The Study Of The Effect Of Surface Step And Void On The Initial Plasticity Yield Of Single Crystal Copper

As the research of MEMS gradually deeps, it is increasingly important to studythe properties of nano-materials. Inside and in the surface of actual nano materialsoften exist defects, such as voids and surface steps, which destroy the integrity ofmaterial structure and induce stress concentration, affecting its initial plasticity yield,and furthermore temperature also affects the initial plasticity of materials. So in thearticle, the effect of surface step, void and temperature on initial plasticity of singlecrystal copper is investigated with molecular dynamics simulation. The single crystalcopper nano-indentation with surface step modeled, the effect of surface step oninitial plasticity of single crystal copper is discussed, and as stress concentration,surface step only effect the initial plasticity near the step, resulting lower initial yieldload Fyand strength σythan that of no step, hardly having no effect on Fyand σyaway from step, and furthermore the effect of the connection between d and ayon Fyand σydenotes that when-1.59<d/ay<1.29, Fyand σyremarkably lowers, beyond ithaving no effect on Fyand σythat fluctuate round that of no step. the effect of stepheight on initial yield indicates that the lower the step is, the smaller the impact is,and Fyand σydecreases with the increase of h/d, meaning that the bigger h is and thesmaller d near the step is, the more serious the effect of the step is. the effect ofindenter radius on initial yield shows that as the radius increases, Fyandcorresponding indenting depth δymagnifies and σyslightly minishes, and however thevariation trend of Fyand σywith the value of d has no difference. The single crystalcopper nano-indentation with single void simulated, the phenomenon is discoveredthat initial plasticity of single crystal copper is both influenced by void radius Rvandthe distance dvbetween the void center and surface, it is found that when Rv/dv﹥0.35,σyreduces with the increase of Rv/dv, when Rv/dv﹤0.35, σyapproaches that of no void,and the dislocation spreading is hindered by the void, when Rv/dv=0.35, the blockreaches the most critical and σyreaches the greatest. The single crystal copper stretchwith single void simulated, σyfalls with the increase of Rv, dislocation nucleating andextending near the void, and the effect of temperature on the initial yield of singlecrystal copper stretch states that as the temperature rises, the critical stress necessaryto nucleate initial dislocation namely the initial yield strength lowers.