应力比对S135钻杆钢腐蚀疲劳行为的影响

Influence of Stress Ratio on Corrosion Fatigue Behaviour of S135 Drill Pipe Steel

利用疲劳试验机和扫描电镜研究了在弱碱性介质(质量分数为3.0%的KCl溶液)中不同应力比R(0.1,0.3,0.5,0.7)对S135钻杆钢腐蚀疲劳行为的影响,并得到了该钻杆钢腐蚀疲劳裂纹扩展表达式和疲劳裂纹临界撕裂点的应力强度因子幅值ΔK与R的关系式。结果表明:随着R的增大,试样裂纹扩展临界撕裂点和最终撕裂点对应的ΔK逐渐减小(R和临界撕裂点的ΔK值之间呈明显的线性关系),试样的腐蚀疲劳裂纹扩展速率增大,腐蚀疲劳相对寿命减小,裂纹开裂由疲劳条带扩展机制转化为解理扩展机制。

The influences of different stess ratios R （0.1,0.3,0.5,0.7） on the corrosion fatigue behaviour of S135 drill pipe steel in the weak alkali medium （3.0wt% KCl solution） were investigated by the fatigue tester and scanning electron microscope, and then the corrosion fatigue crack propagation rate expression and the relationship of R vs the stress intensity factor range △K at the fatigue crack critical tearing point were obtained. The results show that with the increase of R, the △K at the crack critical and final tearing points of the specimen decreased gradually （the relationship between R and the critical tearing point △K was obviously linear） ; the corrosion fatigue crack propagation rate also increased while corrosion fatigue relative life decreased and the crack mechanism changed from stripe to cleavage fracture.