応力のかたさに及ぼす影響について

炭素鋼焼なまし材の場合

抄録

Hardness value is taken as one of the most important fundamental characteristics of materials. It has been reported, however, that the hardness of metals is influenced by the existing applied or residual stress in materials and so the hardness value measured under stressed state is vague in meaning. In this paper the effect of macroscopic stress on hardness was studied in several annealed carbon steels which had different carbon contents. Stresses on the surface of specimens which were uniaxially or biaxially stressed by bending, were measured by the X-ray technique, and Vickers hardnesses were measured near the points where stresses were measured. We employed the X-ray technique because it was necessary to measure nondestructively the stresses including residual stresses, and this object was attained only by the X-ray technique.
As the result, it was found that the dependence of hardness on the existing macroscopic stress differed according to the sort of materials; and that hard steels were affected by stress more than soft steels in hardness. And the effect of biaxial stress on hardness is greater than that of uniaxial stress. The diagonal length ratio of Vickers indentation along, and perpendicular to, the direction of uniaxial stress depends on the magnitude of stress, and also on the sort of materials.