Patent ID: 7241349

Claim:
A nondestructive evaluating method for quantitatively and nondestructively evaluating aged deterioration in austenitic stainless steel, comprising: an information obtaining step for previously conducting a tensile test for the same kind of austenitic stainless steel as an evaluation target austenitic stainless steel, so as to obtain a relationship between stress and strain, and to apply a stress (σ) having a value changed correspondingly to the relationship between stress and strain to the same kind of austenitic stainless steel to thereby obtain reference minor hysteresis loops, thereby obtaining the correlations between physical quantities as evaluating information for aged deterioration of the evaluation target austenitic stainless steel; a measuring step for measuring the evaluation target austenitic stainless steel to obtain subject minor hysteresis loops, thereby obtaining measured values of the physical quantities from the subject minor hysteresis loops; and an evaluating step for evaluating the aged deterioration in the evaluation target austenitic stainless steel from the measured values obtained in the measuring step and based on the correlations between physical quantities obtained in the information obtaining step; wherein each of the minor hysteresis loops is obtained for each magnetic field amplitude (H a ) to be applied to the material, based on a relationship between the magnetic field intensity (H) and a magnetic flux density (B) of the austenitic stainless steel obtained by measuring the magnetic flux density (B) while stepwise changing the magnetic field amplitude (H a ) within a range of the magnetic field intensity (H) lower than a saturation magnetic field intensity.