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Failure Analysis

Failure analysis is the process of studying and understanding a particular incident where a material or a system has experienced failure, to determine the cause of the failure and most importantly to prevent it from happening again. The significance of failure analysis is the latter half of the definition - impeding a recurrence of the failure. In the world of designing critical products used on a daily basis by millions of people, the integrity of materials is a number one priority. Businesses hire experts to perform failure analysis to ensure the product's quality.

Metal fracture is one type of failure analysis. Brittle metals experience fracture, while ductile metals experience yielding. In order to study different materials and predict their behavior in real life situations, tests are done in a laboratory to characterize performance. There are three tests that are done in metal fracture analysis. Uni-axial tensile and compression tests are performed to determine tensile and compressive stresses, respectively, and torsion tests are performed to yield ultimate shear stress. In the field of metal fracture failure analysis, the brittle materials tend to experience failure as a result of extreme tensile stress and occur suddenly.

Fractography, an important branch of failure analysis, is the intricate study of the failures of metals or systems, performed by evaluating high resolution photographs of the fracture point of orientation. It has been established that a large number of fractures are caused by inclusions, or foreign material trapped in the metal. This foreign material does not have the same characteristics of the parent metal and therefore react differently, and usually unfavorably, under stress. If a crack is present as a result of a foreign material or a void in the cast material, it is likely that a normal tensile stress will cause the crack to propogate and lead to a metal fracture. Fractography is a part of fracture mechanics and is an important part of failure analysis. What fractography does is calibrate scientific theory and actual occurring failures. Studying and quantifying a photograph of a failure point visually helps the engineers to understand the failure analysis and declare results confidently.

In the electronics and manufacturing business, it is extremely important to understand the root cause determination in a failure analysis. A failure modes effects analysis (FMEA) is a common tool used by engineers to brainstorm all the possible causes for a failure. These causes are then ranked by probability and severity to narrow down to the most likely causes. In failure analysis, however, probability is not good enough - confidence is required in a root cause determination because the root cause will provoke a corrective action to be implemented. In order to determine the proper corrective action to employ, the precise root cause must be determined. This is why fractography and metallurgical experts are now used for consultants. By completing a complex failure analysis, the root cause can be expertly determined and a corrective action can be executed flawlessly for prevention of recurring failures.

In failure analysis materials data and evidence must be interpreted accurately and precisely. Take one case of failure, for instance, a turbine blade breaking off inside an engine and destroying the entire system. Someone reading in the newspaper may be blown away and have no idea how anyone could determine the root cause of the tragic event, but a metallographic expert or a materials data interpreter would be excited to begin the failure analysis. The evidence would be collected throughout the entire engine like the different materials of the engine components and fasteners, as well as their reaction to the explosion. After finding the broken turbine blade, they would narrow their search and perhaps take high resolution photographs of the fracture to determine what caused such trauma. In this case, there happened to be a foreign object fused with the metal and the high stress undergone in the engine caused a sudden failure. The interpretation of the materials data and evidence led the engineers to determine the particular root cause of the event and the detailed failure analysis led to more strict foreign object control policies to prevent any future recurrences.