| 摘要 |
PROBLEM TO BE SOLVED: To predict the progres direction of a fatigue crack generated in a member repeatedly receiving axial force load by rotating a magnetostrictive sensor, and measuring a maximum main stress direction obtained from a parameter at the time of expressing the waveform of electromotive force by a specific expression. SOLUTION: A plurality of measuring points 6 are set near an angle-turned weld part 5 in a web 2 to a flange 3. A magnetostrictive sensor installed on a certain measuring point 6 with lift-off of 1 mm, for instance, is rotated, and electromotive force V is measured to obtain its waveform. A parameter C at the time of expressing the obtained waveform of the electromotive force V by V=A+B.COS[2.(θ-C)] is obtained, and parameters C of the other measuring points 6 are obtained in the same way. In this case,θis an angle formed by a maximum main stress direction and a straight line connecting the opening end of a yoke wound with a detecting coil, COS[2.(θ-C)] is a cosine function, and A, B, C are parameters. The maximum main stress directions of the respective measuring points 6 are determined from the obtained parameters C, and the convergent points are obtained and connected to determine the progress direction of a crack.
|
