Performance Analysis of Multibody Mechanical Systems with Imperfect Flexible Joints

Multibody mechanical systems consist of interconnected bodies joined by various joints. Joint imperfections, often stemming from wear, introduce clearances that result in impacts. To mitigate these effects, soft-material bushes are employed to add flexibility. This research evaluates the combined impact of joint flexibility and imperfections on system performance. A mathematical model for the dynamic equations of motion is formulated. The performance of a crank-slider mechanism with imperfect, flexible joints is examined using advanced commercial software that integrates Multibody System dynamics with the Finite Element Method. The findings indicate that while mechanisms with ideal rigid joints exhibit optimal performance, such joints are impractical; inherent clearances generate significant impact forces and peaks in the crank's actuating torque. The results demonstrate that flexible joints attenuate these torque peaks by nearly half. However, this flexibility introduces vibrations, which affect the mechanism's overall performance. This study compares mechanisms with flexible imperfect joints against those with perfect and imperfect rigid joints. Although flexible imperfect joints reduce torque peaks by approximately 50%, they introduce low-amplitude vibrations due to elasticity. Furthermore, simulations show that joint flexibility redistributes contact forces, decreasing the severity of impact stresses that typically accelerate wear and fatigue. These findings indicate that incorporating controlled flexibility into imperfect joints can substantially enhance operational smoothness and durability. Overall, this study provides critical insights for designing more reliable mechanical systems, particularly where joint clearances are unavoidable.