Editing Forensic engineering (section)

==Examples==
[[Image:Plate7new.jpg|thumb|left|200px|Failed fuel pipe at right from a road traffic accident.]]
[[Image:Plate4new.jpg|thumb|left|200px|Close-up of the broken fuel pipe from a road traffic accident.]]
[[Image:Broken fuel pipe.jpg|thumb|left|200px|Close-up of the broken fuel pipe.]]
The broken fuel pipe shown at left caused a serious accident when [[diesel fuel]] poured out from a van onto the road. A following car skidded and the driver was seriously injured when she collided with an oncoming [[lorry]]. [[Scanning electron microscopy]] (SEM) showed that the [[nylon]] connector had fractured by [[stress corrosion cracking]] (SCC) due to a small leak of [[battery acid]]. Nylon is susceptible to [[hydrolysis]] when in contact with [[sulfuric acid]], and only a small leak of acid would have sufficed to start a brittle crack in the [[injection moulded]] [[nylon&nbsp;6,6]] connector by SCC. The crack took about 7 days to grow across the diameter of the tube. The fracture surface showed a mainly brittle surface with striations indicating progressive growth of the crack across the diameter of the pipe. Once the crack had penetrated the inner bore, fuel started leaking onto the road.

The nylon&nbsp;6,6 had been attacked by the following reaction, which was catalyzed by the acid:
:[[image:amide hydrolysis.svg]]

[[Diesel fuel]] is especially hazardous on road surfaces because it forms a thin, oily film that cannot be easily seen by drivers. It is much like [[black ice]] in its slipperiness, so skids are common when diesel leaks occur. The insurers of the van driver admitted liability and the injured driver was compensated.