Abstract
The author considered the general relation between the failure and the stress for annealed steel and cast iron,taking into account the effects of structure upon the strength.In these cases the author assumed that the failure of metallic material would occur in two kinds of forms,namely,tough and brittle, depending on both its own strength (sliding or separating) and type of stress (shearing or nomal tension), but not on its apparent feature. The conclusions were as follows:
(1) The yielding point σxs of steel containing x% of carbon can be formulated as being σ_xs=σ_fs+(σ_ps-σ_fs)(x/0.9)^2/3, \labeleq1
where σfs and σps indicates the yielding point of ferrite and pearlite, respectively.
(2) Proportional limit of steel occurs at the stress σ above σfs, originating in failure in ferrite which was inhibited temporarily by the pearlite phase. The elastic elongation εl of composed phases in that instance may be written as follows: ε_l ≥σ/E+(1+2/m)(σ-σ_fs){(0.9/x)^1/3+(x/0.9)^1/3}/2E \labeleq2
where E is the Young’s modulus of each phase and m is the Poisson’s ratio.
(3) The tensile strength of cast iron σB was discussed,using the following equation: σ_B=(σ_t/α_k)(A-ΔA)/A \labeleq3
where σt is the separating strength of steel part in cast iron, αk is the stress concentration factor,ΔA is the sectional area occupied by the graphite part and A is the total area of specimen.For cast iron,however, the comparison with the experimental data was considerably unsuccessful, because of some arbitral estimations or assumptions.
Besides, the author dealt with problems in bending, torsion and compression for cast iron and with the effect of outer notch for steel and cast iron.
