2005 年 45 巻 2 号 p. 281-287
Tension tests are carried out on smooth and double-notched specimens of SPCC steel plates with various ligaments and notch root radii. By observing the tensile fracture processes, initial cracks are found to occur at the notch roots, the center and the 2 axi-symmetrical inner areas of ligaments for specimens with acute, obtuse and intermediate notches, respectively. In order to clarify the effect of multi-axial stresses on the ductile fracture mechanisms, distributions of multi-axial stress components in the notched specimens are calculated by finite element method. In a specimen undergoing the maximum load, the mean stress shows the largest value at the region where initial cracks just occur. This behavior is discussed with reference to the effects of multi-axial stress components on the initiation and growth of micro-cavities in specimens. The result suggests that the mean stress component should be a dominant factor influencing the fracture behaviors of the ductile steel plates.
