1985 年 3 巻 3 号 p. 525-531
After simulation of microcrackings by three point bending test, effect of some parameters on the microcrackings are studied. Results are as follows.
1) Without hydrogen charge, microcrackings were not detected by M.T.. In this case, those were observed by microcsope, and crack distribution was submitted to logarithmic normal distribution. Mean crack propagation rate in the observation area was 7.1×10-3 mm/hr.
2) With hydrogen charge, crack susceptibility by M.T. increased as current density increased, or as deflection increased. Crack number and crack ratio increased with current density. Test coupon with grinder finish contained more microcrackings than that of as welded.
3) With hydrogen charge in sea water, microcrackings initiated on the surface of test coupon.