Brief Survey of the Recent Researches on Magnetism at the Istituto Elettrotecnico Nazionale Galileo Ferraris - On the Effect of the Crystalline Structure on the Form of Fatigue Curves:The Case of Iron-Nickel Alloys

摘要

A brief survey in its main lines of the research work performed in the last years under sponsorship of the C.N.R. and of the Istituto Nazionale di Fisica Nucleare at the Istituto Elettrotecnico Nazionale is given.nThe possible effect of the crystalline structure on the form of fatigue curves was examined. Different pure iron-nickel alloys melted in vacuo and care¬fully prepared in identical way with different crystalline structures were submitted to rotating bending fatigue. The alloys tested were:(A) face-centred cubic pure Ni, Ni 85 Fe 15, Ni 75 Fe 25, Fe 50 Ni 50, and (B) body-centred cubic:Fe 90 Ni 10, Fe 96.5, Ni 3 Ti 0.5%, pure Fe (0.2% Ti). It .is shown that all the alloys examined have fatigue limit, the only difference being that fatigue curves of the b.c.c. alloys more frequently show a knee and reach the fatigue limit in the region of about 106 cycles, while the face-centred alloys generally reach the limit around 10% 108 cycles. It is suggested that the difference is, for a large part, related to the different form of the strain-hardening curve of the fatigued material, related in turn to the type of structure.