Study On The Influence Of Laser Shock Peening On Fatigue Performence Of LZ50 Axle Steel

With the rapid development of high-speed and heavy-haul railway transportation,the axle becomes more and more serious.Laser shock peening of axle material is novel measure to improve the anti-fatigue property.Thus,study on the influence of laser shock peening on the fatigue property of LZ50 axle steel has theoretical and technical significance for prolonging the service life of axles and improving the running safety of trains.In this study,the laser shock peening was carried out on the surface of the wheel seat.The effects of laser energy and shock times on the hardness,residual stress and depth of the hardened layer of the axle were studied.The optimization of laser shock peening parameters was obtained through fatigue tests.The change of S-N curves of axle specimens before and after laser shock peening was explored through fatigue tests under different loads.Finally,the influence of laser shock peening on the fatigue life of axle was analyzed using ANSYS nCode.The main conclusions are as follows:?1?The surface hardness,surface residual compressive stress,and fatigue life of the LZ50 axle steel were significantly improved after laser shock peening.Under the same laser energy,as the number of impacts increased,the surface hardness and surface residual stress were increased,and the fatigue life was decreased.Under the same number of impact times,as the laser energy increased,the surface hardness and residual stress were increased,and the fatigue life was decreased.The treated axle presented the best fatigue performance when the laser energy was 5.4 J and the impact was one time.?2?The treated and untreated LZ50 axle steels presented similar fracture morphologies.The fatigue cracks had multisource.Many of quasi-cleavage fracture in the propagation area were observed revealing the trans-granular fracture mode.A large number of dimples and second cracks appeared in the final fracture area.?3?The fatigue tests of the LZ50 axle specimens treated with the optimal laser shock peening parameters were carried out.The S-N curves of treated and untreated axle steel were obtained.The fatigue limit of the axle specimen treated with laser shock peening was 168.4MPa.The fatigue limit was increased by 29.2%comparing with the untreated axle steel.?4?Through the ANSYS nCode,the fatigue life of the LZ50 axle strengthened by laser shock under optimal parameters was simulated and analyzed.The fatigue life under the axle load of 15 tons was 1.993×10¹⁴,which was 10%higher than that of the untreated axle steel.