Glass Fracture, Califirnia Glass ExpertPerforms Bottle Failure Analysis

California failure analysis expert witness was asked to perform a detailed failure analysis of a broken wine bottle. Glass fractography was used to determine the root cause failure mode. The failure originated at damage caused by the prop on the cork screw. The fact that there were two damage sites on opposite sides of the bottle and that the cork was only partially removed, indicates that the force to remove the cork was excessive. The donward force on the prongs crushed the top of the bottle at two places and initiated a crack that was driven by the force needed to move the cork. This failure was not the result of a bottle manufacturing defect; it was caused by the high forces needed to move the cork and the type of cork screw used. Upper left is a photograph of the two pieces of the bottle neck. Upper right is a 20X photomicrograph of the failure origin and the initial part of the crack. The arrows show the initial travel direction of the crack. Also, visible is the "crush point" at the beginning of the failure.

Glass Expert Examines a Tempered Glass Window Failure

California failure analysis expert uses glass fractography to perform a glass failure analysis on a tempered glass window failure. The glass fracture analysis showed that the window failure was a result of heating the glass in the center. Due to the heat, the center of the window expanded. This created additional tensile stress on the window edges. Although the window edge was ground and chamfered, there was enough residual damage at the edge that the thermal stresses were able to cause window failure. Upper left shows the failure initiation site on the edge of the window. Upper right is a 40X photo micrograph of the origin on one of the fracture surfaces. The glass fracture analysis showed that the glass failure initiated on the window's edge face and propogated inward until the tensile center of the tempered glass window was reached. At this point the residual tempering stresses caused the entire window to self destruct into small "cubic" pieces. This may be a manufacturing defect because of the severity of the edge damage.