Reliability modeling for dependent competing failure processes based on planar mechanism

Considering the influence of external random shock on the kinematic accuracy of mechanism, a new reliability model of dependent competing failure processes (DCFP) is proposed in this paper. The kinematic accuracy of the mechanism is limited by the original errors such as the dimension error and joint clearance error, and it is also affected by aging and wear-out during service life, thus eventually leading to functional failure. Meanwhile, according to the magnitude of the external random shock, the random shock has different effects on the degradation process of the mechanism. In this study, a DCFP model with accuracy degradation process and multi-type mixed shock is considered. The time-dependent kinematic accuracy reliability model of the planar mechanism is established based on the Gamma degradation theory, effective length model, mechanism kinematic error theory and the fourth moment technique. Moreover, the magnitude of random shock is divided into different regions when the extreme shock, cumulative shock, and δ-shock on mechanism reliability are considered. Finally, a numerical example of the pantograph mechanism is conducted to demonstrate the feasibility and effectiveness of the proposed model. The results show that the kinematic accuracy reliability of the pantograph mechanism reduces with the increasing of wearing capacity and external shocks. According to sensitivity analysis, an effective way to improve the reliability of the planar mechanism is to optimize its strength of the mechanism. The proposed method can be used to evaluate the reliability of planar mechanisms with dependent competing failure modes.