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.

Failure Analysis of Corroding Stainless Steel Probe

Failure analysis expert was asked to determine the cause of deterioration of the tip of a stainless steel (SS) probe used to measure the level of hot tomato juice in a vat. Chemical analysis identified the steel as 304 SS with 0.082% carbon. At best, the carbon limit is on the high end in an alloy that is prone to grain boundary corrosion. Metallographic analysis demonstrated to the corrosion expert that the grain boundaries of the steel were decorated with carbides. The upper left photograph shows the deterioration of the end of the tube. Upper right is a 400X metallograph of a polished and etched sample of the steel. The arrows indicate decorated grain boundaries. Because tomato products have a significant amount of malic acid, 316L stainless steel was reccomended for replacement.

Glass Failure Analysis Expert Examines Failed Champagne Bottle

Glass failure analysis expert performed a root cause failure analysis on a exploding champagne bottle. The user claimed that the bottle exploded when she was using her thumbs to remove the cork. Examination of the bottle revealed a horizontal crush point. This damage was severe and would not have survived the corking operation at the winery. Thus this damage was caused by a tool when it was used by the injured party to remove the cork. There was an indication that this bottle had been in the freezer prior to the accident. Thus, there was little or no internal pressure to aid in the removal of the cork. Thus a tool was used, and this caused the failure. The photograph on the upper left is of the salvaged pieces of the exploding champagne bottle. The photograph on the upper right is of the fracture initiation point and the failure origin.

Glass Failure Analysis Expert Discusses Window Damage

Window damage expert examines window scratching from a metal blade (see above photo). A California glass failure analysis expert was asked to evaluate window damage at a newly constructed home. The windows at this site were scratched during cleaning with a six inch metal blade. The blade traps abrasive dirt and drags it across the glass. Because the dirt is the same hardness as the glass, the window is scratched. The scratches are in a linear array, and their visibility is enhanced by direct sunlight. Glass expert reccomends that windows be cleaned per GANA reccomendations. GANA reccomends that blades never be used to clean windows.

Failure Analysis of a Stair Tread Wood Failure:

Failure analysis expert examined a failed wood stair tread that was the cause of a fall and an injury. The failed tread is shown still mounted in the photo on the left. The re-assembled tread is shown in the photo on the uper right. This tread was screwed in place when the wood was green; in addition, there were no pilot holes drilled for the screws. Failure analysis shows that as the wood dried, the pressure from the screws wedged into the wood caused a wood failure (i.e. the wood split). In additon, the bracket was 0.8 inches from the nose of the tread. Thus, the force from a foot placed on the nose of the tread created enough moment to split the wood apart and cause the person steppimg onto it to slip and fall.