柔度法研究镍铬合金焊材的高温疲劳裂纹扩展行为

ESTIMATION OF FATIGUE CRACK GROWTH RATES FOR NICKEL-CHROMIUM ALLOY WELDING MATERIALS AT HIGH TEMPERATURE USING THE COMPLIANCE METHOD

金属材料的高温疲劳裂纹扩展速率试验,关键问题在于高温环境下精确测量试样的裂纹长度.基于柔度测试技术,通过改进现有高温应变引伸计实现了FFCT试样的高温疲劳裂纹扩展速率测试.利用有限元方法对具有分层构形CT试样的柔度方法进行了研究,获得了分层结构CT试样的等效弹性模量表达式,通过迭代方法对实时裂纹长度进行修正,获得了良好的预测精度.完成了镍铬合金焊带、焊条和焊丝三种焊材常温和350℃下的疲劳裂纹扩展速率试验,获得了相应的疲劳裂纹扩展规律.

The key issue of fatigue crack growth rate testing for metallic materials at high temperature is to measure the on-line crack length of fracture specimen accurately. By improving the existing high-temperature strain extensometer, the fatigue crack growth rate testing for a FFCT （Front force compact tensile） specimen at high temperature was carried out using the compliance method. The compliance method for a CT （compact tensile） specimen which contains two different materials was analyzed using the finite element method. The mathematical expression for the equivalent elastic modulus for this CT specimen was obtained first, and then, the on-line crack length can be corrected exactly using the iterative approach. Finally, a series of fatigue crack growth rate tests for nickel-chromium alloy welding materials at room tem- perature and 350℃ were conducted, and the corresponding fatigue crack growth laws were obtained.