Finite element modeling the influence of edge roundness on the stress and temperature fields induced by high-speed machining

High-speed machining (HSM) may produce parts at high production rates with substantially higher fatigue strengths and increased subsurface micro-hardness and plastic deformation, mostly due to the ploughing of the round cutting tool edge associated with induced stresses, and can have far more superior surface properties than surfaces generated by grinding and polishing. Cutting edge roundness may induce stress and temperature fields on the machined subsurface and influence the finished surface properties, as well as tool life. In this paper, a finite element method (FEM) modeling approach with arbitrary Lagrangian Eulerian (ALE) fully coupled thermal-stress analysis is employed. In order to realistically simulate HSM using edge design tools, an FEM model for orthogonal cutting is designed, and solution techniques such as adaptive meshing and explicit dynamics are performed. A detailed friction modeling at the tool–chip and tool–work interfaces is also carried out. Work material flow around the round edge cutting tool is successfully simulated without implementing a chip separation criterion and without the use of a remeshing scheme. The FEM modeling of the stresses and the resultant surface properties induced by round edge cutting tools is performed for the HSM of AISI 4340 steel. Once FEM simulations are complete for different edge radii and depths of cut, the tool is unloaded and the stresses are relieved. Predicted stress fields are compared with experimentally measured residual stresses obtained from the literature. The results indicate that the round edge design tools influence the stress and temperature fields greatly. An optimization scheme can be developed to identify the most desirable edge design by using the finite element analysis (FEA) scheme presented in this work.     

A practical method for finite element ring rolling simulation using the ALE flow formulation

Finite element ring rolling simulation by conventional Lagrangian codes carries an excessive computational cost. The main reason for this is the large number of incremental stages typically required to complete a full simulation. The nature of ring rolling however means that the amount of deformation taking place in a given increment is relatively small compared with typical metal forming processes. This paper describes measures that make the analysis of ring rolling a practicable proposition. The resulting model is based on a threefold approach, comprising the finite element flow formulation, an arbitrary Lagrangian Eulerian update strategy, and a novel iterative solution scheme called the successive preconditioned conjugate gradient method. The approach exploits the slowly evolving nature of the problem with the effect of reducing the time penalty for each deformation increment. In addition, a number of issues specific to ring rolling have been addressed including the problem of how the mandrel interface is dealt with for arbitrarily shaped rollers. The importance of addressing this particular issue is also illustrated. The method is validated by comparison with earlier experimental work and previously developed models for both pure radial, and radial–axial ring rolling.     

A new stress-based model of friction behavior in machining and its significant impact on residual stresses computed by finite element method

Friction modeling in metal cutting has been recognized as one of the most important and challenging tasks facing researchers engaged in modeling of machining operations. To address this issue from the perspective of predicting machining induced residual stresses, a new stress-based polynomial model of friction behavior in machining is proposed. The feasibility of this methodology is demonstrated by performing finite element analyses. A sensitivity study is performed by comparing the cutting force and residual stress predicted based on this new model with those based on a model using an average coefficient of friction deduced from cutting forces and a model using an average coefficient of friction deduced from stresses. The average coefficient of friction computed based on the measured cutting forces is the conventional approach and is still widely used. The average coefficient of friction due to stresses can be considered as a simplified version of the proposed model. Simulation results show significant difference among the predicted residual stresses. As the proposed model is able to capture the relationship between the normal stress and shear stress on the tool rake face better than the conventional approach can, it has a potential for improving the quality of the prediction of the residual stresses induced by machining.     

预应力硬态切削加工过程的有限元数值模拟研究

基于预应力切削的原理,建立预应力硬态切削42CrMo钢的正交切削热力耦合有限元模型,采用剪切断裂失效准则、单元删除和任意拉格朗日-欧拉(arbitrary Lagrangian Eulerian, ALE)方法实现切屑的分离.研究工件材料的本构关系、切屑分离标准、刀屑接触面的摩擦模型以及热传导方程等切削模拟中的关键技术,得到不同预应力大小对加工表面残余应力的影响关系;将数值模拟结果与实验数据进行比较,两者具有较好的一致性.     

斜齿轮精确建模及有限元模态分析

通过三维造型软件UG实现渐开线斜齿轮的精确建模。采用有限元方法,研究斜齿轮的固有振动特性,分析斜齿 轮的主要振动类型,所得结论反映了斜齿轮的动力学性能,为振动响应求解做了必要的准备。     

Finite element modeling of residual stresses in machining induced by cutting using a tool with finite edge radius

A thermal elastic-viscoplastic finite element model is used to evaluate the residual stresses remaining in a machined component. An improvement in the accuracy of the predicted residual stresses is obtained by: (a) using a modified Johnson–Cook material model that is augmented by a linearly elastic component to describe the material behavior as non-Newtonian fluid; (b) using a remeshing scheme to simulate the material flow in the vicinity of the rounded cutting tool edge without the use of a separation criterion; (c) properly accounting for the unloading path, and (d) considering the thermomechanical coupling effect on deformation. Case studies are performed to study the influence of sequential cuts, cutting conditions, etc., on the residual stresses induced by orthogonal machining.     

汽车碰撞过程并行有限元仿真技术

根据显式有限元的计算特点和神威超级计算机的体系结构,设计了基于消息传递和区域分割的动态显式有 限元的并行算法,给出了基于汽车结构和材料特征的并行化分区算法,提出的算法应用在自行开发的GEFEP-P汽 车碰撞的并行化有限元分析软件,并成功移植到神威Ⅰ超级计算机。算例计算结果表明:采用并行有限元计算,可 以大大提高汽车碰撞过程的仿真计算效率。     

Finite element modeling of micro-milling: Numerical simulation and experimental validation

In this study, micro-milling of Inconel 718 was investigated. For this purpose, cutting tests were conducted by using uncoated tools and taking four different feed rates (1.25, 2.5, 3.75, and 5 µm/flute) and a constant cutting velocity (48 m/min) into account. In numerical modeling, thermomechanical behavior was modeled using the modified Johnson–Cook material model. Analyses were also conducted for different cutting tool edge angles (+8°, 0, and ?8°). In the numerical analyses, cutting force, tool stress, and cutting temperature values were estimated depending on tool rotation and cutting tool edge type and compared with experimental results. When the results obtained from the study are considered, it is seen that the experimental cutting force and temperature values are in harmony with the numerical results. Moreover, it is seen that there is an increase in cutting force, cutting temperature, and stress values depending on the feed rate. In addition, in the numerical analyses for different cutting tool edge geometries it was observed that cutting force temperature and tool stress values varied depending on the edge geometries.     

A 3-D finite element method analysis of cold rolling of thin strip with friction variation

In this paper, a three-dimensional rigid-plastic finite element method (FEM) model to simulate the cold rolling of thin strip with different friction models is described. The effects of rolling parameters, such as work roll diameters and reductions, are analysed in this study. The simulation and experimental values of rolling pressure and spread (the difference of strip width before and after rolling) show a good agreement when friction variation in the roll bite is considered. The roll separating force, spread and forward slip for constant friction and friction variation models are also compared. The friction variation in the roll bite has a significant effect on the simulation results.     

开式压力机焊接机身有限元分析研究

利用有限元软件对160tC型压力机焊接机身进行有限元分析,从而获得机身的等效应力分布和等效位移分布,为提高压力机的强度和刚度、减轻机身重量提供重要的参考依据。