【作者】 钱萍；

【导师】 陈文华；

【作者基本信息】 浙江大学 ， 机械设计及理论， 2010， 博士

【摘要】 航天电连接器作为航天系统中电信号传输、电路连接和实现特定功能的重要配套元件,数量庞大、地位重要。任何一套电连接器的失效都将导致系统发生故障,因此其可靠性的高低直接影响系统是否能可靠地工作。鉴于电连接器在实际工作中会遭受多种环境因素的影响,且目前仍然缺乏电连接器在工作环境应力下的可靠性指标,使得系统的可靠性设计难以进行,造成系统的可靠性得不到保证,因此评估电连接器在工作环境综合应力作用下可靠性的相关技术成为重要的研究课题。本文以Y11X-1419圆形低频电连接器为研究对象,对快速评估产品综合应力作用下可靠性水平的加速寿命试验相关技术进行了全面的研究。第一章阐述了课题的研究背景和重要意义,分析了加速寿命试验统计模型、加速寿命试验优化设计以及加速寿命试验数据的统计分析方法的国内外研究现状以及存在的问题,回顾和总结了航天电连接器的可靠性研究现状及存在的问题,最后给出了论文的主要研究内容和框架结构。第二章从失效机理层面推导了航天电连接器在温度和振动应力综合作用下的可靠性统计模型。首先对航天电连接器接触失效进行分析,从导致接触件失效的内在原因---电连接器接触件表面氧化物和磨损腐蚀物构成的绝缘膜层的增生出发,研究膜层的增长规律,并结合电连接器结构特点,利用渐近分布理论,导出航天电连接器的工作寿命服从二参数的威布尔分布;同时基于化学反应论及微动磨损理论,得出电连接器在温度和振动应力作用下的失效物理方程为广义Eyring模型,从而建立了航天电连接器在温度和振动应力作用下的可靠性统计模型。第三章建立了产品基于定时测试的综合应力加速寿命试验方案优化设计方法。依照产品的可靠性统计模型,利用均匀设计理论确定了综合试验应力的组合方式和试验次数,结合测试时间等概率原则,建立了定时测试下的综合应力试验方案优化设计的数学模型。将优化的加速寿命试验方案与未经优化的一般试验方案进行比较,结果表明,在相同的样本量下,优化试验方案大大提高了试验的估计精度。同时对优化试验方案进行模型初值偏离的鲁棒性分析,为设计稳健性试验方案的初值选择提供了理论依据。第四章建立了定时测试综合应力加速寿命试验方案模拟评价方法。以产品在正常应力水平时中位寿命渐近方差的期望值和标准差作为加速寿命试验方案估计精度和稳定性的考核指标,应用蒙特卡洛模拟方法,建立了定时测试综合应力加速寿命试验的模拟方法,利用定时测试极大似然估计理论,建立了定时测试综合应力加速寿命试验方案模拟评价的数学模型,并以随机抽样的渐近方差的均值和标准离差分别代替其期望值和标准差,提出了试验方案模拟评价的方法。对试验方案的模拟结果表明,所提出的定时测试综合应力加速寿命试验方案的优化理论正确,方法可行。第五章应用估计性能优良的极大似然估计方法对分组试验数据进行统计分析,得到了电连接器的可靠性寿命特征量的估计值,定量评估了电连接器的工作可靠性水平。第六章建立了具有较高估计精度的综合应力加速寿命试验数据的置信区间估计方法。基于现有估计方法中的二步拟合回归方法,将基于大样本理论的Bootstrap方法引入到回归分析方法中,再次利用Bootstrap思想对Bootstrap估计值进行纠偏处理,提出了小样本情况下产品可靠性特征量的Bootstrap回归置信区间估计方法。随机模拟的结果表明,Bootstrap回归区间估计精度均能基本满足给定置信度的要求。第七章提出了产品综合应力可靠性统计模型的验证方法。利用加速寿命试验数据,结合图分析和数值分析方法,验证了电连接器的寿命分布模型;从三维空间角度将失效物理方程准确度的验证问题转化为空间数据点共面性的检验问题,从加速寿命数据的统计检验角度出发,通过对综合应力失效物理方程进行多元线性回归拟合,以表征空间数据点和拟合值的垂直距离平方和与空间数据点本身的离差平方和相对大小的统计量作为检验指标,提出了定量评估失效物理方程准确度的多元线性回归拟合检验的验证方法,对电连接器的可靠性统计模型验证结果表明,该模型能很好地描述电连接器特征寿命在温度和振动综合应力作用下的变化规律;进一步通过扫描电镜分析和能谱分析,证明了从失效机理层面建立可靠性统计模型的合理性,为加速寿命试验方案的优化设计、模拟评价及试验数据的统计分析的正确性提供了有力的依据。最后总结了全文的研究工作,并展望了进一步的研究工作。更多还原

【Abstract】 As the mating elements, hundreds of aerospace electrical connectors play an important role in the aerospace systems for transmitting electric signal, connecting circuit and implementing specific functions. The failure of any set electrical connector will result in the "out of order" system. As a result, the reliability of electrical connector has a direct impact on system whether it can work reliably. However, lack of reliability index of electrical connectors under working stress makes it difficult to carry out the reliability design of system. Electrical connectors would be subjected to a variety of environmental factors in the working status, the related technologies for electrical connectors’ reliability assessment under multiple working stresses have hence become important research topics. In this dissertation, the model Y11X-1419 electrical connector is taken as the object, the relevant technologies of accelerated life test for quick assessment of product reliability under multiple stresses have been comprehensively researched.In chapter 1, the background of the research work and important significance of the dissertation were discussed. The developing history and current situation of some crucial techniques at home and abroad, such as the statistical model of accelerated life test, the optimum design of accelerated life test plan and statiatical analysis methods of test data were reviewed, and the existing problems were presented. The current research situation and problems of electrical connectors were generalized. Finally, the main research contents and the frame structure of this dissertation were given.In chapter 2, the reliability statistical model was derived from the failure mechanism. Firstly failure analysis was carried out for aerospace electrical connectors, based on the underlying causes of contact failure, which is insulation film make-up on the electrical connector contacts surface, the law of film growth was researched. To combine with the electrical connectors structural characteristics, by using the asymptotic distribution theory, the derived product contact life follows the two-parameter Weibull distribution. Based on the chemical reaction and fretting corrosion theory, the failure physics equation between connector life and multiple stresses, which is generalized Eyring model, was derived, consequently the reliability statistical model of electrical connectors under multiple stresses of temperature and vibration was set up.In chapter 3, the optimized design method of constant multiple stresses accelerated life test plan under periodic inspection was proposed. According to the reliability statistical model, by using uniformly test theory, the combined mode of different stresses and testing times were determined, with the principle of equal probability for periodic inspection time, the multiple stresses optimized design mathematic model of electrical connector test plan under periodic inspection was proposed. The result about the multiple stresses optimum design of electrical connector accelerated life test plan under periodic inspection shows that the optimized test plan can greatly raise estimation precision of test data. Meanwhile the robustness analysis was carried out for optimized test plan, the result of analysis provides a theoretical basis for the robustness test plan design with the initial selection of model parameters.In chapter 4, the simulation and evaluation’s method of multiple stresses accelerated life test plans under periodic inspection was built. Taking asymptotic variance expected value and standard deviation of product median life under normal working stresses level as evaluation criteria of accelerated life test plan’s estimation precision and stability respectively, simulation method of multiple stresses accelerated life test under periodic inspection was proposed by the Monte-Carlo method. By using periodic inspection maximum likelihood estimation theory, the mathematic model used for multiple stresses accelerated life test plan’s simulation evaluation was built. Meanwhile, taking the asymptotic variance mean and standard deviation of random samples as a substitute for its expected value and standard deviation respectively, simulation evaluation’s method of test plan was proposed. The result of simulation evaluation of test plan shows that the proposed optimization theory of multiple stresses accelerated life test plan under periodic inspection is true, and the method of that is feasible. In chapter 5, the versatile maximum likelihood estimation method was used for treating the interval data, the estimation value of electrical connector reliability characteristics was obtained, the reliability level of electrical connectors under working stresses was quantitatively assessed.In chapter 6, the high precision confidence interval estimation method of multiple stresses accelerated life test data was proposed. Based on the two-step fitting regression method, leading the Bootstrap estimate method into regression analysis, by correcting the bias of the Bootstrap estimate value, the Bootstrap regression confidence interval estimate method of reliability characteristic statistics under the condition of small samples was proposed. The simulation result shows that confidence interval is satisfied with demand of confidence degree.In chapter 7, the verification method of reliability statistical model under multiple stresses was proposed. Combining with chart analysis and numerical analysis method, the electrical connector life distribution model was certified by statistical analysis of the accelerated life test data. By transforming the accuracy validation problem of accelerated life model into the coplanarity test problem of spatial data points from the perspective of three-dimensional space, from the point of view of statistical test, accelerated life model under multiple stresses was fitted by multiple linear regression method. Taking the statistic as the test target, which characterizes the relative size of the sum of square of vertical distance between the spatial data points and fitted values, and the sum of deviation square of spatial data, the verification method of multiple stresses accelerated life model by using constant stresses accelerated life test data was proposed, which could quantitatively assess the accuracy of accelerated life model. The verification result of aerospace electrical connectors’ reliability statistical model shows that the model can preferably describe the nature of the electrical connectors’ life characteristics variation under multiple stresses of temperature and vibration. By further microscopic analysis of Scanning Electron Microscope and Energy Dispersive System, the rationality of the reliability statistical model established from the failure mechanism was proved.Finally main results and conclusions of this dissertation were systematically summarized. The study emphases of the further research work were discussed and forecast.更多还原