A method to characterize the mechanical properties of undersea cables

A method has been developed to evaluate the mechanical properties of cables containing stranded-strength members in both linear elastic and nonlinear plastic regions. The method extends Cannon and Santana's general system of equations describing the cable mechanical characteristics. In the formulation of the method, the fundamental assumptions made by Cannon and Santana are first examined and justified. Next, instead of using elastic constants for the constituent cable materials in the system of equations, the regression analysis is applied to the tensile and torsional test data of dominating high-strength cable components to obtain least-squares-fit polynomials approximating the stress versus strain and shearing-stress versus shearing-strain curves. By differentiating the polynomials, the tensile and torsional moduli of these cable components as functions of their axial strain and twist are derived. The relations describing the mechanical properties of the cable in both elastic and plastic regions are obtained by substituting the tensile and torsional moduli of the high-strength cable components and the constant moduli for the low-strength cable components into the system of equations in differential form and integrating them. Application of the method to the present experimental undersea-lightguide cable yields excellent agreement with the tensile test results of the cable.