抄録
Low cycle fatigue tests of circumferentially notched flake graphite- and spheroidal graphite-cast irons were performed in rotating bending.
The primary results obtained are summarized as follows:
(1) The fatigue crack propagation curves of cast irons almost coincide with their deflection curves during the fatigue test.
(2) The fatigue striations were observed only in the ferrite regions on the fracture surface of spheroidal graphite cast iron.
(3) The rate of fatigue crack propagation (dl/dN) was closely related to the stress intensity factor K and could be expressed by
dl/dN=CK6.1 for flake graphite cast iron
dl/dN=CK5 for spheroidal graphite cast iron.
(4) Under the low cycle rotating bending tests, the relation between N and σa/σBn for both notched specimens of the flake graphite- and spheroidal graphite-cast irons can be given by almost the same straight line on logarithmic scale coordinates. (N: number of cycle to failure, σa: stress amplitude, σBn: notched tensile strength.)
