起重机主梁疲劳强度的探讨

基于有限元分析结果进行疲劳分析的基本理论、思路及方法,运用ANSYS程序对假定无缺陷和含横向裂纹起重机主梁进行有限元数值模拟,得到交变应力最大部位,预测了起重机主梁疲劳裂纹萌生寿命和裂纹扩展阶段的疲劳寿命,以得到不同裂纹深度的主梁疲劳寿命。     

随机风载下齿轮副接触疲劳裂纹萌生寿命研究

对随机风场进行了模拟,得到了正常发电工况下主轴扭矩的时间历程;建立了齿轮副的三维有限元模型,计算了在静态载荷下齿轮副的应力应变。采用随机载荷雨流计数法对齿轮载荷进行雨流计数,并对结果进行了统计学分析,得到应力均值符合三参数威布尔分布。研究了服从三参数威布尔分布的分布参数对齿轮接触疲劳裂纹萌生寿命的影响。结果表明采用随机载荷相对于采用载荷均值齿轮的接触疲劳裂纹萌生寿命疲劳寿命下降,形状参数增大齿轮接触疲劳裂纹萌生寿命增大,尺度参数和位置参数增大齿轮的接触疲劳裂纹萌生寿命减小。     

大型矿井提升机主轴装置的研究

以矿井单绳缠绕式提升机主轴装置为研究对象,利用三维软件建立了实体模型,导入到AnsysWorkbench中进行了仿真分析。对主轴装置中最重要的零件主轴进行了静力学仿真,结果表明主轴的强度和刚度均能满足使用要求;对主轴装置整体进行了疲劳寿命分析,确定了疲劳寿命循环次数可以满足使用要求;对主轴装置进行了模态分析,为提高提升机运行效率提供了一定理论依据。     

基于ANSYS的单绳矿井提升机主轴静强度与疲劳分析

采用多载荷步加载法,针对典型工况进行单绳矿井提升机主轴的静力学分析;同时基于修正后的疲劳寿命曲线采用Fatigue模块实现主轴的疲劳分析。分析结果校核了主轴的强度和刚度,验算了主轴的疲劳寿命是否满足要求,并为主轴的优化和改进提供了必要的理论依据。     

镍基单晶涡轮叶片榫头疲劳裂纹扩展寿命研究

设计航空发动机涡轮叶片榫头/榫槽接触模拟试验件,基于涡轮叶片的实际工况,进行了榫头/榫槽接触疲劳试验。基于Paris公式提出了榫头接触疲劳裂纹扩展寿命模型,并采用晶体滑移有限元程序对涡轮榫头/榫槽接触进行了有限元模拟。有限元分析得到的疲劳裂纹扩展寿命与试验结果相符,表明提出的疲劳裂纹扩展寿命模型可用于指导分析榫头寿命。     

基于随机有限元法的结构经济寿命分析

基于随机有限元,将材料和载荷等影响结构疲劳寿命的不确定因素视为随机变量,分别对结构的裂纹形成寿命和裂纹扩展寿命进行可靠性分析.将结构的疲劳寿命看成由裂纹形成寿命和裂纹扩展寿命组成的串联系统,并由此确定结构的检修周期.通过随机有限元得到的分析结果与Monte Carlo模拟结果的比较,表明此方法能给出合理的结构检修周期,具有较强的适用性.     

基于Ansys的40Cr钢缺口应力集中疲劳分析

介绍了基于有限元分析结果进行疲劳分析的基本理论、思路及方法,运用ANSYS程序对试样进行有限元数值模拟,得到交变应力最大部位,预测了试样疲劳裂纹的疲劳寿命。     

基于ANSYS软件的矿井提升机主轴的数值模拟

利用ANSYS软件建立了矿井提升机主轴的有限元模型,采用将扭矩转化为多个节点上的周向集中栽荷的扭矩施加方法,在多种工况下进行数值模拟计算,实现了主轴静强度和静刚度的校核,得到了主轴的应力应变分布规律,为矿井提升机主轴结构的改进设计、寿命计算等提供了可靠数据。     

风电机组主轴翻转设备研究及应用

结合风电机组主轴翻转设备的结构和极限工况对本体强度进行有限元分析，确保结构的安全性。对设备中焊接件的焊缝疲劳寿命进行分析，先使用差值法得到焊址位置的应力，然后对焊缝的疲劳寿命进行评估。从设备的结构、主体及焊缝强度校核等方面进行研究，为其它机械设备的设计开发提供指导。设备的开发应用有效解决了风电行业主轴翻转对起重机承载能力的依赖，解决了风电机组生产瓶颈问题。     

直齿轮弯曲疲劳裂纹的扩展行为预测与分析

以渐开线圆柱齿轮为研究对象,在其齿根部存在初始裂纹的前提下,研究齿根疲劳裂纹扩展特性及其寿命;将齿轮啮合过程的动力学计算等效为多个啮合位置的静力分析,得到不同位置的应力强度因子;根据线弹性断裂力学,将裂纹扩展过程线性等效,以K判据分析裂纹是否发生扩展,根据Paris准则计算裂纹扩展量,采用最大周向应力准则确定裂纹扩展角度,得到整个计算周期的应力强度因子、疲劳裂纹扩展路径及疲劳寿命;采用高频试验台对齿轮进行疲劳试验,得到齿轮的疲劳扩展路径,与有限元计算结果进行对比验证;最后分别分析了初始裂纹的尺度、位置和载荷的不同对疲劳裂纹的扩展及疲劳寿命的影响。     

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.     

Fatigue life prediction by statistical approach under constant amplitude loading

In general, the experimental data of fatigue crack growth rates scatter very much even under identical experimental condition such as a constant amplitude loading condition. It is, thus, essential to take into account the data scatter of crack growth rates by using statistical approach for a reliable fatigue crack, propagation analysis. In this study, fatigue crack propagation tests were conducted on a 1.02 mm-thick 2024-T3 aluminum alloy under a constant amplitude loading condition. The distribution of the fatigue crack propagation life is estimated by using the stochastic Markov chain model based on a modified Paris-Erdogan equation to consider the variability of the fatigue crack growth. The fatigue lives estimated by using the Markov chain model are found to be agreed well with the experimental results.     

腐蚀结构损伤评估方法

针对腐蚀环境下老龄化飞机结构表面存在广布随机的腐蚀坑,而使其强度降低这一问题,先采用有限元方法并结合仿真软件ANSYS的参数化分析语言APDL,得到不同形状腐蚀坑底部的有效应力集中系数,然后结合局部应力应变法求解各个腐蚀坑底部在疲劳载荷作用下产生初始裂纹的萌生寿命值,再通过蒙特卡罗方法求解数值积分和非线性方程,得到和腐蚀坑具有相同寿命等效裂纹的尺寸,最后采用神经网络技术建立腐蚀坑各种几何尺寸与等效裂纹深度间的多变量非线性映射关系.为工程实践中用广布裂纹方法处理含随机分布腐蚀坑的老龄化结构提供可能.     

直升机金属动部件的寿命管理

针对某型直升机动部件承受高频低幅振动载荷的特点,探讨安全寿命和损伤容限相结合的寿命控制方法。以直升机的金属主桨叶为例,采用飞行空测载荷数据编制的实测统计载荷谱,通过Miner线性累积损伤理论计算得到裂纹形成寿命与风险率的关系。同时考虑裂纹扩展寿命对降低风险率的贡献,通过断裂力学分析计算出应力强度因子、损伤容限临界裂纹尺寸,建立主桨叶损伤容限分析的工程计算模型,得到裂纹扩展寿命(检查周期)与风险率的关系。     

Effect of stress ratio on the fatigue behaviour of compact bone

During the fatigue process of bone, cracks generally initiate from the inherent defects existing in the bone. The fatigue lives of bone specimens at different stress levels as well as at different stress ratios R were evaluated using a computer simulation in which the crack propagation behaviour initiated from the inherent defects in the bone are herein considered. The S-N curves as well as the distributions of fatigue lives obtained by the simulations accurately conform with the experimental results. With the strain threshold epsilon(max) representing fatigue failure of the bone specimen, the values of 1500 microepsilon for R = -1, 2500 microepsilon for R = 0.1 and 4000 microepsilon for R = 10 were extrapolated from the simulations. These values conform with experimental values reported in the literature. Such conformity indicates that the strain threshold for fatigue failure is associated with the threshold value for crack propagation.     

A new methodology for predicting crack initiation life for rolling contact fatigue based on dislocation and crack propagation

A new methodology for predicting crack initiation life is presented and validated experimentally. The methodology considers that the total fatigue life is the summation of crack initiation life and crack propagation life, since fatigue failures are due to crack initiation and crack propagation. It has been established that the crack propagation life can be estimated based on a modified Paris’ law when the size of crack is larger than a certain value. However, there has been no verified method for estimating the crack initiation life with good accuracy. The proposed methodology for predicting the crack initiation life is based on a dislocation model, and the constants for the model are determined by the crack initiation lives obtained by a new approach. This new approach determines the crack initiation life by subtracting the predicted crack propagation life from the experimentally obtained total fatigue life. The developed crack initiation life model is combined with a crack propagation life model for the prediction of fatigue life. It is noted that the standard deviation in the ratios of experimental life to predicted life by the developed fatigue life model is only 14% of that by the International Standard.     

搅拌摩擦修复2A12铝合金的疲劳性能和裂纹扩展行为

对含预制裂纹的2A12铝合金板进行搅拌摩擦修复试验,并对修复后的试样进行热处理。对修复试样与修复后热处理试样分别进行疲劳寿命与裂纹扩展试验,研究其疲劳性能的变化。结果表明:热处理可使修复试样疲劳寿命延长34.79%,修复试样与修复后热处理试样分别达到母材寿命的36.98%和49.89%,裂纹扩展速率均比母材的快,但修复后热处理试样裂纹扩展速率较修复试样低。疲劳断口显示,母材裂纹源多萌生于表面或亚表面夹杂相,修复试样与修复后热处理试样裂纹源多萌生于修复区和母材的界面,且裂纹源通常不止一处。稳定扩展区修复试样的修复区没有河流花样的解理面,而热处理后试样出现与母材类似的致密紧凑疲劳条带。修复试样瞬断区中由大量细小的等轴韧窝组成,而修复后热处理试样韧窝大小不等,但分布均匀。     

Fatigue cracks at notches

The failure of a component or specimen due to a fatigue crack growing from a notch is considered. Previous methods of analysis involving stress and strain concentration factors are shown to be inadequate. By defining equivalent cracks in notched and un-notched situations as cracks with equal growth rates, the concept of notch contribution to crack length is introduced. Theoretical notch contributions are obtained for a variety of central and edge elliptical notches via stress intensity factor solutions. These results when extended to a very wide range of general notch shapes can be reduced to a useful and simple design rule where e is the contribution to a crack of length l growing from a notch of depth D and root radius . This rule combines the size and shape effects long known to affect fatigue behaviour and defines the extent of the notch field as 0·13√(D).The fatigue crack propagation lives of a wide variety of notches were estimated by this rule and comparisons with experimental values revealed very small errors normally well within the scatter of fatigue lives.The design rule is extended to enable the conventional stress intensity factor method to be employed. A fatigue concentration factor is proposed which takes into account the presence of a fatigue crack which all previous methods have ignored.     

基于固有频率变化的两焊点接头的疲劳损伤参量

使用有限元软件ABAQUS分析两焊点拉剪试样在疲劳裂纹扩展过程中的动态响应,研究固有频率随裂纹面积的变化.将裂纹截面积作为损伤面积,确定损伤与固有频率变化率的关系.利用损伤力学中损伤随寿命的演化规律,对疲劳损伤达到一定程度的试样进行疲劳寿命预测.结果表明,此损伤参量能较好地描述双焊点结构的疲劳破坏过程.     

Effects of carbon black on the fatigue life,critical J-value and fracture morphology and a new estimated equation for natural rubber

This study investigated the fatigue lives and mechanical properties of the carbon black filled natural rubber for the vibration-proof parts of the railway vehicle and automobile. The carbon blacks were one of the sources of crack nucleation and crack propagation in the rubber matrix, like the cementite and the maganese sulfide in iron matrix. Different kinds of carbon blacks resulted in different fatigue lives, critical J-values, and fracture morphologies. It was noticed that the critical J-value remained almost the same regardless of the length of a pre-crack. In addition, different kinds of carbon blacks generated different fracture morphologies, and microscopic and macroscopic roughnesses. The critical J-value has linear relations to the roughness, and it seemed related to the size distribution of carbon black particles. By reviewing all the experimental data, we found the factors that were related to the fatigue lives, and the logarithmic value of the fatigue life could be linearly expressed by the combination of the critical J-value and the macroscopic roughness. We also proposed a new estimative equation of fatigue life.