Fatigue limit estimation device, fatigue limit estimation method, and fatigue limit estimation program

摘要

PROBLEM TO BE SOLVED: To estimate a fatigue limit with high accuracy as compared with the case where a fatigue limit is estimated using an intersection where a plurality of approximate lines intersect. SOLUTION: A fatigue tester obtains a plurality of measurement points indicating dissipation energy q with respect to stress amplitude (S100 to S104). A plurality of boundary patterns defining boundary candidates to be divided into a low temperature area or a high temperature area are set (S106), an approximate function in each area is derived for each boundary pattern (S108), and a low temperature area and a high temperature area are calculated for each boundary pattern. The difference between the measured value of the dissipated energy in each area and the approximate value of the approximate function is derived (S110), and the difference between the measured value of the dissipated energy and the approximate value of the approximate function is evaluated for all boundary patterns. Then, the optimal boundary candidate with which the total sum S is minimized is set as a boundary and is set as a sharp increase point of the dissipated energy (S112). Then, the stress amplitude at the boundary is estimated as the fatigue limit. [Selection diagram] Fig. 5