Failure Analysis of Glass Pitcher

An injury occured to a woman when she poured cold liquid into a warm glass pitcher. The bottom of the pitcher separated from the handle and fell onto her foot and cut the top of her foot severly. The subject pitcher was lost; therefore, Read Consulting was asked to examine an exemplar from the same store and perform a root cause failure analysis. An accident reconstruction was performed. The upper left photograph is of the exemplar pitcher. This appears to be a hand made glass object (there are no parting seams from a mold). In this case, the main part is made first, and the handle is made separately. Later, the handle is attached to the main body. Both pieces are heated till they are soft and the preformed handle is pressed onto the pitcher. If the main body is not hot enough, thermal stresses can be generated that can create cracks on the inner surface of the vessel. This is a product defect that can cause failure. Such cracks were observed on the new examplar. The red arrow inthe left photo shows the general locationof a crack. A closeup of the handle bottom clearly shows cracking (arrow in lower center photograph). This pitcher also failed when cold water was poured into it while it was warm. The cold liquid caused interior tensile stresses. The failure initiated at a pre-existing crack (i.e. manufacturing defect) near the bottom of the handle (upper right photograph). In this case the handle portion of the pitcher separated from the rest of the body.

Broken Jar

Materials Failure Analysis: A broken jam jar was examined to determine the cause of the failure. In this case, the top of the jar separated from the body as the user was trying to twist the metal lid off. The upper left photo is of the severed top of the jar. The lid did not come off. There is an impact point on the glass at the bottom of the photo. In addition, there are two dents to the lid. The upper right photo is a 15X photomicrograph of the fracture surface at the failure origin (red arrow). One can see an impact failure with two crack arrest lines. This jar failed because it had been hit by a hard tool during an attempt to loosen the lid. The dents on the lid suggest that the jar had been hit several times. The root cause was one blow to the glass; it created the crack that was to cause the top to separate from the rest of the jar as the lid was being twisted.

New Construction WIndow Glass Scratching

The window in the photograph above was damaged during post construction

cleaning. Although glass is a hard material, dust, sand and other debris are just as hard and can damage glass. Therefore, one must be careful when cleaning glass. The damage seen in the window above is only visible in direct-oblique light; thus, it is visible at a certain time of the day in sunlight. The scratches literally "light up". There are numerous legal disputes generated by this type of damage. The Glass Association of North America (GANA) has published a bulletin (#01-0300) that is a good reference for cleaning windows.