DIAGNOSTIC METHOD FOR CORROSION FATIGUE LIFE OF METAL MATERIAL

PROBLEM TO BE SOLVED: To provide a method for estimating the corrosion fatigue life of a metal material that is used in such devices as compressors and can not be directly subjected to a corrosion fatigue test to evaluate its life because the device is in an operating environment and to provide highly reliable devices that are appropriate for their design life.SOLUTION: The method is composed of: a process of evaluating the critical temperature for pitting corrosion in an expected operating environment; a process of comparing an expected maximum operating temperature with the critical temperature for pitting corrosion; a process of estimating the depth of pitting corrosion occurring in the expected operating environment; a process of estimating a range of stress intensity factor within the pitting corrosion; and a process of comparing the estimated range of stress intensity factor with the lower limit value for fatigue crack development. By repeating the above processes at intervals of constant time, a time when the estimated range of stress intensity factor becomes equal to the lower limit value for fatigue crack development is predicted, and the life of a device subjected to the evaluation is evaluated.