Review of electromagnetic methods in nondestructive testing of wire ropes

Wire ropes are used extensively in many life sustaining situations. Elevator and mine-hoist cables are two notable examples, but the support cable for aerial tramways, ski chairlifts and gondolas, helicopter and suspension cables we might also mention. In this review, we will deal mainly with wire ropes used in mine hoists, but the results are also relevant for testing support cables for ski lifts. There is an obvious need to perform tests of the integrity of such ropes without in any way impairing their function. Apart from careful visual examination and measurements of the external diameter, the nondestructive test methods available utilize electromagnetic fields, X-rays, or mechanical waves. Here, we will review progress in the electromagnetic methods. The early history of the subject will be described briefly, since this provides a remarkably good introduction to the working principles. We will then progress quickly to the current techniques and operating procedures. Next, we will summarize some of the basic papers that deal with the basic concepts and techniques for testing of cylindrical conductors by both electric and magnetic methods. At this juncture, we call our attention to the extensive related work on electromagnetic probing of geophysical targets such as ore bodies and other subsurface conductors. Finally, we turn to the various recent investigations, primarily of theoretical nature, that have been carried out; we include here only the most recent works.