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J
JS_982441215-Moonstone
15-Moonstone
March 8, 2022
Question

Total Effective Mass is greater than 100%! How could it possible?

  • March 8, 2022
  • 1 reply
  • 2522 views

JS_9824412_0-1646765165811.png

 

The above image shows simulation result of a random vibration analysis. This is the first time I see a vibration simulation result with the total effective mass greater than 100%. How could it be allowed by Simulate to do this? Is there any software patch to prevent this kind of error?

 

1 reply

J
JS_982441215-MoonstoneAuthor
15-Moonstone
March 11, 2022

Any reply from PTC to say "sorry, it's my fault. I will improve it and make sure this nonsense never happen"?

S
sacquarone21-Topaz I
21-Topaz I
March 11, 2022

Hello @JS_9824412 

 

Please take a look first at Mass Participation Factor Results section of Creo SImulate Help Center for a good understanding of Effective Mass versus Total Effective Mass:

  • Effective Mass—percentage indicator of participation of mode. This is the ratio of the mass participation factor to the squared value of the total mass.
  • Total Effective Mass—percentage indicator of participation of modes up to and including indicated mode. This is the sum of effective masses of modes up to and including indicated mode.
In your snapshot, I can see, as per Effective Mass results, that it seems that the low percentages seems to highlight a situation where masses did not participate a lot, leading probably in high number of modes considered to try to acheieve some outcome, and an initial configuration which therefore - also probably - does not allow to have good conditions to produce a good outcome in results of the random vibration analysis in original conditions.
 
That being said, I agree that even if number of modes were high, the "sum of effective masses of modes up to and including indicated mode" should reasonably not be higher that the total mass of the original model.
 
Related to that, please consider we have only one SPR in our whole Knowledge Base which was reported to our R&D in similar conditions. Unfortunately, depsite of lot of requests from TS to impacted customer, R&D did not manage to access the files to reproduce first the issue, in order to investigate this further. SPR was therefore closed without resolution because the initial conditions leading in this unexpected outcome were not clear enough to allow our developers to lead into any conclusion.
 
In other words, if you would like us to have a look at this, we will need you to open a new case to PTC Technical Support, and attach your data to allow us first to reproduce this, and then to open a SPR to our development team, and  ask them for views on what happens in this specific very unusual situation.
 
Regards,
 
Serge
 
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