中文摘要：

针对复杂机械产品在运转使用中的性能退化现象，提出面向时变性能的设计理念和方法。针对复杂机械产品，提出面向时变性能设计所需要解决的三个关键问题：一是要给出一个基准运转工况或者系统时变历程，这是对不同设计方案的时变性能进行评价设定共同的出发点；二是要进行多学科耦合分析，以精确仿真瞬态的系统行为；三是要根据瞬时的系统状态推算系统结构和系统性能的退化过程，从而为设计决策提供依据。结合汽车发动机对象的分析表明，系统磨损等结构退化现象对系统性能的影响非常明显。因此需要根据系统性能的退化分析，寻找影响时变性能的关键因素并加以改善。研究表明：时变性能已经成为决定产品竞争优势的重要因素；通过本文提出的思路和方法，将为有效改进产品的时变性能奠定基础。

英文摘要：

The methodology of designing for time-varying performance of products is analyzed to overcome the system degradation of products during running. For complex mechanical products, the following three key problems are presented to be solved. First, a benchmark of working condition or system degradation process should be set up to evaluate time-varying performance of different design schemes. Second, the coupling among different disciplines should be analyzed to simulate the transient system behaviors of products. Third, the degradation process of system structure and performance should be predicted and analyzed to provide information for the design decision. The case study on the internal combustion engine demonstrates that the system wear or other system degradation phenomena influence the system performance obviously. So the key factors related with performance should be found out and optimized on the basis of system time-varying performance degradation analysis. The research indicates that the time-varying performance is vital to complex products and the methodology presented in this paper will lay a foundation for improving the time-varying performance of products.