Effective Strain Distribution Research Articles

Finite Element Simulation of Multi-Pass Rolling of a Pure Aluminum Target under Different Rolling Routes and Methods

By coordinating the rolling direction and mode, a multi-rolling plastic deformation process for an aluminum (Al) sputter target is proposed to achieve multiple excellent properties, including a uniform and fine grain structure and low defect risk, which are significant in producing high-quality sputtered films. In this work, therefore, DEFORM 3D 10.2 software is adopted to establish three strategies, clock-synchronous rolling, cross-synchronous rolling, and clock–snake rolling. The effect of different rolling routes and modes on the metal flow velocity (MFV), effective strain distribution (ESD), grain size distribution (GSD), damage, and rolling force (RF) are comparatively investigated. The simulation results show that clock–snake rolling can increase the MFV and effective strain by producing a deeper deformation than the others. It provides sufficient energy for dynamic recrystallization to promote grain refinement. In combination with the microstructure homogeneity promoted by the clock rolling route, the GSD from 6.5 to 44.3 μm accounts for about 80.5% of all the grains because of the fact that a randomly oriented grain region is full of high-angle grain boundaries. Compared with the synchronous rolling mode, the decrement in RF maximum reaches up to 51% during the asynchronous rolling process because component energy is consumed to form cross-sheering stress. It remarkably reduces the risk of defects, with a damage value of less than 73%, and simultaneously improves energy efficiency owing to smaller and uniform grains caused by less RF. The results obtained in this work are of great significance as they can guide practical production in the metal target industry.

Microstructural analysis of titanium alloys based on high-temperature phase reconstruction

AbstractThe microstructural evolution of titanium alloys under high-temperature conditions plays a key role in determining their mechanical properties and hot working behavior. This research presents an advanced method for calibrating β phase reconstruction software using in situ testing on Grade 2 titanium, which achieves accurate reconstruction of the parent β phase microstructure. In addition, unique microstructural observations in the forging of Ti-6246 titanium alloy are highlighted, demonstrating the influence of deformation parameters on the resulting β phase grain structures. Using advanced techniques such as electron backscatter diffraction and Burgers orientation relationship-based software, the research elucidates the behavior of these phases under varying thermal and deformation conditions. In Grade 2 titanium, significant grain growth and phase transformation dynamics were observed upon heating beyond the β-transus temperature during in situ calibration of β phase reconstruction software. The analysis demonstrates the effectiveness of the software in precise reconstructing the parent β phase microstructure based on the orientation of the inherited αs phase. Furthermore, the evaluation of hot forming parameters in Ti-6246 alloy shows the influence of deformation temperature and strain rate on the resulting microstructure. Finite element method analysis coupled with dynamic material modeling elucidates the distribution of temperature, strain rate, and effective strain during forging, which aids in the qualitative assessment of hot workability. Microstructural observations in Ti-6246 alloy forging highlight the presence of elongated colonies of αs phase precipitates, indicative of localized strain intensities and deformation temperatures. In addition, EBSD analysis coupled with β phase reconstruction reveals distinct microstructural features in different regions of the forging. In particular, regions subjected to higher strain rates exhibit elongated β phase grains with pronounced disorientation gradients, suggesting intense deformation. Conversely, optimal forging conditions lead to the appearance of unreinforced axisymmetric β phase grains, indicating dynamic recovery processes. Pole figure analysis further emphasizes the Burgers crystallographic relationship between the αs and β phases, confirming that deformation during forging occurs exclusively within the β phase. These results provide valuable insights into the microstructural evolution in titanium alloys under high-temperature conditions, which are essential for optimizing hot working processes and improving mechanical properties. Graphical abstract

Microstructural analysis of titanium alloys based on high-temperature phase reconstruction

AbstractThe microstructural evolution of titanium alloys under high-temperature conditions plays a key role in determining their mechanical properties and hot working behavior. This research presents an advanced method for calibrating β phase reconstruction software using in situ testing on Grade 2 titanium, which achieves accurate reconstruction of the parent β phase microstructure. In addition, unique microstructural observations in the forging of Ti-6246 titanium alloy are highlighted, demonstrating the influence of deformation parameters on the resulting β phase grain structures. Using advanced techniques such as electron backscatter diffraction and Burgers orientation relationship-based software, the research elucidates the behavior of these phases under varying thermal and deformation conditions. In Grade 2 titanium, significant grain growth and phase transformation dynamics were observed upon heating beyond the β-transus temperature during in situ calibration of β phase reconstruction software. The analysis demonstrates the effectiveness of the software in precise reconstructing the parent β phase microstructure based on the orientation of the inherited αs phase. Furthermore, the evaluation of hot forming parameters in Ti-6246 alloy shows the influence of deformation temperature and strain rate on the resulting microstructure. Finite element method analysis coupled with dynamic material modeling elucidates the distribution of temperature, strain rate, and effective strain during forging, which aids in the qualitative assessment of hot workability. Microstructural observations in Ti-6246 alloy forging highlight the presence of elongated colonies of αs phase precipitates, indicative of localized strain intensities and deformation temperatures. In addition, EBSD analysis coupled with β phase reconstruction reveals distinct microstructural features in different regions of the forging. In particular, regions subjected to higher strain rates exhibit elongated β phase grains with pronounced disorientation gradients, suggesting intense deformation. Conversely, optimal forging conditions lead to the appearance of unreinforced axisymmetric β phase grains, indicating dynamic recovery processes. Pole figure analysis further emphasizes the Burgers crystallographic relationship between the αs and β phases, confirming that deformation during forging occurs exclusively within the β phase. These results provide valuable insights into the microstructural evolution in titanium alloys under high-temperature conditions, which are essential for optimizing hot working processes and improving mechanical properties. Graphical abstract

Notched Tensile Fracture of a Fe-15Mn-0.6C-2Al Twinning Induced Plasticity Steel at Room Temperature

The tensile fracture behavior of an Al-bearing TWIP steel was investigated by conducting a series of tensile tests on smooth and notched specimens with different notch geometries, focusing on the effects of evolution of the stress triaxiality and the effective strain during deformation. The flow curve and digital image correlation (DIC) analysis evidenced suppression of dynamic strain aging due to Al addition, and therefore, the effects of local inhomogeneous deformation associated with Portevin-Le Chatelier (PLC) band on fracture could be excluded. The smooth specimen fractured with negligible necking despite the absence of PLC bands. As a result, the effective strain was uniform through the gage section and the stress triaxiality (<i>η</i>) of ~0.33 was nearly unchanged over the entire cross-section up to the maximum load. This led to the fracture surface of the smooth specimen being entirely covered with fine equiaxed dimples. For notched specimens, the fracture strain was drastically reduced with decreasing notch radius, indicating the high notch susceptibility of the steel. The effective strain of the notched specimens was the highest at the edge of the notch root, regardless of the notch radius, so cracks first developed at the surface of the notch root. Although the <i>η</i> at the center of the notched specimens (0.40~0.48 depending on the notch radius) was higher than that of the smooth one, the center of the fracture surface of all notched specimens exhibited dimple features that were very similar to the smooth one, even in size. In contrast, in spite of the same <i>η</i> of ~0.33, fractography at the edge of the notched specimens revealed a fracture mode transition from dimple fracture to void sheet fracture to quasi-cleavage fracture as the notch radius decreased. The present results were rationalized in terms of the local evolution of stress triaxiality and effective strain during deformation, which were analyzed using the finite elemental method and DIC technique. It can be said that the fracture mode of TWIP steel, showing limited necking, was more influenced by the distribution and/or gradient of stress traiaxiality and effective strain rather than their local absolute values - that is, the severer their gradient is, the easier the quasi-cleavage fracture occurs.

Shakedown of metallic sandwich beams when subjected to repeated impact loadings

When a monolithic metallic beam/plate subjected to repeated dynamic loadings with fixed impact level experiences elastoplastic deformation, its measurable deformations may cease to develop for further repetitions of the same dynamic load: this phenomenon was referred to as “pseudo-shakedown” in previous studies (Jones, 2014; Shen and Jones, 1992). Would pseudo-shakedown occur in a metallic sandwich structure under repeated shock loadings remains elusive. A combined experimental and numerical study was carried out to explore whether dynamic shakedown could occur in all-metallic ultralightweight corrugated core sandwich beams. For repeated impact tests, the sandwich beams were fabricated via the sequential process of cutting-stamping-vacuum brazing. When subjected to repeated impact loads (achieved via aluminum foam projectiles launched from a light gas gun), the dynamic responses of each sandwich specimen - including structural evolutions, beam deflections, and deformation/failure modes - were measured. Experimental results revealed that, depending upon the level of impact momentum applied to the sandwich beam, either dynamic shakedown or progressive failure could occur. The method of finite elements (FE) was subsequently employed to simulate the repeated shock tests, which was validated against experimental measurements, with good agreement achieved. To explore the physical mechanisms underlying the observed dynamic shakedown, the FE results of final plastic energy and effective plastic strain distribution in the sandwich beam were extracted and analyzed. When shakedown occurred, the measurable permanent deformation of the sandwich beam kept a relatively stable state, but its plastic energy remained positive, which is different from its monolithic beam/plate counterpart (i.e., plastic energy dropping to zero during dynamic shakedown). Such difference is mainly attributed to stress concentration occurring at the connecting joint points between the corrugated core and face sheets of sandwich and clamped endings, which produces plastic deformations that are difficult to reflect in overall large deformations of the beam. Consequently, the dynamic shakedown of metallic corrugated core sandwich beam captured in this study appears to be inexhaustive and hence may be termed as the “apparent pseudo-shakedown” (with danger lurking in the welding joints as well as clamped endings). Finally, based on a simplified bi-linear hardening constitutive law, the mechanisms underlying the dynamic shakedown of sandwich beam were further discussed from a purely base material point of view.

On the simulation of the small punch creep test—applied to 316L(N) austentic steels

ABSTRACT This paper describes a numerical analysis to predict the deformation and time to rupture of the small punch creep test for 316 L(N) austenitic steel. The constitutive model incorporates elasto-plastic nonlinear kinematic hardening and creep with primary, secondary and tertiary creep calibrated to the RCC-MRx code data. The computations are assessed by comparing with experimental data for a 500 µm thick sample clamped with a diameter of 5 mm loaded with a force 300,400 and 500N at 700°C. The model predicts the experimental observations quite well with respect to minimum deflection rate and time to rupture and its location using a local critical strain criterion. A very important feature is that the deformation and total effective strain distribution at rupture are almost identical for all loads as function of the time divided by the time to rupture.

A novel method for ball forming by cross wedge rolling

In this paper, a novel method for ball forming by cross wedge rolling (CWR) was proposed, and the finite element (FE) simulation and experimental verification were carried out with the 26 mm diameter steel ball as an example. First of all, the die parameters including spreading angle β and forming angle α were selected and the 3D models of the die and guide plate were designed. Then, the FE model was established and preliminary simulation was carried out using the Simufact 16.0 software. The preliminary simulation results showed that the pushing empty defect occurred in the process due to lack of transition from spreading stage to sizing stage and conical die section. Modifying the die design by adopting the method of adding transition spreading angle θ and forming angle α´ increasing with the increase of rolling depth to, the defect could be eliminated and the full filling can be obtained. In addition, the simulation analysis after modified also included effective strain and stress distribution, the kinematic analysis of metal flow, the damage distribution based on the Cockcroft-Latham criterion, the temperature evolution and force parameters in the CWR process. Finally, the rolling experiments and radial rolling force testing experiments were carried out to verify the numerical results. The results indicated that the FE simulation results were consistent with the experimental results through quantitative analysis, which proved that the novel method for ball forming by CWR was feasible simultaneously.

Finite element modelling and microstructural correlation of hot forged Al-Zn-Mg-Cu alloy (T6) using DEFORM-3D

Thermomechanical processing is a globally practised method for upgraded microstructural and mechanical characteristics. But the varying strain during thermomechanical processing results in a varying microstructural characteristic throughout the specimen. Thus understanding the impact of strain and microstructural evolution in different regions with a deformed specimen is vital. The presented study discusses the finite element modelling of hot forged Al-Zn-Mg-Cu alloy mapped with microstructural evolution in different regions at an optimum working condition of 450 °C-0.001 s−1. The finite element analysis of the deformed specimens in the optimum working region has indicated a large effective strain variation (0 to 1.75) throughout the deformed specimens. The effective strain distribution delineated very high strain values at the edges and least on the centre region (cross-sectional area). The FEM simulation also indicated an increased chance of damage near the edges of the specimens. Further progressing within the deformed specimen, the effective strain increased towards the specimen's core. The microstructural correlation using EBSD IPF analysis indicated the high angle grain boundary (HAGB) fraction of 62% in the centre region and 50.5% in the longitudinal ends of the specimen. The GOS map indicated a dominantly recrystallized microstructure. A higher extent of DRX was observed in the centre region (93%) compared to the end region (78%). The microstructural evolution is due to cDRX, and the microstructural evolution is well correlated with the strain variation.

Cogging process design of M50 bearing steel for billet quality

This study proposes a method to determine cogging process parameters aiming at homogeneous effective strain distribution and grain size uniformity and refinement during the manufacturing M50-bearing steel billets. The design parameters were selected as feed, number of rotation, depth schedule, and forging ratio. The Billet Quality Index (BQI) is introduced to comprehensively evaluate the effective strain distribution and grain size number (ASTM E112) of the final billet and used as the objective function for the process design. The results of effective strain distribution and grain size number are obtained through finite element simulation, and these values are used to investigate the BQI of the final billet. For the finite element analysis to calculate the temperature field and grain size, the heat transfer coefficients determined by reverse engineering and the grain growth model coefficients were used compared with the experimental measurements. The Taguchi method investigates the influence of parameters on BQI, excluding the forging ratio. Optimal process parameters, including forging ratio, are determined using a Deep Neural Network (DNN) regression model, targeting BQI minimization. The BQI prediction accuracy of the DNN regression model is 98.83%, emphasizing the effectiveness of DNN despite the limited dataset size. The optimized cogging process reduces the total process time by 2.394 h and improves the BQI by 6.91% compared to the minimum BQI in the dataset. The optimized cogging process promotes homogeneous effective strain distribution, grain refinement, and uniformity, enhancing billet manufacturing efficiency.

Effects of equal channel angular rolling process on the mechanical properties of Al-Cu two-layer sheets: experimental and numerical approaches

Abstract This study investigates the mechanical properties and microstructural characteristics of explosion-welded Al/Cu two-layer strips during the ECAR process using finite element simulations and experiments. Furthermore, the explosion-welded Al/Cu two-layer strip was examined with various configurations to determine the effects of die angle and friction coefficient on the distributions of effective strain and stress. In addition, the experimental and computational approaches were utilized to explore the ECAR process in two routes, RA and RC, for three directions. Finite element simulations were run and validated using experimental data. The findings show that the ECAR method is effective to enhance the mechanical characteristics of the strips. Moreover, the obtained results represent that the ECAR process reduced the size of the grains. Furthermore, it was shown that by increasing the number of routes in the ECAR process, the stress values were increased. However, the ductility of the two-layer strip was decreased. According to the current study, the route and the number of routes used in the ECAR process have a considerable effect on the strength of the two-layer strip.

The Cold Forming Analysis of Eccentric Parts

In this study, a multi-stage cold forming process for the manufacture of eccentric parts is studied numerically with low carbon steel AISI 1022. The forming processes through five stages and four stages include two-step forward extrusion, eccentric upsetting, and backward extrusion over a moving punch. The numerical simulations of cold forming are conducted using the code of DEFORM-3D. The formability of the workpiece is studied numerically, such as the effect on forging load responses, maximum forging loads, effective stress and effective strain distributions and metal flow pattern. The maximum effective stress of 819 MPa at the third stage is the largest among the stages. The maximum effective stresses of the last stages for the four-stage forming and five-stage forming are almost the same. The effective strain distributions of the last stages for the four-stage forming and five-stage forming are very similar. The flow line distributions of the last stages both for the four-stage forming and five-stage forming are also very similar. For the maximum axial forging force and forming energy, the third stage of eccentric upsetting at the upper end is the largest among the stages. The total maximum axial forging loads from the first to the last stages are 795.8kN for the five-stage forming and 590.4kN for the four-stage forming; and the total forming energies are about 0.751kJ for the five-stage forming and 0.671kJ for the four-stage forming. Although the total maximum axial forging loads and total forming energy of the four-stage forming are smaller than those of the five-stage forming, the maximum lateral forging force in the last stage of the four-stage forming is almost five times that of the last stage of the five-stage forming. Increasing lateral forging force may lead to wear and damage of the punch. Moreover, the inner surfaces of the hexagonal cavity at the upper end are relatively uneven because of simultaneous eccentric upsetting and backward extrusion in the last stage of the four-stage forming.

Analysis of the Effect of Thickness on the Performance of Polymeric Heart Valves

Polymeric heart valves (PHVs) are a promising and more affordable alternative to mechanical heart valves (MHVs) and bioprosthetic heart valves (BHVs). Materials with good durability and biocompatibility used for PHVs have always been the research focus in the field of prosthetic heart valves for many years, and leaflet thickness is a major design parameter for PHVs. The study aims to discuss the relationship between material properties and valve thickness, provided that the basic functions of PHVs are qualified. The fluid−structure interaction (FSI) approach was employed to obtain a more reliable solution of the effective orifice area (EOA), regurgitant fraction (RF), and stress and strain distribution of the valves with different thicknesses under three materials: Carbothane PC−3585A, xSIBS and SIBS−CNTs. This study demonstrates that the smaller elastic modulus of Carbothane PC−3585A allowed for a thicker valve (>0.3 mm) to be produced, while for materials with an elastic modulus higher than that of xSIBS (2.8 MPa), a thickness less than 0.2 mm would be a good attempt to meet the RF standard. What is more, when the elastic modulus is higher than 23.9 MPa, the thickness of the PHV is recommended to be 0.l–0.15 mm. Reducing the RF is one of the directions of PHV optimization in the future. Reducing the thickness and improving other design parameters are reliable means to reduce the RF for materials with high and low elastic modulus, respectively.

The Study of Multi-Stage Cold Forming Process for the Manufacture of Relief Valve Regulating Nuts

Cold forging is widely used in many industries. Multi-stage cold forming is usually utilized in forging fasteners. In this study, numerical simulation and experimental investigations were carried out on a five-stage cold-forming process for the manufacturing of low-carbon steel AISI 1010 relief valve regulating nuts. The forming process through five stages included preparation and centering for backward extrusion, backward extrusion over die pin, upset, backward extrusion over a moving punch, and piercing. The formability of the workpiece was studied, such as the effects on forming force response, maximum forming force, effective stress and effective strain distributions, metal flow patterns, and strength. A comparison of the forming forces obtained in the forming experiment with the numerical simulation results of the five-stage cold forming showed a good agreement with the trend of the forming force growth. For the maximum forming force and forming energy, the fourth stage of backward extrusion over the moving punch at the upper face was the largest among the five stages. The total maximum forming forces from the first to the fifth stages were numerically 440.9 kN and experimentally 449.4 kN, meaning the FE simulation and experimental results were in good agreement. The numerically simulated effective strain distributions were consistent with the experimentally tested hardness distributions. Highly compacted grain flow lines also resulted in higher hardness. The overall hardness of the workpiece formed by five-stage cold forming increased by 31% compared to the initial billet. The hardness of the workpiece increased with the forming stages, and the strain-hardening effect was obvious. The strength of the workpiece was significantly increased by five-stage cold forming.

Evolution of dynamic recrystallization behavior and simulation of isothermal compression of Zn–22Al alloy

Isothermal compression tests of Zn–22Al alloy were carried out under varying conditions of temperature (25, 100, 150,200, and 250 °C) and strain rate (0.001, 0.01, 0.1, and 1s−1). The commonly exhibited feature for all the flow stress curves includes the exhibition of softening behavior after peak stress due to the occurrence of dynamic recrystallization (DRX) and dynamic recovery (DRV). The work hardening rate, kinetic recovery model, peak strain, and critical strain for different deformation conditions were determined. A DRX kinetic model was constructed and subsequently validated using experimental results. The DEFORM-3D finite element (FE) software was used to simulate the distribution of effective strain and DRX during isothermal compression by importing the flow behavior and DRX kinetic model. The maximum value of the effective strain under different compression conditions was located in the center of the compressed samples. The main reason for the non-uniform distribution of Xdrx is related to the non-uniform distribution of the effective strain. Also, the simulated results are consistent with the experimental results.

Simulation study on microstructure evolution during the backward extrusion process of magnesium alloy wheel

Magnesium (Mg) alloy wheels can reduce emissions in the context of environmental protection. Further study on Mg alloy wheels is required in light of the enormous automotive market since it is still unknown how the microstructure is evolving for the backward extrusion (BE) process of Mg alloy wheels. In this paper, a numerical model of the Mg alloy wheel was established based on industrial production, and the physical field and dynamic recrystallization (DRX) evolution of cylindrical billet and truncated cone billet on the forming process of Mg alloy wheels were analyzed, as well as the accuracy of the simulation results was verified by physical simulation in laboratory conditions and industrial production. The wheel bottom is in adiabatic temperature rise and the temperature is higher than that of the rim during the wheel forming process, while the effective strain distribution and uniformity are lower than that of the rim. The DRX volume fraction and grain size are consistent with the effective strain evolution. The truncated cone billet can effectively improve the DRX volume fraction and refine the grain size of the wheel compared with the cylindrical billets. This work can provide theoretical guidance for the BE process of Mg alloy wheels.

Simulation of deformation behaviour of Aluminium 7075 during Equal Channel Angular Pressing (ECAP)

This paper presents a finite element simulation of equal channel angular pressing (ECAP) since it is one of the most common and successful severe plastic deformation techniques. This study reports the influence of the most significant factors influencing the ECAP technique. Through finite element simulation, the effect of the die geometry, workpiece geometry, and the pressing speed on the effective strain distributions, damage, and pressing loads, were investigated. The influence of the ECAP method on different material models is also presented. Additionally, the prospective expansion and future applications of ECAP are herein highlighted. From the results, the die geometry of a 90° channel imparts the highest strains during ECAP. Additionally, specimens of rectangular geometry are susceptible to cracking and damage as compared to circular samples. It was found that very high processing speeds (>7mm/sec) are undesirable during ECAP since they cause very high internal stresses to the structure of the workpieces. Besides, processing at room temperature can achieve homogeneous strain distribution with minimum sample damage.

Inhomogeneity of microstructure and mechanical properties in compression-type bulk formed specimens

The effect of elongation and spreading in a material on strain and microstructure inhomogeneity during compression-type bulk forming processes was investigated to improve the strain homogeneity of the materials. For systematic investigation, four different compression-type forming processes, namely wire flat rolling, plate flat rolling, wire caliber rolling, and uniaxial compression, were compared. Strain inhomogeneity and macroscopic shear bands (MSBs) were clearly observed during the compression-type bulk forming processes based on a comparative study on the shape change, effective strain and hardness distributions, and microstructural evolution in twinning-induced plasticity steel. The flat-rolled wire had the largest strain inhomogeneity, followed by the caliber-rolled wire, compressed specimen, and flat-rolled plate in the listed order. The inhomogeneity of the strain distribution along the horizontal direction tended to increase with the pure spreading during the forming process. Meanwhile, the inhomogeneity of the strain distribution along the vertical direction increased with decreasing elongation during the process. Therefore, a small pure spreading and large elongation of the specimen result in more homogeneous and higher quality products in the compression-type bulk forming process. For instance, the flat-rolled plate exhibited weak MSBs and low strain inhomogeneity because of the small pure spreading and large elongation during the forming process.

Investigation of mechanical properties of laser welded dual-phase steels at macro and micro levels

The current automotive industry uses new technology in materials processing and lightweight materials to minimize vehicle weight and fuel consumption. As a result, Tailor-Welded Blanks (TWB) are used in regions where additional strength or stiffness is necessary in body-in-white, thus decreasing weight. In this paper, TWB were produced by joining DP600 with 1.8 mm and DP800 with 0.8 mm and 1.5 mm using CO2 laser welding. The effects of laser power and welding speed on the mechanical properties of TWB were investigated. The flow behaviors of the TWB were obtained from tensile tests. The microstructures of the weld zones of the base materials and TWB were revealed, and the numerical analyzes of the microstructures were performed by micromechanical modeling with a 2D representative volume element (RVE). Effective stress and plastic strain distributions in the microstructures and macroscopic flow curves of the base materials and the weld zones were obtained. The uniaxial tensile tests of the samples were modeled, and the flow behaviors of the TWB were obtained with micromechanical modeling. The results showed a significant change in stress distribution and strain localization depending on the grain size of constituents and the thickness ratios of the TWB at micro and macro scales, respectively. The numerical flow curves obtained using the RVE method were in good agreement with those of the experimental.

Enhancement of Accuracy in Multi-Point Stretch Forming: Cushion Stretching

Multi-point stretch forming (MPSF) is one of the flexible manufacturing processes that uses the reconfigurable tools to produce the three-dimensional sheet metal components. An elastic cushion is placed between the tools and sheet surfaces to avoid direct contact and reduce the dimples as well as wrinkles. The cushion is also known to play an important role as it directly affects the component surface characteristics (accuracy and quality) and thickness strain distribution. An attempt made to apply stretching on the cushion resulted in enhancement of accuracy. In the present work, an analytical methodology is proposed to predict the initial thickness of cushion and stretching load necessary to apply on the cushion. FEA of MPSF of the spherical geometry is carried out with and without application of stretching load on the cushion. Results indicate that effective stress and strain distributions are more uniform when the stretching is applied to cushion thickness in certain range. Proposed methodology can be effectively used to determine initial cushion thickness before stretch and stretch load necessary to achieve chosen final cushion thickness to enhance the accuracy of sheet metal components formed using MPSF.

Microstructure and mechanical behavior of Ti/Cu/Ti laminated composites produced by corrugated and flat rolling

Ti/Cu/Ti laminated composites were fabricated by corrugated rolling (CR) and flat rolling (FR) method. Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron microscopy, numerical simulation methods, peel and tensile examinations. The effect of CR and FR was comparatively analyzed. The results showed that the CR and FR laminated composites exhibited different effective plastic strain distributions of the Ti layer and Cu layer at the interface. The recrystallization texture, prismatic texture and pyramidal texture were developed in the Ti layer by CR, while the R-Goss texture and shear texture were developed in the Cu layer by CR. The typical deformation texture components were developed in the Ti layer and Cu layer of FR laminated composites. The CR laminated composites had higher bond strength, tensile strength and ductility.