Tolerance design of revolute clearance joints for aero-engine planar maneuvering mechanism by uncertain dynamic performance evaluation

Abstract

The planar maneuvering mechanism’s motion accuracy and dynamic performance are critical for aero-engine power adjustment and vibration reduction. The uncertain clearance tolerances in the revolute joints lead to uncertainty in the joint contact characteristics and the mechanism’s dynamic performance. The combination of multiple joints’ clearance tolerances can be rationally designed and selected to balance the economy of joint manufacturing and the reliability of mechanism performance. In this paper, the uncertainty relationship between clearance tolerances of the joints and mechanism characteristics is investigated by using fuzzy sets and fuzzy algorithms. A new conformal contact model is established to accurately evaluate the contact forces of the revolute joint containing small clearance, which is demonstrated to have better performance when the joint clearance is small by comparing with two traditional models. The mechanism’s dynamic model is constructed, which introduces the contact forces and dissipation effect of multiple joints. Then, the fuzzy distribution and the fuzzy decomposition theory are applied to represent and grade clearance tolerance, respectively. The uncertain static contact characteristic of the joint is studied at different clearance tolerances by using the fuzzy transformation method, and the corresponding clearance tolerances can be designed and selected according to the specific required elastic contact force. Meanwhile, the uncertainty mapping relationship between the clearance tolerance of multiple joints and mechanism dynamic performance is also established, and the combination of multiple joints’ clearance tolerances can be rationally selected based on the evaluation results of uncertain dynamic performance. The proposed method provides a significant reference to realize the specified mechanism’s performance requirement by designing the joint clearance tolerance.