Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 02, 2019 - November 04, 2019
A quasi-static tensile test and impact tensile tests (tensile speeds: 2 m / s, 5 m / s, 10 m / s) were carried out on hexagon bolts and nuts, and the effect of strain rate on the impact tensile properties were investigated. The actual tensile speed was calculated from the stroke-time diagram obtained from the test results, and the strain rate was calculated by dividing the thread length by the actual tensile speed. Comparing the tensile strength of the quasi-static tensile test with that of the impact tensile test, the tensile strength increased by 8% at 1.9 × 102 /s, 30% at 6.6 × 102 /s, and 51% at 1.1 × 103 /s. It was also found that the elongation increases only when the strain rate is 1.9 × 102 /s. It was also confirmed that the macro fracture surface changed from a cup and cone shape to a shear shape. From the macro observation of the fracture surface, a large amount of unevenness was formed at the center of the fracture surface, and a fibrous fracture surface was formed at the outer edge of the fracture surface. SEM observation of the fracture surface revealed that equiaxed dimples and elongated dimples mixed at the center of the fracture surface, and elongated dimples were dominant at the outer edge of the fracture surface.
