X70管线钢在模拟土壤介质中裂纹扩展特性研究

Investigation on the crack propagation characteristics of X70 pipeline steel in the synthetic soil solution.

试验研究了X70管线钢在模拟土壤介质 0 5mol/LNa2 CO3 + 1mol/LNaHCO3 溶液中和循环载荷下的裂纹扩展特性和宏观规律。结果表明 ,裂纹扩展主要受裂尖应力强度因子幅的控制。不同的应力比下 ,裂纹扩展呈现明显的门槛值特征 ,随着应力比的升高 ,裂纹扩展的门槛值降低。在碱性碳酸盐溶液 (pH =9 3)中 ,加载频率对裂纹扩展速率没有明显的影响 ;在中性碳酸盐溶液 (pH =7 0 )中 ,裂纹扩展速率随加载频率的降低而升高 ,呈现明显的频率效应。中性碳酸盐溶液中的裂纹扩展速率高于碱性碳酸盐溶液的裂纹扩展速率 ,且随加载频率的降低 。

The crack propagation of X70 pipeline steel in the synthetic soil solution 0.5mol/L Na 2CO 3 +1mol/L NaHCO 3 under cyclic loading is investigated. The characteristics of the crack propagation and affecting factors are analyzed as well. Experimental results indicate that the crack propagation is controlled mainly by the crack tip stress intensity factor range K. The crack propagation presents evident threshold characteristic under different stress ratio R. The crack propagation threshold value K th decreases with the increase of R. The loading frequency has little effect on the crack propagation rates in the alkaline solution (pH=9.3). The crack propagation rate increases with the decrease of loading frequency in the neutral solution (pH=7.0). The crack propagation rate is higher in the neutral solution than in the alkaline solution, especially in the condition of lower loading frequency.