高应力气门弹簧疲劳可靠性方法研究

发布时间：2018-06-05 22:19

本文选题：高应力气门弹簧 + 疲劳断裂　；参考：《机械科学研究总院》2012年硕士论文

【摘要】：弹簧是各类机械设备、装置的重要零部件。近年来，随着主机对弹簧性能要求的提高，高应力弹簧随之出现。通常高应力弹簧是指服役应力大于800MPa的弹簧，其主要应用领域和产品是：汽车用高应力弹簧、高速机车用高应力弹性元件、大型工程机减震及缓冲弹簧、电力装备及管路系统平衡弹簧、阀门用弹簧等。高应力气门弹簧是国家中长期科技发展规划纲要中重要的基础零部件，其质量的优劣直接影响着主机的性能和安全。随着我国经济技术的迅猛发展，主机对高应力气门弹簧轻量化、高可靠性、高疲劳寿命等要求越来越高。高应力气门弹簧具有设计承载应力大、应力幅变化大、更换困难、工作环境复杂及高疲劳寿命要求和抗松弛性能要求高等特点。其中高的疲劳寿命和高抗松弛性能要求是各项要求中最为核心的要求，只有保证高的疲劳寿命和抗松弛性才能满足主机在寿命期内的正常运行。随着高应力气门弹簧设计制造水平的进一步提高，，其疲劳性能、抗松弛性能要求越来越引起人们的关注，所以本文着重对高应力气门弹簧可靠性分析进行研究。基于以上分析，本文采用了基于疲劳断裂的高应力气门弹簧疲劳可靠性分析和基于负荷衰减的高应力气门弹簧疲劳可靠性分析两种方法对高应力气门弹簧进行疲劳可靠性分析。重点开展了以下几方面的研究工作：（1）结合弹簧内部残余应力分析，系统研究了高应力气门弹簧疲劳强度和疲劳寿命的特点，并给出了影响高应力气门弹簧疲劳性能的关键因素；（2）在高应力气门弹簧疲劳强度分析的基础上，重点研究了喷丸强化工艺提高高应力气门弹簧疲劳性能的强化原理；结合相关理论分析对喷丸强化两种强化机制进行了试验验证；（3）分析了高应力气门弹簧高疲劳可靠性要求的原因，重点讨论了高应力气门弹簧疲劳失效的两种判据，并给出了高应力气门弹簧疲劳可靠性分析的流程；（4）在传统疲劳断裂寿命的前提下，研究了基于三参数威布尔分布的高应力气门弹簧P-S-N曲线的数学模型和拟合方法；在此基础上研究了基于三参数威布尔分布的高应力气门弹簧疲劳剩余寿命的可靠性数学模型和分析方法；（5）分析了高应力气门弹簧疲劳寿命试验方法和应力水平的设计方法；在疲劳寿命试验基础上，研究了高应力气门弹簧负荷衰减数据统计和处理方法，给出了不同可靠度水平下负荷衰减与应力循环次数的关系；分析了不同应力循环系数、不同应力水平和不同喷丸条件下高应力气门弹簧负荷衰减的趋势；最后在失效模式为指定负荷衰减率的前提下，运用二维概率模型方法给出了基于负荷衰减的高应力气门弹簧P-S-N曲线的拟合方法和实例分析。
[Abstract]:Spring is an important part of all kinds of machinery and equipment. In recent years, with the improvement of spring performance requirements, high-stress springs appear. Generally, high stress spring is a spring whose service stress is greater than 800MPa. Its main application fields and products are: high stress spring for automobile, high stress elastic element for high speed locomotive, shock absorber and buffer spring for large engineering machine, Power equipment and piping system balance spring, valve spring, etc. The high stress valve spring is an important basic component in the national medium and long term science and technology development program. Its quality directly affects the performance and safety of the main engine. With the rapid development of economy and technology in China, the requirements of the main engine for high stress valve spring are more and more high, such as lightweight, high reliability and high fatigue life. The high stress valve spring has the characteristics of large design load stress, large variation of stress amplitude, difficult replacement, complex working environment, high fatigue life and high relaxation resistance. Among them, high fatigue life and high anti-relaxation performance requirements are the most important requirements, only to ensure a high fatigue life and anti-relaxation can meet the normal operation of the host during the life cycle. With the further improvement of the design and manufacture level of high stress valve spring, more and more attention has been paid to its fatigue performance and relaxation resistance. Therefore, the reliability analysis of high stress valve spring has been studied in this paper. Based on the above analysis, fatigue reliability analysis of high stress valve spring based on fatigue fracture and fatigue reliability analysis of high stress valve spring based on load attenuation are adopted in this paper. Emphasis has been placed on the following areas of research: 1) the characteristics of fatigue strength and fatigue life of high stress valve spring are systematically studied, and the key factors influencing the fatigue performance of high stress valve spring are given. 2) on the basis of fatigue strength analysis of high stress valve spring, the strengthening principle of shot peening technology to improve fatigue performance of high stress valve spring is studied emphatically, and two strengthening mechanisms of shot peening strengthening are verified by combining relevant theory analysis. The reason of high fatigue reliability requirement of high stress valve spring is analyzed, two kinds of fatigue failure criteria of high stress valve spring are discussed emphatically, and the flow chart of fatigue reliability analysis of high stress valve spring is given. 4) on the premise of traditional fatigue fracture life, the mathematical model and fitting method of P-S-N curve of high stress valve spring based on three-parameter Weibull distribution are studied. On this basis, the reliability mathematical model and analysis method of fatigue residual life of high stress valve spring based on three-parameter Weibull distribution are studied. The fatigue life test method and stress level design method of high stress valve spring are analyzed, and the statistical and processing methods of load attenuation data of high stress valve spring are studied on the basis of fatigue life test. The relationship between the load attenuation and the number of stress cycles at different reliability levels is given, and the trend of load attenuation of high stress valve springs under different stress cycle coefficients, different stress levels and different shot peening conditions is analyzed. Finally, under the premise that the failure mode is the specified load attenuation rate, the fitting method of the P-S-N curve of the high stress valve spring based on the load attenuation and the analysis of an example are given by using the two-dimensional probability model method.
【学位授予单位】：机械科学研究总院
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH135

【参考文献】