In order to study the behavior of crack opening displacement at the maximum load, CODmax, per British Standard 5762, the COD tests were conducted using 3.7% Ni-Cr-Mo-V steel in the upper shelf region. The test results obtained are as follows.
(1) The CODmax value depends on the specimen size and yield strength of the material.
(2) The CODmax value increases with increasing specimen size, of which the tendency is remarkable in the material with lower yield strength.
(3) When the yield strength increases, the CODmax value decreases, especially more remarkable in the larger specimen.
(4) The following correlation between CODmax and 2mm V-notch Charpy impact energy is confirmed.
CODmax/σY=m'(CVN-us/σY-0.11)
(5) The constant m' depends on the specimen thickness B.
m'=0.010√B
