Spring/dashpots in Abaqus/Explicit

[anthaivn2019]

dear all

I am conducting wave analysis in the ground.
1/ Abaqus required with dynamic analysis using SpringA.can help me example create SRINGA in analysis like?
2/ Example of dashpots coefficient.

Many thanks,

Hoang An

 

[FEA way]

SPRINGA element should be attached to 2 nodes. It acts in the line joining these two nodes. It may be linear or non-linear. To assign it either choose Interaction Module —> Special —> Springs/Dashpots —> Create —> Connect two points —> Axis: Follow line of action in CAE or use *ELEMENT, TYPE=SPRINGA in the input file.

The value of dashpot coefficient depends on what you want to achieve in the simulation, what is the value of damping required in your analysis. For more information search for simple/linear/single degree of freedom oscillator.

 

[Erik Panos Kostson]

If you want to absorb waves in the ground and at the boundaries (so not to get reflections and mode conversion) than the damping is related to the acoustic impedance of the P or S wave you are looking at in the ground. SO in 1D if we have a long. P wave then the damping coefficient should be equal to the specific impedance rho * c_speed_long). In 2 D it is more complex.

Also infinite elements might be possible - or in the worst case just make the domain big enough to avoid reflections.

See also here for more details:

https://pdfs.semanticscholar.org/ace2/e0c20e93ccedf9bd82708d9c8d8be4a82253.pdf

 

[anthaivn2019]

dear all,

I am simulating moving rollers with dynamic loads both in harmony.
Results:
(1) at position 5m, 20m velocity in the z direction is the same.
(2) when adding alpha, beta damping coefficient, the x, y velocity changes; velocity in the z-direction remains constant (1).
I am looking for parameters related to velocity in z.

Do you have any way about this problem?

Many thanks,

Hoang An

 

[Erik Panos Kostson]

What are you doing - transient moving (vehicle..) load analysis on what (road soil...)?

 

[FEA way]

Can you attach more pictures showing where are the boundary conditions applied and where are the springs/dasphots acting ?

 

[anthaivn2019]

I model soil by Drucker prager.

 

[anthaivn2019]

this is the model i use spring.

 

[FEA way]

And what are the BCs ? It would be best if you could attach .inp file.

So the spring is acting between the two nodes on the top and bottom of the solid domain representing the road, right ? Is it supposed to change the compliance of the road ? I’m not an expert in road analyses but this approach does not seem correct for me. It should be done through material definition.

 

[anthaivn2019]

The material I added damping factor: alpha and beta Rayleigh, only works for velocity results V1 (x), V2 .
If so, what additional parameters do I need in the material to determine the velocity reduction V3 (z).

Many thanks,

 

[FEA way]

You can try defining bulk viscosity but material (Rayleigh) damping is actually the one that should be adjusted.

 

[anthaivn2019]

Do you have example soil model for my reference.

thanks

 

[FEA way]

Check the following references (Abaqus documentation):
- Example Problems Guide —> Mass Diffusion and Soils Analyses —> Soils analyses
- Benchmarks Guide —> Analysis Tests —> Soils analysis

You can find there several examples with detailed description, models (inp files) and of course material data including Drucker-Prager model.

Apart from articles there’s even a book „Applied Soil Mechanics with ABAQUS Applications” by S. Helwany that you may find interesting.