Application of Internal Friction Damping as a Nondestructive Evaluation Technique for Wire Rope
Authors: Hochrein A.A. , Thiruvengadam A.P. , Sherrard J.R. 
Published: October 2008

ABSTRACT
This paper discusses the technical feasibility of applying internal friction damping (IFD) as a nondestructive evaluation (NDE) technique to wire rope. The paper addresses the technical feasibility, laboratory testing on wire rope, and the associated test results on various samples of wire rope. These tests were eva1uated in a series of laboratory experiments by measuring the internal friction damping during which several test parameters were changed. The test parameters including the tensile load, frequency of test load, exposure time of rope to load and variations in rope construction are discussed from the standpoint of IFD-NDE measurements.
This paper discusses the methodology for applying the IFD technique to wire rope material and construction. The experimental apparatus and specific laboratory technique are then discussed as applied to different constructions of wire rope. Next, the paper discusses the experimental results and relates them to the feasibility of employing this technique as a method of monitoring for the real world assessment of wire rope deterioration in performance. The various rope construction characteristics as tested in dry conditions are discussed. Moreover, a comparison of the affect of IFD to wire rope fatigue load conditions is presented. The paper concludes with specific conclusions and recommendations for further investigation into large diameter wire rope testing and inspection for the ultimate potential development of this technique as a real time monitoring system for marine wire rope performance.

INTRODUCTION
Wire rope has been used extensively for more than a century as the tension member in a wide variety of marine and offshore applications. The high strength to weight ratio, flexibility and relatively low cost are the major advantages for wide spread application of wire rope in the offshore industry. Despite extensive practical experience and field use in operation, in service wire rope failures resulting in major production delays are not uncommon, even with the present state of- technology. No reliable nondestructive evaluation techniques have been available for establishing the retirement before failure criteria of in-service wire rope Furthermore, in recent years the size and type of wire rope has become more diverse and technically sophisticated. It has long been recognized that a suitable nondestructive evaluation technique is needed to detect various modes of incipient wire rope failures during in-service operations. Therefore, in order to assist in this effort to determine a nondestructive technique 'applicable to wire rope, DAEDALEAN ASSOCIATES, INCORPORATED (DAI), in conjunction with the UNITED STATES COAST GUARD, has conducted a feasibility study regarding the application of the internal friction damping - nondestructive evaluation (IFD-NDE) technique to laboratory wire rope samples. This nondestructive technique utilizes the phenomenon of internal friction in materials to detect incipient failure. Wire rope samples, 6 × 19 and 6 × 37 independent wire rope core (IWRC), 6 × 19 and 6 × 37 fiber core, 1/2 inch diameter, were tested in the laboratory using the IFD-NDE technique and instrumentation. This technical paper addresses the feasibility program's objectives, scope, equipment, experimental results and conclusions.