汽车传动系统零部件动态可靠性敏感度及随机参数相关性判别研究

The vehicle driveline is an important system including transmitting components, with which it can realize the transformation and transmission function of the mechanical energy. And the reliability based design of the transmitting system can ensure the vehicle's safety under running and also an indirect approach to improve the dynamic characteristics, fuel economy and emission identities of the vehicle. The strength of the drivelink and the environmental load working on the transmission system are all specified with dynamic stochastic characteristics.As a result of those aformentioned,the traditional analysis model and methods of reliability can not reflect the impacts of the random factors acting on the dynamic response characteristics of the drivelink as well as the results derived from the reliability analysis. And in addition, for lack of the experimental and statistical data, the designer will identify the correlation coefficients of each failure modes by experience or just ignore them. So there will be large error or even wrong values in the reliability evaluation under that supposition. To solve those problems proposed, the investigation here combining the simulation methods of random loads, reliability design theory, reliability based sensitivity analysis, reliablity based equilibrium design and correlation analysis, from the perspective of evaluating the sensitivities of reliability to the correlation coefficients to choose the random parameters and the correlation coefficients of each failure modes in the relaibility analysis problems, proposed a new method for reliability and reliability based sensitivity analysis and the theory principle of choosing the correlation coefficients. Therefore, the reliability and the effect of designed parameters to the reliability will be calculated with higher accuracy and the method and theory put forward here supports the reliability optimization design of the random structure system with theory foundations.

汽车传动系统是汽车实现机械能转换和传递的重要部件系统，传动系可靠性设计既可以直接地保证系统安全运行，又可以间接地提高汽车的动力性、燃油经济性和排放特性等。传动系零部件的强度和传动系所承受的环境载荷都存在着动态随机特性，常规的传动系零部件可靠性分析模型与方法，将无法反映出这些随机因素对传动系动态响应特性和可靠性分析计算结果的影响。另外，多数情况下设计者凭经验近似地指定或忽略随机参数或失效模式间的相关系数，所计算的可靠度一定存在着误差，甚至得出不正确结果。本研究将随机载荷模拟仿真方法与可靠性设计、可靠性敏感度分析、可靠性均衡设计、相关性分析等理论相结合，从可靠性对相关系数敏感度角度探索可靠性分析和设计中的随机参数或失效模式间的相关系数选取问题，提出相关系数选取的理论原则和相关失效模式下动态可靠性灵敏度分析新方法，从而更精确地计算可靠度及分析设计参数对可靠性影响，为可靠性优化设计提供理论依据。

课题针对汽车传动系统零部件的研究包括两个方面，一是动态可靠性敏感度的研究，车辆磨损零件随着运行时间的延长和磨损，磨损可靠度是由磨损速度决定的。通常情况下，零件磨损速度与汽车行驶速度、表面质量、环境温度、运行时间等有关。当零部件由于磨损而偏离原有设计尺寸时，逐渐可靠性降低甚至失效。对于车辆磨损零件渐变可靠性进行了深入研究。由于强度退化和载荷作用过程的随机性，导致可靠性随时间逐渐降低的渐变特性。研究采用矩理论、可靠性理论，剩余强度理论等讨论了车辆磨损零件的可靠性设计问题，从而对车辆磨损零件进行科学的可靠性预测具有一定的研究价值。为了提高发动机配气机构传动系统的工作性能，防止共振失效。项目根据配气机构传动系统的固有频率与凸轮激振频率的差绝对值不超过规定槛值的关系准则，定义了配气机构传动系统共振的准失效状态，同时根据可靠性技术推导出参数为正态随机变量时的准失效概率表达式，提出了避免振动的可靠性分析方法。另外，配气机构传动链脱节是内燃机工作运行的故障之一，传动链脱节概率的计算是定量分析传动链脱节的有效手段。在基本随机变量的概率特性已知的情况下，采用随机摄动方法，提出了配气机构传动链脱节概率计算方法，可以迅速准确地得到传动链脱节的概率信息。二是随机参数相关性判别的研究，从可靠性对相关系数敏感度的角度探讨了可靠性分析和设计中的随机参数的相关系数选取问题，根据可靠性灵敏度的计算结果建立了随机参数之间的相关系数选取的理论原则，给出随机参数之间相关性的判据，根据所获得的相关系数选取的理论方法选取随机参数的相关系数量值，讨论了相关系数对可靠性的影响，以改变设计者凭经验近似地指定相关系数或者忽略相关系数进行可靠性设计的状况。将相关系数量值选取的理论原则应用到机械的可靠性设计之中，可以准确地给出机械可靠性的度量，从而准确的获得设计参数的变化对可靠性的影响规律，从而为机械设计、制造、使用提供坚实的理论支撑。