Numerical analysis of friction stir welding process

Friction stir welding (FSW), which has several advantages over the conventional welding processes, is a solid-state welding process where no gross melting of the material being welded takes place. Despite significant advances over the last decade, the fundamental knowledge of thermomechanical processes during FSW is still not completely understood. To gain physical insight into the FSW process and the evaluation of the critical parameters, the development of models and simulation techniques is a necessity. In this article, the available literature on modeling of FSW has been reviewed followed by details of an attempt to understand the interaction between process parameters from a simulation study, performed using commercially available nonlinear finite element (FE) code DEFORM. The distributions of temperature, residual stress, strain, and strain rates were analyzed across various regions of the weld apart from material flow as a means of evaluating process efficiency and the quality of the weld. The distribution of process parameters is of importance in the prediction of the occurrence of welding defects, and to locate areas of concern for the metallurgist. The suitability of this modeling tool to simulate the FSW process has been discussed. The lack of the detailed material constitutive information and other thermal and physical properties at conditions such as very high strain rates and elevated temperatures seems to be the limiting factor while modeling the FSW process.     

Application of a feasible formability diagram for the effective design in stamping processes of automotive panels

The objective of this study is to propose a method of process design that uses a feasible formability diagram, which denotes the safe region without fracture and wrinkle, for the effective and rapid design of stamping processes. To determine the feasible formability diagram, FE-analyses have been performed for combinations of process variables that correspond to the orthogonal array of design of experiments. Subsequently, the characteristic values for fracture and wrinkle have been estimated from the results of FE-analyses on the basis of the forming limit diagram. The characteristic values for all combinations within a whole range of process variables have been predicted through the training of an artificial neural network. The feasible formability diagram has been finally determined for all combinations of process variables. The stamping processes of automotive panels to support suspension module, such as the turret suspension and the wheel house, have been taken as examples to verify the effectiveness of process design through feasible formability diagram. A comparison of the FE-simulation results with the experimental results reveals that the design of stamping processes through feasible formability diagram is efficient and suitable for actual processes.     

Tool design guidelines for the equal channel angular swaging (ECAS) process

A new severe plastic deformation (SPD) process of “equal channel angular swaging” (ECAS) is developed by combining the conventional equal channel angular pressing with the incremental bulk metal forming method rotary swaging. The ECAS tool system contains four forming zones in a single forming pass. In the current study, the effect of the multi-stage forming process on both the strain distribution and the material deformation is investigated by means of finite element (FE) simulations and these simulations are verified with model experiments. The results serve as tool design guidelines for the ECAS process.     

钢包旋转塔臂架的补强措施及有限元分析

某炼钢厂从德国DEMAG公司进口的两台钢包旋转塔已运行了多年,经检测发现该塔臂架有一处薄弱部位,并对其进行补强。后因生产的需要,承载能力提高到450 t,发现旋转塔臂架立臂工艺孔截面段的强度稍弱,稍大于材料的许用应力。为此再次提出了补强措施,经过对两种方案进行有限元分析比较之后效果良好,确定了立臂工艺孔截面段的强度能满足提升450 t承载能力的要求。     

钢管冷拔过程计算机有限元仿真研究

采用计算机仿真技术代替传统方法 ,对钢管冷拔过程进行了各种工艺参数下的500余次模拟 ,研究了钢管横裂、纵裂、尺寸变化等问题 ,得到了100多个各主要参量的数学模型 ,开发出了钢管冷拔过程的CAD系统。     

Decomposing deviations of scanned surfaces of sheet metal assemblies

We present a finite-element-based approach to support quality assurance for assembly processes of non-rigid sheet metal parts in the automotive and aerospace industries. These parts have adjustable mechanical boundaries, making it possible to compensate geometrical deviations caused by the production process of components. Every part produced must be adjusted individually. Determining what boundaries to adjust to and in what direction is challenging and requires experience. Our goal was to identify sources of measured surface deviations after part assembly and provide valuable information to the quality assurance engineer. We solve the corresponding parameter estimation problem via a least-squares approach. From the estimated parameter states that led to measured deviations, additional visualizations are calculated to support the inspection engineer when deriving countermeasures.     

Stochastic analysis and robust optimization for a deck lid inner panel stamping

FE-simulation and optimization are widely used in the stamping process to improve design quality and shorten development cycle. However, the current simulation and optimization may lead to non-robust results due to not considering the variation of material and process parameters. In this study, a novel stochastic analysis and robust optimization approach is proposed to improve the stamping robustness, where the uncertainties are involved to reflect manufacturing reality. A meta-model based stochastic analysis method is developed, where FE-simulation, uniform design and response surface methodology (RSM) are used to construct meta-model, based on which Monte-Carlo simulation is performed to predict the influence of input parameters variation on the final product quality. By applying the stochastic analysis, uniform design and RSM, the mean and the standard deviation (SD) of product quality are calculated as functions of the controllable process parameters. The robust optimization model composed of mean and SD is constructed and solved, the result of which is compared with the deterministic one to show its advantages. It is demonstrated that the product quality variations are reduced significantly, and quality targets (reject rate) are achieved under the robust optimal solution. The developed approach offers rapid and reliable results for engineers to deal with potential stamping problems during the early phase of product and tooling design, saving more time and resources.     

薄壁管无模内高压成形的实验研究与数值模拟

针对内压和轴压共同作用下的薄壁管无模内高压成形及加载控制稳定性问题进行了实验及数值模拟。实验结果表明,适度的起皱有助于提高薄壁管内高压成形的成形极限。有限元数值模拟证明,在轴压偏高而内压相对偏低的情况下,降低内压的增长率有助于抑制起皱的发展。出于对控制实现的考虑,有必要将内压轴压的匹配关系转换为内压轴向压缩位移的匹配关系。     

钢管热连轧过程横断面壁厚变化的三维有限元模拟

针对20号钢Φ119.0mm×9.25mm规格全浮动芯棒无缝钢管8机架连轧过程进行了有限元模拟仿真分析,得到了热连轧管各机架出口等效塑性应变以及荒管壁厚变化情况,分析了轧制力和芯棒力的变化特点。研究表明,连轧管减壁量和外直径变化主要集中于开始第1~第6个机架,在第7、第8机架减壁作用很小,最终荒管壁厚均匀,且形状圆整。稳定连轧阶段的轧制力依轧制顺序呈递减趋势,第7、第8机架轧制力很小;同时芯棒力大于各机架轧制力,钢管内壁承受的作用力和塑性应变较大,应对芯棒表面进行合理润滑。模拟得到的壁厚、外径及轧制压力与实测结果吻合较好。