Stress corrosion and fatigue affect Class 80x fleets, says ORR report
The Office of Rail and Road’s interim report into cracking issues affecting Hitachi Class 800-802 trains says stress corrosion cracking affected lifting plates, while fatigue cracking was the mechanism for cracks in yaw damper mountings. While communications between affected parties are generally regarded to have been effective, some concerns have been raised.
Stress corrosion cracking (SCC) occurs in susceptible materials – in this case the 7000 series aluminium alloy used on parts of the bodyshells when exposed to a corrosive substance while under stress. The ORR’s report says the corrosive environment for this alloy is one which contains chlorides – commonly encountered in coastal areas and during cold weather when salt is used to manage snow and ice. This corrosive environment, says the report, is considered to be endemic in the UK, and arises from high humidity, rain and sea water exposure.
There are various forms of potential stress, but the report says it ‘notably can be introduced during the welding process when fabricating a…
