Study On The Prediction Of The Critical Dimensions For Inclusions In Wheel Rim Crack

During the service of locomotive wheels,the wheels bear cyclic loads.When the wheel is subjected to a large abnormal vibration load?such as bearing failure,limit working condition,etc.?,if there are large oxide inclusions in the 10mm²0mm range under the wheel tread at the same time,then,The stress concentration around the inclusions may induce the wheel rim crack,which leads to the fatigue crack of the wheel rim,that is,the rim crack.Since wheel rim cracking can cause serious train accidents,railway wheel manufacturers must know the composition,shape,and size of large inclusions that induce rim crack,to avoid the appearance of large inclusions that cause the rim crack in the manufacturing line,and to ensure the inclusion size does not exceed the safety requirements from the inspection line,so as to improve the quality of the wheel products.In order to meet the above requirements,the prediction of critical size of inclusions inducing wheel rim crack is studied in this paper.According to the theory of linear elastic fracture mechanics,the critical dimension of inclusions is a function of the shear-type crack?type II crack?threshold value(?K_II,th)and the shear stress???of inclusions.In combination with the simulation,?K_II,th can be obtained.At the same time,the shear stress?at different depths can be simulated,and then according to the shape of the captured inclusions,the inclusions can be accurately obtained under the premise of the shape of the known inclusions.Critical size.If?K_II,th can be obtained through experiments and simulation,at the same time,the shear stress?at different depths can be simulated,so that the critical size of inclusions can be accurately obtained under the condition of known inclusions shape and size.In this paper,the critical length of type II crack propagation is tested by self-designed tooling,The Contour integral solution module in ABAQUS is used to solve the stress field intensity factors corresponding to different crack lengths.The critical crack length is brought into Contour integral,and the threshold value of the stress intensity factor of the type II crack of a certain type of wheel material is obtained by simulation,the?K_II,th is 7.49 MPa?m?1/2;At the same time,by establishing a real finite element model of a wheel and a rail,the stress in the actual rim is calculated,and the shear stress amplitude??at 10 mm,12 mm,15 mm and20 mm under the tread is obtained under normal working conditions are:302 MPa,209 MPa,138 MPa and 78 MPa;under extreme conditions,the shear stress amplitudes??at 10 mm,12mm,15 mm and 20 mm under the tread are 461 MPa,337 MPa,216 MPa and 122 MPa,respectively;In addition,the composition,shape and size of seven large inclusions were obtained by fatigue experiments.According to statistical analysis,the large inclusions in the wheel rim are oxides,and the shape is elliptical,and the ratio of the long and short axes is between 2 and 7.According to the critical value of stress intensity factor obtained by the test,the rim stress distribution at different depths and the shape of the large inclusions obtained by the test,combined with the theory of fracture mechanics,the critical dimension prediction result of the wheel rim inclusions of a certain type of wheel is:the size of the inclusions induced by splitting All of them are millimeter-scale inclusions.Under normal working conditions and extreme working conditions,the critical dimension of large inclusions induced by splitting increases significantly with increasing depth.When the projected area of large inclusions is certain,the length of inclusions is half.When the ratio of the axes a/b is equal to 2,the risk of inclusions is the lowest.