ADVANCED MATERIALS & PROCESSES | MARCH 2026 25 destructive testing on the parts. Extreme caution and planning must be considered before any potentially destructive testing is performed and proper testing standards must be adhered to. A Word of Caution. The author often had the problem of someone presenting a singular failed part and wanting to know “what caused the failure.” The part presented was nearly always from a returned planetary gear drive unit that had several dozen individual components. On occasion, the part presented was the only component returned by the customer from a failed planetary drive unit. What the customer really wanted to know was why the planetary wheel drive had failed. It was often found that a well-meaning mechanic had disassembled the failed unit, found what they thought was the culprit, and returned it for determination of the failure. There was no way to determine the cause of the failed planetary gear drive without reviewing the entire unit and all the parts in the assembly. Not only was the failure investigation hindered by disassembly of the planetary unit but valuable evidence regarding the failure may well have been lost forever. These situations need to be reported in the investigation as part of the preparation and evidence found during the initial stages of the investigation. In cases such as this where vital information regarding the failure event has been withheld or is unavailable, the TRC will most likely never be determined, and the failure will become a cold case. Attempting to perform a failure investi- gation without having all the information regarding the failure will treat symptoms at best and result in loss of credibility for the team and/or analyst. P-4 People. There are two different groups of people involved in the 8P process. The first group consists of the team leader and members of the investigation team. The second group is comprised of individuals who can provide useful information regarding the failure. It is imperative to remember that a team approach is always required for an effective investigation, be it a team of two or a team of 100. During an investigation it is extremely important to interview as many of the people familiar with the failure as possible. Sometimes the smallest detail can provide the key to identifying TRC of the failure. It is very advantageous to be able to interview the end user of the product. If that is not possible for the team leader, the marketing or other customer contact should be included on the team and tasked with providing the customer contact. After speaking with the end user or individual closest to the failure, find any and all witnesses or persons with knowledge of the failure or application at the time of the failure. Check with sales, marketing, and maintenance personnel to determine if there have been reports of similar failures that the material had possibly not been returned for evaluation. Include suppliers of components associated with the failure on the team to learn from their product knowledge. The bottom line is to continue interviewing until as much evidence and information has been received as possible regarding the failure. It is vitality important to maintain good written records of information gained from interviews for future reference and inclusion in the final report. P-5 Processes. To help determine the source of a failure it is important to identify and understand the processes the component or components are produced with and that have been utilized for their manufacturing and assembly. This includes the actual processes and the engineering and manufacturing specifications. Review of the processes includes determining and analyzing if there have been any changes to the specifications or the manufacturing processes of the com- ponents. In addition to in-house manu- facturing processes, processes that define the lifecycle of the product are also important to review such as: • Shipping and delivery of the product • Storage of the product • Maintenance of the product • Actual application of the product There must be a defined plan and focused understanding of what will be reviewed before beginning the investigation. The preparation must be directed at understanding not only the failed component(s), but additionally the system in which the component(s) being investigated are utilized in. Care and caution must be exercised not to go down the wrong path due to biased testimony from individuals presenting the problem or failure. Some of the steps included in the preparation are: • Ask lots of questions to under- stand and define the scope of the investigation • Develop the investigation plan • Identify the failure mechanism and mode(s) • Develop the initial team structure • Develop potential specific team member assignments • Carefully document all information obtained • Initiate the investigation P-3 Parts. A thorough review of the intended and actual function of the part(s) involved in the failure must be completed before any physical testing is performed. Additionally, a review of system-related components, assemblies, and component interactions should be investigated prior to physical testing of components. Often the failed part presented for analysis is not the cause of the “failure” but the result of a different failure event or issue within a failed system. It is vital to analyze and understand not only the failed component but also the components and systems the failed component was associated with. Having reviewed the problem and collected as much history surrounding the failure event as possible, it is now time to examine the part(s) involved in the failure. Only after the planning, preparation, and understanding of the issue should any physical examination or testing be performed on the failed component(s). This may also include contact and approval of the customer or legal department prior to any
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