GREENHILL'S FORMULA AND THE MECHANICS OF CABLE HOCKLING
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 Greenhill's 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 Greenhill's 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 less than 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.
- Find a library where document is available. Order URL: http://worldcat.org/isbn/Proj02303455807
- Final Report on one phase of a continuing NRL problem.
Naval Research Laboratory4555 Overlook Avenue, SW
Washington, DC United States 20375-5320
- Rosenthal, F
- Publication Date: 1975-11
- Features: References;
- Pagination: 29 p.
- TRT Terms: Design; Mechanical failure; Mooring cables; Rope; Wire rope
- Old TRIS Terms: Cable failure; Rope technology
- Subject Areas: Design; Marine Transportation;
- Accession Number: 00128445
- Record Type: Publication
- Source Agency: Ship Structure Committee
- ISBN: Proj 023-03-45-5807
- Report/Paper Numbers: NRL 7940 Final Rpt.
- Files: TRIS
- Created Date: Dec 29 1975 12:00AM