Thick-walled stainless steel optical tubes used in steel armored cables sustain severe forces arising from the axial strain of the bulk cable, core pressure caused by the squeezing effect of the helically wrapped armor wires, and external forces on the cable. The conditions which result in collapse of the optical tube are investigated by applying established plasticity theory and then extending this theory to develop new equations for the case of a work-hardening material. The theoretical criteria for the onset of tube collapse are identified. Theoretical, experimental, and field results are then combined to identify conditions which increase the risk of tube collapse. It is concluded that tube collapse will not occur in properly manufactured cables unless one or more of four special conditions exist. These conditions are unusually large external pressure on the tube caused by more than two layers of steel armor, non-hydrostatic radially-dominated external pressure on helical tubes, severe external forces on the cable, and amplification of core pressure on the optical tube resulting from the cable geometric design. [S1050-0472(00)01202-2]

Issue Section:
Technical Papers
Keywords:
optical cables, stainless steel, plasticity, work hardening, Thick-Walled Tubes, Collapse, Cables, Plasticity, Optical Fibers, Work Hardening
Topics:
Cables, Collapse, Stress, Plasticity, Pressure, Work hardening, Stainless steel, Tension
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