低温下高强钢缺口板断裂试验及数值分析

Fracture experiments and numerical analysis of structural steel notched plates at low temperature

为研究低温下结构钢断裂机理及抗断设防,在冷脆转换温度(-45℃±2℃)下对10个16mm厚高强钢缺口板进行了单向拉伸断裂试验,研究缺口尺寸(a,2b)对高强钢断裂模式的影响。试验结果表明:初始裂纹形成于缺口边缘内侧,断口心部有一条清晰的起裂棱。低温下缺口板断裂强度变化较大且明显高于常温环境,缺口愈尖锐,断裂延性愈差。对高强钢缺口板断裂试验进行基于静水应力型广义屈服模型和Mises屈服模型的数值模拟分析,结果显示广义屈服模型较Mises屈服模型具有较高精度,并用已有的椭球面断裂准则、Hancock等效应变断裂准则和Wierzbicki等效应变断裂准则进行断裂分析和对比验证,表明金属椭球面断裂模型对预测中等厚度高强钢缺口板的初始开裂有较高精度和较广的普适性。

To study rupture mechanism and fracture design of structural steel at the low temperature, fracture experiments were tested on 10 notched plates with the thickness of 16 mm at the ductile-brittle transition temperature （ - 45℃±2℃ ）. The load displacement curves of notched plates were recorded accurately and the results of experiments indicated that the first crack initiated at the notched edge and expanded rapidly along the width of the plates. Finally, the specimens fractured at the critical section and there was a clear edge. Fracture strength at the low temperature was obviously higher than the specimens at room temperature ,and the more the gap was sharp, the more the fracture ductile was poor. By numerically simulating the fracture stress field of the notched plates at initial cracking based on generalized yield model and Mises yield model,it showed that the generalized yield model was more accurately than the Mises yield model. Comparing the ellipsoid metal fracture criterion, Hancock equivalent strain fracture criterion and Wierzbicki equivalent strain fracture criterion, which showed that the applicability and accuracy of the ellipsoid metal fracture criterion were comparatively verified.