Transient Dynamics And Fatigue Analysis Of The Diesel Engine Mianbearing

In the diesel engine operation,the mainbearing bears the bolt preload,bearing force over the surplus and mechanical force of the crankshanft,the mainbearing fatigue damage will cause the engine to stop working,lead to a great economic and property losses.With diesel power lifting,more attention has been paid to the safety of mainbearing.But now research is still not perfect,some scholars use statics method to research mainbearings.For certain types of diesel engines,oil film pressure is appied to the finite element model as the load boundary conditions,and transient dynamics are used to predict the fatigue life of the main bearing structures.For a 12-cylinder diesel engine model,and based on the reduced dynamic substructure mode synthesis method to establish a model of the crankshaft lubrication system,to study the characteristics of the crankshaft vibration and lubrication system with flexible coupling multi-body dynamics and lubrication methods,and with the test results Compare,verify the correctness of the model.The results found: the 6th mainbearing withstand greater bearing force and torque,lubrication is relatively poor.We built a simplified model of the 12 V diesel engine,and taking into account the contact between the contact surface and bolt preload.Dynamic film pressure is appied to the finite element model as a load boundary condition,use transient dynamics method to study the dynamic response of the mainbearing structure.The results showed that: on both sides of the main bearing cap,stress concentration is showed in a fillet between two preloaded bolts,but far less than the yield stress limit of the material,is a high cycle fatigue problems.For stress concentration node of the main bearing structures,use a simplified method of rainflow counting to process its load-time history,and get stress cycles.Using nominal stress fatigue analysis methods(ie,S-N curve),combining Miner linear fatigue damage cumulative theory,predicted fatigue life of the mainbearing system.The results show that:the fatigue life of the stress concentration part of the mainbearing can meet the requirements of the engine.