焊接接头材料低周疲劳断口的分形分析

FRACTAL ANALYSIS OF FRACTURE SURFACE OF WELDING JOINT UNDER LOW CYCLE FATIGUE

对16MnR压力容器用钢焊接接头应变控制的低周疲劳试验,运用计算机视觉系统测量疲劳断裂粗糙表面,用二维变差法(Variation Method)计算了断口(焊缝金属和焊接热影响区)的Hausdorff维数,发现其随循环滞回能的增加而降低,焊接热影响区断口的Hausdorff维数的变化比焊缝金属断口的Hausdorff维数变化大;建立了疲劳寿命同Hausdorff维数的关系,说明分形维数愈大疲劳寿命愈长。

Hausdorff dimension of fracture surface roughness of welding joint, both weld metal and heat-affected zone, of pressure vessel steel 16MnR, tested under strain-controlled low-cycle fatigue, was examined with computer vision system and by two-dimensional variation method. Results show that it decreases with the increase of cyclic hysteresis energy. The Hausdorff dimension variation at heat-affected zone is higher than that of weld metal. It is believed that the higher the fractal dimension is, the longer the fatigue life will be.