Analyze the components for similarities and differences. The cable sample, which was approximately seven inches long, had been cleaned and extensively handled between the failure and the time of delivery to Amersham. At the request of the NRC, no destructive tests were performed on this sample. The outside test laboratory identified the cause of the cable breaks as a combination of tensile overload, fatigue and corrosion fatigue. Inspection of the fracture faces showed plastic deformation on some strands, indicating tensile failure, and smooth breaks on others, indicating brittle failure mode.
Corrosion fatigue refers to the simultaneous action of corrosion and fatigue.
In this situation, the endurance limit under alternating stress such as flexing is lowered when a specimen is subjected to a corrosive environment. The fracture surfaces of the inner wires were corroded, indicating that these wires probably failed before the failure of the whole cable. The test lab also analyzed Teleflex cable and individual wires supplied by the manufacturer. The wires were pulled to failure, and the fracture surfaces were examined to confirm the characterization of the tensile and brittle failure modes. This study showed that individual wires and cables pulled to tensile failure had fracture surfaces that were generally more consistent with tensile overload failure than the R.A. fracture surfaces.