電磁気探傷法による表面に開口した疲れ割れを検出する場合の応力の影響

抄録

As for the accuracy of surface crack size measurement by electro magnetic testing method, presentation of stress is one of the most serious practical problems in material construction. The author applied detective signals to stresses using magnetic particle testing method, magnetic leakage flux testing method, electrical resistance method and eddy current testing method.
The results obtained in this study are considered to justify the following conclusions:
(1) Magnetic leakage flux density from fatigue cracks is a function of distance between two Hall elements and surface of the test pieces. when tensile stress added to the fatigue cracked test piece, leakage flux density became larger. But, it decreased to zero, when the compressive stress which was from 200 to 250MPa was added to test piece.
(2) The magnetic particle indication was a little influenced by the compressive stress at 250MPa.
(3) In detection of the stress acting on the fatigue surface crack, the indicative value by electrical resistance method became smaller when the compressive stress was applied to test piece.
(4) Tensile stress applied perpendicular to the fatigue cracks gave no change the indicative value by electromagnetic induction testing method, but the compressive stress of 150MPa decreased indicative value.