The Analysis On The Dynamics Behavior Of A Crankshaft-Rolling System And The Research On Its Fatigue Strength

Crankshaft system, as the core component of many instruments used for the transformation of rotary motion and reciprocal motion, has been widely used. It working in a very tough condition, bearing cyclical loads with mutation, eventually leading it to fatigue damage, in some extremely case even cause very serious consequence. However, most crankshaft are enclosed the machine inside, the fatigue destruction always with latency and burst characteristic. How to ensure its reliability becomes an urgent problem in machine design. So, the system dynamic behavior and crankshaft fatigue strength is needed to deep study. Today, researches on I.C.E. sliding bearing crankshaft system is quite advanced, while on the P.A.C rolling bearing system is comparatively weak. That’s the reason, why this topic chose P.A.C crankshaft-rolling bearing system as study object.The topic is originated from the Natural Science Fund for Colleges and Universities in Anhui Province-"Coupling Analysis and Comprehensive Optimization on Multidisciplinary Performances in the P.A.C. Rolling Bearing System (1208085ME77)" and "Coupling Analysis and Application Researches on Multidisciplinary Performances in the I.C.E. Sliding Bearing System (KJ2010A042)". The main task is to study the dynamics behaviors of the crankshaft-rolling bearing system and to make advance for crankshaft fatigue strength analysis, some fundamental work has been already finished by my tutor professor He Zhixian. This paper by introduce elasticity and structural mechanics, offer a new method to deal with crankshaft-rolling bearing system, and by introduce lubrication analysis to give a new way to calculate crankshaft stress, and observe the influence to crankshaft fatigue strength prediction.First, some researches in relative fields abroad and domestic are reviewed in this thesis, the shortages to calculate the crankshaft strength are founded. the direction for future effort is pointed out, then the main innovation of our work is listed in this paper.Second, the crankshaft-rolling bearing system for a4L-20/8type piston air compressor is chosen as the study object. Software UQ Matlab, ANSYS and ADAMS are employed for establishing a rigid-flexible model, and belt transmission force is considered in the model, so dynamical simulation for crankshaft-rolling bearing system can be prepared.Third, the relationship between the force and the deformation in details (such as:bearing material, contact form, rollers shape, internal loads distribution) is obtained to apply the elasticity and structural mechanics. The dynamical simulating model of the crankshaft-rolling bearing system for4L-20/8type air compressor is solved at the standard condition.ie. Crankshaft speed is400r/min. Multidisciplinary dynamics performance are obtained, and the different simulating results between two methods can be observed obviously.Fourth, the dynamical nodal forces applied at the rod bearings are calculated by lubrication theory, so that the load boundary condition can be got to calculate crankshaft stress in ANSYS, a FEM software. The variable curve of the dangerous nodes’stress is obtained. he dangerous nodes’stress is changed periodically according our calculating result.Fifth, the crankshaft fatigue strength is predicted according to the dangerous nodes’stress curve and miner’s accumulating theory is applied to life prediction, while lubrication analysis is also considered.Finally, the main task is summarized in this thesis, some future research work is proposed in the end.