner. Although the models considered are expressed at the continuum scale, the physical principles guiding the development are underlined. This review considers mostly the description of plastic anisotropy under the assumption of isotropic hardening, which includes the case of materials exhibiting the strength-differential effect. However, an extension of the yield function concept to the modeling of the Bauschinger effect and other anisotropic hardening phenomena is briefly introduced.

The yield criterion is an essential component of the mechanical models used for the simulation of sheet metal forming processes. Its capability to describe the anisotropic response of cold-rolled products has a significant influence on the quality of the numerical results. This paper gives a short description of the BBC 2005 yield criterion which is implemented in the finite-element code AutoForm 4.1.1. With the aim of proving the performances of the BBC 2005 model, the results of a standard test (Numisheet 2005 Benchmark#1 – numerical simulation of the deep-drawing and springback of a decklid inner panel) are also presented.

At the beginning, some important experimental methods and analytical concepts related to the development of sheet metal formability assessment as well as theirs chronology are presented. Marciniak-Kuczyński model (M-K) based on a completely new mechanism of the loss of stability is emphasized. It caused a major impact on the development of formability assessment and it has been the most commonly used model for analytical prediction of the forming limit curve FLC. It has been also very useful to investigate the individual effect of material properties and process parameters on the FLC. Some advantages and drawbacks concerning the development of formability assessment based on M-K model are discussed.

The use of a plasticity model that properly describes material behavior is of vital importance for accurate numerical simulation of sheet metal forming, especially for the prediction of springback. For that purpose a large-strain cyclic plasticity model, so-called ‘Yoshida-Uemori model’, was proposed in the kinematic hardening modeling framework. It is able to describe properly material behavior, such as the Bauschinger effect, the workhardening stagnation, strain-range dependent cyclic workhardening, as well as the degradation of unloading stress-strain slope with increasing plastic strain. The model has been implemented into several FE commercial codes, and it is widely used in sheet metal forming industry. By using it, the accurate springback prediction, especially for high strength steel sheets, is made possible.

One common method for the approximation of occurring strains during plastic deformation is based on the application of the slip line theory. If the considered deformation process is well understood the related stress states can be estimated with sufficient accuracy using certain simplifying assumptions. A newly developed semi-analytical approach based on the slip-line theory and the application for metal forming processes is briefly presented in this subchapter.

Impulse based metalworking has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can be used with much lighter and more agile equipment because large static forces do not need to be resisted. Electrically vaporized thin conductors, termed as Vaporizing Foil Actuators (VFA), can be used to develop significantly high driving pressures over short time scales. The driving pressures can be a few GPa’s, and have been used to launch sheet metal workpieces to velocities in excess of 1 km/s. Applications include, but are not limited to, impact welding, forming, embossing, shearing, tube joining, and powder compaction.

In automotive industry the variants of models increase so that the batch size for parts decreases simultaneously. With increasing number of parts and tools, the time for design and try out processes becomes less. Therefore, there is a need for tools which withstand just a low amount of parts and which can be produced in an easy and cheap way. In this case, the use of polymer tools can replace conventional steel and cast iron tools. For forming processes of high strength steels, the polymer tools arereinforced by fiber reinforced plastics. To avoid wear on such a tool, metallic protective coating is applied on the surface. Investigations of forming high strength steel blanks in hybrid tools show that the geometry accuracy is high and the wear is as less as in conventional steel tools. One of the main benefits is the uniform distribution of the contact pressure due to the lower Young’s Modulus of polymer compared to steel. Furthermore, the hybrid tools enable to vary the stiffness locally and temporally without the use several tool inserts, which is helpful for the minimisation of springback.

Starting with its zero-clearance slide guides, the UL Press has an innovative design that delivers the tremendously enhanced dynamic accuracy that makes it the ultimate next-generation forming machine. This paper summarizes its design and features, and also showcases actual forming examples..

Short-Cycle-Stretch-Forming (SCS) combines stretch forming and deep drawing within one stroke. Conventional blankholder is replaced by a set of beads around the part. The beads are pre-stretching the material to enhance dent resistance and increase material strength while thinning the material at the same time. Pre-stretching is followed by the deep drawing. In this stage bead set functions as a blankholder. The amount of retaining force and pre-stretching can be adjustet by varying bead design and surface conditions. SCS technology allows reduction of tool size and required press force and size and will thus function as flexible tool system of the future.

Sheet-Bulk Metal Forming (SBMF) is an innovative class of forming processes which enables the manufacturing of functional components out of sheet metal. This is achieved by the application of sheet and bulk forming operations on sheets of 1 to 5 mm initial thickness with an intended three dimensional material flow. SBMF products are characterized by profound functional integration and subsequently possess a high lightweight potential. In contrast to alternative production technologies, SBMF formed products feature the advantage of improved mechanical properties due to strain hardening and an unbroken fiber course. Furthermore the possibility to produce high accuracy netshaped parts in mass production with a shortened process chain qualifies SBMF as adequate method to meet present and future demands of production.

Factors such as limited draw in and friction against tool surfaces cause difficulty in forming of sheet metals. Most of the strain tends to localize in the wall of the formed part while the bottom, in contact with the punch surface, and the flange, held down with the blank holder do not undergo much deformation. Augmentation of conventional forming processes with electromagnetic forming has been proposed as a method to attain higher draw depths by distributing strains more uniformly and encouraging draw in. In separate experiments, electromagnetic forming coils were embedded either in the bottom of the punch or in the blank holder. In both cases, multiple electromagnetic pulses in the coils followed by movement of the punch lead to higher draw depth as compared to corresponding stamping or deep drawing processes.

In metal forming, lubricants are used to reduce friction between work piece and tool and to increase tool life. However, avoiding lubricants in metal forming would reduce the number of process steps in production by eliminating subsequent cleaning operations, thus reducing environmental impacts and generating substantial economic benefit. Challenges arising from dry metal forming can be addressed by the choice of tool or coating material. The use of diamond tools is an example of an appropriate approach in the field of micro metal forming.

Tailored blank by laser welding started in the mid-1980’s, and is currently applied to automotive body in the world. The purpose is that cost reduction and quality improvement by integrating pressed parts and weight saving by optimum layout of panel thickness and material. World production of tailored blank has been rapidly increasing by expanding applicable parts in each automaker. Toyota started to develop laser butt welding technology and tailored blank forming technology in the 1980’s. In 1989, we used tailored blank that has different material and thickness for side panel of Lexus LS before the rest of the world, and applicable parts are expanding sequentially.

Servo drive presses have the potential to improve process conditions and productivity in metal forming. The first mechanical servo press was pioneered and built in Japan, where several press builders developed gap and straight-sided metal forming presses that utilized this new mechanical servo-drive technology. The screw type servo press has inherent advantages over the crank type servo press. In addition, a new technology called “one shot forming” , which further utilizes the advantages of the servo press, was developed. Next, we developed a parallel control system for the screw type servo press that maintains the parallelism of the press slide under eccentric loading conditions. Utilizing this new control system, “progressive stair-die stamping” technology was developed. In this article, we briefly introduce these new screw type servo press technologies.

The increasing trend of the individualization of products demands an advancing widening of the range of varieties of the goods on offer while at the same time lot sizes decrease. To handle the challenges this implies manufacturing needs to use technologies which allow for a flexible and effective production especially in the lower lot size segment. One process which fulfils these requirements is spinning. Low tool costs and short set-up times enable a flexible and cheaper production in the middle and lower lot size segment compared to conventional forming processes (e.g., deep-drawing). One way to further increase the economic relevance and flexibility of spinning is expanding the range of parts to be produced by non-circular spinning. In the following the process development of the socalled “non-circular spinning” with motion controlled rollers will be described.

Incremental Sheet Forming (ISF) is a flexible sheet forming process suitable for single part and small series production. To form a component, a CNC controlled generic forming tool is moved along the contours of the desired shape and locally induces plastic deformations. Hence, the final shape of the component is obtained stepwise as a sum of all localized plastic deformations. However, the basic process shows several process limits, such as long process time, material thinning and limited geometrical accuracy. Here, a Hybrid Sheet Metal Processing Center is presented that addresses these process limits. It allows for combining stretch forming with ISF, performing laser assisted ISF as well as pre- and post-processing in one concerted machine setup.

Normally, work-hardening effects limit the deformation that can be attained during cold working processes like spinning. By integrating self-induced heat generation (based on deliberately added friction processes) more complex forming operations become possible. This in-process heat treatment thus makes it feasible to dramatically extend the existing forming limits and produce more complex geometries, as well as favorable part properties (e.g. microstructure) from a wide variety of alloys. It is then possible to use semi-finished parts like sheet metal blanks, profiles, tubes and also solids for friction spinning.

The dieless NC forming process was developed in Japan as a flexible, alternative manufacturing method to effectively prototype sheet metal stampings and produce production panels with complex shapes in small quantities. It is extremely cost effective, as conventional tooling is not required. Incremental forming technology is developing as an effective method for producing automotive service parts, adding styling details to existing panels, forming thick sheets, and forming tubes.

The TwinTool is a tooling concept to speed up the incremental sheet forming process. In this concept two additional linear axes of motion are added to the conventional tooling setup, each of them featured with an own forming tool. While working in parallel, this tooling concept aims at decreasing the process time. However, the TwinTool is a result of a comprehensive study where concepts different in kinematics and flexibility are compared to each other with the objective to incoperate multiple forming zones acting simultaneously during the incremental sheet forming process. Those variants as well as a realized TwinTool prototype are described in this paper.

After the identification and classification of laser forming mechanism the potentials of this technology in the field of adjustment was discovered. In order to use the possibilities in the field of micro systems technology the idea of specifically designed, task specific actuators was born and researched. The detected challenge of actuator design has been addressed with suitable algorithms models. The paper gives an overview of the possibilities and explains how the design challenge has been overcome.

Metal spinning is used to form hollow, axially symmetric sheet components. However, it is limited by two features: a die (mandrel) is required for each product; the process is limited to production of axially symmetric components. Spinning has developed over time with major improvements in automation and quality of produced parts. Yet, given its age, the process has seen almost no change from the original configuration and the two limitations have not yet been overcome successfully. This study presents new insight into the role of the mandrel in spinning, which has led to design of a novel process allowing mandrel-free production of non-axisymmetric components.

Technologies of micro piercing with a slant angle have been developing for more than two decades. The technologies are used for the producing orifice plates, which is one of the most important parts for automobiles in terms of energy consumption and environmental issue. Orifice plate has 1 to 18 holes with slant angles from 0 (vertical) to over 45 degree. The orifices need to assure the flow volumes and spray angles of gasoline flow. To control the flow function, many characteristics, such as hole diameter, sheared surface, entrance condition, burr, hole angle and so on, are controlled by high accuracy punch and die with small clearance and precise positioning. As developing these technologies, progressive die system has developed. Different phenomena are observed between vertical and slant angled piercing in piercing force and material deformation.

Fine blanking is a well-established process for the production of near net shape components with high quality. The produced parts are characterized by a smooth sheared edge up to 100 %, excellent surface properties with good flatness and little burr as well as close tolerances for near net shape manufacturing. These process characteristics are suitable for the efficient production of spur gears with large batch size. In this work, the application of fine blanking was extended for the production of helical gears. Therefore, the fine blanking process was modified with an additional rotary movement of the dies to realize the manufacturing of helical gears. In this contribution the process idea, experimental and numerical work as well as the potential of fine blanked helical gears is presented.

The

edge-fracture-tensile-test

is an innovative examination method, which offers the possibility to characterise high strength steels with respect to edge crack sensitivity. Manufacturing processes, such as expansion and stretch flanging, which generate an uniaxial tensile stress on the components shear cut edge, lead to edge fracture. In particular, deformation and material damage of the component’s edge, caused by the shear cutting process, reduce the residual formability and prefer edge fracture initiation. A modular shear cutting tool generates

edge-fracture-tensile-samples

with different shear cutting process parameters. The

edge-fracture-tensile-test

investigates one-sided shear cut

edge-fracturetensile-tensile-samples

with regard to the residual formability of the shear cut edge.

The break through shock during sheet metal blanking operations generates uncontrolled high reverse loads, mechanical vibrations and loud noise that may cause problems such as fatigue cracks in the press components, premature wear in tooling and great discomfort for press operators. In this paper, the application of magneto-rheological (MR) dampers to reduce the shock response of press systems is considered with the aim of evaluating, through full-scale experiments, feasibility and practicability of their implementation and understanding the potential benefits in comparison with conventional dampers.

Within the manufacturing process of sheet metals, blanking represents an essential process operation. As the industrial application of high-strength multi-phase steels grows, the blanking process must consider high blanking and shear forces, which are characteristic for processing these materials. This paper presents options for reducing these forces. Experiments were performed utilizing a novel tool concept, which can correlate necessary blanking forces to the punch stroke in three dimensions and in the direct force path. Results from three different AHSS materials are presented showing the variation of decisive blanking parameters such as die clearance, shearing angle and sheet positioning angle.

Environmental as well as economic aspects have led to various changes in main industrial sectors like the automotive branch. One particular trend is the urge to reduce the fuel consumption by lightweight design of structural components. Due to rising safety requirements those structural components also need to provide high strength and crashworthiness. A possible approach to combine the idea of weight reduction and enhanced crashworthiness is the production of load-aligned semi-finished products that can be further processed to structural parts. Therefore, the flexible rolling process has been invented in the past years and is nowadays used on a large industrial scale. The basic principle of flexible rolling is an online adaption of the roll gap during a cold rolling process resulting in a thickness distribution of the strip in rolling direction. These so called tailor rolled blanks (TRBs) are successfully used to manufacture structural parts with non-uniform thickness.

Vertical strip casting enables the near-net-shape production of hot rolled steel strip in a compact process. In less than half a second, the liquid steel melt solidifies in contact with the casting rolls to a one to five millimetres thin strip. Since the strip casting process combines casting and rolling in one single process, slab re-heating and numerous hot rolling steps can be eliminated. Thus, an efficient, economical and environmental friendly production of steel is possible. Today, strip casting of steel is already used in a few industrial steel plants. Recent developments allow for the production and further processing of advanced high strength steels and steels with a nanocrystalline structure by strip casting. Regarding the process design, research activities focus on casting of tailored strips with defined thickness distribution across the strip length or width. Thus, strip casting can be used for the production of tailored hot strips in a considerable shortened process.

It has been long recognized that the shape and crown of rolled strips are important for in terms not only of product quality but also of material yield and stable rolling. Furthermore, to raise productivity and to save energy, it is necessary that schedule of rolling, for example thickness, width or materials, is free from constraints. Consequently, it has strongly required that the development of rolling mill to control the shape and crown of rolled strips. A “pair cross type” rolling mill (hereinafter PC mill) has been developed for these requirements. The upper rolls and lower rolls are skewed in a pair which consists of work roll and back-up roll, and PC mills are capable of freely controlling the shape and crown of rolled strips. The first PC mill was put into a practical use at Nippon Steel Corporation Hirohata Works (Now, Nippon Steel & Sumitomo Metal Corporation) in 1984 and PC mills are widely used in the world and they contribute to the achievement of high accuracy and quality of rolled strips through the superior strip crown and flatness controllability.

In hot rolling, the productivity or quality of rolled strips is required to be improved and the ultra-thin rolled strips are also required. In order to achieve these requirements, it is necessary that unstable rolling is prevented, especially for head and tail ends, and that cooling of rolled strips is uniform. To meet these requirements, the completely continuous finish rolling, so called” endless hot strip rolling “,has been developed and put into a practical operation at Kawasaki Steel Corporation (now, JFE Steel Corporation) in 1996. This unique technology has realized finish rolling under an uninterrupted tension between rolling stands. As a result, the productivity, quality and stability of rolling have been improved. In addition, the ultra-thin strips with a thickness of less than 1.0mm, and strips with excellent workability by applying heavy lubrication over the full length of the rolled strips have been produced.

The rolled strip shape is one of important factors in determining the quality of rolled products. The improved strip shape increases not only productivity but also product quality. Thus, it was desired to develop a new type of mill which is capable of controlling the rolled strip shape even with changes in rolling conditions. The performance of a conventional 4-High mill is not satisfactory in these requirements. A new 6-High cold rolling mill (hereinafter HC-MILL) has been developed in order to solve these shape problems. The HC-MILL for steel rolling was put into a practical operation at Nippon Steel Corporation at Yahata Works (now, Nippon Steel & Sumitomo Metal Corporation) in 1974 and HC-MILLs are widely used in the world and they contribute to the achievement of the controllability of the rolled strip shape and quality through the superior strip flatness controllability.

Riblet structures on surfaces can reduce friction drag in turbulent flow. The optimal riblet geometry depends on the fluidic application. Fluid dynamic analyses have revealed that the application of riblets on compressor blades of jet engines promises to reduce fuel consumption and, thus, CO2 as well as nitrogen oxide emissions. Due to high operating temperatures the application of riblet films on compressor blades is not feasible. Alternatively, riblet structures can be manufactured directly on a metallic blade. Incremental riblet rolling is among possible manufacturing processes. This forming process has been designed at the Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University. It goes along with a major advantage compared to riblet manufacturing by machining or laser structuring: Riblet rolling induces strain hardening and compressive residual stresses. These properties can almost fully compensate the reduced load capacity resulting from the notch effect which accompanies riblet structures.

TR forging process for heavy crankshafts was a breakthrough in forging technology. In the first design connecting rods with joints, which transferred vertical force of the press into two horizontal forces, were applied. The modified process combines upsetting along the shaft axis with bending of the arm. In the former stage of the process a volume of the material satisfactory to form various shapes of arms is gathered. The task of the latter stage of the process was to forge the arm. Therefore, this innovative process allowed efficient forging of a variety of crankshafts. General idea of the process is described in the paper. Numerical simulations were applied to design the best forging technology.

The direct recycling of aluminum alloy machining chips into finished or semi-finished products by hot extrusion is a promising approach to increase the energy efficiency of aluminum recycling and to overcome the problem of material loss due to oxidation during remelting. However, the mechanical properties of the chip-based products are often inferior compared to those based on originally cast material. Critical factors to achieve sound bonding of the chips and therefore favorable mechanical properties of the chip-based products are the shear, pressure and strain affecting the chips during the extrusion process. In the process of chip extrusion with integrated equal channel angular pressing (iECAP), the chips are pressed through channels intersected by an angle before the actual extrusion process. This additional deformation increases the shear, pressure and strain acting on the chips and therefore improve the mechanical properties of the chip-based extrudates.

Although the graphite base lubricants exhibit good performances in lowing friction and preventing galling in hot forging, they make the working environment dirty and produce large amount of liquid waste. Water-soluble non-graphite type hot forging lubricants are developed to solve the problems of graphite lubricants. The developed lubricants exhibit very good performances if they are dried well, but they are easily squeezed out in the semi-dry condition. This problem is solved by adding bonding substances which change the lubricants to be extremely viscous when they are semi-dried.

The composite extrusion process allows the continuous embedding of reinforcing or functional elements into a metallic matrix material. Thereby, the economic advantages of the conventional direct extrusion can be combined with the advantages of a multi-material profile design. By using lightweight materials like aluminum or magnesium as a matrix, the profiles possess a low density associated with good mechanical properties. To improve the tensile strength and the stiffness of the profiles, high strength materials, such as high strength steel or ceramic oxide fibers can be integrated during the process. Furthermore composite extrusion allows the embedding of functional elements like isolated electric conductors, which allows a signal or data transmission through the profile.

Novel billet design was introduced in an effort to better control material flow during the co-extrusion of bi-metallic shapes and tubes. In order to minimize the amount of material that is extruded “out of geometrical tolerance” (measured by the interface location) as a result of non-concurrent material flow, the core length in the initial billet is shortened. Extrusion was simulated using DEFORM 2D™ finite element modeling (FEM) software and confirmed by actual extrusion experiments on an industrial press. Results for a specific billet geometry extruded using a selected extrusion ratio for plain carbon/stainless steel tubes are presented. It has been shown that by reducing the core length in the initial billet by approximately 10% - 20%, concurrent material flow is promoted and the amount of out of tolerance material is minimized. The presented innovation was first developed for solid bi-metallic profiles made from different aluminum alloys and then applied to bi-metallic ferrous tubes showing general application of the proposed invention.

Curved profiles are essential components in lightweight constructions. Besides weight reduction, the preservation or even the improvement of functions in the component are pursued. Space-frame concepts are an option to achieve these aims, in which straight and curved extruded profiles are applied. With regard to design aspects, curved profiles gain in importance. Conventionally curved aluminum profiles are manufactured by the process chain including straight bar extrusion, stretching and bending. In comparison to conventional bending processes, the innovative curved profile extrusion offers great advantages concerning a precise, flexible, and cost effective production as well as the possibility to use innovative lightweight materials, such as magnesium or reinforced alloys. Besides the process principles and advantages, several results of investigations of fundamental and application-oriented research in the field of curved profile extrusion are presented in this paper.

The joining of a shaft-hub connection by lateral extrusion allows savings in energy costs, reduced investments as well as economizing logistical efforts and makes tolerances between both parts less important compared with a conventional joining process. The key challenges of such new process management methods are the prior layout of optimal friction conditions and of internal hub profile parameters during the manufacturing process on the one hand and the usage requirements on the other hand. If a non-cylindrical internal hub profile is used for producing a shaft-hub connection by lateral extrusion, a combination of positive and non-positive connection types occurs. Such a connection type shows significantly higher amount of torque transmission capability compared to a conventional shaft-hub-connection [1].

Working principle of net shape forging which utilizes flow relief axis or flow relief hole is newly proposed. Based on this principle, actual production of gear toothed components for automobile is successfully practiced. Because of the simplicity of the idea, wide range of practical applicability is expected.

Enclosed die forging of automobile parts such as cross pins and tripods necessitates two punches moving oppositely with the same velocity. Although multi-axial presses are constructed for this purpose, simple methods on ordinary cold forging presses are requested. To realize an equivalent motion for enclosed die forging on a press with a single driving axis, a die set using a pantograph links is invented. In this die set, the upper punch is driven with the press speed and the lower punch is kept still. The die is mounted on the middle plate fixed to the intermediate hinges of the pantograph, and as a result the relative velocities of the punches satisfy the requested relation. The die is usually divided horizontally for extracting the formed product from the die cavity. It is shown that vertical division of the die can eliminate the parting lines on the extruded rods with good circularity.

Serration joining, a joining method of a serrated rotor shaft and a holed disk, is developed to manufacture efficiently automobiles axle parts with high torsional strength. The rotor shaft, which is serrated by cold extrusion before hardening by heat treatment, is pushed into the hole of the soft disk at room temperature. This serrated shaft plastically indented the disk and consequently the shaft and the disk are joined. The teeth formed on the disk are strengthened by work-hardening and the torsional yielding strength of the joint is 1.5 times as high as that of a mechanical assembly.

In orbital forging, the workpiece placed in the lower die moves towards the upper die with orbital motion. Thus, the forging force is applied only to a limited area of the workpiece surface at a given time and the required force could be substantially lower as comparing to conventional forging where a whole workpiece is deformed at once. This paper begins with presentation of past development of orbital forging processes. Special attention is paid to the driving mechanism of the upper die proposed by Z. Marciniak, which made a significant breakthrough within the knowledge of orbital forging. It had become possible to obtain four types of orbital motion of the die what improved processing range and production of parts with a big variety of shapes. Next, development of orbital forging presses as well as further applications and potential challenges in the field of orbital forging processes are discussed.

The double cup extrusion test was developed and used extensively for evaluating lubricants in cold forging. This test emulates the high material/tool interface pressures and large surface expansion that occur in industrial cold forging operations. This short paper summarizes the principles of this test and illustrates how it is used to evaluate environmentally friendly lubricants.

An extrusion method for manufacturing a scroll product for an air compressor having long spiral fin is developed. In this extrusion method, a floating counter tool supported by a constant force controls the length of the extruded spiral fin uniform and the surface of the extruded end flat. Although the average counter pressure to make a uniform length is about 3 % of the flow stress, the pressure to flatten the extruded end is higher than 40% of the flow stress.

The combination of a further developed Equal Channel Angular Swaging (ECAS) process and the subsequent infeed rotary swaging is a promising process chain for the continuous production of permanent magnets. The ECAS process enables a grain refinement as well as an induction of high defect densities in materials. Both effects lead to a higher coercive field strength. In comparison to other SPD-processes lower forming forces are needed and a continuous production is possible. Highly textured magnetically anisotropic samples are realized by a subsequent infeed rotary swaging process.

A non-reactive cold forging coating, named as dry in-place coating, is developed to replace zinc phosphate coating for cold forging operations. This new coating is formed by dipping the billet into liquid lubricant bath with subsequent drying, and consists of two layers; the upper layer provides a low friction with the tool surface and the lower layer protects the tool surface by avoiding direct contact with the billet surface. The new coating has been used successfully for closed die forging of inner racers, tripods, pinion gears and introduced in 13 countries.

The incremental tube forming process is an innovative approach to manufacture three-dimensionally bent tubes with varying cross sections. The process combination of a tube bending and a tube spinning process leads to a significantly reduced bending moment as well as to a reduced springback compared to a conventional bending process. Therefore, this innovative process combination is especially suitable for the manufacture of high-strength materials as well as thin-walled tubes. Besides the mentioned process phenomena the process allows the manufacture of tubes with varying cross sections. The diameter as well as the wall thickness of the tube can be varied and, therefore, the cross section can be adapted to the load case applied during the subsequent usage of the bent tubular part.

The fabrication of load-adapted parts is one of the main objectives of component lightweight design. In the field of profile manufacturing load adaption is achieved by varying the cross section geometry according to the occurring sevice loads. In this regard, incremental profile forming (IPF) allows the manufacturing of profiles with varying cross section geometries along the center axis of the profile. Due to the incremental character of the procedure, the process flexibility is high. Furthermore, a comparatively high diversity of geometries is typical for IPF, since tool-independent profile cross section geometries are realized.

This article presents an innovative computer numerical control (CNC) tube forming method, called MOS bending, which manufactures flexibly and 3-dimensionally bent tubes and was put into practical use in industry. The machine for MOS bending is mainly composed of a bending die and a guide cylinder. Numerically controlled positioning of the bending die in vertical and horizontal directions realizes flexible bending in arbitrary bending radius and arbitrary direction. The variety of the bent shapes includes conventional 2-dimensional arcs, convoluted patterns in a plane, extremely large bending radii, 3-dimensional solenoids and other 3-dimensional complex shapes. The flexibly bent tubes are suitable for ornamental usages as interior and exterior decorations as well as automotive components. MOS bending revolutionarily changes the image of tube bending. The above and other benefits of MOS bending are reviewed here, together with its mechanism and some examples of products.

Plastic instability waves in thin-walled tubes subjected to axial compression are utilized to develop an innovative and environmental friendly joining technology for connecting tubes and fixing tubes to sheets in situations where the axis of the branch tube or sheet is perpendicular or inclined to the axis of the main body tube. The technology is an alternative to conventional joining based on mechanical fixing with fasteners, welding and structural adhesive bonding that allows connecting dissimilar materials (e.g. metals and polymers) and copes with the growing concerns on the demand, lifecycle and recycling of materials.

An innovative tube forming process is utilized to shape commercial tubes made from a variety of materials and available in many shapes into seamless, real size, metallic liners for composite overwrapped pressure vessels (COPV’s) that are commonly utilized in aerospace applications. The process makes use of unconventional dies with very sharp edges and recyclable metallic mandrels made from a low melting point alloy that prevent collapse by wrinkling and local instability.

A new roll-based process and machine for three-dimensional bending of beams with symmetrical and asymmetrical cross-sections have been developed. Compared to conventional processes like stretch bending, the advantage of the Torque Superposed Spatial (TSS) bending is the kinematic adjustment of the bending contour, leading to higher flexibility and cost efficiency, especially in small batch production. To define the spatial geometry of the workpiece, a torque is superposed to the bending moment. Process principle, process control and the machine design of the new process are presented.

Tube hydroforming is a technology of manufacturing tubular products, in which a tube set in a die is deformed by internal high pressure and axial feeding from both ends of the tube in accordance with the die shape. The origin of tube hydroforming is T-forming, by which a branch is formed in a tube by hydraulic bulging. It has been used for manufacturing small parts such as fittings for piping, bicycle frames, and bellows. Today, tube hydroforming has become highly advanced in combination with computer technology, and it has become possible to form consolidated lightweight high-rigidity hollow parts with complicated cross sections. Products are applied to automotive parts or structural components that require weight reduction. The weight reduction of automobiles improves their fuel consumption, conserves resources and energy, and reduces the CO

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content in the exhaust gas. Tube hydroforming is therefore an important technology in preventing global warming. This paper describes briefly the practical innovation of tube hydroforming technology in Japan.

A smart hot stamping process consisting of resistance heating, water quenching, servo press and hot trimming is introduced to improve the productivity. A big furnace is replaced with resistance heating, and laser cutting is eliminated by hot trimming. The productivity is improved by resistance heating, water quenching and the servo press. The quenching time is shorted by water quenching added to die quenching. The time for resistance heating is matched with the forming and quenching times. Tailored die quenching, hot spline forming and tube hot stamping are also introduced.

The new innovative materials enable the production of rail vehicles with excellent crash safety as well as with less weight. This article presents the results of the research project “Crash-safe front modules for rail vehicles of aluminium foam”. The team of the project consists of user, manufacturer and developer. The partners are Bombardier Transportation, Wilhelm Schmidt Co., AMIC Angewandte Micromesstechnik Co. and Chair of Design and Manufacturing of The Technical University of Cottbus. The main object of this research project was the developing of technology for the production of front module for ITINO-Trainset of aluminium foam sandwich (AFS). The technical and economic feasibility of front modules made of this innovative material should be demonstrated.

Creating metal‐ceramic composites by plastic deformation driven by compression is the most versatile method as it can nearly preserve the microstructure of the metal phase and a variety of reinforcements and morphologies can be used. The great limitation of this process is that very high pressures are needed for effective consolidation (usually about 3 times the flow stress of the metal phase). If, however, plastic deformation can be developed by some other renewable and repeatable means, a relatively small global and external pressure can drive the material to a fully‐consolidated state. Phase transformations, thermal expansion mismatch and the volumetric changes produced by a remote pressure can drive local deviatoric stresses in the vicinity of the particles that provide plastic deformation and if these strains are renewed a small remote external pressure can be used to consolidate the composite. This paper shows that pressure cycling of heterogeneous composites with a compressibility mismatch is a particularly simple and effective way to develop composites of high density in the solid state.

Classical hot forging process chains for the manufacturing of high performance components consist of numerous heating and cooling cycles. These cycles lead to a high optimization potential of ecological and economical aspects. Hereby, the heat of the hot forging process can be used for an integrated final heat treatment of the forged components. Depending on the cooling rate different microstructures can be set in steel forgings. By an isothermal heat treatment after a rapid and controlled cooling a bainitic microstructure can be set, which combines high strength with high toughness of the material. With the numerical simulation of the microstructural transformation, from the austenitic starting phase into the bainitic microstructure, an optimization of the process development of hot forging processes with a subsequent heat treatment can be achieved.

Micro tube hydroforming system based on floating a micro-die assembly in a pressurized chamber is an innovative system which can allow fabrication of complex micro tubular products. In this system, the fluid pressure inside the chamber which surrounds the die and punches is the same as the pressure required to hydroform the tube. The unique features of this system are its capability to hydroform complex micro tubular parts irrespective of whether the material require material feeding, the ability to hydroform very small tubing because material feeding can be achieved by employing non-hollow punches, and the ability to hydroform multiple parts with ease because the fluid intake to the pressurized chamber is independent of the number of micro tubes to be hydroformed.

In order to reduce tubes dimensions, improve their surface finish and obtain requested mechanical properties, tube drawing is one of the most effective and flexible methods used since centuries. Many parameters influence the results obtained such as tool geometry, friction, drawing force, or the amount of thickness reduction. A lot of investigations have been done studying these effects. A significant effect on the local material’s flow is given by abandoning the pass line during drawing leading to an asymmetric deformation over the circumference of the tube. Tube drawing with a tilted die shows a considerable variation in eccentricity in drawn tubes. A similar strong effect is given by shifting the dies – a guiding die and a die for reduction. A third, very effective possibility is the use of local heating, therewith influencing the flow conditions locally. Using these parameters in a controlled way makes possible to influence eccentricity precisely.