Aluminum Wire Rope Polyethylene Sheathing Failure

摘要

The results of an investigation of the cracking of the polyethylene (PE)sheathing on aluminum wire rope used on CF Ships are reported. The cracking had not been observed previously and there was concern that this might be related to a change in material or storage conditions. Thermal analysis techniques, such as differential scanning calorimetry (DSC) and pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) indicated that the failed sheathing was higher density PE than the sheathing that did not crack. Analysis of the fracture surface of the cracked sheathing indicated that it had failed by a brittle slow crack growth mechanism. The failure of the higher density PE was attributed to stresses introduced when the sheathed wire rope was transferred to a reel with a smaller diameter. Although the wire rope with the uncracked sheathing had also been transferred to a reel with a smaller diameter, low density PE is less susceptible to this type of cracking.