Influence Of Inclusions On Plastic Damage And Crack Initiation Of LZ50 Steel

As an important part of train,axle is not only used for bearing,but also plays a driving,guiding and driving function.Its fracture damage directly affects transportation safety.However,in the production process of axle steel,internal defects such as inclusions will inevitably appear,resulting in uneven material of the axle steel,which directly affects the quality of the axle steel.Therefore,it is important to study the deformation and damage process of axle steel caused by inclusions and the influence of inclusions on the generation of cracks in axle steel.Taking the LZ50 steel as an example in this paper,the effect of inclusions on the deformation behavior and crack initiation of the material was studied by combining the experiment with the ABAQUS finite element simulation.Firstly,on the Gleeble-3500 thermal simulation testing machine,high temperature tensile and compressive experiments were performed on LZ50 steel samples under different deformation parameters,and the relationship between the tensile and compressive stress curves was compared.The fracture morphology of the tensile specimens was observed by scanning electron microscopy.It is found that the presence of inclusions leads to ductile fracture of the material,and the damage mechanism is plastic damage.Under the tensile stress,the separation of inclusion and matrix forms micro-holes,and the micro-holes grow until they become macroscopic cracks,leading to the fracture of the material.Secondly,on the basis of the high temperature tensile experiments,the simulation results of the model with or without the addition of the damage criterion and the model with or without the inclusion of inclusions were compared separately using ABAQUS finite element software to build the correct model.And the validity of the model was verified.The established model was used to simulate the process of damage initiation and damage evolution in the plastic deformation of materials caused by inclusions,and the effects of different temperatures and strain rates on damage initiation and cracking of the model with inclusions were analyzed.Finally,based on the ABAQUS finite element simulation,the influence of the location,size and shape of inclusion on the crack at the interface between inclusion and matrix was analyzed,and the following conclusions were drawn:Inclusions located on the surface of the material are more harmful;the larger the radius of inclusions,the more easily the material will be damaged;when the direction of the external stress is parallel to the long axis of the elliptical inclusion,the material is subjected to the greatest stress.