The Effects of Voyaging on the Magnetization of Ship Models.

The effects of voyaging on the magnetization of ship models were tested by subjecting two sample rods, one of HY100 steel and one of HY130 steel to an apparatus for supply of cyclic stress of two amplitudes, approximately fifty and one hundred microstrains, as measured by resistance to strain gauge bridges. A circuit was built to measure changes in magnetic induction. Results showed an increase in initial susceptibility for both rods. HY130 proved more susceptible than HY100 in all cases. The Rayleigh coefficient was measured for each steel, and these were compared with the slope of the normal susceptibility with strain amplitude to determine the fracture of domains responsive to stress. An increase in magnetization in the presence of a field, related to the log of the number of cycles, was observed. The change of the magnetization with the first cycle of stress was found to be large in comparison to changes which occurred through subsequent cycles. Continuation of vibration for several months is now seen as adequate to produce comparable first cycle and long-term effects. Thus, a model for changes in magnetization of Navy ships with time has been established. Author