This agency should take immediate actions to adopt the compulsory notification and investigation of the failures of orthopaedic implants and implement a more reliable certification procedure of implants to ensure the protection of the Brazilian health care patients. The current organization and transparency of the Brazilian Health Regulatory Agency (ANVISA) for the investigation and prevention of the failure of orthopaedic implants can be criticised as severely flawed. In contrast, the transparency of the National Land Transportation Agency (ANTT) for the investigation of railway accidents is considered to be deficient. The implementation and achieved transparency of the National Civil Aviation Agency (ANAC) for the investigation of aircraft accidents are recognized as state of the art and is consistent with the economic importance of this sector for the country. Three cases of failure analysis (aircraft landing gear, cast railway wheel and unalloyed Ti orthopaedic implant) representing three different industry sectors were selected to compose a critical study of their respective regulatory agency in Brazil. The abnormal loads absorbed by the outer cylinder during the landing procedure, associated with the presence of fatigue pre-cracks, may be concluded as the cause for this failure.
#Bae jetstream 32 x plane crack free#
The fatigue crack observed in the landing gear was nucleated on the intersection of the aligned microstructure with the free surface, condition that should be avoided by efficient design of structural components. The elongated morphology of primary and secondary precipitates aligned perpendicular to the loading direction is thought to be responsible for the lower fracture toughness observed for TL orientation. TL orientation showed additional propagation along the boundaries between recrystallized and unrecrystallized regions. Fractographic observation of KIC test pieces showed that unstable crack propagation occurred preferentially along the boundaries of recrystallized grains. Fracture toughness KIC tests confirmed that LT orientation presented KIC values 60% higher than TL, although it presented comparatively a higher proportion of intergranular fracture. Both stable and unstable crack propagation occurred preferentially parallel to the orientation of the microstructure. Fractographic examination revealed that the unstable crack propagation was originated in the fatigue cracks, which were approximately 0.6 mm deep, and occurred mainly by a mechanism of ductile intergranular fracture.
The material presented an oriented partially recrystallized microstructure, with the unrecrystallized areas showing intense intragranular precipitation, while the recrystallized areas presented fine intergranular precipitation. The landing gear of an aircraft failed during its landing procedure due to the fracture of the outer cylinder, which is manufactured from an Al–5.7Zn–2.7Mg–0.5Mn–0.5Cu alloy.
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