Application of Internal Friction Damping as a Nondestructive Evaluation Technique for Synthetic Ropes Used as SPM Hawsers in Deepwater Ports

Abstract

This paper discusses the technical feasibility of applying internal friction damping (IFD) as a non destructive evaluation technique for synthetic ropes. Marine applications of interest for synthetic ropes include mooring lines and towing hawsers with specific emphasis in this paper on lines for single point moorings (SPM) in deep water ports (DWP). The theory of internal friction damping is briefly presented here as it has been historically applied to metallic materials. The paper then discusses the methodology for application of the IFD technique to synthetic rope material and construction. The experimental apparatus and specific laboratory technique are then discussed as applied to 6 and 8 inch circumference rope. Next, the paper discusses the experimental results and relates them to the feasibility of employing this technique as a monitoring method for the real world assessment of rope deterioration/performance. The characteristics of ropes when tested in both wet and dry conditions are discussed. A comparison of the effect of IFD to various synthetic rope failure mechanisms is presented. The paper concludes with specific conclusions and recommendations for further investigation into large synthetic rope testing and inspection for the ultimate potential development of this technique as a real time monitoring system for marine synthetic rope performance.--

Condition Monitoring Technologies for Synthetic Fiber Ropes - a Review

“…The authors were able to show that the damping of virgin ropes were higher than that of the overstressed ropes, and showed a correlation between the damping and the rope breaking strength. Yeager, Hochrein, and Sherrard (1982) evaluated the internal friction damping technique for marine application in 1982. Williams, Hainsworth, and Lee (1984) also published a paper on using acoustic ultrasonic NDT to evaluate the condition of fiber ropes.…”