Materials Design and Applications II

Predicting the life of blanking punch is one of the major concerns in designing compound dies. Finite element analysis is performed to determine the maximum and minimum principal stresses through which fatigue limit of punch is estimated. The factors affecting the life of punch are examined and a mathematical model is established using artificial neural network (ANN) and adaptive neuro fuzzy inference systems (ANFIS). The developed model is utilized to evaluate the life of punch for varied load conditions. Comparative evaluation of ANN and ANFIS results suggested that the later model is superior in predicting the life of punch and it can be effectively utilized in machine tool applications.

Duplex stainless steels (DSS) are corrosion resistant alloys (CRA) which became largely employed due to its excellent combination of high strength, pitting corrosion resistance and toughness. The steel with basic composition 21.0–23.0%Cr, 4.5–6.5%Ni, 2.5–3.5%Mo, 0.08–0.20%N was developed in the 1980s and became the most popular DSS used in the oil and gas industry. The mechanical properties and corrosion resistance are optimized with a microstructure containing equal parts of ferrite (δ) and austenite (γ). This balanced microstructure is obtained by the chemical composition control and heat treatment. A solution treatment at 1050–1100 °C followed by water cooling is recommended. Although other heat treatments are not common in DSS, a significant hardening effect can be obtained by short duration exposition to 475 °C. Long thermal aging in the 350–550 °C interval has been extensively studied by many authors, and was proved to cause embrittlement and decrease of corrosion resistance, due to spinodal decomposition of ferrite into Cr-rich (α′) and Cr-depleted (α″) regions. However, a heat treatment at 475 °C for 4 h or 8 h may increase the yield and ultimate tensile strength without significant decrease of toughness and corrosion resistance, as observed previously. The goal of this work is to compare the microstructure, mechanical properties and corrosion resistance of two duplex stainless steels with similar composition, but produced by different methods: hot rolling and powder metallurgy PM/HIP. These two fabrication processes may be concurrent for some applications, such as manifolds in the oil and gas industry. The response of both materials to short duration aging at 475 °C was compared.

Low carbon steel with 9%Ni is used in cryogenic services, in which high toughness and strength are required. One of the main concepts of physical metallurgy is that the toughness and strength may be increased by grain refinement. In martensitic steels, the grain size that can be measured is the previous austenite grain size (PAGS). The goal of this work is to reveal and measure the PAGS’s of different specimens of 9%Ni low carbon steel and correlate these results with hardness and low temperature toughness. The decrease of PAGS’s improve the toughness of specimens quenched and quenched and tempered.

The (α + β) Ti6Al4V alloy is widely used in different industrial applications and in medicine. The decrease in the content of the α-strengthening element Al in Ti5Al4V as opposed to conventional Ti6Al4V alloy reduces the hardness as Al is a solid solution hardener but simultaneously, the alloy is expected to have lower cytotoxicity, improved plasticity and low precipitation hardening ability at precipitation temperature. The role of the alloying elements and the influence of heat treatment on corrosion resistance of Ti5Al4V and Ti6Al4V alloys have been studied after a short and long-term immersion in Ringer (RS), phosphate buffer saline (PBS) with and without the addition of H2O2, and 5 M HCl at 37 ± 0.1 °C. It has been found out that lower pH and higher Cl− concentration in RS make the surface of the alloys more prone to pitting corrosion and showing nobler corrosion potentials at the same time, in contrast to PBS where salt films of insoluble products are formed on some pits. The potentiodynamic polarisation measurements show higher anodic reaction rate after a 30-days’ period of immersion in PBS and H2O2 for both alloys. The dissolution of Ti, Al, and V and oxidation in 5 M HCl are the highest for solution treated Ti6Al4V and Ti5Al4V alloys, while the corrosion rate for the 10-days’ period in the acid was the lowest for the as-received Ti5Al4V.

In sand casting of metallic alloys, the cooling rate is a key parameter that affects the microstructure and the appearance of defects and residual stresses in the end cast components. In this work, a numerical model was developed to simulate the cooling of a duplex stainless steel casting on a furan-bonded sand mold. The heat transfer coefficient (HTC) as a function of temperature was determined by an inverse method. A good agreement between experimental and numerical cooling curves was achieved, showing the importance of estimating HTC as a function of temperature. On the basis of these results, it is possible to calculate thermal residual stresses and model the microstructure of duplex stainless steel castings with complex geometries.

This paper describes rheological tests, drop tests and bulletproof tests of materials which are planned to be used as elements of bulletproof vests as well as in high impact protective equipment. Rheological tests of a homogenous composition of methyl-, phenyl-, borosiloxane polymers (KM material) performed for variable values of stress and strain at a fixed frequency of 1 Hz showed that the loss modulus exceeds the storage modulus throughout the whole tested range of shear stress so that the energy is more dissipated than stored. In the drop tests, same-mass samples of three materials, i.e. the KM material, the shear thickening fluid STF1 and the commercial shear thickening polymer ZB were tested. For a given impact energy (Ei = 35 J) and impact velocity (Vi = 1.9 m/s), the ZB material shows the best protective capability. In the ballistic tests, the sample with the KM material was tested with the use of .44 Magnum SJHP (semi-jacketed hollow-point) bullet following NIJ Standard-0101.04 for IIIA bulletproof class. The results were compared to the bulletproof tests of the ZB material from previous works. Better protective capability was achieved in the case of a commercial material. However, the tested KM material also exhibited the energy dissipation capability. Further work is needed to investigate the effectiveness of the KM material in a different type of casing.

Mechanical alloying (MA) and spark plasma sintering (SPS) was employed to synthesize the Mg60Zn35Ca5 alloy. SPS, which is also known as the field-assisted sintering technique, plasma-activated sintering, pulsed electric current sintering, or plasma pressure-compaction, appears to be promising for manufacturing a biodegradable Mg60Zn35Ca5 alloy. SPS is a sintering technology that utilizes Joule heating via a pulsed electric current to achieve densification. SPS allows very fast heating and cooling rates, very short holding time, and the possibility of obtaining fully dense samples at comparatively low sintering temperatures, typically a few hundred degrees lower than normal hot pressing. The Joule heating could lead to further improved densification via localized plastic flow at the necks of connected particles during sintering. The structure and compressive strength of the Mg60Zn35Ca5 alloy were investigated. In the X-ray diffraction (XRD) patterns of the representative Mg60Zn35Ca5 powder after 13 h of MA, a broad diffraction peak corresponding to the amorphous phase is noticed. The results by XRD show that the Mg60Zn35Ca5 alloy after sintering has a multiphase structure. The investigated alloy shows a slightly higher compressive strength (264–300 MPa) compared to the crystalline Mg-based alloy (250 MPa) and exhibits properties appropriate for medical applications.

The main aim of this article is to find a progressive composition of plaster mixture consisting of lime hydrate, siliceous aggregates and a waste material admixture. Recycled finely ground brick powder appears to be a suitable material for lime or cement plasters. It exhibits good pozzolanic characteristics and actively participates in creation of bonds within the material structure. The brick dust primarily comes from the production of thermal insulating brick blocks. Therefore, recycling of this waste leads to improvement of ecological and economic aspects. In our previous studies, the effect of ceramic waste on properties of ceramic-based plasters has been studied and it was found out that the most promising solution is to partially replace fine aggregates and lime hydrate by ceramic powder as it can participate in pozzolanic reactions and it also plays a role of a filler. Ceramic powder significantly improved all studied material parameters presented in this article. Therefore, this article is an extension of previous studies and brings new insights to the topic, for example time horizon of the study. The first part of this article is focused on the analysis of the pozzolanic reaction. The effectivity of the ceramic waste on pozzolanic reactions was studied on pastes prepared only from lime hydrate with different amounts of ceramic powder replacement (from 10 to 70 mass% of ceramic waste). The pastes were stored in a climatic chamber under constant temperature and humidity conditions. The pozzolanic reactions were studied after 28 and 360 days of hydration using selected experimental measurements, namely characteristics of the pore system, mechanical properties and thermal analysis (DSC/TG). Based on the obtained results, the best paste was selected for the design of the plaster mixture enriched by siliceous sand. The same properties of the newly designed plaster were studied to confirm the effectivity of this mixture.

Colombia is a country that frames a great cultural tradition with artisanal developments throughout all its regions, which allows a different approach to the use and practice of different materials when it comes to creation processes. One of the most common materials, or that can be found easily in the vast majority of regions is ceramics. And ceramics is a great world yet to be explored in terms of processes, developments and even transformation of raw materials. The main objective of this research is to analyze and evaluate the final results of the behavior of different types of clays such as red, black and gray when combined with pigments from the coloring processes, such as patinas, enamels and engobes. In this way the pedagogical process will consist of the manufacture of a series of test tubes validated in a controlled cooking process and including different percentages of pigments in combinations defined with each of the clays; In this way, a visual catalog of ceramic finishes will be obtained through which the different desired results can be observed in a methodical way when carrying out serial crafts processes by the students; result that will be a considerable input to implement practical classes, talks or workshops, to minimize expenses or losses of both products and material and additional is intended to encourage manufacturing processes of handicrafts in Colombia.

The main disadvantage of gypsum as a building material is the loss of its mechanical properties in a wet environment and therefore the use of pure gypsum is limited only to the interior of buildings. The resistance of gypsum materials against moisture can be improved by the addition of any pozzolanic material and an activator of the pozzolanic reaction to the gypsum. The water-resistant CSH phases are formed by the reaction and the resulting gypsum-based materials evince better behaviour in a wet environment. Several ternary materials, composed of gypsum, lime, several types of pozzolans (silica fume, ground bricks, granulated blast-furnace slag) and silica sand were studied. The best resistance against water was achieved by the material containing silica fume, but its strength was lower than the strength of the other materials. Simplex optimization was used to design a composite with better mechanical properties. Maximum compressive strength was set as the goal of the optimization with regard to the fact, that silica fume is a relatively expensive material. After several steps, an optimized material with greater strength, containing reasonable amount of silica fume was designed.

The final quality of ceramic parts is strongly related with the raw materials, which have different origins, are available in nature in different places, and present heterogeneous characteristics. The particularities of ceramic manufacturing process, like hardness and moisture of pastes, drying and firing cycles, atmospheres, etc., are a multiplicity of factors that causes variability of properties on the final parts, affecting their use in several applications. This work presents a study carried out in a ceramic company that produces products for hotelware, namely coffee plates and mugs. The objective was study the influence of the firing temperature on the porosity, measured by the water absorption capacity. Taking into account the great influence of the energy costs on the final price of the pieces, it was intended to determine the lowest sintering temperature compatible with these ceramics request. It was found that the highest porosity values (about 23%) occurred at temperatures of 750 °C. From 850 to 1050 °C, the porosity variation is not significant, ranging from 21 to 22%, so it is not necessary to use higher sintering temperatures, which significantly increases the cost of the product.

Polymeric microspheres have a wide range of medical and cosmetic applications and synthesis of these microparticles is the subject of numerous studies. The strategy of incorporating polymer microspheres into three-dimensional matrices to construct controlled-release materials have been attracting increased attention in recent years. The aim of this study was to obtain new materials by means of incorporating polymer microparticles (containing Calendula officinalis flower extract) in the three-dimensional polymer matrix with a porous structure. The microspheres were produced from κ-carrageenan, κ-carrageenan with addition of locust bean gum or sorbitol by extrusion and 2-phase emulsion methods. In the next step, microspheres were incorporated into a collagen/gelatin/hydroxyethyl cellulose matrix and materials were cross-linked using EDC/NHS mixture. The mechanical properties (Young’s modulus) of the obtained materials were characterized. The porous polymeric matrices combined with κ-carrageenan microparticles may become the basis for a new cosmetic or dermatological formulation. The size of the microparticles, their composition and quantity have a significant influence on their mechanical properties.

Natural fiber research is getting attention worldwide due to its sustainability and ecofriendly nature. It combines low density and interesting properties. Curaua fiber is an abundant natural fiber, which has low cost and several applications. The mechanical properties have a strong dependence on the interface adhesion between the fiber and the polymer matrix. In this work, surface modifications induced by sodium hydroxide (NaOH) on Curaua fibers were studied in order to investigate NaOH as a chemical agent in fiber reinforced epoxy polymer composites. Raw fibers were treated with 1%, 3% and 5 wt% sodium hydroxide solution for different periods of time (24, 72 and 168 h) at room temperature. Specimens of treated Curaua/Epoxy composites were tested and compared in tensile and in flexion to observe the mechanical properties. DMA analyses were performed to evaluate the composites physical properties due to temperature variation. Results showed that fibers treated with 5% of sodium hydroxide for 72 h produced improved superficial roughness increasing mechanical properties. The results also showed an increase in the viscoelastic stiffness of the epoxy matrix by the incorporation of Curaua fibers.

A number of combination studies on the use of plate-screws, which has become a traditional method in fracture treatment, have been conducted to obtain a more rigid joint. These studies in the literature were reviewed and it was seen that the effect of the position of the compression screw, used with the aim of making the fracture line come closer to each other during fracture fixation, on the fatigue strength of the joint hasn’t been investigated. Within the scope of this study, a screw combination study by including Limited Contact Dynamic Compression Plate (LC-DCP) plates that possess combined hole properties was carried out. Three different combinations were created during the study. In these combinations, the unlocked screw that was located on the part where the force was applied and that was used for compression was placed in different holes and fatigue strengths of the joints were investigated under dynamic bending force. As a result of the study, it was observed that as the compression screw moved away from the fracture line, fatigue strength of the joint consisting of plate, screw and bone decreased. In addition, it was found that all the joints in the 3rd combination got damaged as a result of the fracture of the bone.

This paper describes the optimum design and life cycle cost (LCC) assessment of timber roofs for sustainable construction. For this purpose, collar beam roof construction in a typical single-family house was analyzed. Special focus was placed on the impact of the patch cross-section position for different rafter spacing. The calculations were performed for four roof angles (15°, 30°, 45°, 60°). The main goal was to find the optimum LCC for each angle. It was found that smaller rafter spacing generates a higher assembly cost and takes more time to construct. On the other hand, the wood cost for these elements is lower. The implications of LCC were evaluated to find out which patch and rafter cross-section, as well as rafter spacing for each roof angle is the most economical solution.

The packaging industry, besides motivation, usability and appealing to the costumer, considers the protection of products a necessity and obligation for its success, contemplating all the necessary steps to reach the desired goal. The current paper presents the research and development work, conducted in the scope of the Master Program in Product and Industrial Design of University of Porto (MDIP), in partnership with Bosch Security Systems. The main objective was the study and development of a new material—Air Pack—for the packaging industry. Firstly, several studies of the material were carried out in order to characterize its operation and benefits, more focused on the industry but with big impact in the research field. Two solutions were developed for the company products, taking into account their complexity, shape and implementation on the manufacturing process. Principles such as consumer usability, the nature of packaging, technical protection aspects and methods of transport were well established in both projects. The new material allowed the company and the university to cooperate with each other, granting the student space to understand the business world but also indispensable research. Finally, the material is a good improvement for the packaging industry, where mechanical properties are sometimes better compared to materials such as EPS. The two solutions developed showed that the material can be shaped for a specific product. This material offers a more cost competitive approach to packaging materials and a significant reduction in volume and storage space occupation.

Nowadays, about 121.000 pediatric hospitalizations occur every year in Portuguese hospitals. Hospital admission is a process in which individuals are imposed to change their routines and daily habits and be integrated in a completely new environment. For children, this process is worse than for adults and it leads to undesirable feelings, such as fear and anxiety, which can result in a traumatic experience that negatively affects the recovering process. This paper presents the research work that has been conducted in the scope of the Master Program in Product and Industrial Design of University of Porto, seeking to understand how Design, along with the strategies already used to reduce the negative impact caused by hospitalizations in children’s life, can be used to create a toy that promotes moments of abstraction from the environment in which children are inserted in, as well as moments of play combined with learning and physical, cognitive and social development. Based on the analysis of data collected, a building toy was developed, “Boneco Cubo”, composed by different parts that can be attached to each other in different ways and that intends to contribute to a better integration in the hospital environment while simultaneously stimulating the children’s development. It also intends to be an ally to healthcare professionals as an instrument of children development evaluation.

In recent years, sustainable development has frequently appeared in technical and non-technical publications, particularly in regards to the pressing issues of high level of consumption and constant increase of waste in production processes. This has brought serious consequences in the environmental degradation, mainly due to the faster discarding of products, especially packaging. The process of packaging development must comply with the requirements of environmental preservation. This paper aims at evaluates packaging sustainability, company packages, two of them fulfilling for environmental requirements development by the National Institute of Technology (INT) in Rio de Janeiro, Brazil, and other two are not considered environmental constraints in the design. The evaluation was developed using a checklist approach, a qualitative evaluation instrument that defines the level of attendance of sustainability requirements. Some of the criteria used were: sustainable materials, reuse, reuse during harvest, post-harvest, transportation, exhibition and placement at the point of sale and reduce costs for the producer and the final vendor. Finally, the checklist approach served to define: what is the best package of sustainable behavior? and can be used in other similar studies.

A magneto-rheological clutch was designed and built in order to modify the speed of an axial rotor mounted in front of a centrifugal pump. The main goal by modifying the speed of the axial rotor is to increase the operating regimes with less cavitation and to uniform the flow at the inlet of the pump impeller. The magneto-rheological clutch is tested separately on a preliminary test rig, in order to analyse in detail, the working parameters (generated torque, the interior and exterior temperature). Also, the test rig serves testing different MR fluids available on the market as well as several MR fluids developed and characterized in our laboratory. The preliminary test rig consists in one fixed (2500 rpm) and one variable speed electric motors (2000–2500 rpm), a torque transducer (0–20 Nm), the magneto-rheological clutch, temperature sensors as well as a control and acquisition system. The aim of this study is to provide a first experimental evaluation of the magneto-rheological clutch designed and built for a special application. First, the paper presents the problem and our solution using the MRC. Second, we focus on the magneto-rheological clutch and the test rig; the magnetic and mechanical design of the clutch is presented, while for the test rig the operating conditions will be described. The third part analyses the results: the generated torque and power at different speeds, the interior and exterior temperature. The last section draws the conclusions.

A magneto-rheological brake (MRB) is designed and embedded in a swirl generator apparatus in order to control the runner speed. Several swirling flow configurations are obtained slowing down the runner speed. The main challenge for MRB is associated with its operation under water conditions. As a result, two magneto-rheological fluids (a conventional one and one based on ferrofluid) are selected together with an appropriate sealing solution to avoid expelling the solid particles. Firstly, a commercial magneto-rheological fluid (MRF 336AG) manufactured by Lord Co. is tested in MRB. Secondly, a nano-micro composite magneto-rheological fluid, with 35% volume fraction of the micron-size iron particles (SMR 35%Fe), designed and manufactured by Magnetic Fluids Laboratory from Romanian Academy—Timisoara Branch was selected for experimental investigations. The mechanical solution designed for MRB is presented. The magneto-rheological properties determined for both MRFs are compared. Challenging investigations were performed at several runner speeds with MRB under water conditions. A relative speed variation behaviour associated with the runner rotation has been identified due to rupture and rebuild of large chain-like agglomerates in the MRF. This relative speed variation is directly correlated with the braking level of MRB. The conclusions are drawn in the last section together with the future work.

In modern mechanical engineering, there is increased need to find solutions for fast manufacturing of real prototypes. One of these is the fast-growing up-to-date CAD/CAM/CAE system enabling to create digital prototypes. Using CAD systems the conceptual design is analyzed and tested before producing the real prototype. This reduces the compliance costs for manufacturing of the physical models and tooling as well as the production time of the prototype is lessened several times. With the development of technology, and especially in medicine, it is necessary to produce prototypes that can be obtained relatively quickly and meet the requirements of accuracy. Rapid prototyping technologies have such capabilities that they can reproduce digital models with their manufacturer’s precision. To determine the accuracy of printing, a SLA system is used. To determine the accuracy of printing, a SLA system is used. One of the peculiarities of making a detail by this method is the appearance of distortions in the initial stage of construction at large rectilinear plots. In order to determine the minimum printing deviations, a strategy for printing prototype models at a different slope of 0°–90° was used. Patterns are made with coordinate networks, enabling post-print deviations to be evaluated by matching the digital model. The present study will be useful in developing prototype models for micro and nanotechnology in mechanical engineering and medicine, providing a solution for their optimal location with minimal deviations.

Glass fiber reinforced polymers (GFRP) are composite materials widely used in all fields of applications. Once cured to near net shape, GFRP parts often need several finishing operations such as trimming, milling or drilling in order to meet final dimensions and accommodate fastening hardware. The cutting temperature is crucial when dealing with such finishing operations for synthetic composite materials. Cutting temperatures higher than the glass transition temperature (Tg) of the resin matrix are highly undesirable: they cause degradation of the matrix around the cut edges, which can severely affect the mechanical performance of the entire component. This research aims to study the effect of adding different particles to the epoxy matrix of glass fiber reinforced polymers (GFRP) on the cutting temperature and surface finish for the trimming operation of this material. Five plaques were made, each with a different epoxy mixture: no additive, wetting agent (WA), WA and clay, WA and wax, WA and clay and wax. From the results, it can be concluded that wax particles significantly decrease the cutting temperature for the trimming process. The maximum recorded temperature was found to be 30% lower than for the reference plaque having no additive. Regarding the surface roughness, the wax particles also seem to have a positive effect, with the Ra value decreasing by a value of up to 32% versus the reference material. The synergy between the clay and the wax particles added to epoxy is promising for improving GFRP machining.

The determination of the applicability range of conventional high-speed steel and sintered high-speed steel is only seemingly simple and obvious. According to the literature, the properties of cutting edges made of both kinds of steel depend mainly on the distribution of carbide phases in the steel. However, earlier research of the present authors indicates that the topography of the surface of cutting edges is at least equally important in determining the functional properties of the edges. Different surface topography in the case of conventional high-speed steel edges and sintered high-speed steel edges leads to different durability of edges in dry friction conditions and in the presence of the lubricant, at different cutting speeds. Contrary to expectations, the sintered high-speed steel edges do not always display better properties than the cutting edges made of conventional high-speed steel. Therefore it is necessary to determine the applicability ranges of both kinds of steel. In article selected fragments of investigations of technological and functional properties of cutting edges made of conventional and sintered high speed steel with similar chemical composition are presented. Investigations of technological and functional properties have comparative character and concern among other things estimation of chemical composition, hardness, structure and durability during toughening steel machining.

This article presents the investigations of durability of the cutting tools (insert cutting edges) made of the nanocrystalline sintered carbides. Cutting insert edges were sintered using the Pulse Plasma Sintering (PPS) method elaborated at the Department of Materials Science Warsaw University of Technology. This article contains the results of comparative investigations of durability of the cutting edges made of WC-5wt% Co nanocrystalline cemented carbides with the TaC-NbC or Cr3C2 growth inhibitor and without it sintered by the PPS method, and cutting edges made of a standard cemented carbides of the same chemical composition (obtained by the Hot Pressing (HP) method) during turning the EN-36CrNiMo4 (PN-36HNM) toughening steel. The nanocrystalline cemented carbides have much higher hardness and smaller average grain size than standard carbides with the same chemical composition. For these reasons, cutting inserts made of the nanocrystalline cemented carbides particularly with TaC-NbC inhibitor have significantly greater hardness and from here greater resistance to wear and greater durability during machining the toughening steel.

Although composite structures can be molded to nearly final shape, they generally require different finishing operations, such as drilling and trimming, to meet dimensional tolerances and enable assembly. Conventional drilling and trimming methods tend to induce internal damage to the composite, mainly in the form of edge delamination, matrix thermal degradation, fiber fracture or fiber pullout. As the damage mechanisms and progression are not yet fully understood, it is crucial that the appropriate tools be used to verify the structural integrity of composite parts. NDT techniques allow observing the extent of damage in composites; however they have limited resolution for shallow edge defects. On the other hand, well-designed tensile tests, made from coupons taken over extra materials intentionally left around a part, are sensitive to the reduction of mechanical properties of trimmed composite samples due to, among others, thermal degradation and smearing of the matrix. In that respect, the main objective of this work is to evaluate the possibility to detect and quantify small edge machining damage using the ultrasonic testing (UT) method and combine this approach with mechanical testing to determine the influence of machining on the quality of trimmed parts. Indeed, a combination of mechanical testing and NDT techniques could provide an interesting avenue to appropriately certify the quality of a machined composite part. A non-destructive testing (NDT) method and tensile mechanical testing will thus be used to characterize the extent and the influence of damage induced by the trimming operation of quasi-isotropic carbon/epoxy composites. First, the resolution and the precision of ultrasonic testing (UT) are evaluated with composite samples comprising internal (artificial) defects. Next, this method is used to evaluate machined samples prepared by using high performance machining tools for composites. It is shown that the UT technique is able to detect the very small edge defects induced by trimming. Then, mechanical testing of narrow tensile coupons is performed to compare impact of milling, abrasive cutting and sanding on the quality of trimmed surfaces. Results suggest that some type of damage could efficiently be quantified when coupons of reduced width is used to magnify the influence of defects on the measured strength.

Gamma titanium aluminides are a new generation of light materials that compete with nickel or cobalt superalloys, when it comes to the manufacture of very high resistance requirement components such as low and high-pressure compressor blades, in the case of aeronautical applications. Machining is a process used to manufacture such components. However, in available literature, the specific information regarding machining performance of gamma titanium aluminides is scarce. The present research focused on the comparative study of the performance of coated tungsten carbide (WC-Co) inserts with round geometry in face milling operation of a gamma titanium aluminide alloy (Ti-48Al-2Nb-0.7Cr-0.3Si). Six different cutting-inserts in a combination of three different compositions of WC-Co substrates and two edge-geometries (XL and XM) recommended for conventional titanium alloys were tested. Milling experiments were carried out for different cutting speed, depth of cut and chip thickness. The results are discussed in terms of the correlation between cutting parameters with cutting force, surface roughness and work-hardening. The study showed that chip thickness, significantly affected the machined surface integrity in related with the tool insert geometry. Insert type C-XL showed better performance for cutting speed to 45 m/min, while inserts types A-XL and B-XM showed better behavior for cutting speed to 70 m/min.

The semi-circular specimen under three-point bending loading (SCB specimen) may be used for determining mode I and mixed-mode (I and II) fracture toughness for brittle materials; this subject is covered in several references. This paper presents T-stress and stress intensity factor for SCB specimen in mode I and mixed-mode (I and II), exploring direct uses of finite element method to calculate those parameters. The commercial FE software ABAQUS was used to model the SCB specimen. Several cases including different crack lengths for investigating mode I, various crack angles for mixed-mode (I and II) and T-stress are presented. Since SCB specimen is loaded in bending, a comparison of the SCB and SE (B) specimen (ASTM E399-08 standard) was performed for mode I, discussing dimensions and amount of material involved. Finally, the result obtained from the presented finite element model are compared with results from the literature.

The aim of this work is to analyse fatigue crack propagation under pure mode II and mixed mode I-II loading conditions. Bidimensional numerical simulations were carried out using models created with the software Abaqus Standard, making use of the conventional finite element method to calculate the stress intensity factors and of the extended finite element method to predict the crack propagation path. The experimental tests were performed on single edge notch specimens, under asymmetrical four-point bending. By varying the position of supports and loads relatively to the crack several situations of mixed mode loading I-II and pure mode II were achieved. The equivalent stress intensity factor for mixed mode I-II and pure mode II was calculated using the finite element method and the software Abaqus Standard. The $$da/dN=f(\Delta K_{eq})$$ d a / d N = f ( Δ K eq ) , where a is the crack length, N is the number o cycles, and $$\Delta K_{eq}$$ Δ K eq is the range of the equivalent stress intensity factor, was obtained and compared with the mode I Paris law equation for the given material, NASGRO material database and other authors’ results. The initial fatigue crack growth (FCG) propagation angles were found to be well described by the minimum strain energy density criterion. Regarding the FCG rates, mixed mode results differ from mode I. Several factors like pre-existing flaws in the material, accumulation of experimental and/or post-processing errors and roughness-induced crack closure may have played a part in the differences obtained between the experimental material curve based on $$K_{eq}$$ K eq and the NASGRO and Paris law equations based upon $$K_{I}$$ K I . It is however noted that other authors also found some difference in the da / dN versus $$\Delta K_{eq}$$ Δ K eq or versus $$\Delta K_{I}$$ Δ K I relationships. Finally, as regards cracks paths, xFEM predictions and experiments showed a variable degree of agreement: very good in some cases, and only approximate in others.

Aluminum and its alloys are frequently used in industry due to their low density as well as their high strength and corrosion resistance. Although the most common welding methods for aluminum are TIG, MIG, and plasma, due to the high temperatures during welding, the metallurgical precipitates formed in the heat affected zone disrupt the interior and affect the mechanical properties negatively. Friction welding of tube to tube plate using an external tool (FWTPET) which is a fairly new method has been developed to overcome this shortcoming and tube to tube plate welding has started to be made with this method. In this study, aluminum alloy AA6063 tubes were successfully joined to AA6082 plate by FWTPET. The welding groove on the plate, the gap between the tube and the plate, and the tube projection length were studied experimentally. The effects of all parameters on shear strength, micro hardness, and the formation of internal structure of the weld zone were investigated, as a result the optimum welding parameters are founded.

In the present paper, we aim to analyze the effect of the design parameters of micro-textured surfaces on the anti-fingerprint function. For this purpose, a numerical model of the finger contact was developed to simulate the mechanical response of the finger loaded over differently micro-textured surfaces. Interestingly, this model enables the measurement of the touched area (i.e. stained area by fingerprints). A statistical analysis was conducted using a full factorial design in order to investigate the effect of the height, width and pitch describing the surface texture. The statistical significance of the parameters effects as well as the effects of their interactions was discussed. Results have shown that both the height and the interaction between the height and the pitch have significant influences on the real area of the finger contact. An optimal compromise between the height and the pitch is recommended to reduce the touched area. The obtained results highlighted by the statistical analyses can provide a guideline for the design of anti-fingerprint surfaces.

In the present paper, mechanical properties of multilayer coatings were investigated. To that end, an analytical model dedicated for characterizing the thin multilayer behaviors was considered. In this study, the nanoindentation tests on film/substrate material systems were systematically investigated using finite element modeling (FEM). Hence, the considered model of Mercier et al. is efficient for measuring meaningful mechanical properties of thin film materials up to a critical ratio Ef/Es = 1.18 (with Ef the Young’s modulus of the film and Es the Young’s modulus of the substrate). But, for Ef/Es ≥ 1.18 a divergence of the model was observed. The main error is caused by a wrong estimation of the contact surface Ac between the indenter tip and the film surface. As a matter of fact, for a soft film on a hard substrate (Ef/Es < 1.18) the deformation is almost localized at the film. However, for Ef/Es ≥ 1.18 the deformation spreads at the substrate which induces a wrong value of contact surface Ac.

Three different dual-phase steels are selected (DP500, DP600 and DP780) to study and analyze the effect of microstructure on formability behaviour for this kind of materials, which are nowadays commonly used in sheet metal forming. This class of advanced high strength steels have a microstructure predominantly composed by a soft ferritic matrix, which ensures good formability, combined with hard martensite particles that give the material its strength. Moreover, the mechanical behaviour of dual-phase steels can be affected by the volume fraction of martensite present in the material matrix, thus providing different levels of formability. This paper presents a formability study and a limiting drawing ratio identification of dual-phase steel sheets, with different amounts of martensite, using a deep drawing test. Experiments and finite element simulations have been performed to analyze and compare the obtained results for this kind of advanced high strength steels. Different experimental tests have been performed with different loading conditions, such as tensile test, biaxial bulge test and Swift test in which formability can be dependent on mechanical properties of material and loading conditions. It is shown that selected materials have a decreasing formability with higher content of martensite, independently from the loading conditions or different material characteristics (e.g. different evolution of anisotropy with rolling direction).

In recent years, extensive research was carried out on the development at lightweight materials, combining metals with polymers, so-called composite sandwich metal/polymer materials, in order to face the safety and environmental requirements. These materials are composed by metal sheet skins with reduced thickness and a polymer core. However, the combination of steel with other materials poses new challenges, due to their new or different behavior and non-homogeneity of deformation, needing also a different approach to material characterization and formability analysis. This contribution presents the issues concerning material characterization and behavior for this kind of materials in addition to using and proposing appropriate approaches for traditional testing methodology. Fundamental mechanical characterization is obtained by using, not only the uniaxial tensile test, but including also hydraulic bulge test. Formability characterization for this hybrid material includes hole expansion tests and deep drawing Erichsen test, being also discussed the adequacy and differences between homogeneous and composite material results. Numerical simulations were performed to study the influence of tool geometry during the hole expansion test. For the HET to be adequate for both of types of materials, heterogeneous hybrid material and homogenous metal sheets, the increase of the die or punch radius dimensions demonstrated to be the best option to get the material formability behavior without compromising the adequacy of selected tests.

This study presents experimental and numerical results of a development prototype tool that includes blank-holder plates of variable stiffness. The application is analyzed for high-strength steel parts and tailor welded blanks manufactured from dissimilar steel grades using laser welding. A numerical model was constructed within the Ansys software platform incorporating appropriate material constitutive models parameters for high-strength Dual-Phase steels. The obtained results show a positive control of springback geometries. Experimental tests were performed on the relevant geometries. The presented numerical and experimental results constitute a validation of a variable-stiffness blank-holder approach for this particular case study.