Low Cycle Fatigue Life Of Space Bearings Based On Elastoplastic Damage Constitutive Model

Rolling bearings are all important parts of the rotating mechanism.Rolling bearings used in the aerospace sector are sometimes subject to overload failures,this load exceeds the rated static load of the rolling bearing.And the overload conditions often lead to plastic deformation of the bearing rolling element and the inner and outer ring raceway contact area.The accumulation of plastic deformation eventually leads to fatigue failure of the bearing,which is called low cycle fatigue failure.In order to better explore the fatigue life of rolling bearings under aerospace overload conditions,The elastoplastic constitutive model of GCr15 coupling damage is established,and the low cycle fatigue life of rolling bearing is studied.The model of low cycle fatigue life of rolling bearing under reasonable space condition is established.Therefore,this paper mainly from the following aspects of the bearing steel material constitutive and bearing low cycle fatigue life prediction research.Firstly,the basic theory of elastoplastic constitutive is studied.Based on the cyclic properties of bearing steel GCr15,the non-destructive elastoplastic constitutive equation of GCr15 is established by using the unified plastic constitutive model theory.The damage evolution equation of GCr15 was established by studying the Lemaitre damage theory,and the equivalent strain theory was used to couple the damage to the non-destructive elastoplastic constitutive mechanism.The elastoplastic constitutive model of coupling damage was established.The elastoplastic constitutive equation of the coupling damage is established by the backward Euler method,and the implicit stress integral is carried out.At the same time,the consistency tangent stiffness matrix of the material is obtained by solving the differential equation.On the basis of the previous step,the solution process of elastoplastic damage constitutive equation is written by FORTRAN language.And the elastomeric damage constitutive relation is embedded into finite element software ABAQUS through user program UMAT.The damage behavior of bearing steel GCr15 under uniaxial and cyclic loading is analyzed by ABAQUS,and the parameters in the constitutive equation of elastoplastic damage are analyzed.Finally,the theory of low cycle fatigue life prediction is studied,the finite element analysis model of cylindrical roller bearing is established in ABAQUS by combining the constitutive equation of elastoplastic damage of GCr15.The low cyclefatigue life of rolling bearings is studied by means of mathematical modeling and finite element analysis.And a prediction model of low cycle fatigue life for rolling bearings under aerospace overload conditions is established.The fatigue life of the rolling bearing under different overload conditions is studied.The damage,the equivalent stress and the change of the plastic strain and the influence on the life of the rolling bearing are analyzed.The low cycle fatigue life of rolling bearings was calculated by the established prediction model and verified by experiments.The results show that the proposed model can reasonably predict the low cycle fatigue life of rolling bearings under aerospace overload conditions.