High Pressure Bottle Failure Analysis Tests

Glass failure analysis requires looking at failed bottles and determining the cause of failure. The failure analysis procedure includes carefully examining the crack pattern and the failure origin. It also helps to have failures with known causes to confirm the conclusions. In this case bottles were purposly broken using hydraulic pressure. Their performance was documented for future use. Numerous bottles were tested, and all showed similar failure characteristics. All bottle failures were caused by "hoop stress"; thus they started as a straight crack parallel to the axis of the bottle and then branched out. Microscopically, all the over pressure glass bottle failures originated as a slow growing crack and formed a distinct fracture mirror surrounded by mist hackle. Upper left is a photograph of a representative over pressure failure. This particular failure originated on the body of the bottle. Others originated on the heel, but all had the same characteristics. Upper right is a 40X photomicrograph the origin of the failure. It consists of a slow growth fracture mirror surrounded by mist hackle. The small arrows indicate the crack travel direction. During falure analysis, a glass failure analysis expert can compare the unknown glass failure to this example to aid in determining the cause of the failure.

Glass Expert Performs Beer Bottle Failure Analysis

Glass failure analysis expert witness performs a failure analysis on a broken beer bottle. According to the witness the bottle "explosion" occured as the bottle was being set down. The glass expert examined the failed bottle and the failure analysis showed that the bottle failure resulted from damage to tbe knurl on the bottom of the bottle. The bottle must have hit a hard object when being placed down. The upper left photograph is of the re-assembled bottom of the bottle. The crack comes up from the bottom. Thus the origin is contained in the heel of the bottle. Upper right is a 40X photomicrograph of the portion of the heel containing the failure origin. The failure originated at a chip in the knurl on the bottom of the bottle. This is not a manufacturing defect. It is a result of damage caused by the user.

California Glass Expert Discusses Nickel Sulfide in Tempered Glass

In glass failure analysis one uses evidence such as the the attached photograph to demonstrate that a nickel sulfide particle can initiate tempered glass failure. The NiS particle is at the center of expanding Wallner lines. The Wallner lines are used by the glass failure analysis expert to track the direction of the crack growth. In this case the Wallner lines are spreading from a single point; thus, this is the failure origin and the NiS particle is the cause of the tempered glass failure. The California glass expert has seen numerous examples of this type of glass failure.