抄録
Stereo measurements of the stretched region in the fracture toughness specimens used for J-integral tests were carried out by examining the shape and the angle to the crack plane with a scanning electron microscope.
It was found that the shape of the stretched zone consisted of two portions, one of which forms a gradual slope and the other a steep slope to the plane of pre-crack. The scatter of the measured values of the angle of the stretched zone to the crack plane was very large, ranging from 10 to 48 degrees. However, in many cases the angle was about 33 degrees. As the result of stereo matching observations, unsymmetrical profiles of the stretched zone were often found even though the widths were equal in a pair of the fracture surfaces. As compared with the scanning and transmission electoron fractographs taken from the same stretched zone, the same features in size were obtained from both fractographs.
