Study of Fatigue Strength Simulation under Corrosion Environments

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This research is the development and proposed of a simulation method under a corrosion environments. The fatigue strength of the member that receives a pulsating load under corrosion environment is requested by calculation, without carrying out a corrosion fatigue test. It did on the basis of a study of crack initiation and propagation behavior under a corrosion environment.The method that combines and carries out a static corrosion pit growth rate and a fracture mecanics method was proposed. It calculated by using a simulation method that proposed. And it went a comparison between simulated fatigue strength and corrosion fatigue test results. The efficacy of the simulation method that proposed was confirmed. That the simulation of the fatigue strength in a pulsating load condition under corrosion environment is possible was found out.The main result are as follows.1) A simulation method that it requests because an early period pit size change with the time progress and request the lifetime under an optional early period pit size by static corrosion by fracture mechanics was proposed.2) A simulation method that requests a crack propagation rate diagram under corrosion environment directly after crack occurrence and supposea crack occurrence condition was proposed.3) That the fatigue strength by the simulation and corrosion fatigue test, by simulation are agreeing well to quantitative to qualitative was able to confirm.4) As for most of a spread lifetime of a fatigue crack depth is spent in a growing period to a half extent of the thickness.5) A corrosion pit is possible a simulation with surface crack spread from one main pit, if those dynamic interference are disregarded, although it greatly occurs in a material surface.6) Although it is possible a simulation by the method that proposed even in pulsating load condition under the result was not able to confirm.