弱刚度结构件切削加工残余应力的研究

弱刚度结构件具有刚度差和材料去除量大等特点,加工过程中产生的残余应力容易导致其加工变形,尤其对于精度要求高且厚度不均匀的弱刚度结构件,更有必要研究切削加工残余应力的影响因素,从而为控制弱刚度结构件的加工变形提供基础。根据正交切削理论和热弹塑性有限元理论建立了切削加工的三维有限元模型,对材料为40CrNiMo的变厚度弱刚度结构件进行了切削加工模拟,对切削过程中的残余应力进行了有限元计算。通过对比不同切削参数情况下残余应力的分布,得到了残余应力随切削参数的变化规律;将变厚度弱刚度结构件的加工分为二次等厚度的切削加工,通过与一次加工得到的残余应力进行对比,得到了2种不同加工工序对变厚度弱刚度结构件的残余应力影响规律。     

飞机整体框类结构件铣削加工的模拟研究

针对航空整体结构件铣削加工变形的复杂制造问题，建立了三维铣削加工有限元模型。深入研究了材料模型、残余应力施加、动态切削载荷、材料去除等铣削加工模拟所涉及的关键技术．并详细论述了铣削加工模拟过程。应用该模型对某框类结构件进行了不同铣削顺序的加工模拟，通过零件变形模拟值与实验加工所得零件变形值的比较，证明该有限元模型可以实现对零件铣削加工变形规律的预测。     

基于SIGINI子程序的零件残余应力变形数值模拟研究

为提高飞机性能,整体结构件成为飞机广泛采用的主要承力构件,而整体结构件毛坯由于残余应力的存在往往导致加工后出现较大变形影响零件精度。根据模锻毛坯件的残余应力测试试验数据,逆向构建了初始应力仿真模型,采用用户子程序SIGINI施加初始应力场,运用生死单元法对分层材料进行去除。结果表明,通过表层残余应力试验数据逆向构建初始残余应力分布场计算变形的可行性,同时可以直观分析生死单元法逐层杀死单元过程中,初始残余应力的释放过程,与零件加工后的变形测量结果对比,有较高的吻合性。     

航空结构件残余应力释放引起加工变形的数值模拟

航空铝合金结构件毛坯在成形过程中产生很大的残余应力,使其在后续机械加工过程中极易发生翘曲变形,采用有限元数值模拟技术,建立了航空铝合金板材残余应力释放引起加工变形的力学模型,分析了在7075T7351铝合金板材材料去除过程中残余应力释放引起的加工变形规律,并针对7075T7351隔框零件进行铣削加工变形实验研究,并与有限元模拟结果进行比较,验证了数值模拟结果具有较高的精确度。     

残余应力作用下的航空整体结构件加工变形仿真

铝合金预拉伸板在成型过程中会产生较大的残余应力,在切削过程中毛坯的初始残余应力的释放对整体结构件的宏观变形有重要的影响。在弹塑性力学的基础上,综合运用Hypermesh和ABAQUS建立残余应力单因素作用下的三维铣削仿真加工变形场的有限元模型,利用生死单元技术模拟了材料的去除,分析了铝合金板材材料去除过程中残余应力释放引起的加工变形规律。并且运用Hypermesh提高了有限元前处理的速度,解决了复杂模型的残余应力加载困难与单元去除困难的问题。     

飞机整体结构件加工变形的产生和对策

分析了整体结构件加工变形的产生机理。通过两个实例，说明了整体结构件已去除材料残余应力的释放和切削加工表面残余应力对工件变形的影响。提出了深冷处理消除毛坯残余应力、高速切削和切削加工工艺优化等抑制整体结构件加工变形的策略。针对整体结构件弯曲变形，提出了校正需要满足的基本曲率关系．     

预应力切削加工TC4钛合金表面残余应力的有限元模拟

采用预应力切削方法对TC4钛合金进行加工,建立了预应力切削TC4钛合金的有限元模型,模拟了不同预应力下锯齿状切屑的形成过程及加工表面的残余应力分布情况,然后将模拟结果与试验结果进行了对比。结果表明:预应力切削可以调整已加工表面的残余应力分布状态和应力值,在弹性变形范围内,预应力越大,加工后表面的残余压应力越大,残余压应力的分布也越深;预应力对锯齿状切屑的形成无明显影响;模拟结果和试验结果具有较好的一致性。     

残余应力重分布引起的结构件铣削变形研究

航空铝合金结构件毛坯在成形过程中产生很大的残余应力,使得其在后续机械加工过程中极易发生翘曲变形,这已经成为国防武器快速开发和高效加工的瓶颈.采用有限元数值模拟技术,建立了航空铝合金板材残余应力释放引起加工变形的力学模型,分析了在7050T7451铝合金板材材料去除过程中残余应力释放引起的加工变形规律,并针对7050T7451隔框零件进行铣削加工变形实验研究,并与有限元模拟结果进行比较,验证了数值模拟结果具有较高的精确度.     

基于热力耦合模型的切削加工残余应力的模拟及试验研究

航空精密薄壁零件具有复杂的型腔结构,切削加工残余应力是薄壁零件精度稳定性的重要影响因素,因此必须对切削加工残余应力进行研究。根据热—弹塑性有限元理论,建立切削加工三维有限元模型,对航空铝合金材料Al2A12进行切削加工非线性弹塑性有限元模拟分析,对切削加工表面残余应力进行预测和计算。通过有限元分析,得到不同切削参数、刀具参数条件下的已加工表面残余应力的模拟结果,并对结果进行比较分析,得到各个因素对工件已加工表面残余应力的基本影响规律;进行不同加工工序条件下的切削加工残余应力的有限元模拟,在加工表面已有一次切削加工残余应力分布的情况下,进行二次切削加工有限元模拟,得到二次切削加工对工件已加工表面残余应力的影响规律;并且进行不同切削参数对残余应力影响的试验研究,验证有限元模型的正确性。     

2124铝合金薄壁结构件整体加工变形仿真分析

薄壁结构件的整体轮廓变形主要是由其毛坯内部残余应力重新分布而引起的,根据双面槽腔薄壁结构件的结构特点建立了薄壁件铣削加工的有限元模型,系统地研究了残余应力的施加,材料去除加工过程所涉及的关键技术,并通过优化薄壁整体结构件的装夹方案以及多个特征结构的加工顺序,控制了薄壁整体结构件的加工变形。     

Comparison and analysis of main effect elements of machining distortion for aluminum alloy and titanium alloy aircraft monolithic component

Main effect elements of machining distortion for aluminum alloy and titanium alloy aircraft monolithic component are investigated by finite element simulation and experiment. Based on an analysis of milling process characters, finite element models of machining distortion are developed. Considering the action of initial residual stress, finite element simulation and analysis of machining distortion for aluminum alloy aircraft monolithic component are performed. Initial residual stress, cutting loads, and coupling action of these two effect factors are taken into account, respectively, to perform finite element simulations of machining distortion for titanium alloy aircraft monolithic component. The finite element simulation results are compared with experiment results and found to be in good agreement, indicating the validation of the proposed finite element models. The research results show that the initial residual stress in the blank is the main effect element of machining distortion for aluminum alloy aircraft monolithic component, while cutting loads (including cutting force and temperature) are the main effect element of machining distortion for titanium alloy aircraft monolithic component. To decrease machining distortion of aluminum alloy aircraft monolithic component, the initial residual stress in the blank must be controlled first. Similarly, to decrease machining distortion of titanium alloy aircraft monolithic component, the cutting loads must be controlled first.     

Machining distortion minimization for the manufacturing of aeronautical structure

The distortion of machined parts is a major concern in the manufacture of aeronautical monolithic structures. We investigated the influence of material removal partition on residual stress in high-strength aluminum alloy parts to minimize machining distortion. In the present study, a methodology of minimizing machining distortion based on an accurate cross-sectional residual stress determination is presented, which can be applied to avoid or minimize part distortions in advance by adapting machining strategies or process conditions. A powerful contour method was used first to measure bulk residual stress within the blank. Next, a finite element model was applied to predict machining distortion based on measured residual stress for analyzing part distortion. Finally, experimental verification was provided by comparing measured distortion and predicted distortion by the finite element analysis. This simulation showed that part distortion is mainly affected by the partition of material removal in T-shaped components. Our results also indicate that distortion can be minimized by optimizing the partition of material removal to ensure a symmetrical distribution of residual stress in the part so that the residual stress-induced bending moment could reach self equilibrium.     

残余应力引起的铣削变形有限元分析

应用弹性力学理论推导出了二维连续铣削过程中工件内应力再分布及其引起变形的计算递推公式.解决了有限元建模、初始应力加载、变形评估等仿真关键技术,建立了残余应力引起铣削变形的二维有限元仿真模型.最后对实例进行了仿真计算,分析了残余应力引起的加工变形规律,并用解析法对仿真结果的进行了验证.     

钛合金TC4退火数值模拟

毛坯残余应力对薄壁件整体加工变形有重要影响。利用大型通用有限元软件ANSYS10.0对钛合金TC4进行退火过程数值模拟研究,通过数值模拟获得了退火过程中温度的变化、残余应力的分布及最终冷却后的残余应力状态。为研究TC4的加工变形规律,提供了具有初始残余应力场的数字化毛坯。     

A novel prediction model for thin plate deflections considering milling residual stresses

Residual stresses induced by machining coupled with the initial stresses can significantly impact mechanical properties of workpieces such as distortion, corrosion resistance, and dimensional stability. The redistribution pattern of residual stresses is extremely complex. The stress relieving can seriously deform the workpieces and reduce the fatigue life. Therefore, deflection prediction is critical for design, control, analysis, and management of machining. In this paper, an integrated modeling method is introduced to predict the deflection caused by milling residual stresses, to be more exact, to map the relationship between the deflections and the cutting parameters. Response surface design (RSD) is utilized to develop a new mathematical model which can predict the residual stress profiles of the workpieces along the cutting direction based on different cutting parameters. Then, the deflections are derived based on the estimated stress profiles and mechanics of materials theory. A finite element analysis model (FEM)-based simulation experiment using aluminum alloy 6061 as a case study has been implemented. The results from experiments indicate that the proposed approach could precisely estimate the residual stress profiles for given cutting parameters and effectively predict the deflections of the workpieces caused by residual stress.     

高速铣削加工汽车覆盖件模具表面残余应力研究

汽车覆盖件模具的高速加工具有特征型面形状复杂、材料硬度大、结构尺寸大、表面精度要求高等特点,在高速切削加工过程中,属于难加工产品。残余应力的存在促使疲劳裂纹形成与扩展、促进腐蚀、促进模具的关键型面变形,因此汽车覆盖件尺寸的稳定性和加工质量与其密切相关。本文在数值模拟思想的指导下,利用有限元解法,研究了高速铣削加工表面的残余应力对加工变形的影响,给出了预测残余应力数值的解析模型,具有重要的理论及现实意义。     

高档数控机床基础件低应力制造特性的研究

围绕高档数控机床基础件的低应力制造问题,研究了残余应力的分布规律,提出从优化制造过程工艺参数出发的降低残余应力方法。明确了铸造、机加工是两个对残余应力的产生起主导作用的工艺环节,采用有限元法对某加工中心床身进行了残余应力分析,得出了该床身在铸造与机加工环节的残余应力大小及分布情况。据此优化铸造残余应力振动时效处理的工艺参数,并分析了铣削加工参数对残余应力的影响。分析结果对数控机床大型基础件的低应力制造提供理论依据,有效保证基础件精度和稳定性。     

基亏ANSYS的某摇臂组件电子束焊有限元模拟

利用ANSYS有限元分析软件以及APDL的二次开发,编写了不锈钢材料0Cr15Ni5Cu2Ti的电子束焊的模拟程序。建立了圆周焊缝电子柬焊接的有限元模型,用数值模拟的方法从理论上分析焊接过程、焊缝应力分布和收缩变形。通过研究焊接过程中焊接时序、温度控制等关键问题,摸索出最佳电子束焊接工艺参数。试验表明,该工艺方法获得了较好的焊缝质量。有限元分析方法为焊接工艺参数的选择及优化提供了理论指导和参考,缩短了工艺试验周期,节约了费用。