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Let us assume we have a motor with a bearing which is exhibited to wear. Over time, we can observe higher vibration, increased noise and the motor speed reduces due to the bearing fault. In the end, the bearing fails and the motor is not able to provide its specified function (drive something) anymore (called failure).

My Issue: I am not sure what would be the right name of the failure mode in this case. I found a lot of sources that call this the "bearing failure mode". However, according to ISO Condition Monitoring 13372:2012 a failure mode is the "observable manifestation of a fault". So, I think in this case observable are the loss of speed, increased noise and the higher vibrations and I would call my failure mode: "higher vibratons, increased noise and speed loss". In this case, "bearing failure" would be the name of the failure cause. Furthermore, there are other causes that result in the same observalbe properties and so one failure mode can have several root causes, right?

What is right and why? I do not want to over complicate this, but I need some clearity here. It is also interesting regarding FMECA. This is a "Failure mode effects and criticality analysis" in which the concept of a potential failure mode plays a big role. Is there a good and reliable source (literature) with examples how to differentiate what a failure mode is? What is the best practice?

user3352632
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  • How much wear are you measuring? – Solar Mike Dec 07 '19 at 17:30
  • Depending on the failure with bearing, will be noise too. – Leafk Dec 07 '19 at 19:11
  • @SolarMike I don't know how the amount of wear realtes to my question? I am more interested in defining the concept of failure mode in this particular case. – user3352632 Dec 08 '19 at 21:08
  • @Leafk you are right, it is typical to have also incresed noise. I updated my question accordingly. Can you answer my question regarding the concept of a failure mode? – user3352632 Dec 08 '19 at 21:10
  • First comes noise and a bit of vibration - usually a while to serious failure which is why I asked... If you have real examples of the amount of play and the consequences, then you may get somewhere otherwise there are two possibilites : « ok » and « knackered »... – Solar Mike Dec 08 '19 at 21:12
  • @SolarMike, thanks for your fast reply. If I understand you right, you would call this failure mode "knackered"? – user3352632 Dec 08 '19 at 21:18

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