机电产品在服役期间因零件失效而产生故障，重组维修破坏了原有的系统可靠性模型，因而需要对设备可靠性问题重新进行研究和评价。基于机电系统中零件的失效时间分布密度函数，研究了在重组维护过程中机电系统服役期间零件年龄结构的分布规律，发展了机电系统可靠性数学模型。通过仿真研究，探讨了系统服役期间年龄结构、可靠度和失效率的发展规律，定量地研究了失效时间分布密度函数的参数对系统可靠度的影响。这对于评估机械系统的可靠性和全生命周期的失效率，制定合理的维修策略具有重要意义。

The mechanical equipment faults result from parts failure in the period of service time. Due to reassembly and maintenance, the reliability model for mechanical equipment is broken, so it is necessary to research and estimate the safety reliability of mechanical system. Based on the timetofailure density function of parts, the mechanical system reliability model is constructed to track the change course of age structure of part population for the mechanical systems that are reassembled and maintained. By means of simulation of the system reliability model, concerned parameters with mechanical systems service life are defined.The paper discusses how the timetofailure density function hase influence on the service life for mechanical systems undergoing reassembly and maintenance. It is significant for estimating reliability and failure rate of systems and establishing reasonable maintenance policies.