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201.
The present paper presents the necessary crack growth statistics and suggests stochastic models for a reliability analysis of the fatigue fracture of welded steel plate joints. The reliability levels are derived from extensive testing with fillet-welded joints for which the entire crack growth history has been measured, not only the final fatigue life. The statistics for the time to reach given crack depths are determined. Fracture-mechanics-derived crack growth curves are fitted to the measured experimental curves and the best fit defines the growth parameters involved for each test specimen. The derived statistics and distribution function for these parameters are used as variables in a Monte Carlo simulation (MCS). In addition a Markov model is developed as an alternative stochastic model. It is a Markov chain for which the discrete damage states are related to chosen crack depths in the material. This model works directly with the experimental time statistics. It is a “stochastic bulk approach” not involving any random variables or fracture mechanics modeling. Both models are fitted to the data base and scaled to in-service conditions. Both methods are compared and discussed. The aim is to provide data for the variables used in a MCS and to develop a Markov chain for fast reliability calculation, especially when predicting the most likely influence of numerous future inspections. 相似文献
202.
钢轨踏面斜裂纹伤损原因及对策的研究 总被引:19,自引:1,他引:18
广深准高速铁路全长139km。对准高速区段和非准高速区段曲线上钢轨进行探伤检查,发现在44个曲线,37km长的范围内存在踏面斜裂纹,斜裂纹主要发生在上下行上股钢轨,斜裂纹呈成段、非连续、跳跃式分布。踏面斜裂纹及断口的宏观形貌和理化检验与分析表明,踏面斜裂纹伤损属于滚动接触疲劳裂纹伤损类型。研究认为:钢轨性能、线路状况、车辆性能及运行速度、车轮踏面形状等是产生斜裂纹的主要原因。提高钢轨的接触疲劳强度,在曲线上使用微合金淬火钢轨,研究和改善轮轨接触方式,加强轨道的养护维修,合理地进行预防性打磨和校正性打磨是解决钢轨踏面斜裂纹伤损的主要措施。 相似文献
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通过恒电流加速模拟试验,研究了钢材锈蚀对钢-混凝土组合梁的耐久性影响规律;通过对试验结果的回归分析,得到了栓钉锈蚀后钢-混凝土组合梁抗弯承载力的计算公式。试验结果表明:随着通电时间的增大,栓钉的锈蚀率增大,组合梁的承载力降低;当通电量相同时,末刷防锈漆试件中的钢梁的锈蚀增加,栓钉的锈蚀降低,其承载力较高;随着栓钉锈蚀率的增大,梁刚度降低,在荷载作用下,梁的相对滑移变大。 相似文献
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208.
为了分析机场复合道面结构在新一代大型飞机多轮荷载作用下的力学响应规律,文章以A380-800飞机为例,应用大型通用有限元程序ABAQUS建立了复合道面结构三维有限元模型,分析了多轮荷载不同组合方式作用下道面结构的力学响应。通过计算不同布载形式下道面结构的疲劳寿命,并结合应力的分布规律,得出结论:复合道面在多轮荷载作用下产生空间叠加效应;A380-800可采用3轴双轮6轮组作为道面结构设计时的最不利荷载组合;当考虑空间叠加效应时,15 m×15 m的模型尺寸是合理的。 相似文献
209.
基于疲劳强度谱分析的火炬塔支撑结构设计 总被引:1,自引:1,他引:0
火炬塔是FPSO上主要装置之一,火炬塔支撑结构的疲劳强度是结构设计重点关注的对象。在介绍疲劳谱分析方法及BV-Homer软件的基础上,总结整理出基于该软件的疲劳谱分析的基本流程,利用BV-Homer软件对火炬塔支撑结构原设计方案的疲劳损伤进行了分析校核,根据计算结果对支撑结构设计方案进行了修改。研究表明:原设计方案的疲劳强度不满足规范要求,修改方案的疲劳寿命大幅提高,满足规范要求;火炬塔支撑外侧主管及外侧热点的疲劳损伤较大,设计时需要重点关注;增加肘板、热点区域结构板厚是提高疲劳强度的有效方式;基于谱疲劳分析的结构疲劳强度分析方法可应用于其他类似结构。 相似文献
210.
The present paper addresses the stresses in dynamic steel tube umbilicals at the platform hang-off exposed to large motions corresponding to an extreme storm condition. Experimental tests were carried out by mounting fibre-optic Braggs inside steel tubes of a 9 m long umbilical specimen. Then the specimen was exposed to constant tension and dynamic curvature by means of a bellmouth and the stresses were measured. Realizing that the geometry of the umbilical cross section was too complex to apply full 3D modeling, a beam and penalty contact modeling procedure was applied to describe the extreme stress behavior. Then a simplified method was proposed to determine the contact stiffness which was further validated by full scale umbilical axial stiffness testing. As hoop contact interfaces between steel tubes and separation fillers were observed in the test specimen, a tailor-made contact element was formulated to facilitate hoop contact. Different modeling alternatives were used to investigate the hoop contact effect on the extreme axial stress and Coulomb friction stress range, which were further validated against measured dynamic axial stress. Good correlation was found by the combination of describing all contact interfaces and constraints due to the grooves in the inner sheath. 相似文献