Failure Analysis of Broken Tempered Glass Window

Failure analysis of tempered glass windows is normally impossible because the failed window falls apart into a large number of similar pieces, and locating the origin is impossible. However, there are cases when the window remains intact, and root cause failure analysis is possible. In this case the glass expert was able to preserve the origin and perform the failure analysis. Three failed windows were analyzed. In all cases the cause of failures were caused by a nickel sulfide contaminant particle (NiS). In one case, the NiS particle was visible in a macro-photograph. This is seen in the top left photograph. The other two images are photomicrographs of the NiS particle as it appears on the fracture surface at the origin. it is rare to be able to see the particle with the naked eye, but this is an exaple of such an event. The composition of the particle was determined to be Ni and S using energy dispersion spectroscopy. Failures of this nature are well understood and documented

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.

Nickel Sulfide Particles in Tempered Glass

Glass failure analysis expert witness performs a failure analysis on a tempered glass window. The failure was initiated by a nickel sulfide, NiS particle. The glass failure analysis expert was able to retrieve both halves of the failure origin. One side of the failure origin contained the protruding NiS particle. On the other side of the failure origin there was a hole out of which the NiS particle had pulled out when the two halves of the failure origin were separated. Above are two photographs of the two halves of the failure origin retrieved during the failure analysis. These photomicrographs were taken at 100X magnification using Nomarski interference contrast optics. This is a manufacturing defect. The NiS entered the glass during the melting operation.

GLass Expert Discusses Nickel Sulfide Spontaneous Failures

Glass failure analysis expert witness demonstrates that in the case of the spontaneous failure of tempered glass, the tempered glass failure is caused by the NiS particle. The failed glass door was taken apart to reveal the NiS particle. At this point the Wallner lines surrounding the NiS particle were located. The Wallner lines domonstrate that the NiS particle is in the center of the failure origin, and must be the cause of failure. The upper left photograph is a 20X photomicrograph of the NiS particle and its surroundings taken using Nomarski optics. Upper right is the same photomicrograph upon which arrows have been placed to show the crack travel directions as indicated by the Wallner lines. One can see that the NiS particle is at the center of the origin, and is the cause of the failure.

Failure Analysis Expert Performs Glass Failure Analysis

Glass expert performs a failure analysis on a failed tempered glass door. The spontaneous glass failure was analyzed to determine the cause of failure. This was one of several doors that failed spontaneously on a new high rise. Fortunately the door did not fall apart; thus, the failure origin could be preserved. The upper left photo shows the failure origin (arrow). The origin was taken apart, and at the center was a spherical 180 micron diameter nickel sulfide particle, NiS particle. During the glass failure analysis, a scanning electron microscope, SEM, image of the particle is shown in the upper right. Elemental analysis of the particle showed it to consist of nickel and sulfur. The SEM image also shows initial Wallner lines that are spiral in shape and are leaving the particle. This identifies the NiS particle as the cause of the failure

Glass Failure Expert Looks at Tempered Glass Failure

Glass expert analyzed a broken tempered glass door. He was able to preserve the origin and perform a failure analysis. The spontaneous glass failure started in the center of the window and was caused by a nickel sulfide particle (NiS particle). This failure mechanism is well known and has been documented by others. In this case, the glass expert spent some time documenting the initial crack growth. The upper left photomicrograph shows two sets of Wallner lines spreading away from the general location of the 100 micron diameter spherical nickel sulfide particle. The photomicrograph on the upper right shows a circular crack arrest line surrounding the NiS particle. This circular artifact identifies the NiS particle (a manufacturing defect) as the cause of the failure. In addition, it also indicates that the crack stopped at least once before the glass went to failure. At first the crack started as a round crack due to the stresses from the nickel sulfide particle. Later the residual stresses in the glass took control. The circular crack opened up and turned into the classic sets of Wallner lines found in root cause failure analysis of tempered glass.