Abstract
To study the impact fatigue, it is very important to know the value of the impact stresses. Usually U(energy)-N curves are used for the impact fatigue, so we cannot compare the results with other impact fatigue data or non-impact fatigue data. So, we studied the relation between the impact stress and the impact energy, using test pieces of various shapes and sizes, under five different impact conditions. The stresses were measured with wire-strain gages. The impact loads were obtained from the strain of supports of a modified Matsumuras impact fatigue-testing machine. The results obtained were as follows: (1) In the elastic region, the strains of the test pieces and the impact loads are proportional to \sqrtU. (U: impact energy) (2) The ratio of energy absorbed by the test pieces and the impact energy (ηT) decreases when the size of test pieces increases. (3) In the case of impact load, the effect of the modulus of section is smaller than in the case of static load, so we must consider the size effect in studying impact fatigue.
