汽车悬架稳定杆连杆支架的疲劳仿真分析及结构优化

针对某型车辆常规耐久性试验过程中稳定杆连杆支架出现断裂的问题,对稳定杆连杆支架进行疲劳寿命分析和结构优化.首先运用ANSYS软件建立稳定杆连杆支架的有限元模型;然后基于静态有限元疲劳分析方法对连杆支架进行强度分析计算,并依据强度分析结果对稳定杆连杆支架进行疲劳寿命预测分析;其次根据等强梁理论对稳定杆连杆支架进行结构优化,支架截面由原来的等截面改为变截面,并对优化后的结构进行疲劳寿命预测;最后通过疲劳台架试验和裂纹断口分析,验证仿真分析结果.通过台架试验和仿真结果的对比可以得出,稳定杆连杆支架优化前后其疲劳寿命预测准确,优化后结构疲劳寿命符合预期.     

基于瞬态动力学分析的波纹管结构优化

目的 优化波纹管结构尺寸,最大程度地减小波纹管的应力集中,提高波纹管的疲劳寿命。方法 利用ANSYS Workbench对真空灭弧室用波纹管进行参数化建模,对其耦合速度压力复杂工况进行瞬态动力学分析,借助DOE(DesignofExperiment)技术对波纹管关键几何参数进行单目标优化设计,对优化结果进行强度校核和疲劳寿命计算。结果 优化结果符合设计要求,波纹管在耦合速度压力复杂工况下满足强度的同时,最大等效应力减小了28.8%,疲劳寿命由3 064次提高到32 260次。结论 优化后的结构有效减小了波纹管危险部位的应力集中,疲劳寿命得到提高。     

基于MSC.Fatigue的汽车驱动桥壳疲劳寿命预估

运用三维造型软件Pro/Engineer Wildfire2.0建立某型商用车驱动桥后桥壳的实体模型.依据有限元基本理论,进一步建立该桥壳的有限元模型,并在通用有限元分析系统MSC.Nastran中进行有限元应力分析.基于应力分析结果,采用有效的疲劳寿命预估方法,利用专业耐久性疲劳寿命分析系统MSC.Fatigue对该桥壳进行全寿命分析,得到桥壳整体的疲劳寿命分布和危险点的寿命值.通过与台架疲劳试验的桥壳失效情况相对比,预估结果与试验结果一致.而后对在试验中发生破坏的桥壳进行疲劳断口的微观分析.最终在试验与仿真分析结果的基础上提出对该型桥壳生产的改进方案。     

超声载荷下TC4钛合金的疲劳寿命分析

通过计算裂纹尖端应力强度因子及疲劳裂纹扩展速率da/d N,由C.Paris模型推导出安全寿命Nf,由Bathias公式计算"哑铃"状钛合金试样的裂纹扩展寿命。通过理论计算和有限元分析超声疲劳"哑铃"状试样,得出应力最大位置。利用有限元仿真和实验数据分析TC4钛合金疲劳寿命。在20 k Hz的超声疲劳试验中,试样的断口位置表明:TC4钛合金材料内部缺陷是试样萌生裂纹使断裂位置偏离最大应力处的主要原因。并得出疲劳裂纹萌生阶段寿命决定"哑铃"状试样的疲劳寿命。     

汽车悬架控制臂拉压溃分析及疲劳寿命预测

以某汽车的后悬架上控制臂为研究对象,建立悬架控制臂有限元仿真模型。对悬架控制臂在拉、压工况下,进行拉溃力和压溃力分析,并进行试验验证。试验结果表明,该控制臂拉、压溃试验结果与有限元分析结果基本一致。通过对该控制臂进行有限元分析,提取危险部位的应力应变信息建立疲劳损伤参量,引入临界平面法建立疲劳寿命预测模型。运用该模型进行疲劳寿命分析与预测,并进行试验验证。疲劳试验结果表明,控制臂疲劳寿命的平均试验值与预测值比较贴近,说明所采用的疲劳损伤模型,可以应用于汽车金属零部件的疲劳寿命预测上。     

交通信号支撑结构疲劳裂纹扩展有限元分析

为了解决交通信号支撑结构疲劳裂纹扩展的问题,利用ANSYS软件对已有的信号支撑结构静力和疲劳试验分别建模分析,并用有限元结果与试验结果进行对比。研究表明:静力加载模型中,圆钢管上最大Mises应力为413.7 MPa,有限元结果与试验结果较为接近;裂纹最深点△K_Ⅱ和△K_Ⅲ值较小,△K_eff与△K_Ⅰ几乎完全相等,裂纹扩展寿命主要受△K_Ⅰ值的影响;远离裂纹端点处各点的△K_Ⅰ值呈现出M形状;Bowness公式计算得到的裂纹最深点的△K_Ⅰ值比有限元结果大,利用该公式预测交通信号支撑结构端板与圆钢管焊接节点的疲劳寿命较为保守。     

基于nCode Design-Life的某车架疲劳可靠性分析

针对某型半挂牵引车车架局部出现裂纹或者断裂现象,通过有限元理论和疲劳分析理论相结合进行了车架的有限元分析和疲劳可靠性分析.首先对该车架进行了建模和有限元静态特性分析,然后定义了特定的时间载荷序列数据和材料参数,选用了S-N疲劳设计和静态疲劳分析方法,利用疲劳分析软件nCode Design-Life对该车架进行疲劳可靠性分析,得出该车架的疲劳结果云图和各节点的疲劳寿命,并从相关云图中确定出车架容易破坏的位置和其寿命之后再进行样车实验验证.     

金属疲劳裂纹扩展规律及其微观机制(中)

二、疲劳裂纹扩展的力学方程 远在本世纪三十年代中期,人们已认识到疲劳裂纹是工程设计中的一个严重问题。Deforest等为了确定疲劳裂纹出现后金属的剩余寿命,首次开展了一项探索裂纹扩展的研究工作。此后,人们对疲劳裂纹扩展过程进行了大量的试验与理论分析,建立一些半经验式和解析式力学方程,有的已应用于零件与结构的实际寿命的估算中。 1.早期的裂纹扩展公式 表3列出了一些早期的疲劳裂纹扩展的半经验公式。这些公式在一定试验条件下是     

疲劳损伤对波纹管耐连多硫酸腐蚀性能的影响

针对催化裂化装置用波纹管使用中所面临的连多硫酸应力腐蚀问题,采用热态连多硫酸腐蚀模拟装置,试验研究了固溶态Incoloy825波纹管的耐连多硫酸应力腐蚀性能,并利用金相显微镜、SEM、EDX等手段分析了腐蚀波纹管的表面形貌和断口特征,探讨了设计疲劳寿命及累积疲劳损伤对波纹管连多硫酸应力腐蚀敏感性的影响规律。结果表明,在60℃的H2SxO6溶液中,设计疲劳寿命及累积疲劳损伤对固溶态Incoloy825波纹管的腐蚀敏感性影响显著。设计疲劳寿命越低、累积疲劳损伤越大,则越易形成应力腐蚀裂纹。     

钢丝绳拉伸疲劳寿命仿真分析与试验研究

为研究钢丝绳在拉伸载荷下的疲劳寿命预测问题,以6×36 WS结构钢丝绳为研究对象,建立了钢丝绳的有限元模型,仿真分析了其在轴向拉伸载荷下的应力分布。对仿真结果中应力最大的钢丝进行拉伸疲劳试验,得到钢丝试件的载荷寿命曲线。在此基础上进行了钢丝绳疲劳寿命的仿真分析,并通过钢丝绳的疲劳试验进行了验证。钢丝绳疲劳仿真结果表明,在轴向拉伸载荷作用下,最大应力位于相邻两个绳股接触区域,对应的此处区域疲劳寿命最短。钢丝绳疲劳寿命仿真与试验结果具有较好的吻合度,由仿真数据拟合的载荷寿命曲线为钢丝绳疲劳寿命的预测提供了依据。     

Numerical study on fatigue crack growth in railway wheels under the influence of residual stresses

Accurate prediction of fatigue crack growth on railway wheels and the influence of residual stresses by finite element method (FEM) modeling can affect the maintenance planning. Therefore, investigation of rolling contact fatigue and its effect on rolling members life seem necessary. The objective of this paper is to provide a prediction of rolling contact fatigue crack growth in the rail wheel under the influence of stress field from mechanical loads and heat treatment process of a railway wheel. A 3D nonlinear stress analysis model has been applied to estimate stress fields of the railway mono-block wheel in heat treatment process. Finite element analysis model is presented applying the elastic–plastic finite element analysis for the rail wheel under variable thermal loads. The stress history is then used to calculate stress intensity factors (SIFs) and fatigue life of railway wheel. The effect of several parameters, vertical loads, initial crack length and friction coefficient between the wheel and rail, on the fatigue life in railway wheels is investigated using the suggested 3-D finite element model. Three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.     

Evaluation of fatigue life of aluminium alloy wheels under bending loads

This paper presents the details of S–N curve for aluminium alloy (Al) A356.2‐T6 and fatigue life of alloy wheels under bending load of cornering fatigue test (CFT). Development of S–N curve has been carried out by conducting rotary bending fatigue test at different stress levels as per Standards IS 5075. The rotary bending fatigue test has been performed under constant amplitude fatigue loading. The CFT of the wheel in normal driving mode has been carried out as per the procedure given in Japanese Industrial Standard Disc Wheels (JIS D_4103). It has been observed from the test that the cracks are initiated at the spoke and hub joining area closer to spanner hole on the front face of the wheel. Fatigue life of the alloy wheel has been predicted by finite element analysis (FEA), simulating the realistic test conditions. From finite element analysis, it has been observed that the maximum stress occurs at the mounting face of the wheel. Further, it has been observed that there is significant difference between the computed fatigue life and experimental value. Parametric study has been carried out for reliable fatigue life estimation and proposed an appropriate safety factor for fatigue life estimation under rotary bending test.     

Fatigue life of cold‐expanded fastener holes with interference‐fit fasteners at short edge margins

The fatigue life of 7075‐T6 aluminium specimens with countersunk fastener holes with cold expansion and interference‐fit fasteners with short edge margins was studied. The study was performed experimentally and through finite element analysis. The experiments measured the total fatigue life and crack growth. The results from the finite element analysis consisted of tangential residual stress profiles, which were combined with applied cyclic stresses for fatigue analysis. The experiments showed that the fatigue life improved with interference‐fit fasteners and cold expansion at all edge margins. The fatigue life also increased with increasing edge margin. The finite element results were used to make fatigue life predictions that corresponded reasonably well with the experimental results.     

Modelling and fatigue life assessment of orthotropic bridge deck details using FEM

The fatigue life estimation of orthotropic steel bridge decks using the finite element method is most frequently associated with the application of the structural hot spot stress approach or the effective notch stress approach, rather than the traditional nominal stress approach. The application of these approaches to a welded joint with cut-out holes in orthotropic bridge decks, where it is not easy to distinguish the non-linear stress caused by the notch at the weld toe from the stress concentration effect emanating from the hole in the detail, was investigated. The results of the finite element calculations were compared with the results of the fatigue tests which were carried out on full-scale specimens. The results of the finite element analyses revealed that the structural hot spot stresses obtained from the shell element models were unrealistically high when the welds were omitted. Moreover, the way in which the welds were represented had a substantial influence on the magnitude of the hot spot stress. The results of the analysis when using the effective notch stress approach showed that the agreement between the estimated fatigue life using this approach and the fatigue life obtained from the fatigue tests was good.     

Fatigue of cold worked ribbed reinforcing bar—a fracture mechanics approach

A theoretical method for the prediction of fatigue life of structural members containing external stress raisers has been developed. The method is based on a linear elastic fracture mechanics approach to fatigue. The theory has been applied to fatigue of Torbar steel in concrete beams. The required parameters for such application were obtained from fatigue tests on samples and finite element analysis of cracked bars. Comparisons between the theory and experimental data taken from other investigations have shown that the theory predicts a reasonable lower limit fatigue life of Torbar in concrete beams. The theory has also successfully predicted the effect of the minimum stress on the fatigue life of this type of bar.     

工况环境下振动对波纹管疲劳性能的影响

研究了热网波纹管在工作应力、工作介质及工作温度等工况环境下系统振动对其疲劳性能的影响，采用显微组织分析、硬度分析、SEM分析等手段对波纹管的失效情况进行了分析。结果表明：波纹管的疲劳裂纹从内、外表面两侧起裂，并向材料中心方向扩展至尖端相近时，发生瞬断，裂纹相接处呈韧性断裂。工况环境下振动对波纹管残余应力起到了一定的消除作用，并显著提升了波纹管的抗疲劳性能。     

Fatigue life prediction of friction stir spot welds based on cyclic strain range with hardness distribution and finite element analysis

The main aim of the present study is to investigate the fatigue behavior of single friction stir spot welds (FSSW) using strain-based modified Morrow’s damage equation. The correlation between microhardness, cyclic material constants, and mechanical strength of different zones around the FSSW are assumed to be proportional to the base material hardness. Experimental fatigue tests of friction stir spot welded specimens have been carried out using a constant amplitude load control servo-hydraulic fatigue testing machine. ANSYS finite element code has been used to simulate a single tensile shear friction stir spot welded joint, and non-linear elastic-plastic finite element analysis has been employed to obtain the values of local equivalent stress and strain near the notch roots of the joints. The results based on the numerical predictions have been compared with the experimental fatigue test data. It has been shown that the strain-based approach does a very good job for estimating the fatigue life of friction stir spot welded joints.     

液压模块挂车刚柔耦合动态响应特性及摆臂疲劳分析

为了研究重型液压模块挂车动态响应特性及其摆臂疲劳强度的问题,基于有限元分析方法与刚柔多体动力学理论,建立挂车刚柔耦合多体动力学模型,以路面不平度作为仿真的激励信号,结合振动试验验证模型的准确性。对挂车在不同的运行工况下,进行动态响应仿真分析。将多体动力学仿真结果作为有限元分析的动载荷,计算获得疲劳分析所需要的应力时间历程,运用局部应力应变法对摆臂进行疲劳寿命预测。计算结果表明,摆臂应力集中部位出现在已发生断裂的断面位置及应力水平已进入塑性状态。挂车在B级、C级与D级路面下的运行,危险点的疲劳寿命均大于挂车使用年限。而在正弦形凹凸路面冲击下,危险点的疲劳寿命随正弦形幅值与车速增加而明显减短。根据仿真计算结果,可提出适用的运行工况以提高挂车运行安全性与运输效率。