衝撃曲げ疲労試験における動的応力拡大係数の評価

抄録

The relationship between the impact fatigue crack growth rate and the stress intensity factor range has been investigated by using the impact fatigue testing machines of several types. However, in evaluating the stress intensity factor the influence of the inertia effect has not yet been completely elucidated. The purpose of the present paper was to establish the mensuration of the dynamic stress intensity factor in the repeated impact three point bending test, and to investigate the effect of impact loading on fatigue crack growth rate.
Contact force between the falling cylinder and the cracked beam was analyzed by applying the Hertz law and the compressive force in the cylinder was determined. The dynamic stress intensity factor was also determined by using the simple formula developed in the previous paper. Comparison of the analytical results with the experimental ones suggests that in the low impact velocity range, the dynamic stress intensity factor can be fairly well estimated by the static formula together with the output of the strain gauges which are glued on the cylinder.
Impact fatigue tests were carried out on the specimens of annealed 0.46% carbon steel and aluminum alloy. The experimental results indicate that the influence of duration of impulsive loads is larger for carbon steel than for aluminum alloy.