Effects of striker shape and attached position of strain gage on measured load in instrumented Charpy impact test

Instrumented Charpy impact test is widely used for the evaluation of toughn ess of many kinds of materials such as steel, aluminum alloys, polymers and ceramics with small scale specimens. In the test, therefore, it is importa nt to record an accurate impact load. Generally, one can obtain measured lo ad in the instrumented Charpy impact test by multiplying the output signal from strain gage attached to the instrumented striker by load-calibration f actor assuming a liner relationship between the strain gage signal and appl ied load. Although JIS or ISO describes about the instrumented striker, amp lifier, data processing parameter and etc., detailed method on load measure ment is hardly described in any standard. In the present study, two types of striker were used. The strain gages were attached to 4 positions in each striker. Instrumented Charpy impact test w as carried out using these strikers in order to investigate the effect of S age position on actual impact load. By the finite element analysis, the eff ect of the strain gage position on the measured load was also investigated. As the result, it became dear that the accurate impact load was not measur ed around the end of slit which was introduced to release the constraining effect of deformation of the gage position from surrounding hammer; the eff ect of the vibration of the hammer appeared strongly around this position. However, it was possible to pre vent the effect of such vibration by attach ing the gage away from such position.