抄録
The fatigue notch sensitivity of nodular cast iron was investigated on the collared specimens with various fillet radii with the object of comparing it with that of 0.6% C steel having nearly equal tensile strength; and the shift of rupture area was examined as a function of stress level or fatigue life.
When four kinds of fatigue notch factors βKD, βg, βKS and βS were introduced, the conclusions were summerlized as follows. (E.L.=Endurance Limit)
βKD=E.L. of plain nodular cast iron specimens/E.L. of notched nodular cast iron specimens=Apparent fatigue notch factor of nodular cast iron.
βg=E.L. of the plain steel specimens having correlative matrix with nodular cast iron/E.L. of plain nodular cast iron specimens.
βKS=E.L. of the plain steel specimens having correlative matrix with nodular cast iron/E.L. of the notched steel specimens having correlative matrix with nodular cast iron
βS=E.L. of the plain tteel specimens having correlative matrix with nodular cast iron/E.L. of notched nodular castiron specimens.
1) The apparent fatigue notch factor of nodular cast iron (βKD) is much smaller than the fatigue notch factor of the steel having nearly equal tensile strength.
2) βg depends on the states of graphite and matrix of nodular cast iron, being 1.5∼1.6 in the present test. (normalized nodular cast iron)
3) βS is much smaller than the product of βg and βKS, and nearly equal to the bigger of the two βg and βKS.
4) Accordingly, being βg bigger than βKS, the apparent fatigue notch factor of nodular cast iron (βKD) is nearly equal to 1 unity.
5) The estimation of working stress level or fatigue life by the shift of rupture area appears possible as well in the case of nodular cast iron.
