Porcelain Failure Analysis

California failure analysis lab is able to show similarities between glass failure analysis and porcelain failure analysis. The predominant tool for tracking a crack in glass is to look at "Wallner lines" These can tell the direction of travel of a crack in glass. This allows the glass failure expert to trace the crack back to the origin. He can then analyze the origin microscopically to determine the root cause of the failure. Glass is a smooth material, and the Wallner lines are readily visible. Porcelain is also a brittle material, and it also fails in a brittle manner. The difference is that the porcelain fracture surface is grainy and artifacts on the porcelain fracture surface (such as Wallner lines) are very difficult to see. Above are photographs of the fracture surfaces of two bending failures, one glass and one porcelain. The Wallner lines on the glass fracture surface are obvious and readily visible. The Wallner lines on the porcelain surface are very difficult to see and are best seen in oblique light. A sample of each is given above for the reader to see the differences/

Glass Expert Performs Failure Analysis of Drinking Glass

In order to simulate potential cracking of a heavy bottom drinking glass still hot from a commercial dishwasher, a glass was immersed in 140°F water till stabile. The glass was removed and ice water was then poured into the glass. A glass failure analysis expert witness then performed a failure analysis on the resulting cracked drinking glass. The drinking glass tested is not new; therefore, there is random handling damage present both inside and outside the tumbler. The upper left photo shows the overall cracking resulting from thermal shock. To the right is a photograph of the cracked bottom of the glass. The location of the crack origin is indicated. The crack started in the center of the bottom on the inside surface. When the ice water hit the hot interior bottom, it put the interior surface in tension, and this started the glass cracking. Upper right is a 25X photomicrograph of the crack origin. The failure began at a point where there is a small bruise. It is important to see that there is no major handling damage at this origin. This is because the failure was driven by thermal stresses not mechanical stresses. In addition, the initial part of the crack at the origin is not straight. The direction of the stresses are changing even when the crack is initiating.

Champagne Bottle Glass Failure Analysis

Glass failure expert performed a complete glass failure analysis on numerous champagne bottles that had failed in the riddling process. These bottles are used for riddling and they are made from a large amount of re-cycled glass. Several of these bottle failures initiated at a site that had a piece of unmelted cullet (Note: Cullet is ground glass that is re-melted). The photographs above show one such failure from two vantages. The "lump" of unmelted cullet was larger in diameter than the thickness of the glass (0.120"). The bottle manufactrurer was made aware of the manufacturing process problem and is in the process of fixing it. This is a manufacturing defect that could potentially become a product liability.

Wine Bottle Failure Analysis

Glass Failure Analysis Expert Witness Performs Wine Bottle Failure Analysis. In this product liability case the user was injured as the cork was being extracted. The glass failure expert witness performed a glass failure analysis and determined that the bottle failure initiated at the very top of the bottle. Thus, the cork screw could not have caused the damage that initiated the failure. Unopened bottles from the same case were examined, and it was discovered that the rod that pushed the cork in was very close to the glass in three of the four bottles that were examined. This indicates that the failed bottle was damaged during the corking operation. In addition, the forces used to extract the cork drove the pre-existing crack to failure. The photograph on the upper left is of the failed bottle top. In this photo the origin and crack travel direction are indicated. Upper right is a top down photo of a cork from one of the unopened bottles. The impression made in the cork is from the rod that pushed the compressed cork into the bottle. One can see from the impression that the rod was not centered. This indicates that the subject bottle failed due to corking damage. This is a manufacturing defect.

Glass Bottle Failure Analysis

Glass failure analysis expert performed a root cause failure analysis on a bottle failure. The cap on this bottle had not been removed. The failure analysis revealed a manufacturing defect on the bottle interior. On the upper left photo is a 30X photomicrograph of a portion of the origin on the fracture surface. The arrows show the travel direction of the crack exiting the origin. On the upper right is a 30X photonicrograph of the origin as it appears on the interior surface of the bottle. There is a "chip" associated with the origin; therefore, this is a product defect on the bottle interior.

Glass Failure Analysis of Tramp Glass

As a part of a product liability case, a glass failure expert was asked to determine if a piece of "tramp glass" found by a consumer (Upper left photo) was put into the bottle after it was opened. There was a companion bottle from the same six pack that also had glass contamination(upper right photo). If the tramp glass in the subject bottle was planted, then the glass in the "sister bottle" was also put in by the consumer. These were "twist off" bottles; therefore, it was decided that if the torque needed to remove the cap on the sister bottle was low, this would indicate the cap had been previously removed by the consumer. The removal torque was measured on the sister bottle, and it was twice that measured on control bottles. Thus, the cap on the sister bottle had not been removed, and the glass contamination entered this bottle during bottle manufacturing or bottle filling. From this it was concluded that the tramp glass in the subject bottle is also a manufacturing defect.

Glass Failure Analysis of Laminated and Tempered GLass

Glass failure analysis was performed by a failure analysis expert on a large laminated window of which one layer was tempered glass. The tempered half of the lamination failed. The other half of the window held the system together, and this allowed a failure analysis to be performed. The upper left photo is an over view of the window failure. The arrow indicates the general location of the failure origin of the tempered glass layer. The upper right photo is a closeup of the origin. The arrow indicates the location of a nickel sulfide particle (NiS) that caused the failure. It was reported that the tempered glass had been heat soaked. In this case the heat soak test (HST) did not eliminate on this window before it was sold.

Beer Bottle Impact Failure Analysis

Glass failure expert analyzed a failed beer bottle to determine if there was a product defect. It was stated that the bottle exploded when it was put into a cooler filled with ice. The failure analysis revealed that the bottle had been hit with a sharp object. The photograph on the left is the bottle after re-assembly. The photograph in the center is a closeup of the failure origin from the outside of the bottle, The photo on the right is the failure origin from the inside of the bottle. The hertzian cone from the impact is readily visible. It is obvious that this bottle broke after it was hit on the side. Thus there are no product liability issues or manufacturing defects associated with this failure.