PROBLEM TO BE SOLVED: To provide a fatigue history estimation method and a lifetime estimation method of a metallic material capable of easily and precisely estimating fatigue history of the metallic material and accurately estimating the lifetime of the metallic material.;SOLUTION: A fatigue history estimation method of a metallic material 11 applies an electron backscattering method (EBSD method) to the metallic material 11 that is fatigued with a repeated load and in which a crack 12 has been created. Regarding a cross section in parallel to a load direction, crystal orientation data is obtained at regular intervals by the EBSD method. With an average azimuth of obtained crystal orientation data being a basis orientation, an azimuth difference between each crystal orientation and the basis orientation is represented by concentration difference in color. The fatigue history of the metallic material 11 can be estimated based on the concentration of the peaks 13 shown by dense parts 17 of color extending in a direction intersecting with a crack growth part 12a and an interval 20 between the peaks 13.;COPYRIGHT: (C)2015,JPO&INPIT
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