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.

Glass Expert Discusses Construction Defect

Glass expert analyzed a failed shower enclosement wall made from tempered glass. The failure occured before the homeowner warranty had failed. The contractor refused to replace the glass panel. It was his opinion was that the homeowner had damaged the panel and was responsible. Glass failure analysis determined that the failure initiated under the frame. In addition, there was no damage to the metal frame (i.e. there were no "dings" or "dents"). Therefore, the panel had failed spontaneously as was claimed by the homeowner. The upper left photograph is an overview of the failed panel. Here one can see that the failure emanates from the lower right corner. The upper right photograph is a close up of the corner. As a result of the analysis, the contractor agreed to honor the warranty and replace the tempered glass panel.

Hot Dip Galvanized v.Electro-Galvanized Nails

Metallurgy expert describes the difference between hot dip galvanized nails and electro-galvanized nails. Manufacturers have changed from hot dip galvanizing to electro-galvanizing. The zinc is a sacraficial materail; therefore, the protection afforded by the galvanize layer (zinc) depends on the zinc thickness. All other things being equal, the electro-galvanized nails with the much thinner zinc layer (t= 0.000065"), right photo, will rust sooner than the hot dip galvanized (t= 0.0015"), left photo. It is reccomended that hot dipped nails be used for critical applications.

Glass Expert Analyses a Broken Bottle

Glass failure anlysis expert witness performs a root cause failure analysis on a broken bottle. This bottle broke into pieces (lowerleft figure). A failure analysis determined that the failure origin was in the bottle neck under the plastic cap (lower right figure). The glass expert removed the cap and the the residual polish (top left figure). The neck was cut open from the side opposite the visible crack, and the failure analysis revealed that the failure originated (arrow) at a damage site on the interior of the bottle neck (top right figure). Further study is required to determine the source of the damage.