Stress Measurement by Magnetostriction

Abstract

If a ferromagnetic material, for example nickel, is mechanically stressed, the magnetic permeability changes; the effect is large. The paper shows how the effect can be used to study transient mechanical stresses. The stress is applied, by suitable mechanism, to the ferromagnetic core of a transformer or coil, and the resulting magnetic changes of the core are observed, by the help of appropriate electrical circuits, on the screen of a cathode ray oscillograph, or otherwise. The conditions to be observed for success are set out, and numerical data are given as a guide to the design of magnetostriction stress-measuring devices.