Research On Ultrasonic Impact Deformation Strengthening And Surface Performance Of High-speed Train Brake Discs

With the popularization of high-speed railway lines,the safety requirements for high-speed trains have become more stringent.Stable and reliable braking technology is the prerequisite and guarantee for trains to achieve high-speed operation.As the core of the basic braking device,the brake disc plays a key role.Applying ultrasonic impact strengthening technology to the surface modification of brake discs and improving the mechanical properties and Tribological properties of brake discs is an important direction for exploring the strengthening technology of brake discs.This paper adopts the method of combining computer simulation and basic experiment to carry out research.Theoretical reference is provided for the application of improving the mechanical and fricological performance of the brake disc.(1)The dynamic software LS-DYNA was used to simulate the ultrasonic impact strengthening process of the brake disc material,and the effect of different process parameters on the equivalent residual stress,equivalent plastic strain and surface morphology of the brake disc specimen was studied.The results show that the equivalent stress field spreads radially around the affected area,showing a trend of first increasing and then decreasing along the depth direction,and the maximum residual stress appears in the subsurface layer.With the increase of static pressure and impact time,the equivalent residual compressive stress and equivalent plastic strain of the brake disc specimens increase,and the dents of the surface impact pits deepen.(2)Use the grain analysis module of the finite element software DEFORM-3D to simulate and analyze the grain refinement process of the surface layer of the ultrasonic shock-strengthened brake disc.The results show that the ultrasonic impact strengthening causes the dislocation density inside the material to change continuously.As the dislocation density increases,the internal structure of the material begins to recrystallize dynamically,the number of grain boundaries on the surface of the sample increases,and the grains are significantly refined.The larger the grain size of the sample matrix is closer to the brake disc.(3)Design a complete test of the ultrasonic impact strengthening of the brake disc to study the influence of different process parameters on the strengthening effect.The results show that the surface roughness of the brake disc specimens strengthened by ultrasonic impact is reduced,the surface layer introduces the residual compressive stress field,and the surface hardness is also effectively improved.Increasing the static pressure and impact time can reduce the surface roughness,but excessive static pressure will aggravate the wear of the impact head and make the surface roughness rebound.The residual compressive stress and microhardness of the surface layer increase with the increase of static pressure and impact time.