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J. Japan Inst. Metals, Vol. 15, No. 9 (1951),

pp. 395-402

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On the Relation between Structure and Strength (I). On the Static la Failure of Steel and Cast Iron

**
F. Matsumoto
**

#### 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 σ_{xs} of steel containing x% of carbon can be formulated as being

σ_{xs}=σ_{fs}+(σ_{ps}-σ_{fs})(x/0.9)^{2/3}, ·····(1) |

where σ_{fs} and σ_{ps} indicates the yielding point of ferrite and pearlite, respectively.

(2) Proportional limit of steel occurs at the stress σ above σ_{fs}, originating in failure in ferrite which was inhibited temporarily by the pearlite phase. The elastic elongation ε_{l} 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 ·····(2) |

where E is the Young's modulus of each phase and m is the Poisson's ratio.

(3) The tensile strength of cast iron σ_{B} was discussed,using the following equation:
σ_{B}=(σ_{t}/α_{k})(A-Δ
A)/A ·····(3) |

where σ_{t} is the separating strength of steel part in cast iron, α_{k} is the stress concentration factor,Δ A 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.

(Received 1950/12/18)

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