Amplitude based frequency response simulation in Abaqus

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Discussion Overview

The discussion revolves around setting up a frequency response simulation in Abaqus, specifically focusing on applying displacement as an input to a node rather than as base excitation. The participants explore the feasibility of this approach and seek guidance on the analysis setup, including the use of amplitude in steps over a specified frequency range.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Sam George inquires about applying a displacement of 0.2 mm at a concerned frequency of 100 Hz and seeks advice on setting this up in Abaqus, particularly if amplitude can be applied in steps over a frequency range of 0-200 Hz.
  • A participant welcomes Sam and asks about previous simulations done in Abaqus, suggesting a Google search for frequency analysis resources.
  • One participant cites Abaqus documentation indicating that nonzero displacements cannot be prescribed directly as boundary conditions in mode-based dynamic response procedures, suggesting the use of base motion or force instead.
  • The same participant reiterates the documentation's point about the limitations of applying nonzero displacement or acceleration history definitions in mode-based steady-state dynamic analysis.
  • Sam acknowledges the information and indicates a preference to proceed with applying a force instead of displacement.

Areas of Agreement / Disagreement

Participants generally agree on the limitations of applying nonzero displacements directly in Abaqus, with some proposing alternative methods such as using base motion or applying a force. However, the discussion remains unresolved regarding the best approach to achieve the desired simulation setup.

Contextual Notes

The discussion highlights limitations in the Abaqus software regarding boundary conditions in mode-based dynamic response procedures, but does not resolve the implications of these limitations for Sam's specific analysis setup.

Sam George
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TL;DR
Enforce displacement in Frequency Response Simulation
Hi,

I have inputs like displacement of a driving mechanism and then the frequency of concern .

Displacement: 0.2 mm
Concerned Frequency: 100 Hz


I would like to evaluate a part with the input displacement applied to a node and not as base excitation.
It can be sweep over the frequency range 0-200Hz

How do we set it up in Abaqus, can we give amplitude in steps over the frequency range?

Please guide me with a link or syntax on how to proceed with the analysis setup.

Regards,
Sam George
 
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Here’s a quote from Abaqus documentation (chapter about SSD analyses):

It is not possible to prescribe nonzero displacements and rotations directly as boundary conditions in mode-based dynamic response procedures. Therefore, in a mode-based steady-state dynamic analysis, the motion of nodes can be specified only as base motion; nonzero displacement or acceleration history definitions given as boundary conditions are ignored, and any changes in the support conditions from the eigenfrequency extraction step are flagged as errors.

So you have to either use a base motion BC or apply a force instead.
 
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FEAnalyst said:
Here’s a quote from Abaqus documentation (chapter about SSD analyses):

It is not possible to prescribe nonzero displacements and rotations directly as boundary conditions in mode-based dynamic response procedures. Therefore, in a mode-based steady-state dynamic analysis, the motion of nodes can be specified only as base motion; nonzero displacement or acceleration history definitions given as boundary conditions are ignored, and any changes in the support conditions from the eigenfrequency extraction step are flagged as errors.

So you have to either use a base motion BC or apply a force instead.
Thanks for the reply, I think I will have go with using Force.
 

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