Glass Expert Performs Failure Analy on Low E Windows

California failure analysis lab was asked to determine why windows in an expensive hilltop home failed. The windows in question were Lo- E windows that were tinted to absorb infra-red light. At this location two south facing, side-by-side windows cracked. The window expert at Read Consulting was asked to perform a glass failure analysis to determine the root cause of the failure. For this failure analysis the site of the origin was cut from the window and  the failure origin was examined using a low power optical microscope. Both windows failed in an identical manner. Thermal expansion of the center of the Low-E window put the ground glass window edges in tension.A damage site from either the window sizing or window seaming processes was activated by the thermally generated stresses and cracked these windows. Please refer to the photographs above.    

Glass Expert Discusses Visibility of NiS Particles

Tempered glass failure analysis is mainly difficult because the panel disintegrates into a very large number of semi identical particles; therefore, the failure origin is impossible to locate. In several cases Read Consulting has had the opportunity to examine several failed (caused by Nickel Sulfide, NiS, particles) tempered glass panels that have remained intact. In some cases the windows were laminated; in the others, the windows remained verticle and stayed interlocked. Once the origin is located and preserved, an eyeloop or low power microscope is all that is required to see the NiS particle. The upper left photograph is a macrophotograph of an inplace failed laminated window. In this case the NiS particle is visible to the naked eye. It is a sphericle particle on the fracture surface. Upper right is an 8X photo-micrograph of the particle after the window has been taken apart. This root cause failure analysis does not require scanning electron microscope. This type of tempered glass fracture analysis merely needs an intact failed window.

Glass Expert Performs a Wine Bottle Failure Analysis

California glass expert performs a failure analysis on a wine bottle failure. In this case the root cause of the failure was due to an impact on the top of the bottle finish. it is apparent that this bottle was hit on the top. This is shown by the photomicrograph.

Failure Analysis of Reed Switch Glass Failure

Glass expert performed a root cause failure analysis on failed reed switches. The upper left photograph shows the type of reed switch that was failing. This switch consists of two ferromagnetic "blades" that are enclosed in glass. At either end are leads that pass through glass-to-metal seals. The sealed tube is filled with inert gas which is introduced through a side tube that is heat sealed after the gas has been introduced. The switch is activated magnetically. The glass expert performed a glass failure analysis and determined that the glass envelopes were cracking due to the presence of mechanical damage (i.e. scratches) on the outer surface of the glass. All the cracks initiated at a flaw and then proceeded circumferentially till the two halves of the crack met on the opposite side from the origin. It is believed that the source of the failure stress was thermal stress generated by heating during potting and assembly. WIthout the pre-existing flaw on the outer glass surface, the switch would not have failed. The center photograph shows the initial crack leaving the origin in two directions. These two halves of the crack eventually meet on the side opposite the origin. The upper right photograph shows the surface flaw where the crack originated. These switches failed as a result of a manufacturing defect.

Glass Failure Expert Witness Analyzes Failed Wine Bottle

Glass expert performed a root cause failure analysis of a broken wine bottle. The bottle had broken at the neck into three pieces (Upper left photograph). One piece still contained the cork with the cork screw still in place. In this case the the cork screw was off center and had exited the cork when it was being "screwed" in. The side of the cork screw crushed the interior wall of the bottle neck, and this initiated the failure. The upper right photograph is of the re-assembled top of the bottle. In it one can see the exposed edge of the cork screw and the "crush" defect on the interior of the bottle neck. With this type of cork screw the cork is pried out with a lever force. In this case, this force was sufficient to cause failure and injuryto the person opening the bottle. With this type of cork screw the user must be careful to center it, or he could be injured.

This glass failure analysis showed that the failure was a result of operator error. There was no manufacturing defect.

Glass Failure Analysis Expert Examines Failed Champagne Bottle

Glass failure analysis expert performed a root cause failure analysis on a exploding champagne bottle. The user claimed that the bottle exploded when she was using her thumbs to remove the cork. Examination of the bottle revealed a horizontal crush point. This damage was severe and would not have survived the corking operation at the winery. Thus this damage was caused by a tool when it was used by the injured party to remove the cork. There was an indication that this bottle had been in the freezer prior to the accident. Thus, there was little or no internal pressure to aid in the removal of the cork. Thus a tool was used, and this caused the failure. The photograph on the upper left is of the salvaged pieces of the exploding champagne bottle. The photograph on the upper right is of the fracture initiation point and the failure origin.

Wine Bottle Failure Analysis

Glass failure analysis expert locates the origin of a failed wine bottle. Thye failure origin is at the top of the bottle on the inside rim. The origin is a crush spot on the inner rim. This was too high to be caused by a cork screw. It is believed that the damage occured before the bottle was purchased. Root cause of the failure is mechanical damage to the top of the bottle on the inner rim of the neck.

Manufacturing Engineer and Product Liability

Product Liability, Design Defects and Manufacturing Defects are obvious arenas for an experienced manufacturing engineer or process engineer. He has the insight to best evaluate manufacturing defects in product liability cases. Naturally, he must first perform a complete root cause failure analysis to determine if there was product misuse, a manufacturing defect or a design defect. Naturally it is a benifit if the chosen engineer has experience with similar products, materials and processes in question. This is an asset because he can relate the defect back to a specific process step. In addition, he will be familiar with what is necessary for correct product development. An example is a case where a product failed after a short time in service. He is best qualified to determine if the product or process development procedures were thorough and proper. For example, he can determine if the proper accelerated life tests were performed to determine the product performance over its expected lifetime. Product development and process development usually occur in four stages: concept, bread board, pilot production and full production. An important aspect of this cycle is to determine if there are potential circumstances during normal use that might cause product failure and/or personnel injury. Documented tests must be performed to prove that the hypothetical degradation mechanisms do not cause premature product failure. If this is not done, an unreliable or dangerous product (i.e. poor product safety) may be put on the market. An experienced manufacturing engineer is the best prepared to determine if the product was properly developed to allow for proper product quality. This insight can only be gained from direct hands on manufacturing experience.

Metal Clad Window Failure

During a severe storm a three story house suffered severe water damage. This damage was not caused by flooding; it was caused by large amounts of water entering the top floor of the home as a result of openings to the outside. Read Consulting performed a failure analysis of the property and determine the root cause of the damage. The failure analysis included an inspection of the home and a review of photographs taken of the residence immediately after the storm, and the cause of the water intrusion was determined. Severe rot resulted in the formation of openings in the third floor windows. The windows in this house were expensive metal clad wood windows. Failure analysis determined that moisture had reached the wood structure through seal openings in the exterior metal cladding. This caused swelling of the wood and further opening of the seals; thus the amount of water intrusion was excaserbated. In addition, the moisture was "trapped" in the wood and caused accelerated deterioration. In essence, the wet wood would be at temperatures in excess of 125°F during the warm, hot days. This accelerated wood deterioration (i.e. the wood "composted"). In addition, this degradation was not noticeable because the metal cladding covered the wood. Due to rot, the windows became extremely weak and failed during the storm. The upper left photo shows a window that was so rotten that during the storm, the glass pane slipped down and left a 2" gap at the top. The upper right window failed when the bottom part of the top sash fell away creating an opening. These two windows represent the types of failures discovered on the third floor. These allowed large amounts of water into the home and caused severe damage throughout the house.