Re: [LS-DYNA2] smoothing a vibrating stress curve

[punith ml]

Filter can be used . also  based on points which can smoothen the graph. 

option is available when plotted.

On Sat, Feb 27, 2021 at 5:26 AM Nava Farhadzadeh <nava...@gmail.com> wrote:

Hi,

I have modeled an elastic impact between two bars and a specimen in between. I am looking at my stress-time histories on the bar and there is large vibrations in the stress-time curve. Is there any way in LS-DYNA to smooth it? I'm using surface-surface contact.

Kind regards

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With Regards

Punith.M.L

+ 91-9164165666

[l...@schwer.net]

There are filters available in LS-PrePost among the PlotWindow menus.

 

                --len

 

[James M. Kennedy]

Dear Nava,

 

Perhaps this might be of interest?

 

Bulk Viscosity for Shells and Solids in LS-DYNA by Suri Bala:

 

In any wave propagation code, such as LS-DYNA, which belongs to a family of ‘Hydro’

codes, bulk viscosity is essential to treat shocks. Smooth initial data can lead into shock

discontinuities and if left untreated can result in severe instabilities.

 

https://www.d3view.com/bulk-viscosity-for-shells-and-solids-in-ls-dyna/

 

*CONTROL_BULK_VISCOSITY

 

Purpose: Reset the default values of the bulk viscosity coefficients globally. This may

be advisable for shock wave propagation and some materials. Bulk viscosity is used to

treat shock waves. A viscous term q is added to the pressure to smear the shock dis-

continuities into rapidly varying but continuous transition regions. With this method

the solution is unperturbed away from a shock, the Hugoniot jump conditions remain

valid across the shock transition, and shocks are treated automatically.

 

Please see if these are of help:

 

Schwer, L, :Some Observations on Artificial Bulk Viscosity in LS-DYNA: What NOH Knew

in 1978”, 14th German LS-DYNA Forum, Bamberg, Germany, October, 2016.

 

https://www.dynamore.de/de/download/papers/2016-ls-dyna-forum/Papers%202016/mittwoch-12.10.16/containment-impact-and-rupture/some-observations-on-artificial-bulk-viscosity-in-ls-dyna-what-noh-knew-in-1978

 

“Variables Affecting Smoothed Particle Hydrodynamics Simulation of High-Velocity Flyer Plate

Impact Experiments”

 

https://www.osti.gov/servlets/purl/1178801

 

Bulk Viscosity

 

https://abaqus-docs.mit.edu/2017/English/SIMACAEGSARefMap/simagsa-c-ovwbulkvisc.htm

 

Sincerely,

James M. Kennedy

KBS2 Inc.

February 27, 2021