ABSTRACT
Fault tree analysis is an important method in safety engineering and reliability engineering, which is a top-down method and is able to map the relationship between complex events such as system-level failures and basic events such as component-level failures by creating a logic diagram of the overall system. For the reliability analysis of mechanical systems, it’s extremely important to obtain the quantitative relationship between the failure and the design parameters except the logic relationship between the top event and the basic event in the design stage. However, the conventional fault tree analysis is hard to build such relationship. As a result, this paper extends the conventional fault tree by developing a new arborescence under basic events of fault tree. A kind of custom gate is defined within our new method. The custom gate is used to build the quantitative relation between the process variables (force, deformation and other performance feature), which can be used to characterize the basic failure mode, and basic random variables (dimension parameters, material parameters and load parameters, etc.). According to different failure models, the custom gate can be different. Then the limited state function of the basic event can be presented based on physical model. The procedure of this method is demonstrated in this paper, and different reliability models for mechanical system can be represented clearly. A Monte Carlo method involving dependent variables is provided to calculate probability of the top event. An illustrative example of a lock mechanism is presented to demonstrate the method in this work.
