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The evolution of crystal damage in rolled AA5182-O aluminum alloy sheet was studied by experiment and finite element simulation in this paper. Grain size characteristic on rolling anisotropy was determined by electron backscatter diffraction (EBSD) test and section line method, and the average grain size of R00°and R90° with the rolling direction was achieved. An improved grain modeling method was proposed by adjusting base rectangle and regularity coefficient based on Voronoi method. It established six finite element models of uniaxial tension grains, which considers anisotropic grain size and regularity coefficient. The Gurson–Tvergaard–Needleman (GTN) model was applied to analyze damage evolution of elements in grains, and whose damage parameters were achieved by the tensile test and the response surface method. The mechanical properties of grain boundaries were characterized by cohesive zone model. The Abaqus software was adopted to conduct the uniaxial tension finite element analysis to investigate influence of anisotropic grain size, number, and regularity coefficient on plasticity damage evolution of this material. The results show that when regularity coefficient of is 0.01 and 007, the fracture elongation of 54 grains model which is considering grain sizes of R00° and R90° is the closest to experimental results.

Improvement in accuracy of the predicted results from numerical simulation results into a reduction of cost and time involved in tool design and experimental trials. However, the predicted results from finite element simulations are significantly affected by the chosen yield criterion and work hardening law. The selection of yield criterion and work hardening law depends on the characterization methods used for defining the material behavior. In this work, the mechanical behavior of AA5083-O aluminum alloy sheet is modeled by performing biaxial tensile tests using cruciform specimen and hydraulic bulging experiments in addition to uniaxial tensile tests. Biaxial to uniaxial yield stress ratios are determined using the equal plastic work principle from the flow curves obtained from these tests. The obtained ratios are used to find the coefficients of Yld2000-2d and Hill48 yield criteria which is then used in the numerical simulations of cylindrical cup deep drawing. Numerical simulations are also carried out using uniaxial and biaxial flow curves fitted with different isotropic hardening laws. Thickness distributions and the load-displacement curves are predicted and validated by performing cylindrical cup deep drawing experiments.

The predictive capability of a non-associated flow rule (non-AFR) for the strong plastic anisotropy was assessed. Based on Hill’s 48 function, a constitutive model under a non-AFR was established for aluminum alloy 6014-T4 sheet, in which the plastic potential function and the yield function were identified by Lankford coefficients (r-values) and yield stresses, respectively. Two constitutive models applying Hill’s 48 and Yld2000 functions under the AFR were also established for the comparison with the non-AFR Hill’s 48 model. These constitutive models were numerically carried out on Abaqus/Explicit by user subroutine (VUMAT). The representational ability of constitutive models was assessed in terms of the predictions on yield stresses and r-values. To further verify the simulated results, deep-drawing experiments of a cylindrical cup and a seat pan were performed. Simulation results were compared with the experiments from the aspects of the forming force, the earing profile, and the measured strain field using ex situ 3D DIC (Digital Image Correlation). Comparison results showed that non-AFR Hill’s 48 model gives the best overall prediction performance and requires less effort than the AFR Yld2000 model, indicating the effectiveness and superiority of non-AFR.

Springback behavior of 6016 aluminum alloy in hot stamping was investigated by a series of experiments under different conditions using V-shape dies and a finite element model which was validated reliable was used to further elucidate the springback mechanism. The effects of initial blank temperature, blank-holding force, die closing pressure and die corner radius were studied. It is found that springback decreases remarkably as the initial blank temperature rises up to 500 °C. The springback also reduces with the increase of die holding pressure and the decrease of die corner radius. Under different initial temperatures, the influence of blank-holding force is distinct. In addition, the bending and straightening of the side wall during the stamping process is found to interpret the negative springback phenomenon.

Electrohydraulic forming (EHF), a high-speed forming process, deforms a material by using high-pressure shockwaves in a fluid-filled chamber. When a material is deformed at speeds higher than 100 m/s, its formability can be improved due to the high-strain rate effect. This allows for the production of complex shapes, such as sharp edges. Therefore, in the present study, we confirm improvement in the formability of aluminum alloy 6061-T6 under high-strain rate condition by conducting EHF experiments. The strains of the deformed specimen are measured using a strain measurement apparatus, and they are compared with the values obtained from a quasi-static forming limit diagram. The comparison verified the improvement in formability, in that the material did not fracture even though the strain distribution of the material at high speeds was located higher than the quasi-static forming limit curve. In addition, we perform finite element analysis to observe the deformed material in detail. Finally, we compare the strain distributions obtained in the numerical simulation and the experiment to verify the reliability of the numerical model proposed herein.

Fatigue damage is the damage accumulation process under the repetitive cycle load, which is accompanied by degradation of material properties. It is great significant to study the fatigue life of aluminum alloy in the field of engineering application. The damage characteristics of 6061 aluminum alloy are studied by three-dimensional reconstruction and finite element method to estimate low-cycle fatigue damage based on the X-ray computer tomography. The results show that the estimated damage variables are accordant with those measured experimentally. Moreover, the three-dimensional reconstruction method combined with the finite element analysis method to calculate the material damage can meet the engineering requirements.

The aim of this work was to study the formability of 5754-O aluminum alloy sheet through utilizing the finite element M–K approach. The uniaxial tensile test and the Nakajima test were performed respectively for determining the mechanical properties and the forming limit strain pairs. The finite element M–K approach considering the Swift model, the Yld2000-2d yield function and the groove orientation was developed through utilizing software Abaqus. The predicted forming limit curve (FLC) agreed well with the Nakajima test results. Furthermore, the limit strains with the consideration of pre-strain under uniaxial tensile condition were experimentally determined, and numerically predicted by the original M–K approach. The numerical limit strains under different pre-strain paths and pre-major strains showed that the M–K approach could only predict partial FLC when the effective strain caused by the pre-strain was larger than the one at plane strain state. This phenomenon was interpreted by the evolution of the stress state in the groove of the M–K theory, i.e., the change of the strain path in loading process resulted in the stress state rotation, and consequently made the ratio of major strain increment in the groove to that out the groove increase when the stress state in the groove approached the stress state at plane strain state.

This paper presents the results of the numerical multi-axial material tests for predicting elastoplastic deformation behavior of aluminum alloy sheets under equi-biaxial tension and in-plane tension-compression stress states. In this study, we have performed the numerical biaxial tensile and tension-compression tests of a 5000-series aluminum alloy sheet using the crystal plasticity finite element method based on the mathematical homogenization method which has been developed by the previous studies. We found that the true stress-logarithmic plastic strain (SS) curves calculated by the numerical biaxial tensile test slightly deviate from those measured by the biaxial tensile tests using a cruciform specimen. On the other hand, the results of the numerical tension-compression test demonstrated that the predicted SS curves shows a reasonable agreement with those obtained by the experiment using the biaxial stress-testing machine with comb-shaped dies.

This study is aimed to predict ductile fracture of sheet metal forming for 6016-T4 aluminum alloy (AA6016-T4). Six shapes of tension tests in three directions with respect to the rolling direction have been carried out up to fracture to measure ductile fracture for the sheet. Since the fracture-related parameters determined by finite element simulation are sensitive to plasticity model, the Yld2000-2d and anisotropic Drucker yield functions with a combined Swift-Voce hardening model were firstly identified for AA6016-T4 and then used to compare the prediction accuracy. These constitutive models are implemented into ABAQUS for plane stress condition and S4R shell elements are set for the finite element model. Comparison of the experimental and simulation results indicates that the anisotropic Drucker yield function is more suitable for AA6016-T4 by considering both the computational accuracy and efficiency. Based on these results, fracture loci for AA6016-T4 were represented by four common ductile fracture criteria (Cockcroft–Latham, Rice–Tracey, Clift and DF2012). Three kinds of specimen were employed to calibrate the fracture models by using a hybrid experimental–numerical method. The results show that the DF2012 criterion is more flexible and accurate for AA6016-T4 with the comparison of force–displacement curves. For further validation, these four ductile fracture criteria are also applied to predict the fracture of an automobile inner panel in drawing forming, and the results show that the DF2012 criterion provides sufficient prediction precision for AA6016-T4.

During the last few decades, the enhancement of prediction capability of the sheet metal forming have been increasing dramatically. High accurate yield criteria and wokhardening model (especially, non-linear kinematic hardening model) have a great importance for the prediction of the final shapes of sheet metal. However, the predicted springback accuracy of aluminum alloy sheet metal is not still good due to their complicated plastic deformation behaviors.In the present research, the springback deformation of aluminum alloy sheet metals were investigated by finite element calculation with consideration of initial anisotropy and the Bauschinger effect. In order to examine the effect of the initial and deformation induced anisotropy on the springback deformation, several types of high accurate yield function and hardening rules are utilized in the present research. The calculated springback by Yoshida 6th yield function [1] and Yoshida-Uemori model [2] shows an excellent agreement with the corresponding experimental data, while the other models underestimate the springback.

Earings appear easily during deep drawing of cylindrical parts owing to the anisotropic properties of materials. However, current methods cannot fully utilize the mechanical properties of material, and the number of earings obtained differ with the simulation methods. In order to predict the eight-earing problem in the cylindrical deep drawing of 5754O aluminum alloy sheet, a new method of combining the yield stress and anisotropy index (r-value) to solve the parameters of the Hill48 yield function is proposed. The general formula for the yield stress andr-value in any direction is presented. Taking a 5754O aluminum alloy sheet as an example in this study, the deformation area in deep drawing is divided into several equal sectorial regions based on the anisotropy. The parameters of the Hill48 yield function are solved based on the yield stress andr-value simultaneously for the corresponding deformation area. Finite element simulations of deep drawing based on new and existing methods are carried out for comparison with experimental results. This study provides a convenient and reliable way to predict the formation of eight earings in the deep drawing process, which is expected to be useful in industrial applications. The results of this study lay the foundation for the optimization of the cylindrical deep drawing process, including the optimization of the blank shape to eliminate earing defects on the final product, which is of great importance in the actual production process.

The combined loading tests of 5754O aluminum alloy sheet are used to verify the yield function. Three yield functions are implemented into the commercial finite element model (FEM) code ABAQUS as a user material subroutine UMAT for the FEM simulation of the combined loading tests. The comparison of the simulating and experimental results shows that the modified Yld2000-2d yield function can describe the mechanical behavior of 5754O aluminum alloy sheet under combined loading paths reasonably while other three yield functions do not. The performance of the modified Yld2000-2d yield function on describing the mechanical behavior under combined loading paths is analyzed in detail. It is concluded that the modified Yld2000-2d yield function can be adopted to describe the deformation behavior of 5754O aluminum alloy sheet for industrial applications.

According to meso-damage mechanics, the evolution of the volume of micro-voids is an important factor that contributes to damage and fracture. Improving the prediction accuracy of plastic deformation of aluminum alloy sheet is an important endeavor for studying the influence of various factors on plastic meso-damage evolution. Based on the GTN (Gurson-Tvergaard-Needleman) model, the meso-mechanics and damage evolution of AA5182-O rolled aluminum alloy sheet were studied in this paper. The mechanical properties were obtained through uniaxial tensile tests for studying the effect of the strain rate and sampling direction on each GTN damage parameter. Using the response surface method, the GTN model of each strain rate specimen at R00° was calibrated by the finite element method, and the influence of each damage parameter on the stress–strain and void volume evolution curves are studied. The results show that the strain rate has no effect on the initial void volume fraction and critical void volume fraction but has a significant effect on nucleation void volume fraction and fracture void volume fraction. An increase in the initial void volume fraction will cause the fracture point of the material stress–strain curve to occur earlier but has no obvious effect on the slope of the void volume evolution. As the void nucleation volume fraction increases, the highest point of the true stress–strain curve will decrease, the fracture point will advance, and the slope of the curve will increase in the uniform deformation stage of the void volume evolution. However, increasing the critical void volume fraction and fracture void volume fraction will delay the fracture point of the stress–strain curve.

This paper presents a method of flange compression using a stepped punch and die for effective production of an extremely deep cup with a flange from sheet metal. The proposed method was composed of initial stretching and flange compression, and fracture was prevented during the flange compression as the blank elongates by only compressive force. Optimum forming parameters, which are stepped lengths of the punch and clearance between the punch and the die, were investigated by finite element analyses and experiments. It was possible to produce a deep cup with uniform side wall thickness, which length-to-diameter ratio was 2.00, by the optimization of the forming parameters. In addition, two-step forming, which uses two punches, was proposed for producing an extremely deep cup with a thinner side wall. As a result, the deep cup, which length-to-diameter ratio was 9.23, was obtained.

This work presents experimental studies with numerical modeling, aiming at the development of guidelines for shaping aluminum alloy AA6111-T4, t = 1.5 mm thick, with the use of a shear-slitting operation. During the experimental tests, parametric analyses were conducted for the selected material thickness. For the purposes of the material deformation&rsquo, s analysis, a vision system based on the digital image correlation (DiC) method was used. Numerical models were developed with the use of finite element analysis (FEA) and the mesh-free method: smoothed particle hydrodynamics (SPH), which were used to analyze the residual stress and strain in the cutting zone at different process conditions. The results indicate a significant effect of the horizontal clearance between knives on the width of the deformation zone on sheet cut edge. Together with the clearance value increase, the deformation zone increases. The highest burrs on the cut edge were obtained, when the slitting speed was set to v = 17 m/min, and clearance to hc = 6%t. A strong influence was observed of the horizontal clearance value at high slitting speeds on burr unshapeliness. The most favorable conditions were obtained for v = 32 m/min, hc = 0.062 mm, and rake angle of upper knife for &alpha, = 30&deg, For this configuration, a smooth sheared edge with minimal burr height was obtained.

In this study, three ductile fracture criteria were used to investigate the fracture in U-bending of AA6061-T6 aluminum alloy sheets. Considering the importance of the calibration procedure, three different tension tests including the uniaxial, plane strain, and notched tensions were conducted based on the stress state analysis. The Ayada, Rice-Tracey, and normalized Cockroft-Latham fracture criteria were calibrated through a hybrid experimental-numerical method to determine their critical damage values. Fracture envelopes (i.e., the locus of fracture strains) were constructed for the investigated fracture criteria based on the results of various tension tests in their calibration procedure. The calibrated fracture criteria were implemented in the commercial finite element (FE) code Abaqus/Explicit using an appropriate user subroutine. The numerical simulation of the bending process was performed and validated by relevant experiments. The accuracy of the fracture criteria was investigated by comparing fracture displacements predicted using the FE model with those measured by experiments. According to the obtained results, variations of damage function (fracture criteria) and the type of the calibration test utilized for a certain fracture criterion have significant effects on the critical damage value, the fracture envelope, and the accuracy of the fracture prediction. For all investigated criteria, the prediction is reasonable when the critical damage value was calibrated under the plane-strain tension. Thus, the plane strain tension is the best calibration method for predicting fracture in the U-bending process. The most accurate fracture prediction is obtained by normalized Cockroft-Latham fracture criterion, which was calibrated by the plane strain tension test with 2.52% error in fracture prediction. However, the prediction of fracture displacement in U-bending process is very imprecise and strongly overestimated, when the uniaxial tension was used as the calibration test. The Ayada criterion has the lowest error of 11.83% for predicting the fracture displacement when the uniaxial tension test was used as a calibration method. Also, the maximum prediction error (the lowest accuracy) was found to be 51.97% by the normalized Cockroft-Latham criterion calibrated under the uniaxial tension test. Globally, for the U-bending process, it is recommended to calibrate the critical damage values under the plane strain condition. But, when only the uniaxial tension test is available, the Ayada fracture criterion gives the best prediction.

The present research aimed to investigate the ductile fracture during the forming of 5083-O aluminum alloy sheet and establish a rational criterion to predict it. Seven specimens with different shapes were tension-tested, and the main deformation areas of the specimens were subjected to various stress states ranging from shear to plane strain. Fracture strains, representing the forming limits, were determined by applying a combined experimental–numerical approach. Surface strain fields were measured by using the two-dimensional digital image correlation (DIC) method, while the local stress and strain histories were predicted by finite element (FE) simulations. The stress triaxiality and Lode parameter (characterizing the stress state) of fracture onset were calculated for each specimen. The analysis indicated that the fracture strain was insensitive to the Lode parameter but strongly dependent on the stress triaxiality. The fracture locus in the space of the fracture strain and stress triaxiality fitted in with the Johnson–Cook fracture criterion. The Johnson–Cook fracture criterion was then implemented into the ABAQUS/Explicit code to predict the fracture onsets of three specimens subjected to ball punch deformation. The strain fields of these specimens measured by DIC-3D were in agreement with the numerical results. Their fracture locations and strokes were accurately predicted by using the Johnson–Cook fracture criterion.

The two-stage loading tests of 5754O aluminum alloy sheet were carried out. In the first loading stage, the uniaxial tensile tests of big sheets were carried out. Then small specimens were cut off from the pre-strained big sheets along different directions. And in the second loading stage, the uniaxial tensile tests of the small specimens were performed. From the experimental results, it is found that the initial yield stress of each specimen in the second loading stage decreases when the strain path changes. In addition, when the strain path changes the transient effect appeared and no obvious permanent softening was observed. In this study, in order to describe the hardening behavior of 5754O aluminum alloy sheet under two-stage loading, the Chaboche type combined isotropic–kinematic hardening models were adopted with Yld2000-2d and Hill48 as yield functions. It is proven that no permanent softening can be described with Chaboche type model in two-stage loading. Three methods for determining the parameters of the hardening models were developed in order to establish accurate isotropic–kinematic hardening model describing the hardening behavior of 5754O aluminum alloy sheet under two-stage loading. The established constitutive models were implemented into the commercial FEM code ABAQUS as a user material subroutine (UMAT) for numerical simulations. By comparing the experimental and simulated results of the two-stage loading tests, the isotropic–kinematic hardening models describing the hardening behavior of 5754O aluminum alloy sheet under two-stage loading were accurately determined. Also, the influences of the characterization method of Hill48 yield function on the accuracy of the resulting hardening models were discussed. It is also found that the established isotropic–kinematic hardening model describing the hardening behavior under two-stage loading can describe reasonably the springback profile of the three point bending of the pre-strained specimen.

This paper examines non-isothermal warm forming experiments on AA7xxx-series channel sections at two different initial blank temperatures (187 and 253°C) with room temperature tooling. Supporting non-linear thermo-mechanical finite element simulations are performed, considering multiple stages comprising heating of the blank, transfer to the press, forming, dwell in die and cooling in air to room temperature. Elevated Twist Compression Tests are performed for the lubricant Forge Ease AL278 which allows characterization of friction coefficient as a function of temperature. Based on attached thermocouples during forming, thickness measurements and recorded force-stroke curves, the simulation model is validated. Furthermore, micro hardness measurements on the formed rail are performed to study the effect of heat exposure on the material strength.

The effectiveness of finite element simulation techniques for laser cutting of 1.2-mm-thick aluminium sheets has been studied. Lagrangian and Arbitrary Lagrangian-Eulerian techniques were used to model and simulate laser cutting process. The reliability of finite element results were evaluated by general energy balance analysis and experimental results. Temperature and stress distribution along with heat-affected zone were predicted during the laser-induced process in line with experimental conditions under ABAQUS finite element code. Heat transfer analysis relying on thermal loading was employed to reach the best efficiency. By using field-emission scanning electron microscope, morphological, structural, and elemental changes in the cutting sections were analyzed along with the X-ray diffraction technique. Obtained stress and heat-affected zone are highly dependent on the element type as well as numerical method. Both numerical method, ALE and Lagrangian, are compared to each other in terms of power absorption, cut surface morphology, and cutting efficiency. The results show that ALE method is in good agreement with experimental data.

The deformation behavior of 6000 series aluminum alloy sheets under biaxial tension was precisely measured for linear stress paths, using servo-controlled biaxial tensile tests with both cruciform and tubular specimens. The tubular specimens were fabricated by bending and laser-welding as-received flat sheet materials. Differential work hardening (DWH) behavior was observed; the shapes of the contours of the plastic work constructed in the principal stress space changed with an increase in plastic work. A new constitutive model that can reproduce the DWH behavior was proposed; the model is based on the Yld2000-2d yield function with the exponent and material parameters changing as functions of plastic work. Finite element analysis of hydraulic bulge forming was performed using both the proposed DWH model and the conventional isotropic hardening model based on selected yield functions. The calculated results based on the DWH model were in closest agreement with the experimental results. Thus, the new constitutive model has been verified to be effective for improving the accuracy of the FEA.

Automotive aluminum alloy sheet metal needs to improve the formability and the strength. In this study, the asymmetric rolling process was applied to the aluminum alloy sheet metal generation, because the {111}//ND texture, which corresponds to a part of the shear deformation texture, acts the high-formability. There are many processes of thermo-mechanical processes such as asymmetric and symmetric rollings and heat treatments in the sheet metal generation. We analyzed and optimized the microscopic texture evolution during plastic deformation in the macroscopic multi-stage warm rolling processes of the aluminum alloy sheet A6022 by using a crystallographic homogenized elasto/viscoplastic multi-scale finite element (FE) code and a discrete optimization method. In our multi-scale FE code, two scales ware considered. One is a microscopic polycrystal structure and the other is a macroscopic elastic plastic continuum. A three-dimensional representative volume element, which has initial crystal orientation distribution of the sheet metal is constructed by the electron back scattered diffraction measured pixel data. In order to evaluate the effect of temperature of warm rolling, a thermo-effect was introduced into the elastic/crystalline viscoplastic constitutive equation. Rolling parameters such as ratio of rolling speeds, rolling friction and the rolling temperature were optimized. We confirmed that Lankford value of the optimized sheet improved by 2-stage asymmetric rolling processes compared with commercial A6022-T43 sheet metal.

In this paper, the technology of self-piercing riveting (SPR) with half-hollow rivets was investigated using experiments and numerical simulations with 6063 aluminum alloy sheet. The failure mechanism of SPR aluminum alloy sheet was indicated with the shear model and tear model, which could accurately simulate the sheet structure. Based on the simulation results with finite element method (FEA), the effect of die geometry on static mechanical characteristics, including punch load, failure load and failure displacement, was analyzed. It was discovered that the die pip height and sheet thickness should be designed synthetically for optimal tensile behavior.

The accuracy of cup drawing simulation of aluminum alloy sheets strongly depends on the hardening and yield functions used in the simulation. In this study, stress-strain curves for an AA3104 aluminum alloy sheet were measured by uniaxial tensile and rolling tensile tests to identify parameters for various hardening functions. In addition, in-plane uniaxial tensile, biaxial tensile, and combined tension-compression tests were carried out to measure the successive contours of plastic work in the stress space and the directions of plastic strain rates under linear stress paths. The anisotropic coefficients, α 1-α 8, and exponent M of the Yld2000-2d yield function were determined so that the mean square error of the analytical yield locus from the measured plastic work contour was minimized. Finite element simulations of cup drawing of the aluminum alloy sheet were carried out using the determined parameters for hardening functions and the Yld2000-2d yield function implemented in LS-DYNA. By comparing the simulation results with the results of cup drawing experiments, the effects of the hardening functions on the accuracy of earing profile prediction were investigated.

The failure of AA3003 aluminum alloy sheet metal was predicted for non-isothermal viscous pressure bulging (VPB). Utilizing the coupled thermo-mechanical finite element method combined with ductile fracture criterion, the calculations were carried out for non-isotherm VPB at various temperatures and the influences of the initial temperature of viscous medium on failure mode of bulge specimens were investigated. The results show that the failure modes are different for the non-isothermal VPB with different initial temperatures of viscous medium. For the non-isothermal VPB of AA3003 aluminum alloy sheet with initial temperature of 250 °C, when the initial temperature of viscous medium ranges from 150 to 180 °C, the formability of sheet metal can be improved to a full extent. The validity of the predictions is examined by comparing with experimental results.

The applications of the aluminum alloy sheets to the auto-body panels are dramatically increasing for weight reduction of the automobiles. However, low formability of the aluminum alloy sheet compared to the steel sheet can be obstacles in tool manufacturing processes. Therefore, many of yield criteria for the anisotropic materials such as the aluminum alloy sheet have been observed. In this study, the biaxial tensile test and FLD test for the aluminum alloy sheet are performed. The results are compared with Hill’s 1948 and Hill’s 1990 models by means of theoretical predictions. Finite element analysis was also performed using the proposed method for the real panel. Key Words : Yield Locus, FEM, Aluminum Alloy Sheet 1. 서 론 정용한 심각한 환경오염과 자동차 수요의 급격한 증가에 따른 에너지 자원의 고갈로 인해 이미 선진국에서는 자동차 연비 및 배기가스의 규제를 한층 심하게 강화하고 있는 실정이어서 자동차 재료의 개발동기도 단순한 연비 향상이라는 수준을 넘어 환경규제에 따른 경쟁력 향상을 위한 새로운 기술개발이 자동차 산업에서 절실히 요구되고 있다. 특히, 소재의 경량화는 엔진효율을 높여 자동차의 성능향상을 극대화시키고 그로 인해 연비향상을 도모할 수 있어서, 결국 소재의 경량화는 환경오염방지와 연료절감에 가장 적합하고 효과적인 방법이다[1~4]. 자동차용 내외 판넬에 사용되는 판재의 경량화 추세에 대응하고 이에 따른 성형공문제점을최소화하기위해유한요소해석을이성형해석기술이자동차산업현장에서널리 이용되고 있다. 자동차용 판재 소재는 냉간 압연 제조공정에서 생산되기 때문에 소성 이방성 특성(anisotropic property) 을 갖는다. 이 소성 이방성 특성의 정확한 거동 묘사는 프레스 성형공정의 최적화에 필수적이며 다양한 소성이방성 모델이 제안되어 있다[5]. 일반 강판 성형해석에서 주로 사용되는 Hill’s 1948 이론[6]은 소성 이방성 계수 R값이 1.0보다 작은 비철금속에 대해서는 평면변형 인장과 등 2축 인장에서의 시험결과를 항상 과소평가 하는 것으로 보고되고 있다. 이런 비 정상거동(anomalous behavior)현상으로 인하여 성형해석이 까다로운 것으로 알려져 있다[7]. 비철금속의 비 정상거동을 예측하기 위해 비2차 평면 이방성

Micro-structured surfaces with drag reduction, desorption, and excellent optical performance are widely used in the field of automotive, aerospace, marine applications. Therefore, the manufacturing of the micro-structure on the metal surface is of high impotance. Although the processing methods for micro-patterning of surfaces have progressed in recent years, micro-structure processing is still not used on large metal surfaces. In this paper, a method of roll forming micro-structure on the plate surface is proposed. A simulation model for micro-structure roll forming (MRF) was presented by using three-dimensional finite element method (FEM). The strain and stress, and the displacements caused by micro-structure were analyzed. The results provide theoretical guidance for the design of different micro-structures and the sequence of their processing.

Basing on software MSC. Marc of non-linear finite element analysis, the article has studied the material flow in the process of aluminum alloy superplastic gas bulging forming. By analyzing of the thickness distribution of the molding member it confirm the danger zone in the forming process. By analyzing of pressure loading curve influence on forming part. Because the aluminum alloy is widely used in the industrial departments, it is supposed to improve the ability of forming ability of aluminum alloy by researching the superplastic forming.

Recently, the asymmetric rolling (ASR) process was applied to the aluminum alloy sheet generation to control the micro-crystal structure in order to improve the formability and the strength. Until now, many experimental and numerical studies of ASR process have been carried out, but these schemes have not enough capability to predict the texture evolution at the micro-scale and the sheet formability at the macro-scale. In this study, we develop a process metallurgy design code to analyze and optimize the sheet rolling process. At first, our dynamic-explicit crystallographic homogenized elasto/viscoplastic finite element (two-scale FE) code was applied to analyze ASR sheet deformation and optimized ASR process to generate a high formability sheet metal by employing the response surface method. A texture evolution of ASR sheet metal under an optimum process condition was compared with the experimental results, and the availability of our design code was confirmed. Next, an initial texture for the symmetrical warm rolling was optimized to generate a better formability sheet metal. Consequently, our two-scale FE code combined with the optimization algorithm was verified as a comprehensive tool in the process metallurgy design to predict plastic induced texture evolutions and optimize a rolling process and an initial texture for a high formability sheet generation.

The forming limit diagram (FLD) and forming limit stress diagram (FLSD) of aluminium alloy 1060 under linear and nonlinear strain paths are investigated. The calculation of FLSD is based on experimental FLD using the method proposed by Stoughton. Different from the FLD that varies with the strain path, the FLSD is not sensitive to the strain path. Therefore, FLSD is convenient as a forming limit criterion for multi-stage sheet forming. The influences of the material's yield criteria on FLSD are also discussed by comparison of the Hill's 48, Hill's 79 and Hosford non-quadratic criterion. The impacts of material hardening laws (Voce and Swift models) on translation of FLD and FLSD are analyzed. The Voce hardening law and the Hosford yield criterion are appropriate for the FLSD calculation of the aluminium alloy 1060. The stress calculation program and display interfaces of FLD and FLSD are developed on MATLAB, where the strain data can be input from experiment measurement or FEM calculations.

In this paper, the distribution of magnetic forces of uniform pressure coil and the electromagnetic shaping with die of aluminum alloy 1060 surface parts will be researched using the finite element method. The results show that: Uniform pressure coil can produce a uniform magnetic pressure on the sheet; The springback after electromagnetic aimed stamping is smaller than the springback after normal stamping; Before achieving the best results, with the discharge energy increases, springback will be smaller; with greater punch and die clearance, greater energy will be needed to achieve the best effect; Too large discharge energy will lead sheet bounce after punch, springback increases.

Bending of the aluminum alloy is one of the processes frequently applied during manufacture of aircraft sheet metal. The bending operation involves springback, which is defined as elastic recovery of the part during unloading. In manufacturing industry, it is still a practical and difficult problem to predict the final geometry of the part after springback and to design appropriate tools in order to compensate for springback. In this study, 3D commercially available finite element analysis (FEA) software-MARC is used to analyse bending and springback of different aluminium materials (LY12CZ) with different thickness. The amount of springback, total equivalent plastic strains and equivalent von mises stresses are obtained. Moreover, the relation between bent angle and springback angle, R/t ratio and springback angle are presented and discussed in detail.The comparison results of FEA result and experiment data indicate that the FEM (finite element analysis method) simulation is a power tool for the highly accurate prediction of springback behavior in sheet metal bending.

The sectional finite element analysis of the forming processes for the aluminum-alloy sheet metal known to be planar anisotropic was performed. The two-dimensional rigid-viscoplastic FEM formulation based on the bending augmented membrane theory as well as the anisotropic yield criteria was introduced. For modeling the anomalous behavior of aluminum-alloy sheet metals, Barlat's strain rate potential and Hill's (Journal of the Mechanics and Physics of Solids 1990;38:405–17) non-quadratic yield theory with an isotropic hardening rule were employed. Furthermore, a new method to determine anisotropic coefficients of Barlat's strain rate potential was proposed. For evaluating bending effects in the forming process of aluminum-alloy sheet metals, the bending equivalent forces were calculated in terms of the changes in the interior angle at a node between two linear finite elements and were augmented to the membrane stretch forces. In order to verify the validity of sectional finite element formulation based on the bending augmented membrane theory, the plane strain stretch/draw forming processes of a square cup test were simulated and simulation results are compared with experimental measurements. Friction coefficient was obtained from drawbead friction test. The properties of selected material were obtained from uniaxial tensile tests. Simulation shows good agreement with measurements. For the application of the sectional finite element formulation introduced in this research, the drawing process of a rear seat back upper bracket of passenger cars is simulated assuming plane strain condition. The thinning distribution of the simulation agreed well with that of the measurement, so that the sectional analysis is acceptable in the design and analysis of aluminum-alloy sheet stamping dies.

A so-called damage percolation model is linked with a finite element model of a sheet forming process to offer a comprehensive study of ductile damage evolution. In the current study, a damage percolation code is linked with LS-DYNA, an explicit dynamic FEM code used to introduce local strain gradients and compliance effects due to damage-induced softening. The linked model utilizes a Gurson-based yield surface to account for the softening effects of void damage, while the local damage development and void linkage events are modeled using the damage percolation code. The percolation code accepts detailed second phase particle fields from image analysis of a 2.0×1.6 mm optical micrograph of AA5182 aluminum alloy sheet. The model is applied to a stretch-flange stamping process which is known to be a damage-sensitive operation. The critical conditions for fracture are predicted for various initial stretch flange hole sizes.