焊接残余应力对桥壳疲劳寿命的影响研究

桥壳作为驱动桥的核心零部件,其疲劳寿命对驱动桥乃至整车安全性有决定性的影响,对于制造过程中使用焊接工艺的桥壳,焊接残余应力的影响不容忽略。以某商用车驱动桥桥壳为研究对象,在获得其焊接残余应力分布的基础上,分析焊接残余应力对桥壳在静态载荷和动态循环载荷工况下应力应变响应的影响。使用应变-寿命分析方法对桥壳在弯曲疲劳试验工况下的寿命进行预测,并与台架试验结果进行对比,结果表明考虑焊接残余应力时,疲劳寿命次数和破坏位置的预测结果与试验结果吻合较好,验证桥壳疲劳寿命预测模型的准确性。与不考虑焊接残余应力的模型相比,焊接残余应力导致桥壳疲劳寿命次数降低,且失效位置不同,说明了疲劳寿命预测时考虑焊接残余应力的必要性。本文方法可推广应用于含有焊接残余应力的结构疲劳寿命预测,为结构优化设计提供指导。     

重型汽车前轴疲劳强度分析和评价

重型汽车前轴主要用于支撑车辆重量、转向机件和悬吊支架,其几何形状复杂,是汽车上承受载荷较大的重要部件.通过对某重型汽车前轴的三种结构(旧前轴、新前轴A、新前轴B)设计,选用I-DEAS软件,运用有限元的分析方法,建立模型、划分网格和约束边界条件,分别对其结构强度和疲劳寿命作了相关计算分析,实现了三种前轴结构在工况下的应...     

Using stress relief grooves to reduce stress concentration on axle drive shaft

The axle drive shaft has important roles such as transferring power and changing the steering angle between the axle and the wheel in a power train system. It is used in most heavy construction machinery, where a high degree of reliability is required in the power train system. However, for axle drive shafts with a long span axle, failures are common at the snap ring cut that is machined on the drive shaft when there is significant fatigue damage under repeated loading conditions. Stress relief grooves have been applied at the snap ring cut to reduce the stress concentration and improve the fatigue life of an axle drive shaft. Although several studies have described how the stress concentration can be reduced by the stress relief grooves, details of the geometries of the stress relief grooves have been subject to debate and even controversy. We investigated the effects of the stress relief grooves on the stress concentration, and estimated the fatigue life of the drive shaft by using finite element analysis, taking into account the geometric parameters such as size and location of the stress relief grooves. As a result, the stress relief grooves presented by non-dimensional geometric parameters for an r/h = 1.2 and a d/b = 2.0 enabled a 22.3% reduction of the stress concentration, and a maximum improvement in the fatigue life that was approximately 3.3 times that of drive shaft with no stress relief grooves applied. These can be an index for selecting optimal geometric shapes of the stress relief grooves.     

微型汽车驱动桥壳强度及疲劳寿命分析

对微型汽车桥壳进行理论上的受力分析,计算出其在极限工况下的应力分布,同时对桥壳进行静强度分析,结合理论计算结果验证有限元模型的准确性.在此基础上进行疲劳寿命分析,得出桥壳潜在的危险位置,进行疲劳台架试验验证疲劳分析的准确性,仿真与试验结果一致,说明仿真分析能够在桥壳的设计和试验阶段提供一定的参考,缩减产品开发周期,减少试验次数.     

基于强度变化特征的汽车结构件轻量化设计方法

;提出一种获得结构有限寿命的轻量化设计方法.该方法以结构强度变化特性为基础,以结构强度试验结果为依据,动态强度方程为指导,结构临界载荷为目标,提高设计应力为核心,借助有限元分析实现汽车结构件减重设计.应用此方法对某国产载货车前桥进行减重设计,通过设计该前桥的危险断面,减小前桥的横断面尺寸,降低该前桥的临界载荷,使试验应力提高到能对前桥结构造成强化锻炼的区域.台架疲劳试验表明,虽然每台减轻质量5.5 kg,减重后的前桥仍能达到相关标准要求.这种方法比目前广为采用的以有限元分析和许用应力为基础的无限寿命轻量化设计方法更能充分发挥材料的强度潜力,因而可以在更深层次上实现结构的轻量化.基于强度变化特征的汽车结构轻量化对目前世界上日益强调的汽车轻量化具有重要的学术价值和指导意义.对基于强度变化特征的汽车结构件轻量化设计方法进一步改进和完善后,在其他工程领域也将具有重要的应用和参考价值.     

某型航空发动机涡轮盘低循环疲劳寿命分析

确定发动机零部件的最大应力应变循环是进行零部件寿命研究的重要内容之一.弹塑性有限元分析常用于计算最大应力应变循环,但是由于各种载荷、约束等条件考虑不全面,得到的应力应变循环往往偏大.同时,某些零部件的瞬态温度场是决定其疲劳强度和使用寿命的重要因素,而获得准确的瞬态温度场是非常困难的.文中对某型发动机的高压涡轮盘进行疲劳试验条件下弹塑性有限元分析,对一台涡轮盘的残余应力进行测试,利用稳态温度场计算涡轮盘危险点最大应力应变循环,并根据弹塑性有限元分析和通过残余应力测试得到的最大应力应变循环进行低循环疲劳寿命预测.研究结果表明,弹塑性有限元分析法预测的寿命偏低,由残余应力可以较准确地确定最大应力应变循环.     

Prediction of fatigue life in cold expanded Al-alloy 2024-T3 plates used in double shear lap joints

To predict fatigue crack initiation and fatigue crack growth lives in cold expanded double shear lap joints a numerical method has been employed. The total estimated fatigue lives were compared with available experimental fatigue test results for plain hole and cold expanded hole specimens of Al 2024-T3 in double shear lap joints. Three-dimensional finite element simulations have been performed in order to obtain the created residual stresses field due to cold expansion and subsequent far field longitudinal loading in the double shear lap joint. The obtained stress and strain distributions from the finite element analyses were employed to predict stress concentration factors to calculate fatigue crack initiation and fatigue crack growth lives using AFGROW computer code. The predicted fatigue lives demonstrate that there is a good agreement between the proposed method and experimental fatigue test results.     

应变疲劳可靠性分析的现状及展望

未来是应用塑性变形知识解决结构失效问题的时代,应变疲劳可靠性分析是其中重要问题之一,它在90年代才引起注意,文献很少。现有方法假设Coffin-Manson循环应变—寿命（CSL）关系中的疲劳强度和塑性系数为独立随机变量,强度和塑性指数为常数,实际上它们都是拟合试验数据的相关随机变量。因此,只适于缺乏试验数据时的近似分析。试验揭示了材料的循环应力一应变（CSS）响应存在很大分散性。考虑这一分散性和CSL与CSS关系中材料常数的相关性,建立新的方法是未来值得研究的基础课题。建立考虑平均应变/应力影响和多轴方法,使之应用于工程实践是值得进一步研究的重要课题。     

残余应力对齿轮弯曲疲劳的量化影响研究

随着风电、高铁、掘进等高端装备对齿轮功率密度、服役寿命等要求的提高,齿轮的弯曲疲劳问题日益显著。为提升齿轮弯曲疲劳性能,通过渗碳热处理、喷丸强化等工艺为齿轮引入较高的残余压应力已逐渐成为工业界的标配。为揭示残余应力对齿轮弯曲疲劳性能的量化影响,在最大主应变寿命预测准则中引入残余应力影响项,通过弯曲疲劳试验确定最优残余应力影响系数,进而采用新的试验数据验证模型的准确性。基于工程应用出发,引入修正应力的概念统一不同残余应力状态下的齿轮弯曲应力-寿命(S-N)曲线,研究结果显示,最大主应变准则中,残余应力影响系数取值为0.15时,可实现较高的寿命预测精度,而修正的S-N曲线中,最佳残余应力影响系数为0.25。研究成果可用于工程实际中齿轮弯曲疲劳快速评估。     

拖拉机前桥壳体测量机的设计

介绍了拖拉机前桥壳体测量机的测量原理、数据采样系统的硬件组成及系统软件的设计思路 ,并对测量系统进行了误差分析。     

基于SolidWorks的无杆飞机牵引车驱动桥结构设计仿真分析

目前飞机牵引车是机场主要地面设备之一,其可靠性要求比较高。由于无杆牵引车的工作方式是抱住飞机的前起落架,承受飞机的前轮负载,因此包括驱动桥在内的结构件受到了较大的载荷。文中利用SolidWorks软件建立驱动桥的模型,采用SolidWorks自带的插件CosmosWorks对驱动桥进行受力和疲劳分析,得到其最大变形和最大应力。据此可对驱动桥进行强度校核、结构改进及优化设计。     

SN-25 拖拉机半轴带存活率的疲劳寿命表达式

通过对文献［１］中疲劳试验结果的分析,采用当量切应力表示的疲劳寿命公式进行拟合,得到了其疲劳寿命表达式。统计分析表明,ＳＮ２５拖拉机半轴的疲劳寿命服从对数正态分布,其疲劳抗力系数和理论疲劳极限亦服从对数正态分布,据此,求出了给定存活率下的疲劳寿命表达式。     

低碳Mn-B贝氏体钢在汽车前轴上的应用试验

对低碳Mn-B贝氏体钢制前轴进行疲劳性能、热加工工艺和装车考核等试验。结果表明，低碳Mn-B贝氏体钢制造汽车前轴能降低生产成本．可代替42CrMo调质钢。     

ELASTIC-PLASTIC FINITE ELEMENT ANALYSIS OF THREE-DIMENSIONAL CONTACT-IMPACT AT RAIL JOINT

Using the finite element code ANSYS/LS-DYNA, a dynamic finite element model with anelastic-linear-kinematic-hardening plastic material is established to analyze elastic-plastic stresses inthe railhead in the impact process of wheel and rail occurring at the gap of rail joint. The model isbased on the discrete elastic support condition of the rails, which is suitable for the actual situation ofwheel/track rolling contact. In the analysis the influences of axle load, yield stress and tangent modulus     

Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system. By taking account of the coupling effects, formulas of equivalent stress and strain for cubic single crystal materials are cited. Using the equivalent strain and equivalent stress for such material and a variable k, which is introduced to express the effect of asymmetrical cyclic loading on fatigue life, a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed. On the basis of the yield criterion and constitutive model of cubic single crystal materials, a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed. The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680°C was analyzed. Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis. The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient. A power law exists between k and the failure cycle. The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys. All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens, respectively.     

基于ANSYS的驱动桥壳瞬态动力学和疲劳寿命分析

以有限元法为基础,在建立驱动桥桥壳的有限元力学模型的基础上,先借助有限元软件ANSYS的瞬态动力学分析找出桥壳上的危险点,再通过ANSYS-Fatigue疲劳分析模块对桥壳进行疲劳寿命分析,得到桥壳整体的疲劳寿命分布。桥壳的危险部位主要分布于圆弧过渡区域,与台架实验结果基本一致。从而验证了有限元软件对驱动桥壳理论分析的正确性,为驱动桥壳的设计和相关性能的分析提供了一种方法。     

随机载荷下矿用自卸车后桥壳疲劳寿命分析

矿用自卸车行驶路况非常恶劣,为研究国产首台SF33900型矿用自卸车后桥壳的疲劳寿命,建立后桥壳有限元分析模型,将载荷峰值作用下的仿真应力结果与试验结果进行对比分析,得出两者数值比较接近,从而验证了该模型具有一定的准确性。将动力学分析结果作为后桥壳疲劳寿命分析的随机载荷谱,得出水平路面普通工况下的疲劳寿命分布云图,其最小寿命满足工程要求。为研究载荷变化对后桥壳疲劳寿命的灵敏性,对比分析三处载荷变化对后桥壳疲劳寿命的影响程度,得出后横拉杆和悬架下支点位置受力变化对后桥壳疲劳寿命影响较大。另外,还考虑载荷频率变化对后桥壳疲劳寿命的影响,结果表明,载荷频率变化比幅值变化更能影响疲劳寿命。     

车轮多边形对高速列车车轴疲劳强度影响研究

车轮多边形是铁道车辆一种常见的非圆化病害,对轮对振动和车辆运行安全有明显的影响。在建立刚柔耦合拖车和动车车辆系统动力学模型基础上,将车轮多边形简化为简谐波并将其考虑为车轮轮径的变化,研究20阶车轮多边形对拖车和动车车轴疲劳强度的影响。结果表明,等效应力幅比值与速度呈非线性关系,且拖车和动车峰值出现位置有所不同,拖车峰值位置出现在速度为225 km/h,对应多边形激励频率432.7 Hz;动车不同截面分别在300 km/h、375 km/h时存在峰值,对应多边形激励频率分别为576.5Hz、721.2Hz。在各峰值位置处,多边形幅值的变化对拖车和动车部分截面的等效应力幅比值均有显著影响。拖车和动车车轴等效应力最大值均位于C截面,并且随着车轮多边形幅值的增加,其等效应力显著增大,超过车轴疲劳强度限值,降低车轴使用寿命。研究结果有助于改善20阶车轮多边形对高速列车车轴疲劳强度及弹性振动的影响。     

Fracture Analysis of the Front Axle of Bus under Fatigue Test

用故障树法(FTA)，分析了汽车前轴在疲劳试验中产生断裂的原因，并进行了宏观及微观的断口分析，结果表明加工工艺缺陷是引起疲劳断裂的主要原因。     

A Model for Rolling Bearing Life with Surface and Subsurface Survival—Tribological Effects

Until now the estimation of rolling bearing life has been based on engineering models that consider an equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the rolling contact. Through the years, fatigue surface–originated failures, resulting from reduced lubrication or contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific failure modes originated directly at the surface of the rolling contact can be challenging. In the present article, this issue is addressed by developing a general approach for rolling contact life in which the surface-originated damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is achieved by introducing a function to describe surface-originated failures and coupling it with the traditional subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the new model and its general behavior. The ability of the present general method to provide an account for the surface–subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with reference to endurance testing data.