THE INFLUENCE OF PROOF LOADING ON THE FATIGUE LIFE OF ANCHOR CHAIN

This paper discusses the influence of proof loading on the fatigue life of anchor chain. Experimental fatigue data are presented for smaller scale open link and stud link chain. 10 mm grade 80 lifting chain as used for the fatigue tests, where 10 mm is the diameter of the bar stock forming the links. Stud link chain was fabricated by fillet welding studs into the open link chain. Lifting chain is geometrically similar to anchor chain, and this results in similar stress concentration factors at the location where fatigue cracks originate. All the fatigue tests were conducted in laboratory air. Proof loading was shown to substantially increase the fatigue life of both the stud link and the open link chain. Residual stresses imparted during the proof load operation can explain the increase in fatigue life. A simplified elastic-plastic, stress-strain algorithm demonstrated its ability to model the data trends.