Tempered Glass Failure: Nickel Sulfide Particle

California failure analysis expert examines glass door failure to determine the root cause of the failure. The subject tempered glass door failed spontaneously, and because the glass was verticle, the broken pane remained intact. Read Consulting failure analysis laboratory was able to obtain the origin and perform a root cause failure analysis. The attached 25X Nomarski photomicrograph demonstrates that the glass failure originates at a nickel sulfide (NiS) particle. Once the glass failure has been initiated, the failure is driven by the residual stresses in the thermally tempered glass.  Glass fracture analysis shows the Wallner lines initiating at and expanding from a NiS particle. NiS particles are common in float glass, but they are only a problem in thermally tempered glass. Read Consulting Laboratory performs similar failure analyses on metals, plastics, ceramics and glass on a regular basis 

Chicago High Rise Window Failures

A Northern California failure analysis expert witness performs a glass failure analysis on broken tempered glass windows removed from a recently built Chicago Illinois high rise. Soon after construction windows in the high rise began to fail. Read Consulting which provides failure analysis services in Santa Rosa California was contracted to determine the cause of failure. A portion of each window containing the failure origin was preserved and sent to the Read Consulting failure analysis laboratory. The failed windows were deconstructed and the fracture surface at the origin was examined microscopically. Root cause failure analysis demonstrated that the high rise windows failed as a result of nickel sulfide, NiS, inclusions in the glass. One photo above show a representative window failure. The other photo is a 500X photomicrograph (taken with Nomarski optics) of one of the NiS particles. It is a 170µ diameter spherical particle. The arrows indicate the direction of the spreading crack.