Failure analysis of large fan blades

This large ventilation fan has failed during its breaking-in period, resulting in blades detaching from the flange and  breaking to bits due to an unknown cause. 

The investigation has found the failure to be the result of defficient design - namely, insufficient strength (hardness) of the flange, relative to the high strength (hardness) of the blade's fastening screws. This allowed for a plastic deformation of the flange threading, after screw fastenning and\or during use, this in turn allowed for a weakening of the screws' pre-stressing. As a result, cyclic bending stresses developed in the screws which eventually led to a fatigue fracture, and failure of the system. 

In addition,  manufacturing defects were found in the flange threading , which together with the high friction factor of the galvanization contributed to insufficient fastening.

Failure analysis of a submerged stainless steel pipeline

Leakage of submerged piping in sewage treatment plant was investigated. Leakage occured through perforation of bent connectors. 

The investigation found the failure to be a result of improper material selection: connectors were made of AISI304 stainless steel, contrary to design requirement of AISI316L employment for the entire piping system (pipes and connectors).

Consequently, galvanic corrosion developed between the two different materials, leading to the observed perforation of the connectors.

Consultancy - Speckled 18K golden jewelry

In this case, we were requested to assist in understanding the origin of stains that appeared on the surface of 18K gold bracelets. 

Examining the stains using Auger electron spectroscopy, it was found that the stains are the result of a 150 Angstrom deep surface layer composed mainly of silver and sulphur. 

Specifically, a silver-rich sub-micron surface layer was detected and underneath this layer, a 24k gold sub-micron layer exists, the remaining material is compsed of 18K Gold. This surface structure is undesired, as the inertness of silver is inferior to that of gold. 

The stains observed on the surface layer contain, in addition to silver, various contaminants originating from deficient cleanlinessof the coating baths. Therefore, in addition to eliminating the silver layers, an improvement of the process contaminant control was recomended.

Failure analysis of a mammography unit

In this investigation the imaging head of a mammography unit suddenly dropped due to a failure of the steel cable lifting mechanism. 

Investigation of the damaged steel cable and the spiral pulley showed that the cable condition has deteriorated over a long time period during which single wires tore due to fatigue, while the remaining wires tore due to overload. The cable rails inside the pulley were also damaged due to cable motion outside the rails.

These findings pointed us to believe that unit cables were improperly assembled on the pulley, leadng to fatigue and mechanical damages to the puley and cables, and resulting in failure of the system.

Failure analysis of scuba diving tank explosions

In this case multiple events of scuba diving tank explosions prompted a study aimed at determining the root cause of the failures.

The in-depth investigation which included fractography, metalography and chemical analysis, and stress analysis led to the following conclusions:

1.        Tanks  material microstructure was deficient and inappropriate for sea water exposure, leading to stress corrosion cracking.

2.       Scuba tanks were not designed according to leak-before-break principle, thus, cracking reached critical size before traversing wall thickness which ultimately led to uncontrolled catastrophic longitudinal fracturing i.e. explosion of the tanks.

The explosion of similar scuba tanks around the world together with the understanding of the underlying causes of the explosions have led the French manufacturer to recall these tanks and withdraw them from use.

Leading Israeli Scientist Declares Pomegranate Inscription Authentic

http://www.anchorstone.com/news-mainmenu/biblical-archaeology/360-Leading-Israeli-Scientist-Declares-Pomegranate-Inscription-Authentic.html

The thumb-sized pomegranate is believed to be the only existent relic from Solomon's Temple in Jerusalem. Around the shoulder of the pomegranate there is a carefully incised inscription in early Hebrew characters, part of which is broken off, which reads: "qodes kohanim I-beyt [yahwe]h". "Sacred donation for the priests of (in) the House of [Yahwe]h." "House of Yahweh" most probably refers to the Temple in Jerusalem. The pomegranate was Solomon's favorite motif and decorated the capitals of the two freestanding columns at the entrance to the Temple in Jerusalem (1 Kings 7:21).