A faulty production of concrete plates caused excessive cracking and an environmental risk Exposing the reinforced steel verified the Non-destructive testing indication of steel "saving" During a project acceptance phase, at a construction site, cracked concrete plates were discovered. The cracking phenomenon was detected at the bottom face of the plates on 90 of the whole units that were 50% of the boards. Nondestructive testing by radiography method was preformed in order to detect both setting and size of the reinforcing steel, inside the concrete plates. The inspection indicated a difference of 50% in the reinforcing steel diameter compared with the designed diameter. In simple words, the steel was half the diameter it should have been. Furthermore, the actual steel setting was different from the designed. In order to verify the unexpected radiography results, a single plate was mechanically dismantled - the diameter of the reinforcing steel was, indeed, 6 mm while the designed diameter was 12 mm. As a result, all the plates in that site were replaced thus resulting as a $100,000 damage. Why did the crane collapse? The crane after it collapsed While lifting a 0.5 ton load of ceramic plates, in Northern Israel, a crane suddenly collapsed on a 12-story building. Visual inspection at-site detected two unexpected fractured components- one wheel boogie and a boom element parallel to the 10 story level. It was suspected that the failure of these items was caused by the presence of a preliminary crack within these components. Laboratory geometric measurements of the components fracture zone did indicate local necking that implies of overload mechanism. Microscopic inspection using SEM validated the failure mechanism of these components to be a sudden overloading event. In order to evaluate possible cause, using computerized models several scenarios were simulated. The following was the result of that analysis: A. In the morning of the event, rough wind existed and drove the crane     on its rail until it reached the rail-end stoppers. B. When reaching the stoppers the crane sprung backwards and one of     the wheels didn't return to its place on the rail. C. Standing on three wheels only enabled a limited safe working zone for     the crane to work. D. When exceeding that zone, the crane collapsed. Did the cause of failure of the Electro-mechanic part was indeed a corrosion attack?! A preliminary crack at the bending area (X70) Customers that complained of an inner defect within the Electro-mechanic system returned a critical failed component. The system has been operating for 15 years, at various customers' premises without any problems, up to the last 2 years where problems arose. Checking back records, the manufacturer found that the only significant change done within the manufacturing process was changing the subcontractor that was conducting the gold plating of the part. The manufacturer naturally suspected that corrosion developed due to poor gold plating. Furthermore, he assumed that the corrosion was the reason for electrical disconnection. 20 part were dismantled, cut, chemically identified and examined metallurgically but corrosion products presence that were depicted could not explain the electrical disconnection. SEM inspection revealed cracking and fracture phenomenon in the electrical wires. It was detected that the manufacturer did not take into consideration sharp angles and bending of the electrical wires while stamping the wire plate. As a result prior to gold plating of the wires microcracks were already induced and later-on they developed into fractures. The manufacturer checked both manufacturing procedure and tools and found that the stamping equipment used to create wire plate was damaged and created sharp angles and cracks. The manufacturer then adjusted the equipment and redesigned the board's layout. Is it possible to reconstruct an electrical board once damaged? And if it is possible, how? Electrical parts contactors with chlorine debris One of the last manufacturing stages of an electrical board is the exposure to cyclic temperature load in a regular environment. During one of the tests it was suspected that there was a malfunction in the low temperature furnace. Boards were examined and found damaged at the contactor areas. Based on the assumption that the boards were exposed to a very low temperature and therefore water condensed on them, the manufacturer tried to reconstruct a couple of boards by just drying them. The laboratory obtained one board and one motherboard in order to determine the cause of damage. Optical examination (X50) revealed that the motherboard that was basically made of aluminum foil was covered with white deposit especially along the rim. The damage to the electrical parts was characterized as white deposits on the contactors. A chemical analysis using SEM/EDX method revealed high concentrations of Chlorine that characterizes a Chlorine-based solution and not condensed water. The results of the research indicated that the cleaning method used by the manufacturer in trying to reconstruct the boards was neither suitable nor effective. Because of the long time period that has past since damage occurrence the reconstruction of the boards was not profitable and the total damage reached $50,000.
	Home | Profile | Services | Personnel & Articles | Laboratory Reviews | Feedback Ruppin Collage Campus, Emek Hefer 40250 Israel Tel: 972-9-8988491 Fax: 972-9-8988129 info@ifaisrael.com