坯料外形对镁合金矩形盒拉深成形的影响

坯料外形的确定是镁合金矩形盒拉深成形的一个重要问题。本文利用MSC．Marc有限元软件模拟了在同一套模具和成形条件下，采用不同外形坯料时镁合金矩形盒的拉深成形过程，依据数值模拟结果分析了不同坯料外形对镁合金矩形盒拉深成形的影响，结果表明矩形圆角坯料较其他坯料的成形性能好。此外，通过实验论证了有限元模拟的可靠性。     

热轧AZ31镁合金薄板的室温成形性

针对AZ31镁合金板材室温冲压成形较差的特点,采用不同轧制温度获得镁合金板材,使用半球形凸模胀形,绘制镁合金室温成形极限图并分析轧制温度对镁合金板材组织和室温成形能力的影响.发现AZ31镁合金板材的成形性能不仅与晶粒尺寸有关,还与晶粒取向有关.基面织构的减弱可明显提高板材的胀形性能,在基面织构强度相似的情况下,晶粒尺寸对板材的成形性能起决定性影响.      

有限元分析锥台转角对镁合金板材成形性的影响

采用锥台剪切变形新工艺制备镁合金板材,通过DEFORM-3D软件进行有限元模拟仿真,分析了锥台转角对锥台剪切变形镁合金板材成形性的影响,数值模拟了105°,120°,135°和150°4种不同锥台转角的模具对挤压镁合金板材的平均应力、等效应变、金属流速的影响规律。研究结果表明:不同锥台转角对挤压板材成形性能有着显著影响。当锥台转角逐渐增加时,锥台转角为120°的挤压模具,挤压后板材上拉应力出现的比例最小。随着锥台转角的增大,挤压后板材的等效应变随之减小,由2.63减小至1.88,但在锥台转角为120°时等效应变分布相对其他锥台转角较均匀。增加锥台转角,金属流速在120°时相对均匀,其不均匀程度参数值为0.007。此外,实验验证了锥台转角为120°时,锥台剪切变形镁合金板材表现出优越的成形性。     

基于正交试验的汽车油箱底壳的成形分析

以汽车油箱底壳为研究对象,利用有限元仿真软件建立了油箱底壳冲压成形的有限元模型,并进行拉延数值模拟;对压边力、摩擦系数、屈服强度、抗拉强度、n值、r值等6个因素进行正交试验设计,并通过仿真软件进行模拟分析,确定了6个因素对本零件冲压成形质量的影响程度;并对数据对比分析,找到了最优的材料工艺参数组合,为实际生产质量合格的产品提供科学依据。     

ZK60合金多道次ECAP晶粒组织模拟和实验分析

采用刚粘塑性有限元软件对ZK60合金四道次等通道转角挤压(ECAP)过程进行数值模拟。对一至四道次ECAP试样进行晶粒组织模拟,观察晶粒细化程度的分布和变化规律。通过多道次ECAP实验,利用金相显微观察试样头部和尾部的晶粒尺寸的变化以及动态再结晶形成机理。对比有限元数值模拟与实验组织分析结果,探索利用有限元模拟与实验分析相结合的方法,研究镁合金ECAP成形过程的晶粒组织变化规律。     

钢丝拉拔过程损伤模型及模拟计算

  为研究材料拉拔成型过程中的损伤问题,以1860MPa级PC钢绞线为研究对象,运用损伤力学理论分析了钢丝拉拔成形过程,采用ABAQUS软件建立了钢丝拉拔成形过程的材料损伤有限元模型,并利用该有限元模型计算了拉拔形变过程中材料损伤的演化规律。计算结果表明,钢丝经单道次拉拔形变后,材料损伤值呈周期性分布,其损伤最大值始终出现在某几个节点上。随着形变量增加,钢丝损伤值也逐渐增加,从第1道次的0.0034逐渐增加到第8道次的0.0136,但增加的幅度逐渐减小。对于模具顶角为8°钢丝拉拔,单道次压缩率为16%～18%,损伤分布也较均匀,最大损伤值也较小。     

铝合金在两种应力状态下损伤的有限元模拟

通过对铝合金（6063）进行缺口拉伸及纯剪切试验，研究了铝合金在这两种应力状态下的损伤没断裂机制。研究结果表明：缺口拉伸试验中，缺口根部产生相对较高的三轴应力，随着应力的不断升高，微孔洞的体积分数不断增大。当达到材料的临界孔洞体积分数时，试样断裂；纯剪切试验中，在材料内部几乎没有产生微孔洞而产生了剪切带。显微裂纹首先在剪切带中产生，随着裂纹的进一步扩展，最终导致试样断裂；用改进的Gurson模型和Johnson-cook模型分别模拟缺口拉伸和纯剪切试验，横拟的工程应力-应变曲城与试验的工程应力，应变曲线符台得很好。另外根据有限元模拟和试验数据还得出了6063（T6）铝合金缺口试样中微孔洞损伤的经验演化方程。     

数值模拟在汽车板成形中的应用

在汽车和冶金工业中,板成形数值模拟广泛地应用于零件的选材和模具的设计.文章论述了板成形数值模拟的基本方法及其发挥的重要作用,并采用动力显式有限元软件DYNA3D对轿车顶板的冲压成形过程进行仿真计算,分析了成形安全裕度.     

中厚板轧制过程的数值模拟分析

在中厚板轧制成形过程中采用有限元方法进行数值模拟分析可以为实际生产提供合理的工艺参数，便于延长轧机的寿命。提高产品质量和减少试错过程的消耗等。文中阐述了利用有限元软件对中厚板轧制成形过程的非线性数值模拟分析中的一些广为关心的问题，包括：摩擦力在轧件表面的分布情况以及摩擦力大小对轧制过程的影响；材料的等向强化模型、运动强化模型和混合强化模型对中厚板轧制过程的影响；热一力耦合对厚板轧制成形过程的影响及其数值模拟分析方法。     

钨铜粉末轧制的有限元模拟研究

选用Drucker-Prager/Cap模型来描述钨铜粉末的轧制变形行为,建立钨铜粉末轧制有限元模拟模型。利用Abaqus有限元分析软件研究钨铜粉末轧制成形过程中轧辊辊缝、轧制速度和轧制温度等工艺参数对板材相对密度的影响,并将模拟结果与粉末轧制实验结果进行对比。结果表明:钨铜合金粉末轧制过程中,轧辊辊缝越大,轧制所得板材的相对密度越小,密度分布越均匀;轧制速度越快,板材的相对密度越小,边缘低密度区域越小,密度分布越均匀;轧制温度越高,板材的相对密度越大,粉末流动性越好。将模拟结果和实验结果对比,两者基本一致,最大误差为4.1%,表明有限元模型的可靠性。     

A numerical and experimental study of deformation characteristics of the plane strain punch stretching test

Recently, a simple new test method called the plane strain stretching (PSS) test has been developed to evaluate the stamping formability of sheet materials. The PSS test has been proven to have good reproducibility and show good correlation with press performance. In order to clarify the deformation characteristics of the PSS test and investigate the effect of material and process variables on the performance of the PSS test, three-dimensional finite element simulations for the PSS test were performed and the results compared with experiments.     

Application of Taguchi Method on Biaxial Stretch Forming of Friction Stir Processed Mg AZ31B Alloy

The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.     

A plane strain punch stretching test for evaluating stamping formability of steel sheets

A simple simulative test was developed to evaluate the stamping formability of steel sheets in plane strain stretching deformation. The stamping formability was evaluated by the limiting punch height (LPH) value in the plane strain punch stretching (PSS) test compared to the minimum of the limiting dome height (LDHo) value in the hemispherical punch stretching test, the standard LDH test. The PSS test shows a stable plane strain deformation and a good reproducibility with less scattering data. Moreover, the LPH value in the PSS test ranks well the stamping formability of various sheet materials and shows good correlations with press performance. Formerly Head, Metal Forming Research Laboratory, Research Institute of Industrial Science and Technology     

Incremental Sheet Metal Forming: Numerical Simulation and Rapid Prototyping Process to make an Automobile White‐Body

In order to make an automobile body structure, incremental sheet metal forming is introduced as a rapid prototyping process. Numerical modeling of the process is initially used to predict the deformation of the sheet metal to avoid failure during the incremental forming process using ABAQUS/Explicit finite element code and OYANE's ductile fracture criterion via a VUMAT user material. An automobile CAD model is then designed, and segmented into several parts in order to accommodate the working space of the CNC machine and formability of sheet metal. After that, CAM software is used to generate a tool‐path for making wooden‐dies and all small parts. Finally, a welding process is applied to join all parts which were cut by laser cutting after incremental sheet forming process.     

Experimental and Numerical Study of Electromagnetic Forming of AZ31B Magnesium Alloy Sheet

Wrought magnesium alloys are interesting materials for automotive and aeronautical industries due to their low density in comparison to steel and aluminium alloys, making them ideal candidates when designing a lower weight vehicle. However, due to their hexagonal close‐packed (hcp) crystal structure, magnesium alloys exhibit low formability at room temperature. For that reason, in this study a high velocity forming process, electromagnetic forming (EMF), was used to study the formability of AZ31B magnesium alloy sheet at high strain rates. In the first stage of this work, specimens of AZ31B magnesium alloy sheet have been characterised by uniaxial tensile tests at quasi‐static and dynamic strain rates at room temperature. The influence of the strain rate is outlined and the parameters of Johnson‐Cook constitutive material model were fit to experimental results. In the second stage, sheets of AZ31B magnesium alloy have been biaxially deformed by electromagnetic forming process using different coil and die configurations. Deformation values measured from electromagnetically formed parts are compared to the ones achieved by conventional forming technologies. Finally, numerical study using an alternative method for computing the electromagnetic fields in the EMF process simulation, a combination of Finite Element Method (FEM) for conductor parts and Boundary Element Method (BEM) for insulators, is shown.     

基于Drucker-Prager/Cap模型的W–Cu20粉末轧制数值模拟

将Drucker-Prager/Cap塑性模型引入到高硬度W–Cu20粉末轧制有限元分析中,利用巴西圆盘试验、单轴压缩试验以及模压试验得到Drucker-Prager/Cap塑性模型参数,借助商业有限元软件ABAQUS以及Fortran自编的VUSDFLD子程序,建立粉末轧制的有限元模型,并与实际试验进行了比对。结果表明:模拟结果中的板料相对密度和板料厚度与实际实验结果吻合较好,最大误差为4.47%,说明Drucker-Prager/Cap塑性模型对粉末轧制工艺研究有参考意义。     

Nonisothermal punch stretching: Measurements and finite element modeling simulations

In order to investigate the role of thermal effects in punch stretching, a simple nonisothermal forming operation was carried out and was simulated using finite element modeling (FEM). A heated hemispherical punch deformed a steel sheet which was fully clamped between room-temperature circular dies. Strains were measured at standard punch heights for comparison with FEM-simulated ones. The strain distributions were in reasonable agreement, and the qualitative changes in the distributions with punch temperature were predicted very well by the simulations. The form of the nonisothermal FEM formulation was verified by these agreements. Increased punch temperature improves formability by lowering the peak strain in the punch-sheet contact region. Nonisothermality can play a significant role in distributing strains throughout a deforming sheet under conditions similar to these. S. LATREILLE, formerly Granduate Student, The Ohio State Univerity     

A better sheet formability test

A new test for sheet metal formability was designed, constructed, and used to evaluate several coated and uncoated sheet materials. Results from the OSU Formability Test were also compared with standard limiting dome height (LDH) tests and with finite element simulations. These results show that the new test is more reproducible, even using relatively uncontrolled equipment, more closely follows the desirable plane-strain path, and takes roughly one fifth of the time to perform relative to LDH. Moreover, there is good correlation between formability evaluated using the two tests. Strain measurements and finite element simulations revealed that the improvements are a result of the new test geometry, which produces more stable and repeatable plane-strain states near the fracture location. Formerly Graduate Research Assistant, The Ohio State University Formerly Postdoctoral Researcher, The Ohio State University     

The use of the finite-element method to design an optimized tool for the plain-strain punch stretching test

The tool geometry of the plane-strain punch stretching (PSS) test was optimized by computer simulation to assure test reliability. A three-dimensional, finite-element method (FEM) was used to optimize the three design variables: the punch length, punch crown, and punch corner radius. Experiments confirmed the plane-strain condition predicted by experiment. From this simulative study, we can conclude that the optimized punch shape of the PSS test, with ellipsoidal shape, exhibits stable performance when evaluating the stamping formability of sheet materials. Clearly, the optimized punch geometry with a punch crown of 3 mm, punch corner radius of 6 mm, and punch length of 72 mm shows better reliability compared with that of the original PSS test.     

铍板材深冲压成形异形件探讨

冲压成形是金属板材加工异形件的最基本方式。金属材质不同,冲压成形异形件的难易程度不同,主要影响因素是冲压成形性能和冲压成形极限。文章结合铍板材的冲压成形性能和冲压成形极限,对铍板材冲压成形异形件的难易性作了探讨。