高能气动喷丸致纯铜细晶化的实验与模拟

Experimental investigation and finite element simulation on grain refinement of copper due to shot peening

高能气动喷丸是通过剧烈塑性变形产生细晶材料的方法之一.用纯铜作为实验材料在高能气动喷丸实验机上作喷丸实验,利用表面形貌仪、显微硬度仪以及电子背散射衍射方法对经喷丸处理的试样进行表面粗糙度、硬度及晶粒尺度的测量.结果表明,表面粗糙度随处理时间的增长呈指数衰减趋势;晶粒尺度细化了一个量级,由初始的25.48μm细化至2.52μm;且显微硬度由原来的0.58GPa增加到1.25GPa.量纲分析得到喷丸过程的5个无量纲参数,利用有限元模拟研究了无量纲参数的影响.自编制程序产生丸粒的随机碰撞并调用Ansys/ls-dyna模拟碰撞过程,并将模拟1000次碰撞的结果与相应的实验值进行了比较.

Shot Peening（SP）is a typical severe plastic deformation method to produce ultra-fine grains of metallic materials.An experimental investigation is carried out on pure copper specimens by means of a shot peening machine driven by high energy air pressure,a surface roughness measurment tester,a micro-hardness indenter,an optical microscope and a scanning electron microscope equipped with electrical back scatter diffraction apparatus.The results showed that surface roughness takes on an exponential decay with disposal time,and that the grain size in the specimens with 1333.3s is 2.52 microns compared with the original value of 25.48 microns,i.e.it is refined by one order of magnitude.The micro-hardness testing on the specimen showed the hardness increased from 0.58GPa to 1.25GPa after SP treatment.On the other hand,a dimensional analysis is performed to examine SP process so that to obtain five dimensionless parameters and the method of finite element simulation is used to analyze the effect of dimensionless parameters on surface roughness.In order to further understand SP process,we used VB to write the sub-program for the random impact simulation,which then incorporated with finite element code Ansys/ls-dyna so as to simulate the collision process between balls and sample.And simulated results and experimental results were compared to verify the finite element model.