鋳鉄の音速に及ぼす応力とひずみの影響

抄録

  Flaky, CV and spheroidal graphite cast irons were tested. Sound velocity in cast iron decreases irreversibly with stress. The decrease of sound velocity in low tensile strength cast iron takes place from a low tensile stress range, whereas the decrease in high tensile strength cast iron does in high stress range. The decrease of the velocity takes place at compressive stress nearly twice the tensile strength. It is greater in the direction normal to the elongation than in the direction of elongation and is proportional to the strain. The effect of strain relates to generation of crack and gap in graphite and matrix. Young's modulus, E(kgf/mm²), of stress applied cast iron is approximated by equations (1) and (2)
    E=21500A'_ef+1000(1−A_ef)      (1)
    A'_ef=A_ef−x                                  (2)
where A'_ef is the effective area fraction of matrix in stress applied cast iron, A_ef is the effective area fraction of matrix in the cast state, and x is the area fraction of crack and gap induced by stress. When a graphite–matrix gap forms, the term 1000(1−A_ef) in equation (1) is negligible and the Young's modulus of cast iron decreases.