Failure Analysis Expert Witness Examines Failed Rivet

A failure analysis expert witness performed a rivet fialure analysis of a rivet involved in a ladder failure. The failed rivet, which is a hollow end rivet, was found to be too short for the intended application. The photo on the upper left is a cross section of the failed rivet in question. The clinch allowance of this rivet was inadequate and over time the folded over portion failed from fatigue and allowed the joint to open. The center photograph is of a similar rivet. One can see that this rivet has very little left to grip on the hollow end. This rivet has not failed; however, it does show significant deterioration. Upper right is a rivet that has the proper clinch allowance. In additon, this rivet does not show any signs of deterioration.

CPVC Plastic Failure Analysis of Hot Water Pipe Fitting

Plastic failure expert performs a failure analysis on a failed CPVC 90° 3/4 inch elbow. This elbow was in a 150°F hot water recirculation system in a large facility. Plastic fatigue was the alledged cause of failure. However, a plastic failure analysis found no evidence of fatigue. Instead, the detailed root cause failure analysis indicated that this elbow had molding defects and had deteriorated in service; in the top left photograph one can see that the CPVC inner and outer surfaces have turned brown. The failure originated at a stress concentration point caused by the interior 90° angle. It initiated as a brittle fracture on the outside. It then became an overload failure in mid thickness. Finally, there were layer separations toward the interior of the elbow. The photo on the right is of the vent hole. This shows that the CPVC came out in layers. Thus, during plastic molding there were layers of CPVC that did not "recombine". Given that this elbow is formulated to operate continuosly at 180°F, this elbow was a defective product due to both plastic molding defects and plastic formulation problems.