Abstract
In order to research for the relation between the microscopic structure of steels and the process in progress of fatigue, we measured the changes of magnetic properties due to torsional fatigue in 0.8% C steel wires with various heat-treatments and as drawn. The changes of magnetic properties were measured from differential hysteresis loops between the test- and standard specimen on the cathode-ray oscillograph. From this experimental results, we found that the processes in progress of fatigue differed between the steels with fibre structure and heat-treated structure. That is, in the steel with fibre structure, fatigue did not make progress until a certain number of cycles of twisting stress was repeated, and after that made progress rapidly. But in the steels with heat-treated structure, fatigue made progress gradually or rapidly with the increase of the number of cycles.
