Time-dependent strength reliability analysis of four-link mechanisms based on extreme moment method

Strength is crucial in the design of structural and mechanical systems. Although current research predominantly focuses on the structural strength reliability, there is a marked scarcity of studies addressing the strength reliability of mechanical mechanisms. Unlike static structures, the dynamic properties of mechanical systems often evolve over time, complicating the assessment of their strength reliability. Mechanical operations may indeed entail the risk of strength failure. Consequently, this article explores the time-dependent strength reliability of four-link mechanisms. Initially, a finite element model of the four-link mechanism is developed, incorporating the effects of material properties and applied loads on the dynamic behaviour of the mechanism. Subsequently, a time-dependent reliability method predicated on extreme moments is introduced to calculate the strength reliability of four-link mechanisms. This involves evaluating the fractional moments of stress extremes using the rotational quasi-symmetric point method (RQ-SPM) and determining extreme responses from quasi-symmetric points via Kriging. Furthermore, employing the maximum entropy method (MEM), constrained by fractional moments and extreme responses, the probability density function (PDF) of stress extremum is derived, allowing for the calculation of strength reliability through PDF integration. The efficacy and precision of this approach are corroborated by the Monte Carlo method and a double-loop Kriging surrogate model method, confirming the method's high efficiency and accuracy.