The Fatigue Strength Analysis Of Crankshaft Based On The Multi-body Dynamics And The Dynamic Characteristics Research Of The Cracked Crankshaft

Crankshaft is an important part of internal combustion engine;its performance is closely related to the reliability and life of the internal combustion engine.During engine working,crankshaft bears the complex and alternating stress of torsion and bending,which can generate the serious stress concentration effect in some parts of the crankshaft,thus fatigue cracks occur easily at maximum stress parts of crankshaft.So it is necessary to check the fatigue strength of crankshaft.In addition,if the crankshaft crack,and not to be found in time,will lead to broken shaft accidents.So it is highly indispensable to develop the research on detection of crankshaft crack.In this paper,a certain model of crankshaft of a diesel engine manufacturing enterprise was taken as the main research object.Firstly,the entity model and assembly of the diesel engine crank connecting rod mechanism was established using UG software.The assembly model was imported into multi-body dynamics software ADAMS to establish a reasonable simulation model of crank connecting rod mechanism.Dynamic simulation was carried out under the rated conditions,providing accurate boundary conditions for finite element analysis of crankshaft.Then,according to the crankshaft load boundary conditions derive from the simulation analysis,the finite element model of the crankshaft and bearing assembly was established and the linear and nonlinear contact analysis was carried out in ANSYS workbench,in order to gain stress of the dangerous parts of crankshaft.And on this basis,the crankshaft fatigue strength was checked.the results show that the crankshaft can meet the requirements of fatigue strength.Finally,the effects of two form cracks on the dynamic characteristics of crankshaft have been researched.Studies have shown that the dynamic characteristics of crankshaft is closely linked to the depth and location of crack;the natural frequency of crankshaft will decrease to varying degrees with the increase in depth of crack;When the crack is occurred,the low order natural frequency decrease is more noticeable,and the first order natural frequency change rate is the largest.Above research methods and conclusions,laid a certain foundation for the study on the detection of crankshaft crack.