Modeling the multi-degradation mechanisms of combined tribocorrosion interacting with static and cyclic loaded surfaces of passive metals exposed to seawater

摘要

In many engineering applications, component surfaces are exposed to wear in a corrosive environment. Such tribo-components are usually structural elements, also supporting applied static and/or cyclic tensile loading. One example is the large hydraulic cylinder piston rods working in the splash zone on board offshore drilling vessels providing tensioning of drilling risers. Many of these piston rods tend to fail due to severe surface damages causing leakage in the cylinder sealing system. The failure analysis of these piston rods indicate that the combined degradation effects of surface wear and corrosion during mechanical tensile loading, both static and cyclic, produces a total material loss much greater than adding the separate material losses from corrosion and wear alone. No studies dealing with the synergy of applied static and cyclic tensile loading interacting with tribocorrosion have been reported in the literature. However the tribocorrosion behavior of passive metals in several environments has been studied by different authors showing that the synergistic effect of wear and corrosion provide a significant contribution to the total material loss. This paper aims at describing and modeling the interaction of applied fatigue and tensile stresses, known as corrosion fatigue (CF) and stress corrosion cracking (SCC) mechanisms, in a tribocorrosion situation such as a simulated piston rod application described above. In the present work, two multidegradation theories are presented as basis for the development of a proposed mathematical model of multi-degradation.