交变应力与环境耦合作用下拉索腐蚀疲劳损伤机理研究

Damage and Failure Mechanism of the Stayed-cable with Corrosion Fatigue under Alternating Stress and Environmental Coupling

通过开展室内盐雾加速腐蚀试验,研究分析了各种应力状态下腐蚀钢丝的腐蚀失重量及弹性模量、抗拉强度等力学性能的变化,得出腐蚀钢丝各种力学性能中断后伸长率对疲劳腐蚀最为敏感的结论。在试验开展的基础上,以细观损伤力学为研究手段,并结合断裂力学强度准则,分析了环境腐蚀、应力腐蚀和疲劳腐蚀各自的特征、机理。腐蚀斜拉索的腐蚀疲劳损伤主要是由于腐蚀造成的钢丝表面的蚀坑,进而导致应力集中现象,加之氢致开裂,导致裂纹不断萌生、发展,研究分析了应用腐蚀疲劳裂纹扩展门槛值作为点蚀坑向腐蚀疲劳裂纹转化的判据的方法,并通过数值手段,分析了钢丝全面腐蚀、表面蚀坑深度、蚀坑形状和蚀坑纵向净间距对钢丝应力分布状态和疲劳寿命的影响。

Through laboratory accelerated salt spray corrosion experiments, changes of mechanical performance under various stress are analyzed such as the corrosion weight loss of the steel, elastic modulus, and tensile strength, and a conclusion is drawn that that the elongation is most sensitive. On the base of experiments carried out already, by the means of microscopic damage mechanics, and combiningfracture mechanics strength criterion, this paper is to study environmental corrosion, stress corrosion and corrosion fatigue characteristics of each mechanism. Stay cable corrosion fatigue damage is mainly caused by corrosion pits on steel surface, leading to the stress concentration, combined with hydrogen induced cracking. In this condition the initiation cracks would be constantly formed and developed. This paper also study the application of corrosion fatigue crack growth threshold as the criterion of transformation of pitting corrosion to crack, by numerical methods, a comprehensive analysis of the steel corrosion, surface pitting depth, shape and vertical net spacing of pits on the steels effect on stress distribution and fatigue life.