Abstract
Thin plate specimens of annealed 7-3 brass were subjected to gaseous ammonia under the loading conditions of constant displacement of tension, and constant deflection of bending and equi-biaxial bending. The followings are the summary of the results obtained
(1) The time to crack nucleation, defined as the time when the applied stress fell down 3% of the initial value, was found to become shorter in the order of equi-biaxial bending, tension, and bending tests. The ratio of crack growth period to total life was 0.35 in the case of tension and 0.20∼0.24 in the case of bending. In the bending test under the stress level of 4kg/mm2, the specimen did not fracture although cracks were nucleated.
(2) The surface stress measured by X-rays was found to decrease markedly with the nucleation of plural cracks. At the time ratio t/tf of 0.7, the mean span between adjacent cracks became nearly equal to the mean crack length and the stress on the specimen surface vanished. X-ray measurement of the surface stress was proposed in the present study to be a possible non-destructive method for monitoring the progress of damage due to stress corrosion cracking.
