Tool and process design for progressive forming of an automotive bracket part using finite element analysis

This paper deals with the design procedure of the tool and process for automotive bracket part fabrication. Finite element analysis is introduced to the progressive process to investigate the causes of defects that occur during the forming and bending stages. This paper proposes a new guideline for the progressive process design that modifies the intermediate stages in the progressive process. Finite element analysis and pilot tests are performed again using new strip layout and tool shapes to confirm the validity of the proposed process design. The analysis result shows that the modified process design eliminates defects such as non-uniform thickness distribution and initiation of crack. Then, the automotive bracket part is successfully fabricated through pilot tests using the progressive tools designed in accordance with the proposed guideline.     

Three-dimensional finite element analysis of multi-stage hot forming of railway wheels

Three-dimensional finite element analyses has been carried out using DEFORM 3D software on multi-stage hot forming of railway wheels involving the processes of upsetting, forging, and punching of wheels. Thermal analysis related to heating the blank in furnace and all intermediate heat transfer stages between deforming operations have been conducted. Rigid viscoplastic finite element method has been utilized for coupled thermo-mechanical analysis of the processes. Modeling of punching the wheel bore has been carried out using Cockcroft and Latham fracture criterion. Evolution of thermo-mechanical parameters at selected points within the workpiece has been studied in detail. The method of simulating the effects of various process parameters has been explained using relevant mathematical relations. This study shows that design, optimization, and analysis of process perturbations for multi-stage railway wheel manufacturing process can be done efficiently in three-dimensional finite element simulations instead of conventional time and cost intensive trials. It might be necessary to use the results of finite element analysis in shop-floor to enhance productivity and reduce wheel rejection.     

Strain gradient plasticity based finite element analysis of ultra-fine wire drawing process

Steady-state rigid-plastic finite element analysis coupled with strain gradient plasticity theory has been performed to examine the size effect of material on its plastic deformation behavior and find an optimal semi-cone angle of die which minimizes the drawing energy in the ultra-fine wire drawing process. A stream-line tracing method was adopted to calculate strain component at each element and a strain surface function was introduced to compute the equivalent strain gradient of each element. Introduction of this function enables us to use an established FE code without renewal of its main structure. Hence, the constitutive equation in FE formulation is changed to couple the strain gradient plasticity. A series of FE simulation reveals that significant differences in drawing stress are observed when material size approaches its intrinsic material length. When the strain gradient plasticity theory is reflected on the steady-state FE analysis, the optimal semi-cone angle of the die is reduced by 30%. The variation of optimal semi-cone angle is attributable to considerable increment of homogeneous deformation when the material size reaches its intrinsic material length.     

Dynamic analysis of electromagnetic sheet metal forming process using finite element method

This paper presents a simple and efficient method for the analysis of dynamic behavior of the workpiece in the electromagnetic forming process. A two-dimensional (2D) axisymmetric finite element model with the equations of electrical equivalent circuit, electromagnetic field, and mechanical field has been developed for calculating the discharge currents through the forming coil, the magnetic forces acting on the workpiece, and the plastic deformation of the workpiece. By considering the effects of the sheet geometry and velocity on the above parameters, the method realizes the full coupling between the electromagnetic fields and the workpiece deformation, which should be more accurate than the existing loose coupling and sequential coupling simulation methods.     

Phase transformation-based finite element modeling to predict strength and deformation of press-hardened tubular automotive part

In this paper, a new tool design for hot stamping taking advantage of both direct quenching and indirect die quenching is proposed to fabricate the coupled torsion beam axle which is formed from the original tubular-shaped part. This newly proposed hot stamping applies spray of the water before the upper die gets into contact with the tubular part, which significantly enhances the cooling capacity. For other region that cannot be covered by the direct spray, the conventional die quenching method in direct hot stamping process is used. Moreover, for the analysis of the deformation behavior during the proposed hot stamping process, the finite element analysis, which takes the deformation and strengthening induced by the cooling and phase transformation into account, has been carried out. From the analysis, the larger shape change when the cooling time is shorter than 15 s could be explained by the incomplete martensitic phase transformation and phase transformation plastic strain. When the cooling time is short the residual stress after cooling is much higher than those for the longer cooling times.     

Analysis and design of flat-die hot extrusion process 1. Three-dimensional finite element analysis

Non-steady-state-coupled three-dimensional analysis is required for investigating complex material flow in practical flat-die hot extrusion processes of aluminum alloys in various channel sections. It is important since the material flow behavior actually determines the amount of distortion of the extruded product. Thus, a non-steady thermo-rigid-viscoplastic finite element program was developed for numerical simulations of the process. Since severely deforming elements of the workpiece can easily interfere with the sharp edges of the flat-die, an automatic remeshing module based on a simple section-sweeping scheme and new contact algorithm were incorporated to allow continuous simulation without manual intervention with less volume loss and computation time. With developed finite element program, non-steady finite element analyses of extrusion processes were carried out for two types of channel-section with constant bearing length of 5 mm. From simulation results, it was found that the exit velocity of the workpiece varied depending on the cross-sectional thickness of the exit and the amount of deflection of the workpiece was not greatly affected by variations of either the workpiece temperature or punch velocity under the present simulation conditions.     

Finite element analysis of the effects of martensitic phase transformation in TRIP steel sheet forming

This paper aims at investigating the effects of the martensitic phase transformation on the formability of unstable austenitic steel sheets. To this end, the constitutive model developed by Iwamoto and Tsuta (International Journal of Plasticity 2002;18:1583–606) has been implemented in the user's material subroutine of the finite element code Abaqus/Explicit. The different contributions of the martensitic transformation to the overall plastic behaviour are analysed with the aim of assessing their influence in sheet-metal forming. The effects of transformation strains, and of the stress-state dependence of the kinetics of phase transformation are critically discussed in the case of the cup drawing test. The simulation results are also compared with experimental cup tests from the literature.     

Research on the influence of hot stamping process parameters on phase field evolution by thermal-mechanical phase coupling finite element

In order to study the effect of austenitizing temperature and packing time on phase evolution more accurate, a coupling element finite model of hot stamping process of BR1500HS is established based on the platform of DEFORM-3D, which takes the interaction of heat, plastic work, and phase transformation into consideration. The simulated results reveal that the final microstructure mainly consists of martensite, and the martensite volume fraction increases at an austenitizing temperature range from 800 to 900 °C and has a little change with the increasing packing time. Subsequently, a series of physical experiments are conducted to evaluate the reliability of the simulated results. The micrographs show that influence of the austenitizing temperature and packing time on martensite volume fraction is consistent with the simulated results. Further, the tested hardness distribution also proved that the present thermal-mechanical phase coupling element finite model is an effective tool to predict the microstructure during the hot stamping process.     

Investigation on chatter stability of thin-walled parts considering its flexibility based on finite element analysis

High-speed milling of thin-walled part is a widely used application for aerospace industry. The low rigidity components, large quantities of material removed in machining progress, are in the risk of the instability of the progress. In this paper, the thin-walled parts have the similar characteristics with the tools. Therefore, the dynamic model and the stability critical condition determined by the relative dynamic behavior between tool subsystem and workpiece subsystem are put forward. The thin-walled parts’ dynamic character varies greatly with time when machining. The whole workpiece has been divided into several stages by finite element analysis (FEA) so that its various modal parameters in the milling progress can be obtained gradually; thus, the variation due to metal removal has been accurately taken into account. The stability critical condition is predicted by frequency domain method based on the dynamic behavior of the two subsystems. With the respect to time-varying critical stability condition, a three-dimensional lobe diagram has been developed to show the changing conditions of chatter. Finally, the proposed methods and models were proven by series milling experiments.     

Study of void closure in hot radial forging process using 3D nonlinear finite element analysis

Hot radial forging is used to reduce porosity and increase strength for large-diameter billets. The goal of this research is to study void closure behavior in the hot radial forging process. A nonlinear coupled finite element model is developed to investigate the deformation mechanism of internal void defects during the hot radial forging process. The model is formulated in a three-dimensional frame and a viscoplastic material model has been used to describe the material behavior subjected to large deformation and high temperature. A global–local technique is employed to obtain accurate solutions around the void region. The effects of void location, mandrel, die shape, and the reduction of the tube thickness on the final void reduction are systematically investigated. The predicted reductions for central longitudinal voids in hot upsetting and hot rolling processes are in good agreement with experimental findings. The simulation results provide a valuable procedure for the design of porosity reduction during the hot radial forging process.     

Light-weight design and fatigue characteristics of automotive knuckle by using finite element analysis

Journal of Mechanical Science and Technology - In order to reduce automobile operating costs and solve environmental problems, it has recently become an important issue to lightly design a vehicle...     

隔离体法在有限元接触分析中的应用

这里针对施加初始预紧力时超高压密封容器有限元整体接触计算不收敛的情况,给出一种近似的计算思路—隔离体法。运用此方法,建立了该容器密封接触计算的等效隔离体模型,并运用有限元软件对该模型进行了计算,同时利用密封线比压判断准则对计算结果进行等效判断。经工程试验验证,计算结果合理,表明该近似方法的有效性。     

框式热压机机架有限元分析及结构优化设计

针对某型号框式热压机的框形板上横板与侧板拐角处发生断裂这一问题,利用Pro/E软件建立了热压机机架结构参数化模型,运用ANSYS软件时其机架进行有限元分析,找出了原结构设计存在的问题.在机架满足具有足够的强度和刚度的前提下,以机架结构的质量最轻为目标,对热压机的机架进行了结构参数优化设计.优化后的框架结构与原结构相比,使热压机质量减轻了约9%,最大应力降低了约23%,获得了较为理想的结构和尺寸,实现了增加热压机的使用寿命及降低制造成本的目的.     

Finite element analysis and design optimization of low plasticity burnishing process

In the present study, Low Plasticity Burnishing (LPB®) process on the half-space specimen has been simulated using a 3D explicit nonlinear finite element model. The developed finite element model is then used to investigate the effect of main parameters including ball diameter, burnishing force, burnishing feed, and number of passes on the resultant profile of residual stress and plastic deformation. Due to high computational cost associated with the nonlinear finite element model and in order to practically conduct design optimization of the LPB process, the design of experiment combined with the response surface methodology has been used to develop smooth response functions to efficiently and accurately approximate the residual stress profile and plastic deformation over the entire design space. Finally in order to improve the LPB process, a design optimization using the developed response functions has been formulated to obtain the optimum set of parameters such that a deep residual compressive stress with small plastic deformation is generated throughout the thickness of component.     

Three-dimensional thermo-elastic–plastic finite element modeling of quenching process of plain-carbon steel in couple with phase transformation

This study focuses on finite element investigations of quenching process which is commonly applied to improve mechanical properties such as strength, hardness, and wear/fatigue resistances, etc. During the quenching process, various kinds of microstructures evolve depending on the cooling rate and temperature variation within the steel. This microstructural evolution has a significant effect on the final dimension and geometry of the mechanical parts. In order to investigate the effect of temperature variation and phase transformation on the dimensional change and stress distribution, thermo-elastic–plastic constitutive equation coupled with the mechanical strain, thermal strain, phase transformation strain, and transformation induced plasticity is described in detail. Using the constitutive equation introduced, a finite element program was developed and used to predict distributions of the temperature, volume fraction of each phase transformed, and stress and dimensional change of the cylindrical specimen, shaft with key groove, and cam-lobe made of carbon steel. It was found out that numerically obtained values such as temperature history and stress distribution were in good agreement with the data available in the literature for the cylindrical carbon steel specimen. The developed program can be used for better understanding of mechanics involved with the quenching process.     

Predicting the hardening depth of a sprocket by finite element analysis and its experimental validation for an induction hardening process

Journal of Mechanical Science and Technology - Case hardening, or surface hardening, is the process of hardening of a metal object at its outer surface while allowing its core to remain relatively...     

热流道板的热平衡及温度场的有限元分析

热平衡是热流道系统的核心问题之一,热流道板的主要任务是恒温地将熔体从主流道送入各个单独喷嘴.热流道板必须处于热平衡状态,热损失必须通过加热来补偿.通过分析热流道板的热损失,进行加热器功率的计算,并利用ANSYS软件分析热流道板的温度场.     

新型线香机的设计及零件的有限元分析

在新型线香机的制香过程中,压香板是极其重要的部件之一,其挤压力和强度直接影响整个制香的生产过程。在分析了传统制香方法特点的基础上,对新型线香机挤压零件在工作过程中受到的应力进行分析研究,利用Soild Works软件建立新型线香机三维实体的虚拟样机,并对线香机的重要零件压香板进行有限元分析。研究结果表明,通过对比三种不同结构压香板的应力云图,球形结构的压香板的最大应力都有较大的减小,从而确定新型线香机重要零件压香板的理想的结构形状,有效地降低了制香过程中压香板的受力大小,提高了压香板的使用寿命。     

波形腹板梁结构研究及其有限元分析

这里提出了桥式起重机的箱型主梁的新型波形腹板结构的设想,并在充分比较和论证的基础上提出了以正弦曲线波形作为腹板的波形。利用大型有限元软件ANSYS对新型腹板和原来的平直腹板进行了综合比较分析,等效应力比原来腹板减少50％左右,说明波形腹板梁的受力情况更好。     

基于接触有限元的预紧组合机架力能分析

针对高频次工作下的陶瓷砖液压机预应力组合机架的整体性以及零部件的疲劳寿命要求高等问题,利用接触有限元方法,建立了能考虑各个零件摩擦接触关系的32 MN液压机预紧组合机架网格模型。通过数值分析结果验证了机架预紧系数的合理性。通过对机架在预紧状态以及工作状态下的VonMises应力场和最大主应力场的分析,确定了机架中易产生疲劳破坏的薄弱区域。分别计算了预紧状态下和工作状态下的机架弹性变形能。研究结果表明,上、下横梁的弯曲弹性变形能是机架能耗的主要部分,该研究结果可以为陶瓷砖液压机的机架结构设计提供有益的参考。