X56钢焊接接头J-R曲线的研究

J-Resistance curves of welded joints for X56 pipeline steel

根据BS7448断裂韧度试验标准,采用多试样方法,测试了X56管线钢焊接接头的低温(-5℃)J-R曲线。取尺寸为B(板厚)×2B、缺口方向为板厚方向、带预制疲劳裂纹的标准试样进行三点弯试验。采用两个夹式引伸计在-5℃下分别得到焊缝和热影响区(HAZ)的双P-V曲线来计算施力点位移,从而得到J积分值。然后对数据点进行拟合得到J-R曲线,计算出J0.2,确定了材料的断裂韧度。通过对HAZ试样剖面分析表明,所有试样的裂纹尖端全部落在HAZ,从而验证了试验结果的可靠性。试验将BS7448标准应用于焊接接头J-R曲线的测定,试验结果为ECA评估提供了重要依据。

In accordance with the BS7448, fracture toughness test standard, J-Resistance curve tests were conducted with the multiple specimen at -5°C in welded joints of X56 pipeline steel. According to the standard, the specimen with fatigue precrack is a standard three point bending shape that has a rectangular section of B×2B (B: specimen thickness) and notch orientation of thickness direction. And then based on the double P-V(P: load, V: displacement) curves of each weld metal and HAZ (heat affected zone) specimen obtained from the two notch opening displacement, the load-line displacement and the value of J were calculated. Finally, the paper determined the best fit curve through the valid data points, and got J0.2 at all fatigue crack tips locating in HAZ by analyzing the fracture section of HAZ specimen, so the test results of HAZ are reliable. The BS-7448 Part 4, the standard on metallic materials, was applied to establish J-R curves of welded joints. Test results provide reliable evidence for engineering critical assessment.