It is known that the magnetic properties of ferromagnetic materials change under fatigue and applied loads (1,2,3). These changes in the magnetic properties could be used as indicators of the stress state of the material, or possibly for predicting the remaining fatigue life. Previous reports have shown successful implementation of this magnetic measurement technique for NDE of steel samples in a laboratory enviroment. However, for this technique to be practical, a field-usable instrument must be developed. This paper will describe measurements using one such instrument, the Magnescope. It will also discuss the techniques used to evaluate the effects of applied loads, both tensile and compressive, and low cycle fatigue on a variety of materials.
Available at: http://works.bepress.com/david_jiles/13/