Analysis and Experiment were undertaken on the change of the resistance from material accompanying the progress of the fracture surface in the impulsive bending test of a pre-fatigued carbon steel in low temperatures. The S35C carbon steel was tested by the Chalpy impulse testing machine， for five pre-fatigue levels between 0 and 10^5 cycles and also five impulse testing temperature levels between 十30 and ? 90℃. The impulsive resisting energy per a unit area （abbreviated by lREU hereafter）of the total fracture surface of pre-fatigued specimens was denoted by u and that of nonpre- fatigued ones by u_0. For distinction between the IREU of the fracture surface of the pre-fatigued zone and that of the non-pre-fatigued one in one total fracture surface，IREU proportional to the former and to the latter were respectively denoted v and v_0. The change of the impulsive resisting force along with the progress of the impulsive fracture （abbreviated by CIRF hereafter）was observed by the synchroscope. 1）CIRF seemed to be influenced by the stress concentration at the front of the progressing fracture surface，the slope of u value from the bottom of the notch to the interior of the specimen and the change of the modulus of section of the not-yet fractured part. 2）The more pre-fatigued and the lower the tested temperature， the less u. For the same pre-fatigue level u/u_0 lessened along with the lowering of the temperature， reached the minimum value about the ductility transition temperature and began to increase thereafter. 3）v/v_0 was constantly about 0.13 for any pre-fatigue and the test temperature. The lower the temperature， however，the less v_0 and v as well. The change of v_0 and v seemed to reflect the ductility transition phenomenon.
展开▼
