Three-Dimensional Rigid-Plastic FEM Simulation of Bulk Forming Processes with New Contact and Remeshing Techniques

Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.

A NON－INCREMENTAL TIME－SPACE ALGORITHM FOR NUMERICAL SIMULATION OF FORMING PROCESS

A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphson counterpart, the present scheme features an iterative solution procedure on entire time and space domain. Validity and feasibility of foe present scheme are further justiced by the numerical investigation herewith presented.

The Design of a Graphical User Environment for Numerical Simulation of Powder Forming Processes

As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas es. A key component of an integrated environment is the use of computational eng ineering to assist and support solutions for complex design. Computer methods fo r structural, flow and thermal analysis are well developed and have been used in design for many years. Many software packages are now available which provi de an advanced capability. However, they are not designed for modelling of powde r forming processes. This paper describes the powder compaction software (PCS_SU T), which is designed for pre- and post-processing for computational simulatio n of the process compaction of powder. In the PCS_SUT software, the adaptive analysis of transient metal powder forming process is simulated by the finite element method based on deformation theories . The error estimates and adaptive remeshing schemes are applied for updated co -ordinate analysis. A generalized Newmark scheme is used for the time domain di scretization and the final nonlinear equations are solved by a Newton-Raphson p rocedure. An incremental elasto-plastic material model is used to simulate the compaction process. To describe the constitutive model of nonlinear behaviour of powder materials, a combination of Mohr-Coulomb and elliptical yield cap model is applied. This model reflects the yielding, frictional and densification char acteristics of powder along with strain and geometrical hardening which occurs d uring the compaction process. A hardening rule is used to define the dependence of the yield surface on the degree of plastic straining. A plasticity theory for friction is employed in the treatment of the powder-tooling interface. The inv olvement of two different materials, which have contact and relative movement in relation to each other, must be considered. A special formulation for friction modelling is coupled with a material formulation. The interface behaviour betwee n the die and the powder is modelled by using an interface element mesh. In the present paper, we have demonstrated pre- and post-processor finite elem ent software, written in Visual Basic, to generate the graphical model and visua lly display the computed results. The software consist of three main part: · Pre-processor: It is used to create the model, generate an app ropriate finite element grid, apply the appropriate boundary conditions, and vie w the total model. The geometric model can be used to associate the mesh with th e physical attributes such as element properties, material properties, or loads and boundary conditions. · Analysis: It can deal with two-dimensional and axi-symmetric applications for linear and non-linear behaviour of material in static and dyna mic analyses. Both triangular and quadrilateral elements are available in the e lement library, including 3-noded, 6-noded and 7-noded (T6B1) triangles and 4 -noded, 8-noded and 9-noded quadrilaterals. The direct implicit algorithm bas ed on the generalized Newmark scheme is used for the time integration and an aut omatic time step control facility is provided. For non-linear iteration, choice s among fully or modified Newton-Raphson method and quasi-Newton method, using the initial stiffness method, Davidon inverse method or BFGS inverse method, ar e possible. · Post-processor: It provides visualization of the computed resu lts, when the finite element model and analysis have been completed. Post-proce ssing is vital to allow the appropriate interpretation of the completed results of the finite element analysis. It provides the visual means to interpret the va st amounts of computed results generated. Finally, the powder behaviour during the compaction of a multi-level component is numerically simulated by the PCS_SUT software, as shown in Fig.1. The predict ive compaction forces at different displacements are computed and compared with the available experimental

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Studying Formability Limits By Combining Conventional and Incremental Sheet Forming Process

In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre-forming by conventional forming,followed by incremental sheet forming.The main objective is analyzing strain evolution.The pre-forming induced in the conventional forming stage will determine the strain paths,directly influencing the strains produced by the incremental process.To conduct the study,in the conventional processes,strains were imposed in three different ways with distinct true strains.At the incremental stage,the pyramid strategy was adopted with different wall slopes.From the experiments,the true strains and the final geometries were analyzed.Numerical simulation was also employed for the sake of comparison and correlation with the measured data.It could be observed that single-stretch pre-strain was directly proportional to the maximum incremental strains achieved,whereas samples subjected to biaxial pre-strain influenced the formability according to the degree of pre-strain applied.Pre-strain driven by the prior deep-drawing operation did not result,in this particular geometry,in increased formability.

基于Simufact Forming的半空心铆钉自冲铆接参数对铆接成形的影响研究

以1.5 mm+1.5 mm A6062铝合金为研究对象,结合单一变量设计法进行参数组合,使用Simufact forming有限元软件对铆接过程进行模拟仿真,主要研究了凹模深度、凹模凸台高度、冲头速度3个工艺参数对半空心铆钉自冲铆接成形的影响,及参数对几何特征量的影响趋势,为半空心铆钉自冲铆接工艺参数进一步优化提供有益的借鉴。

基于Dynaform的冲压成形工艺因素影响分析

文章结合生产中的实际需要,利用Dynaform软件对某汽车横梁的冲压成形过程进行了数值模拟分析。根据成形零件的质量评价指标,分析压边力、冲压速度、摩擦系数和拉延筋参数变化对冲压件质量产生的影响。在分析过程中较多参数影响导致结果不好,验证开发周期。利用MDO(multidisciplinary design optimization)技术对零件在冲压成形过程中遇到的质量问题,为冲压件工艺设计、模具设计提供设计方案,可以达到有效缩短模具设计及生产调试周期的目的。

基于Dynaform的加油口盒成形工艺分析及优化

依靠经验对外形复杂、需要多次拉延才能成形的汽车覆盖件进行模具及工艺设计困难而效率低。基于板料成形模拟软件Dynaform,对某轿车加油口盒的一次拉延可成形性进行了模拟分析。预测该零件在一次成形过程中存在缺陷,由此提出二次拉延成形的工艺方案。针对零件在成形过程中容易出现拉裂和起皱的部位,进行了工艺优化和模拟验证,获得了满意的工艺方案,对该类零件模具工艺设计具有指导意义。

采用Deform 3D对2A12铝合金锻造变形的模拟研究

锻模模膛的充填能力是锻模设计的关键,它直接影响锻件的质量及锻模的质量与寿命。本文针对锻模模膛充填困难的特点,以2A12铝合金为研究对象,以棒料模锻后的充填高度为控制目标,采用有限元数值模拟试验,模拟了模锻过程,分析坯料的变形行为,讨论了变形过程中坯料的温度变化情况、整体应力的分布和变化情况。

基于DYNAFORM制动壳体件首次拉深成形仿真及模具设计

制动壳体是典型的拉深成形零件,基于DYNAFORM软件对制动壳体首次拉深进行成形过程模拟,并对其工艺参数进行优化。根据优化结果设计出首次拉深模具,进而组织生产。将首次拉深后的毛坯与仿真优化结果比较,二者吻合程度较高。基于DYNAFORM软件进行成形过程仿真,提高了一次产品设计成功率,减少了试模次数。

基于Dynaform的微波炉外壳成形仿真分析与模具设计

针对微波炉外壳冲压时易破裂和回弹的缺点,利用有限元建立了壳体模型及Dynaform软件对冲压过程中板料流动进行了数值仿真,分析并优化了成形工艺参数,在此基础上设计了模具。试模结果表明,工艺参数设置合理,仿真分析结果与实际冲压结果吻合,生产的零件满足了客户使用要求。

采用Deform-3D对5083铝合金车轮锻造过程的模拟研究

利用Deform-3D有限元仿真软件,实现了5083铝合金车轮模锻件在预锻、终锻整个成形过程的数值模拟,分析了预锻、终锻过程中应力和应变分布、载荷计算、材料流动速度及温度场的变化情况,为模具及成形设备的设计提供了可靠依据。经生产实践验证表明,预锻模和终锻模设计合理,锻压工艺适宜。

基于Autoform的铝合金引擎盖成形模拟及优化

基于板料成形数值模拟软件Autoform,采用轻量化铝合金成形某车型引擎盖外板,并进行模拟及优化,以成形极限图、减薄率等为优化目标,对相关工艺参数进行调整,优化成形工艺参数与模面形状,可为相关企业的铝合金引擎盖生产提供参考,推进铝合金外覆盖件在汽车轻量化中的应用。

基于Dynaform的汽车零件冲压成形模拟的研究

在Dynaform软件中,对汽车某冲压件进行冲压模拟分析,提出了具有圆滑特点的工艺补充面的设计思想,有效改善板料在凹模内流动情况,避免拉裂等缺陷产生。通过反复的工艺修改、比较及重分析,确定了合理的工艺补充面及拉延筋的布置形式,仿真计算结果满意。为实际生产提供参考,证明了仿真设计方法的实用性。

基于DYNAFORM叶轮前盖板拉伸成形的数值模拟研究

基于板料成形有限元分析软件DYNAFORM,对不同厚度的叶轮前盖板拉伸成形进行数值模拟,分析板料在不同厚度下的应力、厚度、压边力变化情况。结果表明:板料的相对厚度t/D越大,危险区域所受的应力越小,对拉伸有利;在板料拉伸过程中,压边力的平衡状态不随板料厚度变化而变化,基本保持一稳定的值。叶轮前盖板拉伸成形研究对冲压泵制造具有一定的指导意义。

基于DEFORM的索具接头内孔反挤压成形数值模拟

为研究索具接头内孔挤压成形的可行性,采用有限元方法对索具接头内孔热挤压成形工艺进行了数值模拟分析。从金属流动规律及金属的流线分布两方面分析了索具接头内孔的成形性,并研究了不同挤压条件下索具接头的应力场、应变场及成形件晶粒大小的关系。确定了热挤压工艺参数:初始挤压温度为1 100~1 150℃,挤压速度为10mm/s。通过有限元分析研究得出,内孔成形挤压后金属流线分布合理,无明显交叉、断裂的情况,且成形效果较好,尺寸精度较高。因此,该索具接头内孔热反挤压成形工艺切实可行。

基于Autoform的汽车左右侧围内板前段成形的数值模拟

利用Autoform软件对汽车左、右侧围内板前段进行模拟分析,在压边力、拉深筋等因素已确定的条件下,对板料成形过程中的各个工序进行数值模拟,通过对所得到的成形极限图、厚度减薄率等性能参数的分析,判定各成形工序的合理性,最终确定最优的成形工艺。

基于DEFORM-3D的摩托车消声器尾盖锻压成形分析

利用Deform 3D有限元软件对某越野摩托车消声器的尾盖锻压成形过程进行了数值模拟分析,通过网格划分、有限元方法(FEM)求解器以及点追踪等模块功能的应用,对锻压过程中的速度、应力和应变进行分析,从而得到金属成形过程的流动规律、力学场分布情况以及存在的问题。

基于Dynaform的一种零件连续翻边成形方法

金属板料的翻边成形是板料成形的重要组成部分,也是板料成形中的难点。重点研究折弯并向内的翻边结构,通常采用的成形工艺是先折弯成形后凸缘面翻边成形,通常产生的成形缺陷是凸缘部位产生起皱。利用Dynaform软件,以某企业的家用电器后壳为例,主要针对折弯并向内的翻边结构进行数值模拟,研究成型缺陷并确定合理的成形工艺,以改善成型结果。

Influence of a multi-step process on the thickness reduction error of sheet metal in a flexible rolling process

Flexible rolling is a forming process based on thickness reduction, and the precision of thickness reduction is the key factor affecting bending deformation. The major purpose of the present work is to solve the problem of bending deformation error caused by insufficient thickness reduction. Under the condition of different rolling reductions with the same sheet thickness and the same thickness reduction with different sheet thicknesses, the thickness reduction error of sheet metal is analyzed. In addition, the bending deformation of sheet metal under the same conditions is discussed and the influence of the multi-step forming process on the thickness reduction error is studied. The results show that, under the condition of the same sheet thickness, the thickness reduction error increases with increasing rolling reduction because of an increase in work hardening. As rolling reduction increases, the longitudinal bending deformation decreases because of the decrease of the maximum thickness difference. Under the condition with the same thickness reduction, the thickness reduction error increases because of the decrease of the rolling force with increasing sheet thickness. As the sheet thickness increases, the longitudinal bending deformation increases because of the increase in the maximum thickness difference. A larger bending deformation is divided into a number of small bending deformations in a multi-step forming process, avoiding a sharp increase in the degree of work hardening; the thickness reduction error is effectively reduced in the multi-step forming process. Numerical simulation results agree with the results of the forming experiments.