Accession Number:

ADA018132

Title:

Greenhill's Formula and the Mechanics of Cable Hockling

Descriptive Note:

Final rept.

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

Report Date:

1975-11-07

Pagination or Media Count:

31.0

Abstract:

In the application of marine cables as tension members, serious structural failures have occurred as a result of hockling forming of a loop under torsion combined with insufficient tension. This report endeavors to establish a criterion on end torques and forces for preventing hockling. It is shown that for rods in tension the torque corresponding to Greenhills 100-year- old formula defining the onset of bending is also the maximum torque which can be sustained at that tension. Thus, a straight rod or cable loaded by tension and the Greenhill torque is unstable, and Greenhills formula modified by an appropriate safety factor provides the desired no-hockle criterion. For long straight rods or cables under tension T and twisting moment M, this criterion for stability is M sq. 4TEI, where EI is the bending stiffness under load. The approach used was to numerically solve in nondimensional form the two-point boundary-value problem of the rod under axial end torques and forces. The report includes curves showing torques and forces for the possible range of deflection curves.

Subject Categories:

  • Marine Engineering

Distribution Statement:

APPROVED FOR PUBLIC RELEASE