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。     

基于应力分析的车载低温绝热LNG气瓶的结构优化和疲劳寿命研究北大核心CSCD

为了使车载低温绝热LNG气瓶在服役周期内安全运行,对车载低温绝热LNG气瓶整体结构开展了各典型工况下的强度分析、结构优化和疲劳寿命预测,完成了车载低温绝热LNG气瓶整体结构在5 g冲击下的全流程安全性评价。仿真分析了车载低温绝热LNG气瓶整体结构在6种典型工况下的应力并对结构不连续处进行应力评定,基于整体结构的应力分析对后支撑结构进行了优化,并对最关键主承压结构内胆开展了疲劳寿命预测和评定。通过全流程的应力和疲劳分析、评定研究,结果表明:车载低温绝热LNG气瓶整体结构满足强度要求;通过后支撑的优化,应力最高降低了53%,在最恶劣工况下,应力变化幅值由优化前的78.2 MPa下降为优化后的1.3 MPa,后支撑的疲劳寿命大幅提高;整体结构的疲劳寿命远高于各工况的许用寿命。     

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。     

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。     

汽车稳定杆组织与疲劳性能研究

对28Mn6钢制造的汽车稳定杆，分别采用整体感应加热－整体淬火、连续感应加热淬火两种不同热处理工艺，并进行了台架疲劳寿命试验，采用光学显微镜和扫描电镜，分析了经两种不同热处理工艺处理的稳定杆的金相组织及其早期疲劳断裂的断口形貌，提出，获得细小的高韧性索氏体组织是保证良好疲劳寿命的关键，稳定杆喷丸表面质量，游离铁素体也是影响疲劳性能的重要因素。     

履带车辆传动轴疲劳寿命预测与结构改进

传动轴是履带式车辆传动系统的重要传动构件,由于测试方法和试验条件的限制,在设计传动轴的时候采用静强度设计理论,无法准确反映其在实际复杂任务工况条件下的动态响应性能,给动载荷作用下的机械构件寿命预测带来了很大困难,导致构件的实际寿命和设计寿命有很大的差距.基于ADAMS.ATV建立履带车辆行驶仿真平台,获得了传动轴在各种不同工况条件下的动态载荷.基于MSC.Fatigue疲劳寿命分析软件建立传动轴的疲劳分析模型,获得了传动轴的疲劳寿命,进而仿真分析不同结构对传动轴疲劳寿命的影响规律,对传动轴的结构进行改进.仿真预测实例验证了对复杂工况条件下传动轴进行疲劳寿命预测的可行性.对履带车辆构件结构优化问题进行了探索,研究方法和成果可以推广到相关机械工程领域,具有一定的指导意义.     

某高温重载自润滑关节轴承超载试验失效原因分析

某高温重载自润滑关节轴承台架超载试验后,轴承内圈产生局部裂纹和断裂失效。采用宏观分析和微观分析等方法分析了轴承内圈出现裂纹和断裂的原因,并利用ANSYS有限元分析技术加以考察和验证。结果表明:该关节轴承出现裂纹和断裂是因为内外圈边缘和销钉槽部位未进行倒角处理,从而导致较大的应力集中;根据出现裂纹和断裂的原因以及ANSYS有限元分析结果,优化了该关节轴承的结构,减小了局部应力集中,有利于关节轴承台架试验的正常进行和轴承疲劳寿命的提高。     

考虑结构裂纹扩展的振动疲劳寿命计算方法

工程实践中任何结构都存在不同程度的裂纹损伤,振动激励下动响应与疲劳裂纹扩展之间互相耦合,直接影响结构振动疲劳寿命.为了考虑结构振动疲劳耦合效应对疲劳寿命的影响,提出了一种考虑结构裂纹扩展的振动疲劳寿命计算方法.分析时,通过建立若干个含不同长度裂纹的结构有限元模型模拟结构裂纹扩展,采用Paris方程分段计算结构振动疲劳裂纹扩展寿命,通过试验确定的固有频率降变化规律反推结构裂纹萌生寿命,最后累计得到结构疲劳总寿命.结论表明,仿真计算结果与试验结果比较吻合.     

飞机管道疲劳性能仿真分析与试验验证

为解决实际工况中飞机管道疲劳性能问题，研究飞机管道安装应力环境下的疲劳寿命分析方法，首先，建立飞机管道有限元模型；然后，利用有限元软件ANSYS Workbench对不同轴向装配偏差情况下的管道进行模态分析以及谐响应分析；进而，提取出管道危险点应力幅值，利用材料的S-N曲线进行疲劳寿命预测。最后，设计不同安装应力情况下的管道共振疲劳试验，并对仿真结果进行验证。仿真和试验的对比结果表明：根据仿真和试验得到的管道发生断裂的位置一致，两者管道疲劳寿命循环次数契合，随着轴向装配偏差增大，管道疲劳寿命逐渐下降。     

变刚度橡胶球铰的刚度特性与疲劳寿命分析

进行变刚度橡胶球铰的承载特性研究,有限元数值分析与实验结果均表明其刚度曲线表现为明显的非线性特性。正常载荷工况刚度值小、平稳,极限载荷刚度曲线出现拐点,刚度值显著增大。改变橡胶球铰的止挡高度,会直接影响刚度曲线的拐点位置。可据载荷工况,通过调整止挡高度改变刚度特性。据橡胶超弹特性,用有限元分析数据计算疲劳载荷工况下球铰危险点的等效应力范围,结合S-N曲线对橡胶球铰的疲劳寿命分析预测,并通过台架疲劳实验验证。结果显示橡胶球铰经150万次疲劳试验后未失效,与寿命预测值基本吻合。     

粘接剂对1420铝锂合金压印接头疲劳性能的影响

压印连接以高效率、低能耗的优点在薄板材料连接中被广泛应用,但其连接强度相对较低,鉴于此,压印-粘接复合连接应运而生。本文以1420铝锂合金为原材料,制备了1420同种材料组合的压印接头及压印-粘接复合接头并进行对比。通过拉-剪静态力学试验测定两种接头的静力学强度及承载能力,通过拉-拉动态疲劳试验测定两种接头的动态疲劳性能,采用三参数法拟合疲劳寿命曲线,并对疲劳失效断口进行分析。结果表明:压-粘接头的静强度比压印接头提高了108.17%,接头承载能力提高169.63%。在短寿命区,两种接头均为颈部断裂失效;在中长疲劳寿命区,压-粘接头的疲劳寿命优于压印接头,压-粘接头疲劳断裂位置为压印点,压印接头疲劳断裂位置为下板。对疲劳断口进行SEM分析,发现两组疲劳断口均呈现韧性断裂与脆性断裂同时出现的特征。     

50CrVA扭杆断裂原因分析

对断裂的50CrVA扭杆进行断口宏微观观察、金相组织检查、硬度测试及疲劳强度校核.疲劳强度校核结果说明扭转载荷过大是扭杆疲劳断裂的主要原因.材质分析显示扭杆中含有大尺寸富Zn夹杂物,它促进了疲劳裂纹的萌生,缩短了扭杆的疲劳寿命.     

基于实测道路谱的纯电动轻卡电池包支架动态载荷仿真及疲劳分析

为保证纯电动轻卡电池包支架的疲劳寿命分析与实车试验场道路耐久试验的关联性,提出了一种将多体动力学、疲劳寿命分析及试验场实测道路谱数据相结合的分析方法。采用ADAMS软件建立了由七通道虚拟试验台、电池包支架及整个车架组成的刚柔耦合多体动力学模型,以试验场采集的电池包支架加速度为目标响应信号,采用Femfat.lab软件使用虚拟迭代方法,反求得到了电池包支架疲劳分析的载荷边界条件。采用Miner线性疲劳损伤理论在疲劳仿真软件nCode中分析了电池包支架的疲劳寿命,分析结果显示其寿命能够满足疲劳性能要求,并最终通过了实车试验场道路耐久试验的验证,验证了此方法的工程实用性。所提出的分析方法对于研究电动汽车电池包支架的疲劳性能具有重要的参考价值。     

Fatigue life analysis of crawler chain link of excavator

In this study, the tension of crawler chain link of excavator is measured by experimenting in horizontal straight, pivot steering, and differential steering conditions. A virtual prototype model of excavator is established and its accuracy is verified on the basis of comparing the simulated and experimental tension of chain link in the abovementioned three conditions and adjusting the parameters of the model. The fracture surface morphology of chain link crack is analyzed by scanning electron microscopy. The fracture surface morphology conforms to the fatigue failure. Finite element analysis result indicates that the maximum stress of chain link is lower than the yield strength of material. The area of the maximum stress of chain link presents a crack, which indicates the fatigue failure of chain link. A rigid-flexible coupling virtual prototype model for simulation is established, which consists of a group of chain links of flexible body and other components of rigid bodies. The chain link operates in an entire cycle with the crawler in horizontal straight, climbing, and pivot steering conditions. The stress of key points in the cracked area and the fatigue life of chain link are obtained from the simulation. The comparison between the simulation and experimental data confirms the accuracy of the established virtual prototype model of excavator. Accordingly, the fatigue life of chain link is analyzed, which is usually difficult to achieve by experiment. The proposed analytical method for the fatigue life of components is easy and efficient and can serve as a reference for the fatigue life analysis of other key components of crawler     

Influence of spectrum loading sequences on fatigue life in a high-temperature environment

This paper discusses the fatigue life behaviour of aluminium alloy AA6061-T6 under spectrum loadings. Load sequences in spectrum loadings can have significant effects on fatigue life at room temperature and within the elevated temperature range. The main objective of this paper is to investigate the influences of load sequences effect on fatigue life at elevated temperature. Fatigue strain signal was obtained from the engine mount bracket of an automobile under normal driving conditions. Constant amplitude loading, high-to-low, and low-to-high loading sequences were then derived from the original fatigue strain signal to observe the fatigue behaviour at both room and elevated temperatures. The fatigue test was performed on AA6061-T6 specimen according to the ASTM E466 standard using a 100 kN servo-hydraulic fatigue testing machine within the temperature range of 27–250 °C. The elevated temperature range was chosen based on the maximum temperature of the engine mount bracket and the extreme temperature of the cylinder head that can be reached in service. After the test, fatigue fracture surfaces were sectioned and inspected using a high-magnification microscope. Results show that fatigue life behaviour at room temperature was significantly influenced by the load sequences in spectrum loadings. On the other hand, the effect of load sequences at a higher temperature was reduced.     

轻合金自冲铆微动磨损及疲劳性能研究

选择4组轻合金自冲铆进行疲劳实验,用扫描电子显微镜和能谱仪对其断口进行微动磨损机理分析,并系统地研究了接头疲劳寿命和失效形式的影响因素。结果表明,下板与钉腿区的微动磨损是导致下板沿纽扣断裂和铆钉断裂的主要原因,两板间的微动磨损是导致上板靠钉头断裂的主要原因;微动磨屑主要成分为金属板材氧化物,并对微动磨损起缓冲作用。增加板厚可提高接头疲劳寿命,且疲劳载荷较大时寿命提高更为显著;增加板强可提高接头疲劳寿命,且寿命提高程度受疲劳载荷影响较小。增加板厚使失效形式从上板断裂变为下板断裂,增加板强使失效形式从板材断裂变为铆钉断裂。     

Fatigue strength of steel beams with bracket plates welded to the tension flange

Fatigue tests under three-point bending were carried out on mild steel beams with bracket plates welded to the tension flange. The variables considered were the beam and bracket designs and the position of bracket connected. Particular attention was paid to the effect of configuration in the bracket-ends, which was varied in two distinct cases; in one the taper of the bracket end was straight and in the other it was rounded in three different ways. A good SN correlation was obtained by plotting the results in terms of bending stress range at the location of failure in the flange. This followed from the fact that the propagation of cracks across the flange exhausted the considerable part of fatigue life of beams. Thus the design details did not affect strongly the endurance of beams. However, the initial stage of cracking was sensitive to the types of bracket-ends. The fatigue crack associating with a straight bracket-end originated either from the weld toe on the flange at the bracket-to-flange junction or through the weldment, depending on the relative magnitude of two stresses suffering in the flange and in the bracket plate. The rounding of the bracket-ends prevented the occurrence of fracture through weld due to increase in the flexibility at the bracket-to-flange junction, but it did not improve the strength of crack initiation at the weld toe. It was suggested that the crack initiation of both fracture types in beams was possibly predicted from the results of comparative tests on plate specimens with longitudinal non-load-carrying fillet welds and with transverse load-carrying fillet welds.     

2219铝合金TIG和FSW接头力学及疲劳性能

目的 研究钨极氩弧焊(TIG)和搅拌摩擦焊(FSW)对2219铝合金(母材)力学及疲劳性能的影响。方法 通过拉伸试验,得到了母材、TIG和FSW接头的抗拉强度和伸长率;通过疲劳性能试验测试了母材、TIG和FSW接头在不同应力下相应的疲劳寿命,根据疲劳试验结果绘制了其试样的S-N曲线;使用扫描电子显微镜观察并分析了疲劳断口的形貌特征。结果 未焊接的铝合金母材抗拉强度和伸长率最高,分别为506 MPa和15.92%;TIG接头抗拉强度和伸长率分别为330 MPa和7.65%,FSW接头抗拉强度和伸长率分别为310 MPa和8.74%。母材、TIG和FSW接头等3种疲劳试样在2×10⁶次循环下的疲劳强度分别为129、108、115 MPa,其疲劳断口均可分为裂纹源区、裂纹扩展区和瞬间断裂区,疲劳裂纹分别起始于试样表面的局部变形区、第二相夹杂物和“吻接”缺陷。疲劳裂纹扩展区的主要形貌为疲劳辉纹和二次裂纹,瞬间断裂区以脆性断裂为主。结论 TIG和FSW等2种焊接工艺均导致了2219铝合金的强度、塑韧性和疲劳性能降低,其接头表面的第二相夹杂物和“吻接”缺陷促进了疲劳裂纹的萌生。     

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。     

Berechnung der Wöhler‐Linie für Aluminium‐Gusslegierungen aus dem statischen Zugversuch und dem Dendritenarmabstand

Calculation of the S‐N curve for cast aluminium alloys based on static tensile test and dendrite arm spacing A fatigue life model based on fracture mechanics was developed in order to calculate the S‐N curve for cast aluminium alloys due to the characteristic static tensile test values (0,2 % yield strength, tensile strength, elastic modulus) and to the secondary dendrite arm spacing of the casting structure.