单个弹丸撞击316L不锈钢引起的变形场

Deformation field in 316L stainless steel by single shot peening

运用金属材料表面纳米化试验机对单个弹丸撞击316L不锈钢表面进行了撞击实验;采用激光共聚焦显微镜观察了弹坑的三维形貌,测量不同振动频率下弹坑的直径及离面位移;采用云纹干涉法对弹坑周围的面内应变场进行测量,并分析振动频率及撞击方式对弹坑尺寸、塑性应变大小以及塑性应变区范围的影响;采用有限元方法对单个弹丸垂直撞击试件表面的应变场进行数值模拟,与实验结果进行比较,分析了弹坑周围残余应力的分布。结果表明:随振动频率的增加,弹坑直径和离面位移都增加,频率在50~55 Hz,弹坑直径有突变,离面位移和振动频率呈线性关系;振动频率越大,塑性应变越大,塑性应变分布范围均大于弹坑直径的2倍;同一振动频率下弹丸垂直撞击比倾斜撞击的塑性应变大,而塑性应变分布范围相差不大;面内残余应变场的数值模拟结果和实验结果吻合较好,最大误差小于10%。

The experiment of the single shot impacting the 316L stainless steel surface was carried out using a surface nano-crystallization testing machine. Three-dimensional morphology of the dimple was observed with a laser scanning confocal microscope, and the dimple＇s diameter and off-plane displace- ment in different vibration frequencies were also measured. The in-plane strain around the dimple was measured by molt4 interferometry. The effect of the vibration frequency and the way of impacting on the dimple size, the plastic strain size and the plastic strain zone were also analyzed. In comparison with the experimental result, the strain field was simulated using the finite element method, and the distribution of the residual stress around the dimple was also analyzed. The result showed that the crater diameter and the off-plane displacement increases with the increase of the vibration frequency. When the frequency is from 50 to 55 Hz, the crater diameter experiences mutations. When the shot impacts the surface vertically, the greater the vibration frequency, the greater the plastic strain and plastic strain zone, and the plastic strain zone are two times larger than the crater diameter. The plastic strain by the vertical impact is slightly greater than the plastic strain by the oblique impact, but it has little effect on the plastic strain zone. The experimental U field strain is in fairly good agreement with the numerical simulation result, and the maximum error is less than 10%.