Fracture Characteristics Evaluation by Charpy Impact Bending Test

Charpy impact bending test is a rapid inexpensive test for determining fracture characteristics. Load-time relationships from instrumented Charpy test and their temperature dependency were discussed from a viewpoint of evaluating the fracture characteristics. V-notched and fatigue pre-cracked low carbon steel specimens were tested in the range from liquid nitrogen temperature to room temperature. Slow tensile tests and slow bending tests with Charpy-type specimens were also done in the same temperature range. To evaluate the plane strain fracture toughness, the fatigue pre-cracked specimen was desirable. Absorbed energy in pre-cracked impact test could be used for KIC evaluation under a limitation. The varidity of KIC evaluated could be mostly inspected by the form of the loadtime curve. JIC and COD will be obtained using this test. The loading rate has a small effect on fracture characteristics, and since the values evaluated by Charpy impact test are expedient measures the loading rate effect on them is negligible. Dynamic yield strength and microscopic fracture strength could be given by the instrumented v-notched Charpy test result. To improve this test, the more accurate load measurement is required, while the displacement observation is useless.