Study On Fatigue Crack Propagation Evaluation Method Considering Random Load And Corrosion

Marine structures are subjected to a variety of loads in the marine environment,and due to the continuedinfluence of cumulative damage,fatigue cracks would emerge inevitably.Meanwhile,as a kind of strong corrosive medium,seawater would result in corrosion that have a great effect on the marine structures.Therefore,the structuresare subjected to the coupling of corrosion and fatigue damage,and the damage will be far greater than the damage caused by a single damage,so it is necessary to study the crack propagation under corrosion.In addition,for marine structures under long-term random load,in order to more truly reflect the crack propagation behaviorofdeep-sea structures,it is of great significance to study thecrack propagation behavior under random load.In this paper,based on the ABAQUS platform,according to the function relation between J integral and stress intensity factor,the extended finite element method and the equivalent region integral method are used to develop the program of calculating the stress intensity factor of static crack and quasi-static extended crack.On such basis,the influence of hydrogen concentration on the stress-strain curve and the crack growth threshold is studied.The influence of the hydrogen-induced cracking mechanism on the crack propagation is considered,and a custom element based on the ABAQUS platform is developed to simulate the hydrogen-induced crack.At the same time,the influence of the anodic dissolution on the crack propagation is studied by introducing the relationship between the current density at the crack tip and the strain rate and the strain rate.In addition,random sample data is generated according to the probability density function of the two-parameter Weibull distribution,and the length of the random sample is determined based on unbiasedness and consistency.On this basis,the effect of loading order on the crack propagation rate and the propagationpathis studied.The effects of different loading modes on the propagation path and propagation rate of the crack are obtained.Finally,the equivalent loading mode of the specific Weibull distribution is proposed.In this loading mode,the crack propagation rate is similar to that of random loading.