FAILURE ANALYSIS :

Failure analysis can be defined as the examination of a failed component and of the failure situation inorder to determine the causes of the failure. The purpose of a failure analysis is to define the mechanism and causes of the failure and usually to recommend a solution to the problem.

Most failures involve fracture of the component and thus most failure analysis involve examination of the mechanical loading situation.

Failure of a component indicates it has become completely or partially unusable or has deteriorated to the point that it is undependable or unsafe for normal sustained service. It is possible for fracture to be a result of multiple failure mechanisms or root causes.  A failure analysis can provide the information to identify the appropriate root cause of the failure and failure analysis reports include recommendations to avoid future failures - from component design, through material selection and processing.

The most common modes of failure are corrosion, erosion (including wear and abrasion), fatigue (the slow propagation of a crack during regular use), brittle fracture (instantaneous cracking), ductile fracture and creep (both of which involve plastic deformation). The actual mechanism of failure can be a combination of these modes such as stress corrosion (corrosion accelerated by tensile stress) or erosion-corrosion (erosion promoted by corrosive attack).

Failure analysis and prevention are important functions to all of the engineering disciplines. The materials engineer often plays a lead role in the analysis of failures, whether a component or product fails in service or if failure occurs in manufacturing or during production processing.

1. The first step in conducting any failure analysis is to gain a good  understanding of the conditions under which the part was operating.
2. The second step is to conduct a visual examination, cataloguing and recording the physical evidence at the same time. This serves the functions of:

• Familiarizing the investigators with the evidence.
• Creating a permanent record that can be referred to in light of new information.

3. The third step is to decide on a course of action. Based on the visual examinations and the background information the investigator must outline a plan of action, which is the series of steps that will be needed to successfully complete the case. There are several resources that an investigator can draw on to determine the cause of failure, which can classified into one of the following categories:

• Macroscopic examination
• Microscopic examination

To examine the exact origin of the failure, macroscopic and microscopic examination is necessary.   Recommendations are made on the basis of findings, and remedial measures are suggested to minimize such failures.