It is challenging and important to establish reliability model for mechanical systems with multiple functional performances. This article develops a model of competing failure for mechanical systems under catastrophic failure due to external shocks and multi-functional failures. Shock model is used to analyze the catastrophic failure. Functional failures are demonstrated by functional indicators which are functions of specific variables including constant variables and degradation variables. Functional failure occurs if the functional indicators are beyond a limit δ. Brownian motion with non-linear drift is used to model the process of degradation variables. Besides, there are two kinds of dependence around these failure modes. The dependence of catastrophic failure and functional failure, due to shared external shock source, is illustrated by the instantaneous increments during degradation process; the dependence between multiple functional performances themselves is modeled by copula functions. Reliability of systems is calculated based on this model. A mechanical lock system is chosen as a case to verify the validity and practicability. This model can also be applied for other mechanical systems.

The performance failure and reliability of motion mechanism has a significant effect on industry reliability, operation safety and production economy. Motion precise is one of the typical performance indicators especially for motion mechanism with multibody and joints. Size of joint clearance degenerates with usage such as wear and deformation. Repeated start-stop lead to impact stress and plastic deformation for clearance joint particularly for mechanism with high load and long working cycles. This study attempts to investigate the wear process and performance failure model of multibody mechanism with clearance joints considering plastic deformation and wear. Quantification of plastic deformation caused by repeated impact stress of joints is studied by formulation. Then, a novel wear process model is established, after which performance failure indicator is conducted. A linkage motion mechanism with multi revolution joints is studied to demonstrate proposed methods. This study provides valuable guidelines for degeneration prediction and reliability analysis of motion mechanism.

Many researchers have modeled systems under multiple dependent competing failure processes (MDCFP) in recent years. Typically, those failure processes consist of degradation (soft failure) and random shock (hard failure). In previous papers the threshold of hard failure has been a fixed value, which does not reflect engineering practices. Threshold refers to the ability to resist external random shocks, which shifts with time as the system is used. Thus, this paper establishes a model for MDCFP with instant-shift hard threshold. The hard failure threshold changes with time instantaneously, and it is also influenced by external shocks. This paper also presents a system reliability model. The effectiveness of the presented model is demonstrated by a reliability analysis of the micro-engine at Sandia National Laboratories. In addition, a sensitivity analysis is performed for specific parameters.

Flapping wing aircrafts have demonstrated unique advantages in military and civil fields due to their bio-inspired flight mechanisms. However, non-uniform wear in driving mechanisms remains a critical reliability concern during prolonged operation. This study presents a stochastic wear prediction framework that systematically integrates joint clearance dynamics, contact force variations, and material interaction parameters. Through accelerated life testing with flight condition simulations, the method establishes quantitative correlations between multi-source variables and wear progression patterns. Experimental validation confirms the framework’s effectiveness in predicting asymmetric wear distribution, with comparative analysis showing significant improvements in prediction accuracy over conventional single-factor models. The results identify three dominant wear contributors: dynamic clearance fluctuations, impact force randomness, and material compatibility limitations. These findings directly support the development of adaptive lubrication systems and wear-resistant material selection guidelines, offering practical solutions for enhancing flapping wing aircrafts’ reliability in complex operational scenarios.