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?