WHAT IS ENGINEERING FAILURE ANALYSIS?
Put simply, engineering failure analysis (EFA) is determining why something failed. Collection and analysis of data relevant to the failure allows the investigator to determine the root cause and suggest corrective actions.
Failure is typically related to the design, manufacture, or use of the component and in some cases may be a combination of these three things.
WHY INVESTIGATE A FAILURE?
There are many reasons to investigate a failure. Typically an investigation is undertaken to determine what went wrong and how to avoid it happening again in the future.
For legal cases and insurance claims often the aim is to determine liability and an independent third party such as Explicom is required to carry out a failure investigation and offer expert advice.
For our industrial customers who wish to make warranty claims, investigating a failed component will give valuable information about how the component was manufactured. This in turn helps determine if the root cause of the failure was related to design, manufacture or operation.
CASE STUDIES
Cracking of an Ammonium Nitrate Dryer
After only a year of service, an ammonium nitrate prill dryer in an explosives manufacturer's plant was found to be cracked. The cracking was predominantly associated with the welds and where welds had been removed. The cracking was identified as stress corrosion cracking due to the presence of ammonium nitrate. The failure was attributed to residual stresses in the welds and was a result of the dryer not having been stress relieved during manufacture. For more detail on this failure a paper on the failure can be downloaded here. The paper was published in Engineering Failure Analysis, Volume 18(6), (2011) 1559-1564.
Use of fracture mechanics to understand the cause of failure of raise bore shafts
Raise borers are used to produce vertical shafts in mining and construction. A series of these shafts fractured in operation and the operators blamed the manufacturer of the equipment for providing faulty equipment. An analysis of the material used in the raise bore shafts showed that the shafts were compliant with the specifications of the manufacturer but had failed by fatigue. By analysing the material used in the construction of the shafts and by measuring the size of cracks at the time of fracture, Dr.Clegg was able to use fracture mechanics to demonstrate that the most likely cause of fracture of the shafts was incorrect use by the operators of the equipment. The principles behind this analysis are outlined in a paper co-authored by Dr.Clegg and published in Engineering Failure Analysis.
U.Zerbst, C.Klinger and R.Clegg Fracture Mechanics as a tool in failure analysis - Prospects and limitations. Engineering Failure Analysis Volume 55, (2015), 376-410.
Escalator Stair Failure
An aluminium escalator stair failed at a Brisbane railway station. The failure caused the stair to collide with the top plate of the escalator resulting in a commuter being injured. As part of a wider root-cause-analysis investigation, metallurgical analysis of the failed stair and several neighbouring stairs was carried out. Cracking was found to have occurred through the section of the stair that was used to mount it to the conveyor system. The failure was attributed to the high level of casting defects found in the microstructure. This allowed the customer to determine that the failure was due to a manufacturing issue and not related to the operation or maintenance of the escalator.