基于虚拟正交试验的关节轴承工艺参数优化设计

以GEW12DEM1T关节轴承为研究对象,基于ABAQUS平台建立关节轴承挤压装配过程的有限元仿真模型。基于模拟仿真的虚拟正交试验选取模具半径R1,R2,收口半径Ra,定径带长度h,挤压速度v等重要成形参数,以内外圈最大接触压力Fmax、挤压力峰值Lmax、内外圈最大间隙与最小间隙之差Mmax、轴承端部金属流速均方差SDV为衡量指标。结果表明,影响Fmax,Lmax,Mmax,SDV的因素主次顺序分别为RahR1R2v,RahvR1R2,RahvR1R2,vR2hRaR1;综合考虑轴承质量、挤压力等因素,获得了GEW12DEM1T自润滑关节轴承成形参数的合理取值范围R2=17mm~30mm,R1=4.5mm~5mm,h=6mm~6.3mm,v=20mm/s~40mm/s,Ra=13.9mm~14.2mm。实验验证结果表明,模拟及正交试验优化结果准确有效。     

基于虚拟正交试验的热推弯管工艺参数优化设计

文章对热推弯管成形过程进行数值模拟,选取不同参数和水平进行正交试验设计,将管壁厚度和均匀性量化为壁厚的均值和方差,并基于该两项指标分析试验结果,得出牛角芯模的弯曲角度、扩径比、起始弯曲半径、推制速度、工模间摩擦系数对工艺的影响显著性和规律性,并获得较优的工艺参数值。验证实验结果表明,模拟及正交试验优化结果准确有效,推制管件达到壁厚减薄率和均匀性要求。     

基于虚拟正交试验的TA2弯头冷推制工艺参数优化设计

基于Deform-3D平台,以规格型号为Ф219 mm×5 mm的TA2管坯的冷推弯曲过程为研究对象,建立了有限元仿真模型。选取管坯与芯棒的间隙、管坯与模具的间隙、摩擦系数为影响因素,以成形弯头的壁厚均值和端部截面椭圆度为评价指标,完成基于有限元仿真的虚拟正交试验研究。得出各成形参数对弯头成形的影响规律,确定弯头成形的优化工艺参数组合为内外间隙值1.0 mm、摩擦系数值0.06。验证试验结果表明,模拟及正交试验优化结果准确有效,弯头成形质量符合要求。     

基于虚拟样机技术的锻造操作机控制特性研究(英文)

针对锻造操作机动作功能多、系统复杂、多领域模型耦合的特征,基于虚拟样机技术对锻造操作机的机械系统和液压控制系统进行了建模。采用模型接口的方法搭建了锻造操作机多学科领域协同仿真模型。研究了锻造操作机大车行走、夹钳旋转和夹钳平行升降3个主要动作的稳定性、准确性和快速性。结果表明,该方法可行,对于锻造操作机液压控制系统的优化设计具有一定的理论指导意义。     

基于正交试验的半轴套管热处理工艺研究

采用正交试验对45钢半轴套管进行热处理工艺试验。研究了淬火温度、保温时间、淬火介质、淬火时零件的摆动方式对显微组织和硬度的影响。结果表明,半轴套管的最佳热处理工艺为:淬火温度860℃,保温时间60 min,以8%NaCl水溶液为淬火介质,淬火时半轴套管左右摆动。     

基于正交试验的高速铣削表面质量研究

高加工速度和高表面质量是高速铣削加工技术追求的目标之一。通过分析,找到影响其表面质量的主要因素,设计4因素4水平正交试验,即在刀具参数不变的条件下,研究主轴转速、加工速度、轴向深度、径向深度的不同切削参数对表面质量的影响,找出影响表面质量的决定性因素,为实际操作者选取参数提供参考。     

基于正交试验的端帽激光淬火工艺研究

对自动流量平衡阀过流端帽的表面进行激光淬火研究,利用正交试验对影响激光淬火的因素进行了研究,得出激光淬火的最佳参数以及脉冲电流、扫描速度和离焦量对激光表面硬度和淬硬层深度的影响规律.试验结果表明,只要工艺参数选择适当,可获得很好的表面淬火质量,为激光加工提供了理论指导.     

基于正交试验的高速铣削表面质量研究

高加工速度和高表面质量是高速铣削加工技术追求的目标之一。通过分析,找到影响其表面质量的主要因素,设计4因素4水平正交试验,即在刀具参数不变的条件下,研究主轴转速、加工速度、轴向深度、径向深度的不同切削参数对表面质量的影响,找出影响表面质量的决定性因素,为实际操作者选取参数提供参考。     

基于正交试验法的切削参数优化研究

在数控加工中,切削三要素对加工质量的影响很大,在加工前应找到满足零件质量要求的切削三要素的最佳组合。采用正交试验法分析切削三要素对表面粗糙度的影响,该试验是一个3因素3水平单指标的试验,使用方差分析法进行分析。通过试验,得到了三要素对表面粗糙度的影响规律以及满足加工要求的三要素的最优组合。     

0Cr20Ni32AlTi合金的高温微动磨损及摩擦氧化特性(英文)

在300和400℃、载荷80N的条件下,将0Cr20Ni32AlTi合金以水平垂直交叉接触方式进行微动磨损试验,并采用SEM和XPS对磨痕及磨屑进行分析。结果表明:当位移幅值为10和20μm时,微动分别对应于混合区和滑移区,且材料表面均发生严重的磨损和摩擦氧化。微动过程产生大量颗粒状磨屑,经往复碾压后易粘附、聚集于接触区。摩擦氧化反应的生成物主要由Fe3O4、Fe2O3、Cr2O3和NiO等组成。温度和摩擦作用是影响磨屑氧化转化反应速率的主要因素。微动摩擦作用可以增加0Cr20Ni32AlTi合金表面原子的氧化反应活性并降低氧化反应的活化能,从而加快磨屑氧化转化反应的速率。     

铝熔体旋转喷吹净化动态水模拟试验研究

通过动态水模拟试验考察了喷头转速、气体流量和喷头浸入液体深度三个因素与气泡尺寸的关系,利用二次回归正交试验方法设计试验过程。试验结果表明,可以观察到气泡床的偏移,在特定的容积内喷头转速对气泡尺寸的影响最大,其次是气体流量,而喷头浸入深度对气泡尺寸影响较小。在现有的模拟试验条件下,当喷头转速215 r/min、气体流量2.94 m3/h、喷头浸入深度551 mm时,可以获得最理想的气泡尺寸。用相应设备处理铝熔体时,对铝熔体的含氢量进行测定。结果表明,在适宜的结构空间内,大叶轮、低转速的合理工艺组合可以获得较理想的除气效果。     

航空渐开线花键微动磨损的仿真模拟研究

目的 针对航空渐开线花键微动磨损严重的工程问题,研究多种因素对花键副受力与微动磨损的影响及键齿间的差异。方法 建立以微动磨损机理为基础的渐开线花键副微动模型,通过对比工程检测数据验证了花键副微动模型的合理性,并采用不同的加载方式研究分析各载荷对直升机减速器花键副的影响,并对比分析微动幅值、动载系数以及不对中量对花键传动应力分布与微动磨损的影响。结果 转速载荷的效应均方值远大于转矩载荷的效应均方值。微动幅值为20～80μm,动载系数为1.0～1.5,轴向不对中量为-0.05～0.05 mm,键齿接触应力与磨损量随各因素的增大而增加。键齿啮合区近齿根处的接触压力与微动磨损量均最大。不同向的轴向不对中对齿间差异的影响不同,键齿6～9与键齿15～18受轴向不对中的影响最明显。结论 花键传动中,相较于传动扭矩,传动转速对应力的影响更显著。键齿啮合区近齿根处应力集中较为明显,微动磨损严重。随微动幅值、动载系数与不对中量的增加,微动磨损显著增大,花键副的对中特性能够减小不对中量的影响。键齿的不同啮合区域与键齿间均存在受力与磨损程度上的差异。     

定子定位槽对径向磁力轴承影响的研究

针对有槽不对称的定子结构,利用有限元法对径向磁力轴承的电磁场进行了仿真与计算,并分析了计算结果。提出了几种结构方面的改进措施,为径向磁力轴承进一步的结构优化设计和控制系统的设计提供了依据。     

Design of Hot Stamping Tools with Cooling System

Hot stamping with high strength steel is becoming more popular in automotive industry. In hot stamping, blanks are hot formed and press hardened in a water-cooled tool to achieve high strength. Hence, design of the tool with necessary cooling significantly influences the final properties of the blank and the process time. In this paper a new method based on systematic optimization to design cooling ducts in tool is introduced. The optimization procedure was coupled with FE analysis and a specific evolutionary algorithm. Through this procedure each tool component was separately optimized. Subsequently, the hot stamping process was simulated both thermally and thermo-mechanically with the combination of optimized solutions.     

Optimal Programming of Multi-point Cushion Systems for Sheet Metal Forming

Numerical optimization technique coupled with finite element analysis of the stamping/sheet hydroforming process was developed to predict four possible modes for application of blank holder force (BHF) in multiple-point cushion systems, namely a) BHF constant in space/location and time/stroke, b) BHF variable in time/stroke and constant in space/location, c) BHF variable in space/location and constant in time/stroke and d) BHF variable in space/location and time/stroke. The BHF was predicted by (a) minimizing the risk of failure by tearing (thinning) in the formed part and (b) avoiding wrinkling. The developed technique was applied to predict the BHF to form a) an automotive part (liftgate-inner) from AA6111-T4 aluminum alloy, b) an asymmetric part from aluminum alloy AA5083-H32 by sheet hydroforming process with die (SHF-D) and c) a round cup by sheet hydroforming with punch (SHF-P). Experimental results showed that the FEM based optimization methodology can reduce trial and error effort and is able to predict the blank holder force necessary to form the parts without fracture and wrinkling in the investigated stamping and sheet hydroforming operations.     

Position-dependent dynamics and stability of serial-parallel kinematic machines

Parallel kinematic machines exhibit strong position-dependent dynamic behavior, which changes the stability and the productive cutting conditions within the machine work volume. In this paper, position-dependency of a hybrid serial-parallel scissor kinematic machine is modeled by synthesizing its substructural reduced order finite element models. The model allows the efficient investigation of position-dependency as an alternative to using time consuming full order finite element models. The predicted position dependency of the machine with the reduced order model is experimentally validated. Stability maps are simulated as a function of machine positions to identify the productivity levels within the machine work volume.     

Investigation of surface near residual stress states after micro-cutting by finite element simulation

Surface layer properties, namely residual stresses, surface work hardening and surface roughness, have a great influence on the service life of components. Especially the residual stress state of the surface layer after cutting is of great importance and shows a strong material specific behavior. Therefore the dependence of the residual stresses on the cutting edge radius, which plays a crucial role for micro-cutting, is investigated in chip forming simulations using ABAQUS/Standard. The residual stress states are evaluated for the reference material normalized AISI 1045 and are compared with a model material representing a hardened material state. The process knowledge will be increased by the systematic separation of physical effects leading to material specific residual stress states after cutting. The simulation results are validated by the comparison with experimentally determined residual stress depth profiles, using X-ray diffraction method, showing a good correlation.     

Simultaneous Determination of Flow Stress and Interface Friction by Finite Element Based Inverse Analysis Technique

A finite element based Inverse analysis technique has been developed to determine the flow stress and friction at the tool/workplace interface simultaneously from one set of material tests. The Inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic finite element simulations. The ring compression test and the modified limiting dome height test (sheet blank with a hole at center stretched with a hemispherical punch) were selected for evaluating the method for bulk forming and for sheet forming, respectively. The determined flow stress data were compared with corresponding data obtained Independently using the well-lubricated cylinder compression test and hydraulic bulge test. Results show that the method discussed In the study is efficient and accurate.     

Towards the multi-scale simulation of martensitic phase-transformations: An efficient post-processing approach applied to turning processes

This work presents an efficient finite element based scheme for the prediction of process properties and especially the material condition of workpiece surfaces after turning. This is achieved by using a database generated with the help of a micromechanically motivated material model – capable of simulating interactions of phase transitions and plasticity – for the efficient post-processing of a macroscopic thermo-mechanically coupled finite element simulation of the turning process. This modelling technique is applied to the martensitic part of a functionally graded workpiece which is produced by thermo-mechanically controlled forging processes. Those workpieces provide locally varying material conditions, which are tailored to the later application. The resulting pre-products have to be turned in order to achieve the desired final workpiece geometry and surfaces. Such processes strongly affect material properties such as hardness and ductility. A deterioration of the functionality of the gradation, i.e. the martensitic surface properties, may occur by generation of residual tensile principal stresses which can occur accompanied by white layer formation. These deteriorations can be avoided by adjusting the process parameters appropriately. Especially the cutting speed is supposed to be on a low level (v_c < 80 m/min) to avoid thermally driven formation of a white layer and the generation of tensile residual stresses. It is shown how finite element simulations can give insight into the material interactions and thereby facilitate the support of the process parameter adjustment in order to support efficient and reliable part production in industrial applications.     

XK717数控铣床主轴系统的热特性分析

建立了主轴系统与普通水箱之间的冷却模型，并结合有限元方法，对XK717数控铣床主轴系统进行了热特性分析，得出了水箱设计参数和冷却泵的流量对铣床主轴系统热特性的影响规律，从而为数控铣床主轴冷却系统的设计提供了理论依据，具有一定的指导意义。