增压器压气机三维弹塑性接触的研究

以某柴油机涡轮增压器的压气机为例,采用由参变量变分原理导出的有限元参数二次规划法,并结合多重子结构技术分析求解叶轮与轴套、轴套与轴的三维弹塑性接触问题,针对不同的过盈量、转速和轴套壁厚进行了大量计算,获得了叶轮、轴套与轴之间接触应力的相应分布规律。分析表明随着叶轮与轴套间过盈量的减小,轴套的外表面与内表面的接触应力是线性减小的,而且内表面的接触应力减小较为迅速。因而在采用压力组装法时应严格控制轴套与轴的过盈量,使得轴套和轴间有足够的压力保证叶轮、轴套和轴不会相互脱离,又满足结构强度的要求,并使其产生的不良影响减至最小。当转速一定时,叶轮与轴套接触点的法向相对位移与叶轮的质量分布存在着明显的联系。建议采用非均匀的初始过盈量,以保证不发生相对位移和接触应力的均匀性。这些对于确定合理过盈量,改进设计和提高压气机的寿命,具有实际参考意义。     

压气机叶轮-轴套-轴摩擦接触的有限元分析

以某柴油机涡轮增压器的压气机为例，基于多重子结构技术，建立了增压器压气机叶轮、轴套和轴的三维整体有摩擦弹性接触的计算模型，采用有限元参数二次规划法，对其进行有限元分析。针对不同的过盈量、摩擦因数、轴套壁厚和转速进行计算，获得了叶轮、轴套与轴之间接触应力的分布规律。分析表明，随着叶轮与轴套间过盈量的增大，轴套的外表面与内表面的接触应力是线性增大的，而且内表面的接触应力增加较为迅速，这对于确定合理过盈量和改进设计具有参考意义。     

压气机叶轮过盈配合研究及合理过盈量的确定

车用涡轮增压器的压气机叶轮一般采用过盈配合直接压装在叶轮轴上,通过一定的过盈量传递转矩,是典型的非线性接触问题。利用ANSYS软件,采用子模型结合网格随移技术的分析方法,针对不同过盈量,转速和摩擦系数进行了大量计算,获得了叶轮与轴之间的最大等效应力与最大法向接触应力的分布规律,并根据该规律计算出了可选择的装配过盈量的范围。研究结果表明,此分析方法能够有效反应叶轮与轴之间的受力情况,对实际装配过程具有一定的指导作用。     

大型叶轮超转芯轴过盈量综合研究

叶轮在动平衡后进行超转试验。芯轴与叶轮采用过盈配合进行连接,合适过盈量的选取需避免叶轮的过盈面发生塑性变形;保证叶轮在试验中提供足够的扭矩,不发生打滑、松动。过盈值在没有仿真条件下无法确知在此过盈值下的接触表面压力具体是多大,也无法确定过盈的形变是否达到材料的弹塑变形临界点。本研究针对此种情况,推导出验证过盈值的数学模型,方便工程人员快速核算过盈值取值是否满足叶轮超转试验的要求。     

基于ABAQUS的离心式压缩机转子接触应力分析

离心式压缩机叶轮一般采用过盈配合直接压装在叶轮轴上,通过一定的过盈量传递转矩。为了确定其最佳过盈量的范围及其与接触应力的关系,借助有限元软件ABAQUS,对某大型离心式压缩机叶轮与轴的过盈配合问题进行三维有限元分析,针对不同的过盈量进行了理论计算、静态分析以及动态分析,获得了过盈量与接触应力之间的关系,确定了其最佳过盈量的范围。这对于离心式压缩机的设计具有参考意义。     

汽轮机套装叶轮的应力分析和过盈量的合理设计

本文应用作者提出的求解接触问题的有限元混合变量法对汽轮机套装叶轮进行了分析,提出了合理设计叶轮和轴之间过盈量的两种方案,表明接触问题的有限元法对套装叶轮的应力分析和改进设计有重要意义。     

基于有限元法的离心压缩机叶轮过盈问题探究

基于ANSYS有限元分析软件,对离心压缩机叶轮与轴过盈配合模型进行了仿真分析,分析类型采用接触非线性,有效模拟了实际产品工作状态。在整个分析过程中,研究了影响接触状态的三个主要因素:轴向推力、温度效应、摩擦因数。选取分析结果中的接触面积和传递扭矩作为对比,得到这些因素对接触状态的影响程度。研究成果会对将来叶轮过盈分析和设计提供指导。     

基于ANSYS的轴套过盈配合接触分析

基于过盈配合理论,考虑轴套与轴装配的轴向作用,将二维的圆环面理论模型扩展到三维模型,利用APDL参数化语言对轴套过盈配合进行分析。分析了过盈量、材料的弹性模量、轴套内外径、摩擦因数对接触压力在轴向上分布的影响规律,并且总结归纳了接触压力与上述设计参数的代数关系式,为轴套过盈配合的设计、计算提供了依据。     

基于接触理论的叶轮部装结构分析

大型压缩机组用闭式叶轮多采用轴与轮毂全接触形式进行热装,过盈量一般按经验值选取.由于轮毂处接触面积过大,热装过程中及热装完成后,抱弯主轴的情况时有发生,这是典型的三维接触问题.以某大型压缩机组用闭式叶轮部装结构为研究对象,以非线性接触理论为基础,利用有限元法分析叶轮部装结构在热装过程结束达到稳态后轮毂与轴接触处的内应力大小与分布情况,分析结果可为设计、制造参考.     

离心压缩机叶轮过盈接触及传递扭矩研究

本文针对某离心压缩机叶轮,详细开展了基于有限元方法的非线性接触分析。深入研究了在离心载荷作用下过盈量和最大Von Mises应力、接触压力以及传递扭矩的关系,并根据叶轮做功传递扭矩的要求,给出了叶轮与轴之间适宜过盈量的设计建议和旋转松脱的甄别方法。     

Parametric study on the fatigue life of railways under rolling contact fatigue by three-dimensional numerical analysis

The current paper presents the results of parametric analyses on the stress intensity factor (SIF) of railways with inclined cracks under rolling contact fatigue (RCF). A 3D finite element (FE) model was proposed to demonstrate the shear mechanism in RCF. The feasibility of the suggested numerical model was verified through the SIF (K) obtained from advanced 3D FE analysis compared with existing 2D FE results. Based on the series of FE analyses, the sensitivity analysis on the cracked depth, surface/crack friction coefficients, and inclined angle, which mainly affected SIF history at the cracked tip, was examined. SIF distributions for various locations of the wheel along the cracked tip were also presented.     

大型回转窑支承系统的力学行为分析

对操作工况下大型回转窑支承系统的力学行为规律进行理论分析和接触非线性有限元仿真.根据轮带结构和运行特点,解析导出轮带内壁受简体的压力分布公式,修正了长期以来前人轮带压力公式的不妥之处.基于Ansys及其APDL( Ansys parametric design language)编程,实现对支承系统的多体接触模型在分布压力、摩擦转矩和预紧配合作用下的复杂加载及其边界非线性有限元模拟,获得回转窑支承系统的变形与应力分布规律.结果表明,轮带与托轮之间是循环挤压过程;每回转一周,轮带内外表面的等效应力经历五次脉冲循环,在与托轮接触处的峰值应力达最大.托轮外表面也存在较高接触应力.循环应力集中是使轮带与托轮发生表面疲劳失效的根本原因.过盈配合与支承载荷的双重作用,导致轮孔在与轮轴的配合端面成为托轮强度的最薄弱部位,可解释轮孔开裂或喇叭口失效现象.摩擦转矩使载荷偏置,导致支承系统应力分布非对称,故左右对称模型只适用于停工状态,对操作工况是不准确的.这些认识对回转窑支承系统的设计、检修和窑线调整具有参考价值.     

Elasto-plastic contact problem of laying wire rope using FE analysis

The three-dimensional elasto-plastic contact model, formulated with variational equalities, has been described for laying wire rope in this paper. The augmented Lagrangian multiplier method has been applied to calculate both the normal contact force and friction contact force, and the radial return mapping algorithm has been employed to handle stick/slip phases of friction. With a graphical user interface (GUI), a program for calculating boundary conditions of a three-dimensional finite element modelling is developed to create external files, which are in the format of the ANSYS parametric design language (APDL) and the external files can be accessed by ANSYS for nonlinear analysis. FE simulation of a simple wire strand has been given and the effects of friction coefficient and self-rotating ratio on the contact stress have been analysed. Also the effects of them on the forming stress and strain have been discussed.     

Finite element analysis on global and local estimation for thermo-mechanical response of EPL wafer heating

In this paper, an approach is presented for the computation of the in-plane pattern placement error (PPE) caused by the wafer heating during exposure of electron projection lithography (EPL) using the finite element method (FEM), which is one of candidates in the next-generation lithography (NGL) exposure tools. The PPE is the global and local distortion, and is the thermo-mechanical response due to the thermal deformation of the wafer in the lithography process. The prediction of PPE requires high accuracy for NGL exposure tools. The simultaneous estimation of the global and local PPE to the whole wafer of a full three-dimensional FE model using a solid element requires excessive computation time. A novel technique of numerical simulation is developed and proposed, which is the employment of a shell element combined with previously proposed the dynamic meshing technique (DMT), being possible to predict PPE in realistic computation time with high accuracy. Simulations are performed for the wafer heating of EPL effectively using three techniques, that is the equivalent average heating technique and two proposed techniques. The simulation results agree closely with the result of a full three-dimensional FE analysis, and the required computation time becomes 1/16 or much less of that.     

发动机连杆精细有限元分析模型和算法的研究

在总结大量连杆计算经验的基础上,分析了影响计算精度的各种因素,提出了一个精细有限元组合计算模型：摒弃了各种近似处理方法,计算模型完全根据连杆实际结构确定,计入了连杆组装的全部零件以及活塞销、活塞和曲轴,其间所有配合关系用有摩擦的3维弹性多体接触模型模拟。采用有限元参数二次规划算法,并结合多重多支的子结构技术求解。同时指出了这套理论和方法对于解决这类机械工程问题所具有的优点和广泛的适用性。     

Adaptive multiscale method for two-dimensional nanoscale adhesive contacts

There are two separate traditional approaches to model contact problems: continuum and atomistic theory. Continuum theory is successfully used in many domains, but when the scale of the model comes to nanometer, continuum approximation meets challenges. Atomistic theory can catch the detailed behaviors of an individual atom by using molecular dynamics (MD) or quantum mechanics, although accurately, it is usually time-consuming. A multiscale method coupled MD and finite element (FE) is presented. To mesh the FE region automatically, an adaptive method based on the strain energy gradient is introduced to the multiscale method to constitute an adaptive multiscale method. Utilizing the proposed method, adhesive contacts between a rigid cylinder and an elastic substrate are studied, and the results are compared with full MD simulations. The process of FE meshes refinement shows that adaptive multiscale method can make FE mesh generation more flexible. Comparison of the displacements of boundary atoms in the overlap region with the results from full MD simulations indicates that adaptive multiscale method can transfer displacements effectively. Displacements of atoms and FE nodes on the center line of the multiscale model agree well with that of atoms in full MD simulations, which shows the continuity in the overlap region. Furthermore, the Von Mises stress contours and contact force distributions in the contact region are almost same as full MD simulations. The method presented combines multiscale method and adaptive technique, and can provide a more effective way to multiscale method and to the investigation on nanoscale contact problems.     

A contour integral method to compute the generalized stress intensity factor in complete contacts under sliding conditions

In complete contact fretting problems under global sliding conditions, the stress state at the corner of the contact zone is usually singular (assuming elastic behaviour). This stress state is characterized by two parameters: the order of singularity and the generalized stress intensity factor (GSIF). The former can be analytically calculated for a given problem. However, the GSIF is usually obtained by means of numerical procedures. One of the most used is the application of the stress extrapolation technique in combination with a FE analysis. In this work, a path-independent contour integral is defined which enables the GSIF calculation. Using this novel technique, a much more accurate estimation of the GSIF is obtained for a given discretization. In addition, a refined mesh around the singular point is not needed, because the contour integral can be applied along paths far from the singularity dominated zone due to its path independence.