Analysis of the Formation and Pop Out of Loops in Twisted Cable

Serious failures of ocean cable have resulted from "hockling". When a cable is under tension, helical windings can cause the cable to twist. With relaxation of the tension, loops can form. Reapplication of tension tightens the loop, and at some point the cable may pop out. If it doesn't and hockles instead, serious damage will result. This memorandum analyzes the conditions for loop formation and pop-out. The force versus displacement at the ends of a twisted cable, and the point at which the cable "flips" into a loop, are derived in closed form from the basic differential equations of an elastica.