Glass Failure Analysis, Coffee Pot Failure

 Read Consulting failure analysis laboratory was asked to examine a failed coffee pot that had been abraded with a cleaning pad and then subjected to a series of thermal shock cycles. The pot was heated to 190°C then immediately immersed in 10°C water. The pot appeared to survive till the 51st cycle. On this cycle a crack across the bottom appeared. Glass failure analysis performed on the fracture surfaces revealed a glass fatigue failure. The failure initiated at the location of abrasive damage and the flaw grew incrementally after each quench. It is unique to find actual fatigue in a brittle material. Apparently, the thermal shock stress was short term enough to allow incremental growth. Once the crack started, each quench caused the crack to advance and stop. The result is a crack arrest line.

Chair Failure Analysis, Plastic Lawn Chair

A failed plastic chair was submitted to our failure analysis laboratory for examination. The right rear leg had broken off; however, the initial chair failure occurred on the left rear side. The left rear leg separated from the chair body due to poor bonding and molding porosity at the top of the leg. The failure resulted from manufacturing defects. On the upper right are photographs of the initial failure. There is porosity in the region where the leg is attached to the chair. In addition, the bond line is very narrow. Upper left is a photograph of the same region on an exemplar chair. One can see that the where the leg meets the chair there is severe undercutting. this creates a "stress riser" that reduces the joint strength.

Glass Expert Witness Services

Read Consulting is a California failure analysis laboratory that provides a complete line of glass expert witness services. These include glass failure analysis, window damage assessment,  patent expert witness support and stress testing. In addition Read Consulting also offers glass expert witness support in all areas of glass and ceramic machining and processing.  Process and device patent expertise is also provided.  

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