Prediction of residual stress distribution after turning in turbine disks

The state of a surface region after machining is definitely affected by cutting parameters, such as cutting speed, feed rate, tool nose radius, tool rake angle and the presence of a cutting fluid, which plays a major role in determining friction at the tool–chip interface. The aim of the present study is to develop a finite element model based on the general-purpose nonlinear finite element code MSC.Marc by MSC.Software Corporation. This software is capable of simulating the cutting process of low-pressure turbine disks of aircraft jet engines from its very beginning to steady-state conditions. Basically, the present analysis is a coupled thermo-mechanical dynamic-transient problem, based on the update Lagrangian formulation; no pre-defined path is given for the separation of the chip from the workpiece, since material deformation occurs as a continuous indentation performed by the rigid tool. In addition to the cutting parameters, the main inputs in this analysis are material constitutive data, the friction coefficient at the toolchip interface and the cutting tool temperature. All the relevant variables, like stresses, strains, temperatures, chip shape and residual stresses, are predicted in a wide range of cutting conditions. The results from the model are compared to some basic theories of metal cutting and to an experimental study, concerning orthogonal cutting of steel AISI 316L. Concerning the specific case of turning process of nickel alloy Inconel 718 low-pressure turbine disks, the calculated residual stress are compared to experimental measurements from real machined disks.     

Elastic-plastic stresses in a rotating solid disk

A polynomial stress-strain relation is proposed for rotating disks with non-linear strain hardening materials. The basic equation of the disks with constant thickness and constant density under plane stress is derived from the deformation theory of plasticity, Von Mises’ yield criterion and the proposed stress-strain relation. A computing method for such rotating solid disks is developed and the approximate analytical solution is obtained. The validity of the solution is demonstrated by comparing the analytical calculation results with the finite element ones and very good agreement is found. The proposed solution is much more efficient and eassier to use than the FE approach     

Scientific fundamentals of high-efficiency roll forming technology for axially symmetrical parts of a gas-turbine engine rotor of high-temperature alloy

Fundamentals of the roll forming technology for disks of gas-turbine engines under super-plasticity conditions are stated. Because of deep underlying reasons of materials science, the technology provides a high process efficiency, equipment universality, the possibility of obtaining workpiece blanks with a high accuracy approaching that of the final part, and the development of structural states corresponding to the optimum complex of operational properties of parts [1, 2]. It is shown that a substantial role in roll-forming technology is played by superplastic deformation conditions, which, in contrast to the simple isothermal deformation, allow us to obtain in disks, either the homogeneous structure and isotropic properties, or the regulated gradient structure corresponding to actual temperature-force conditions of the operation of different parts of gas-turbine rotor disks.     

Stresses in rotating disks of materials with different compressive and tensile moduli

The problem of rotating disks of bi-linear elastic materials is treated herein. Stress and deformation states in the disk are obtained and are compared with linear elastic solutions.     

Optimum shape of continuous columns

The problem of rotating disks of bi-linear elastic materials is treated herein. Stress and deformation states in the disk are obtained and are compared with linear elastic solutions.     

基于缺口试件应力状态试验的Johnson-Cook模型参数反演标定方法

Johnson-Cook模型是适用于金属高应变率、大变形的强动载材料模型之一，其对应于材料的参数标定是模型应用的关键。由于没有考虑复杂应力状态对材料性能的影响，在不同应力状态下使用传统标定方法标定的模型进行模拟计算，计算结果与实际情况存在显著的差异。为了减小这种差异，使用6005A-T6铝合金，设计用以表征不同应力状态的缺口试件，在应变率4×10^-4 s^-1条件进行准静态单向拉伸试验。使用一种基于遗传算法的反演标定方法，将不同应力状态条件下的试验数据纳入到遗传算法的训练集中，以Matlab-LS-DYNA联合编程进行数据交互与集成，从而获得标定参数的最优解。结果表明，该方法标定的材料模型参数弥补了传统方法的不足，在复杂应力状态条件下具有更好的适用性。     

基于LMTO算法磁记忆屈服信号的定量化分析

磁记忆法对铁磁性金属构件的应力集中区域具有很好检测效果。但是,目前构件在弹性阶段和塑性阶段的磁记忆信号特征很难被区分,从而无法对构件的应力集中程度和使用寿命进行有效评估。基于固体电子理论建立了磁记忆效应的边界滑移模型,利用线性化M-T轨道算法(LMTO)计算了固体在弹性、塑性阶段,系统的能量变化、不同轨道电子的自旋态密度的变化情况,进而定量分析了构件发生屈服后的磁记忆信号变化规律。研究结果表明,应力集中程度与系统边界滑移能量呈线性正比例关系,与电子自旋态密度峰峰值、磁记忆信号呈线性反比例关系;构件发生塑性形变后,体系能量和电子自旋发生不可逆的变化,磁记忆信号曲线出现转折点;构件每发生一次塑性变形,磁记忆信号初始值都会变小,曲线斜率变小。     

变厚度回转构件的优化设计

论述了变厚度回转构件优化设计的一种数值方法。为该构件的厚度构造一个连续的函数 ,给出它的体积和转动惯量的计算表达式 ,提出变厚度回转构件应力分析计算的数值方法 ,然后将此设计问题转化为数值优化问题。目标函数定义为转动惯量与体积之比。该优化设计方法新颖通用性强 ,可应用于任何盘形旋转构件     

等壁厚螺杆泵定子的有限元分析

重点研究了等壁厚螺杆泵定子橡胶衬垫内轮廓线的变形规律,对其应力和应变分布情况作了辅助性分析;研究均匀内压作用情况下,考虑工作压差以及定子与转子的装配等所引起定子橡胶的变形和受力的变化.利用有限元分析软件Abaqus,对等壁厚螺杆泵定子进行研究,得出了螺杆泵定子在不同工况下的受力状态和变形规律,以及定子材料参数对变形规律的影响.利用此规律可对等壁厚螺杆泵进行优化设计,提高其工作效率.     

某机动式雷达天线阵面结构优化设计方法研究

文中提出了机动式雷达天线阵面结构正向设计方法,对雷达天线阵面进行了轻量化设计.应用经典力学求解天线阵面在静力学工况下的最大应力和变形,将此作为优化约束条件,将阵面质量作为优化目标,建立天线阵面的数学模型,用遗传算法进行第1次设计优化,得到天线阵面的初始结构参数综合考虑静力学工况与动力学工况,进一步用ANSYS系统的APDL建立参数化有限元模型,进行第2次优化,得到天线阵面的结构参数.文中对某型号的机动式雷达天线阵面进行了正向设计,并将优化结果与该雷达现有设计结果进行了分析对比.结果表明该正向设计方法合理,轻量化效果明显.