Fracture Toughness and Thermal Energy Generated at Fracture

Temperature variation of the specimen after the fracture occured was analyzed at room and low temperature environments. It has been shown that, from the temperature measurement, generated thermal energy at the fracture surface is possibly calculated. And, some examples were demonstrated. Thermal energy generated when the Izod impact specimens broke at room temperature were measured and compared with the impact absorbed energy. They are almost identical within 10 % error. This shows that the proposed estimating procedure of the generated energy works well. Assuming that the measured energy is identical to the critical energy re1ease rate, 9 Ic , fracture toughness value KIc can be obtained. Temperature method is found to be quite simple and reasonable to estimate fracture toughness, independently of the linearity and non-linearity of the material. Estimated KIc value for S40C stee1 was 20% larger than the one from 3 points bend JIc test result. This discrepancy is consistent with the difference of two criteria; for starting the crack and for maintaining the crack propagating