抄録
Cast iron is widely used as the material for various machine parts, and the fracturing of the members made of cast iron, presumably due to thermal fatigue, is often experienced in practice. In spite of its importance as an engineering problem, however, the study of thermal fatigue of cast iron is very limited. In the present paper, the experimental results of thermal fatigue on spheroidal graphite cast iron are presented. Comparison has been made of the thermal fatigue tests made under uniaxial thermal stress and those made under multiaxial thermal stresses, using hollow cylindrical specimens and solid cylindrical specimens, and discussion has been made on the relationship between the strength of material under both types of thermal cycling.
The conclusions obtained are follows:
(1) In the case of thermal fatigue of brittle material like cast iron, the number of cycles to fracture is close to that to crack initiation.
(2) Thermal cracks are made near the spheroidal graphites, and propagated so as to stitch them.
(3) The strength of the material subjected to multiaxial thermal stress cycling can be predicted from the fracture life of uniaxial thermal fatigue under the same constraint of thermal strain by employing von Mises' equivalent total strain on the surface of the specimen.
