An Investigation of Random Fatigue Strength of K-Type Tubular Joints and Crack Propagation Behaviors

ＩｎｔｒｏｄｕｃｔｉｏｎＡｓａｓｐｅｃｉａｌｆｏｒｍｏｆｓｔｒｕｃｔｕｒｅｓ,ｔｕｂｕｌａｒｊｏｉｎｔｓ (ｍｕｌｔｉ＿ｄｕｃｔｐｉｐｅｓ)ｗｅｌｄｅｄｂｙｃｉｒｃｕｌａｒｃｙｌｉｎｄｒｉｃａｌｓｈｅｌｌｓ (ｃｉｒｃｕｌａｒｔｕｂｅｓ)ｈａｖｅｂｅｅｎｗｉｄｅｌｙｕｓｅｄｉｎｅｎｇｉｎｅｅｒｉｎｇ .Ｏｎｅｏｆｔｈｅｐｒｉｍａｒｙｆａｃｔｏｒｓｔｈａｔａｒｅｒｅｓｐｏｎｓｉｂｌｅｆｏｒｍａｎｙｓｅｒｉｏｕｓａｃｃｉｄｅｎｔｓｉｓｔｈｅｉｎｓｕｆｆｉｃｉｅｎｔｆａｔｉｇｕｅｓｔｒｅｎｇｔｈｏｆｔｈｅｊｏ…     

沥青路面反射裂缝问题的损伤力学守恒积分

基于损伤力学理论，建立了沥青路面反射裂缝问题的损伤力学守恒积分，证明了在反射裂缝形成过程中应变能密度的守恒性。在此基础上，导出了预估反射裂缝形成寿命的简便方法与公式。本文研究成果对于沥青路面设计与旧路补强设计具有一定理论指导意义。     

不确定性参数系统振动控制闭环特征值的上、下界估计

用凸模型理论讨论参数不确定性系统的振动控制问题。把不确定系统的振动控制转化为确定性问题来处理,然后讨论不确定参数对闭环特征值的影响,提出了闭环系统特征值上、下界的计算公式。     

Accumulative damage near crack tip for welded bridge members: fatigue life determination

The behavior of crack growth for the fatigue damage accumulation near tip where damage is most severe is analyzed. Fatigue life is assessed for the welded members of bridges under traffic loading. Two parts are considered. They consist of the development of a fatigue damage accumulation model for welded bridge members and a method for calculating the stress intensity factor that is needed for evaluating the fatigue life of welded bridge members with cracks. Based on the concept of continuum damage accumulation and fatigue and fatigue crack growth relations, results are obtained to describe the relationship between the cracking count rate and the effective stress intensity factor. Crack growth and fatigue life are found for two types of welded members assisted by using fatigue experimental results. The stress intensity factors are modified by correcting for the geometric shape of the welded members in order to reflect the influence of the weldment and geometry. This is accomplished via the stress intensity factor. The calculated and measured fatigue lives were generally in good agreement for the initial cracking conditions of two types of welded members widely used in steel bridges.     

金属互连结构的电迁移失效分析新算法

综合考虑了电子风、温度梯度、应力梯度和原子密度梯度四种电迁移驱动机制,基于ANSYS软件平台和FORTRAN程序提出一种新的电迁移失效分析算法.通过ANSYS电-热-结构耦合分析获得模型的电流密度分布、温度分布和应力分布,基于FORTRAN编写的原子密度重分布算法获得不同时刻的原子密度,依据空洞生成和扩展失效准则进行电迁移动态空洞演化模拟并得到失效寿命.最后,SWEAT结构与CSP结构的应用算例验证r算法的精度.     

Multiaxial fatigue life prediction of kiln roller under axis line deflection

This paper investigates the multiaxial fatigue life of the roller in rolling contact with wheels with respect to axis line deflection. The multiaxial fatigue criteria proposed by Wang and Brown, together with the ralnflow counting method and Miner- Palmgren＇s rule, are applied to the cumulative damage estimation and life prediction. As the axis line deflection of overlong kilns generally results in asymmetric load distribution on each roller, the load ratio is introduced to describe the deflection for quantitative stress analyses. The stress analyses are performed within the finite element code ANSYS. The tangential friction stress is calculated in terms ：of the condition of the rolling contact area. By taking one roller as an example, the plotted fatigue life versus load ratio curve discovers how the axis line deflection affects the fatigue life. This study is significant to prevent the fatigue failure of the roller and can provide basis to adjust and optimize the axis line of the rotary kiln.     

随机疲劳累积损伤理论研究进展

对疲劳载荷、应力、寿命和强度的随机性分别进行了明确分类．然后,针对在疲劳理论发展史上有代表性的、目前在国内外仍被大量引用的（主要用于裂纹起始阶段的）疲劳累积损伤准则,从力学、概率统计等方面进行了较深入系统的分析．提出疲劳损伤累积具有两类不同的概率机制,即损伤在单一个体内具有的随机性以及损伤在同一母体中不同个体之间具有的分散性．最后,重点介绍了二维概率Miper准则以及有关随机疲劳寿命、随机疲劳强度等方面的研究进展．      

中碳结构钢微动疲劳性能的研究

考察了ＪＺ钢微动疲劳性能以及微动频率和接触压力等因素对微动疲劳寿命的影响,采用宏观力学试验与微观分析结合的方法探讨了ＪＺ钢微动疲劳裂纹的萌生和扩展机制．     

用Eason方法分析静刚性分布脉冲载荷下弹性半空间的瞬态响应

本文研究脉冲载荷下弹性半空间的瞬态响应,用Ｅａｓｏｎ方法得到静刚性分布脉冲裁荷作用下弹性半这间表面中心点生趣位移的精确解析解。     

焊接接头低周疲劳裂纹扩展的统计分析与可靠性最弱环模型

在相同的试验条件下,对１６ＭｎＲ压力容器用钢焊接接头焊缝区、热影响区和母材区,分别做了１５ 根试样的低周疲劳试验,获得了三个区的低周疲劳寿命分布与裂纹扩展规律。试验表明,Ｐａｒｉｓ公式中的两个参数ｍ 和ｃ 分别服从正态分布和对数正态分布,ｍ 和ｌｏｇ ｃ 呈现统计线性关系。根据文中的统计结果,采用蒙特卡洛法对给定的两个裂纹长度间的扩展寿命进行了预测,预测结果与试验结果符合良好。文中还对焊接接头三个区的低周疲劳寿命进行了统计分析,获得了相应的概率密度函数,初步提出了整个焊接接头的可靠性最弱环模型。