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The 1968 MacRobertson Miller Airlines Flight 1750 lost a wing due to improper maintenance leading to fatigue failure. The 1969 F-111A crash due to a fatigue failure of the wing pivot fitting from a material defect resulted in the development of the damage-tolerant approach for fatigue design. [59]
In scientific literature, SBS is also known as building-related illness (BRI), building-related symptoms (BRS), or idiopathic environmental intolerance (IEI). The main identifying observation is an increased incidence of complaints of such symptoms as headache , eye, nose, and throat irritation , fatigue , dizziness , and nausea .
A failure mode may have more causes. For example; "fatigue or corrosion of a structural beam" or "fretting corrosion in an electrical contact" is a failure mechanism and in itself (likely) not a failure mode. The related failure mode (end state) is a "full fracture of structural beam" or "an open electrical contact".
The term fatigue refers to the effect of cyclic or intermittent loads. Cyclic loading due to either oscillating mechanical stress or to alternate heating and cooling is more detrimental than static loading. Under cyclic load, cracks initiate at localized sites within the part and these extend in size during cycling.
Metallurgical failure analysis is the process to determine the mechanism that has caused a metal component to fail.It can identify the cause of failure, providing insight into the root cause and potential solutions to prevent similar failures in the future, as well as culpability, which is important in legal cases. [1]
Fatigue alone is the driving cause of failure in this case, causing the material to fail before oxidation can have much of an effect. [1] TMF still is not fully understood. There are many different models to attempt to predict the behavior and life of materials undergoing TMF loading. The two models presented below take different approaches.
Vibration fatigue is a mechanical engineering term describing material fatigue, caused by forced vibration of random nature. An excited structure responds according to its natural-dynamics modes, which results in a dynamic stress load in the material points. [ 1 ]
With static fatigue materials experience damage or failure under stress levels that are lower than their normal ultimate tensile strengths. [2] The exact details vary with the material type and environmental factors, such as moisture presence [3] and temperature. [4] [5] This phenomenon is closely related to stress corrosion cracking. [1]