桥梁高性能钢HPS485W疲劳裂纹扩展速率试验研究

以国产桥梁用高性能钢HPS485W为研究对象，对7.5mm、12.5mm和19.5mm的HPS485W紧凑拉伸试样分别在应力比R=0.1、R=0.5和R=0.8的疲劳荷载下进行疲劳裂纹扩展速率(da/dN)试验，采用七点递增多项式的方法进行局部拟合求得试样的疲劳裂纹扩展速率。与传统桥梁用钢14MnNb相比，该文试验测得高性能钢HPS485W具有更优越的忍受疲劳裂纹扩展能力。试验结果表明:试样厚度是影响疲劳裂纹扩展速率的关键因素；对同一厚度的试样，疲劳裂纹扩展速率随着应力比R的增大而增大。此外，对19.5mm试样在荷载比R=0.1的情况下，进行工程门槛值的试验测定和理论门槛值的数值求解，分析求得19.5mm的HPS485W的理论门槛值为7.22MPa·m1/2。该文试验得到的HPS485W疲劳裂纹扩展曲线，可用于高性能钢桥的抗疲劳、防断裂设计与寿命预测。

FATIGUE CRACK GROWTH RATE TESTS OF HIGH PERFORMANCE STEEL HPS 485W FOR BRIDGES

This paper is about the research of Chinese high performance steel HPS 485W for bridge engineering.Under fatigue load ratio of R=0.1,R=0.5 and R=0.8,fatigue crack growth rate (da/dN) tests were conducted for HPS 485W compact specimens with thickness of 7.5mm,12.5mm and 19.5mm,respectively.The seven-point incremental polynomial method was adopted for local fitting to obtain fatigue crack growth rate.The tested HPS 485W has better crack growth resistance compared with traditional bridge steel 14MnNb.The test result shows specimen thickness is an influencing factor for crack growth rate,and fatigue crack growth rate increases with the increase of fatigue load ratio R.Furthermore,for 19.5mm HPS 485W specimen under fatigue load with R=0.1,the engineering threshold was tested and numerical calculation was conducted to obtain theoretical threshold.The calculated theoretical threshold is 7.22MPa·m1/2.The fatigue crack growth rate curves obtained can be used for fatigue design,fracture control,and life prediction for high performance steel bridge.