【作者】 许扬；

【导师】 吴甦；

【作者基本信息】 清华大学 ， 管理科学与工程， 2008， 硕士

【摘要】 列车轮对为铁路车辆重要的行走部。在生产和装配过程中轮对往往形成残余应力,而在实际运行当中,轮对因受到复杂的机械和热载荷作用,易形成缺陷。同时车轮辐板上为操作方便设计的辐板孔容易造成应力集中,加速车轮的破坏。含有辐板孔的车轮已经多次引起安全事故。现在役的车轮中还有半数以上的车轮含有辐板孔,只能在十年以内逐步更换,因此辐板孔缺陷已严重威胁着当前铁路行车安全。因此在车轮厂段修期间准确高效的发现辐板孔缺陷并及时进行修理成为铁路行车安全的重要课题。为此应制订相应的车轮磁粉探伤工艺规范。基于当前只存在车轴磁粉探伤工艺规范的情况,本文以检测的准确度、时间和成本为综合优化目标对车轴的磁粉探伤工艺进行参数设计。首先运用热力耦合有限元分析方法揭示了辐板上应力分布并确定了辐板周向区域为重点检测区域。然后以电磁场有限元分析为辅助手段进行试验设计,实地收集数据,并通过方差分析和多元回归方法考察了充磁电流、充磁时间、辐板孔位置和喷磁悬液时间四个主要工艺参数对检测的准确度的关系,再结合上述四个参数与时间和成本关系以多响应曲面方法求解出优化参数值,作为车轮磁粉探伤工艺规范的建议参数值,最后通过现场试验验证了参数设计的结果。与常规的确定车轮磁粉探伤工艺参数方法不同,论文最终强调的思想是:参数设计不仅应该考虑到工艺准确性的要求,还应考虑工艺的时间和成本等其他因素,寻求综合最优,在保证工艺准确性的前提下提高工艺的时间和经济效率。在寻求合适的参数水平时应采用基于数理统计理论的参数设计方法,摒弃单纯依靠经验的方法。更多还原

【Abstract】 The wheelset is an important moving part of the railway vehicles. During manufacturing and assembly process the wheelsets are subject to residual stresses. Apart from that, the wheelsets experience complex mechanical and thermal loads during service and flaws are likely to emerge. Moreover, the sprag holes in the wheel webs, which are manufactured for easy handling, intend to aggrandize stress concentration and lead the wheels to break. In fact the wheels with sprag holes have led to many accidents recently. Over half of the wheels in service contain sprag holes in China and cannot be totally replaced within 10 years. Thus the sprag hole caused flaws have become a severe threat to the railway safety.Consequently it is a central issue to detect sprag hole caused flaws accurately and effectively and repair them in time. It is necessary to establish standards for magnetic inspection process (MIP) of wheels. Now there are only standards of MIP for shafts. Based on the existing standards, this thesis figures out the accuracy, cost and time as indicator for optimization and perform parameter design (PD) for MIP for wheels. At first we quantify the stress distribution in the wheel webs through mechanical-thermal coupled finite element analysis and determine the circumferential region near sprag hole as inspection focus. Then we perform design of experiment (DoE) with the aid of electromagnetic finite element analysis, administrate field surveys and set up the relationship between definition of the magnetic display and four key factors, namely the magnetizing current, magnetizing time, position of the sprag hole during inspection and spray time of magnetic suspension by using methods of variance analysis and multivariate regression. Taking into account the relationship between the four factors and inspection time and cost, we obtain the optimization solution through multi-response surface techniques. This solution could be the recommendation values for MIP standards for wheels. The field test confirms the result of parameter design finally.The emphasis of the thesis is that, distinctive from other methods for determining MIP parameters for wheels, it is more reasonable to consider not only the demand for accuracy but also other factors like time and cost in order to search for overall optimization, i.e. improving the efficiency and economy while maintaining accuracy. Parameter design based on statistical methodology should be the tool to determine parameter values, instead of mere experience and sense.更多还原