Root Cause Failure Analysis. Trinath Sahoo

defects, unfavorable transformation, and metallurgical changes and so deterioration in the performance of final product during the service. These imperfections and discontinuities are mostly process specific and can exist in variety of forms due to improper selection of manufacturing process and their parameters. Therefore, due care must be taken by failure analyst to investigate the presence of any defect, discontinuity or unfavorable features in end produced by manufacturing processes and failed prematurely during the service.

      Poor Assembling

      Error in assembly can result due to various reasons such as ambiguous, insufficient or inappropriate assembly procedure, misalignment, poor workmanship. Sometimes, failures are also caused by the inadvertent error performed by the workers during the assembly. For example, failure of nut and stud assembly (used for holding the car wheel) by fatigue can occur owing to lack of information regarding sequence of tightening the nuts and torque to be used for tightening purpose; under such conditions any sort of loosening of nut which is subjected to external load will lead to fatigue failure.

      Poor Service Conditions

      Failure of an engineering component can occur due to abnormal service condition experienced by them for which they are not designed. These abnormal service conditions may appear in the form of exposure of component to excessively high rate of loading, unfavorable oxidative, corrosive, erosive environment at high or low temperature conditions for which it has not been designed. The contribution of any abnormality in service conditions on the failure can only be established after thorough investigation regarding compatibility of the design, manufacturing (such as heat treatment) and material of the failed components with condition experienced by them during the service.

      Stress overloads, excessive temperatures(hot or cold), inadequate abnormal corrosive environments, excessive speed, shock, thermal and mechanical, and excessive wear are all common misuse or misoperations that can promote premature and material failures. Loss of metal from corrosion including chemical attack, liquid metal corrosion, stress accelerated corrosion, and corrosion fatigue are common. Inadequate or maintenance such as poor lubrication, weld repairs, contamination, and cold straightening without thermal stress relieving and wear compensation can lead to accelerated wear resulting in deformation that promote fatigue, of rotating or static components.

      Poor Maintenance Strategy

      The failure of many moving mechanical components takes place due to poor maintenance plan. A well‐developed maintenance plan indicating each and every important step to be used for maintenance such as what, when, where, who, and how for maintenance, is specified explicitly. Lack of information on proper schedule of maintenance, procedure of the maintenance, frequently causes premature failure of moving components.

Conclusion

In failure analysis, investigation takes place to determine the cause of failure, usually with the aim of taking corrective action to fix the problem and mitigate against further failures. A metallurgical failure analysis takes in to account as much of the information as possible during analysis. The end goal of failure analysis is to provide a determination of the root cause. Analysis of a failed part can be done using destructive testing or non‐destructive testing (NDT). Failure analysis is undertaken across all branches of manufacturing industry to prevent future asset and product fails as well as protecting against potentially dangerous risks to people and the environment.