Investigation On The Influence Of Contact Stiffness Of The Main Bearing Cover Side On The Reliability Of Crankshaft And Bolt

There is often a breakage of crankshaft and bolt with a certain type of diesel engine.Most of the breakages of the crankshaft take place at first connecting rod journal,and the breakages of the bolt take place at inlet side of engine.The interference between the main bearing cover side and the body is from 0.038mm to 0.114mm.But we verify that there is a wide and ultra-narrow problem with the interference.The interference between the main bearing cover and the body produce plastic deformation,in order to resist the deformation of the main bearing cover side of the body and the body will produce contact stiffness.Because of the different amount of interference,the resulting plastic deformation is different,so the contact stiffness is different.For the interference is wide and ultra-narrow,surface contact stiffness is too large and too small.There is of great significance to study the influence of the contact stiffness on breakage ofthe bolt and crankshaft.In this paper,the crankshaft and the bolt are analyzed by static calculation and multi-body dynamics calculation considering the contact stiffness.And the breakage of the crankshaft and bolt are analyzed.The research content is divided into four aspects:(1)The multi-body dynamics calculation consider the contact surface stiffness.Study the influence of the contact stiffness on force of the bearing force.Based on the typing contact theory,the contact stiffness is obtained,then the contact stiffness is applied to the multi-body dynamics calculation by the spring element.The influence of contact stiffness on the vertical force and lateral force of main bearing is analyzed.And the stress component in the axial direction of the bolt is divided into points to get the force of the bolt,and the force of the inlet and outlet side bolts is compared.(2)The influence of side contact stiffness on the main bearing cover is analyzed by static calculation.The influence of the contact stiffness of the side surface on the contact pressure,the inclination of the bolt head surface,the displacement of the main bearing cover is studied.(3)The influence of contact stiffness on bolt vibration and bolt stress was analyzed by static calculation.Evaluate the risk of bolts according to the SWT critical surface method,consistent with the actual bolt fracture position.And the failure mechanism of the bolt was analyzed according to the simulation results.(4)By changing the contact stiffness,simulate the state of reduced preload of the bolt.The force of the bearing and the stress and strain of the crankshaft are analyzed when the preload of the bolt is reduced.Stress and strain of The crankshaft is analyzed,and the failure mechanism of the crankshaft is analyzed by combining the failure phenomenon of the engine.Through the above research,comprehensive simulation results and fault phenomena,the failure mechanism of the bolt and the failure mechanism of the crankshaft are analyzed.In order to avoid the failure,the scope of the interference is regulated.