Construction Defect Analysis, Window Damage

California Failure Analysis Expert Witness performs a glass failure analysis on defective tempered glass windows installed in a public building. One of the construction defects was window scratching. Representative windows were removed and sent to the Read Consulting California failure analysis lab. This allowed a detailed investigation of the window defects. The failure analysis determined that the scratches were caused by post construction cleaning. Upper left is a macrophotograph of a typical set of scratches. Their parallel nature shows them to have been caused by a metal scraper. Upper right is a 40X photomicrograph of a scratched region. These scratches were in the glass. There was no coating on the scratched surface.  

Glass Failure Analysis of Tempered Glass Oven Door

California failure analysis expert witness analyzes a failed tempered glass toaster oven door to determine the cause of failure. The glass door remained intact, and this allowed the failure analysis to be performed. The origin is found to be in the center of a "butterfly" shaped region. There is a crush point that is the origin. The glass failure started at the crush region on the glass door surface and progressed inward till the residual stresses of the thermally tempered glass took over and caused the entire door to break into very small cubes. Upper left is an overview of the failed oven door. Upper right is a photomicrograph of the fracture surface at the origin.

Discussion of Beer Bottle Defect

California failure analysis expert witness discusses bottle defects that can affect the bottle strength. In this case there are a string of bubbles in the glass that are mear the surface. There are cases where these bubbles have reached the surface and have opened. This will weaken the bottle by generating  stress risers and thinning the glass locally. Due to hoop stresses, the strength of the bottle is directly proportional to the glass thickness, there are cases where this type of defect can significantly reduce the glass thickness and the bottle strength. This is particularly important in the case of beer and sodas, where the bottle contents are under pressure (54 to 50 psi). In this case the bubbles have not surfaced, thus the effect on the bottle strength is not as severe.

Brass Plumbing Failure Analysis Stress Corrosion Cracking (SCC)

California failure analysis expert witness has analyzed numerous plumbing failures involving yellow brass (i.e. brass with more than 30% Zn in the alloy). The two major brass failure modes in yellow brass are dezincification and stress corrosion cracking. Above are two samples of stress corrosion cracking. Sress corrosion of yellow brass commonly involves the presence of ammonia along with the presence of stress. Upper left is a photo of a brass ferrule that cracked. The stress came from the clamping force of the ferrule on the rubber hose. These ferrules were covered with an expanded foam insulation that was painted with latex paint. At a minimum the latex paint contained ammonia; it is also believed that there was residual ammonia in the rubber foam insulation. Upper right is a failed flexible bathroom water supply line. The stress in this pipe failure is residual stress from non-uniform bending. It is believed that the ammonia came from houshold cleaners used on the plumbing. In both cases, the cracking is inter granular cracking and is attributed to stress corrosion cracking.

Medical Device Failure Analysis of a Catheter

California failure analysis expert witness performed a failure analysis on a piece of rubber that had been removed from a patient's bladder. The piece was compared with the tip of a new exemplar catheter. Although the piece that was removed surgically was encrusted with salts, it was shown to be part of a catheter.

Failure Analysis Expert Examines a Broken Champagne Bottle

A California failure analysis expert witness was asked to perform a glass failure analysis on a champagne bottle that had failed "spotnaeously". Because champagne is under pressure and in glass, there are warnings not to use a cork screw to remove the cork. However, there are cases where the cork is stuck and people will use a tool to extract the cork. The danger is that the tool can damage the inner wall of the bottle neck and initiate a crack that will cause bottle failure. In the present case, a tool was used to pry the cork out and it caused "chatter" damage on the inner wall of the neck very near the top. This damage initiate a crack that finally caused bottle failure. Upper left is a 20X photomicrograph of the damage to the neck inner wall. Upper right is a 20X photomicrograph of the failure origin on the fracture surface. Again, because a champagne bottle is under pressure, one should never use a tool to remove a stubborn cork. There was no manufacturing defect; this bottle failed as a result of handling damage.

California Failure Analysis Expert Witness Examines Failed Glass Pool Tiles

California glass expert performed a failure analysis on several broken glass tiles. These tiles were above the water line in a swimming pool. The failed tiles were removed and submitted for failure analysis. It was impossible to open the tiles to examine the fracture surface. The thin set mortar had "squeezed" into the crack and was firmly holding the tile pieces together. The tiles were soaked overnight in muriatic acid to allow separation. They could then be pulled apart to expose the fracture surface for failure analysis. The figure above is an 8X photomicrograph of a representative fracture surface. All the failures initiated on the backside of the tile. It appears that the glass tile backside was forced against a small hard particle during mounting in the thin set mortar. The failure initiated at a point on the glass tile backside and srpead into the tile (indicated by the arrows). The root cause of the glass fracture was inpact against a hard particle, The fact that the mortar had squeezed into the crack indicated that the glass tile failure occured during mounting. Perhaps the tile setter was using a mallet to align the glass tiles.