Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 02, 2019 - November 04, 2019
Rolled metallic materials have directionality in crystal grain shape and inclusion distribution. Crack growth in metallic materials occurs due to coalescence of voids generated by inclusions in the material as nuclei. For this reason, these materials have anisotropy in fracture toughness. In the fracture toughness test, the fracture toughness value is the lowest when the rolling surface and the crack plane are parallel to each other. This specimen orientation is S-L or S-T. The purpose of this study is to clarify the relationship between fracture toughness and crack plane position. In this study, SM490A rolled material with a thickness of 100 mm was used as a test material, and compact tension specimens for evaluating fracture toughness values were prepared. In the specimens, the crack surface and the rolling surface are parallel. In addition, five types of test specimens were prepared with crack surface positions of 30 mm, 35 mm, 40 mm, 45 mm, and 50 mm from the material surface. As a result of these tests, the fracture toughness value decreased as the crack plane position approached the thickness center. And the inclusion density in this material increased near the thickness center. From the above results, it is considered that the fracture toughness value of the CT specimen of S-L orientation is affected by the crack plane position because the inclusion density changes in the thickness distribution
