Finite Element Analysis And Experimental Study On Round Rods By Laser Shock Peening

Laser shock processing is a novel surface strengthening technology.It employs laser beam with high energy and short pulse as a tool to strengthen the surface of the material.This paper uses the method of combining numerical simulation and experiment to study residual stress distribution of aluminum alloy round rods and the influence of laser shock peening on material fatigue life.The main contents are as follows:Firstly,based on the the generation principle of laser shock wave and gas dynamics theory,we make a compared study of the peak pressure during laser shock peening process in the non-constrained model and constrained model.According to the detonation wave C-J theory,this paper expounds the principle of the formation of the laser-induced stress field,discusses the transmission mechanism of laser wave in constrained model,establishes the mechanical model of the metal material strengthened by laser shock and derive and estimate the formula of the peak pressure induced by laser shock.Secondly,the aluminum alloy round rods finite element models is established by ABAQUS software to simulate the propagation and attenuation of the stress wave in the aluminum alloy round rods after the cylindrical end face and circular face being shocked by laser.And the residual stress distribution of cylindrical end face and circular face after being shocked by laser single point and multi-points is analyzed separately.The influence of the diameter factor on the distribution of residual stress is studied.At last,the distribution characteristic of residual stress on laser shock strengthened positions are studied through comparing the difference of the distribution regular of residual stress on different region shocked by laser on curved surface.Finally,the laser shock experiment is carried out with 2024 aluminum alloy rods.The fatigue test is conducted with the shocked specimen and the un-shocked specimen respectively to analyze the effect of laser shock process on the fatigue life of round rods.In addition,the micro-structural features of fatigue fracture morphologies of specimens are observed by scanning electron microscopy(SEM).Mechanism of extending fatigue life of aluminum alloy round rods strengthened by laser shock is explained from micro perspective.