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Stress vs Time and Strain vs Time

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(@malith-wanigasuriya)
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Joined: 1 year ago

Hi, I am doing a study on pendulum impact on glass plates using LS Dyna FE software. And I want to take the outputs of strain and stress of the center of the plate which is the location of the impact. Can you explain how do I get those results using DATABASE option in LS DYNA?

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(@joneseffect)
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Joined: 1 year ago

I'm quite new to LS-DYNA so please take what I say with a pinch of salt as I'm not sure whether this would apply to your situation however I can't see why not. 

To get the stress and strain of elements and nodes, you need to enable ELOUT and NODOUT to DATABASE_ASCII_option by changing DT to your simulation's time interval and change Binary to 3 (I'd recommend doing this for all your ASCII_options as it makes it a lot easier to analyse all in one place). 

Next you need to create DATABASE_HISTORY_NODE_SET and SOLID_SET for the nodes and elements respectively that you want to find the stress and strains of. 

Once you've ran your simulation, click binary output in the post section and load the file binout. Click this file and it will show the different ASCII options you selected earlier. For stress and strains, click elout, and then the element set you selected earlier. You can then click either stress, strain, muscle, or history for a range of options, but you'll most likely just want effective stress and effective strain (Von Mises). Once you've selected that, click plot and it will plot your stress across time where you can save it. Do the same for strain.

Finally, for stress vs strain, click x y plot in post and you should see your two plot files you've saved, if not load them up manually. Click cross, then your plot file for the x-axis (strain) at the top and then click again below under curve names to add to x-axis. Repeat for stress for y axis and then click plot, and boom you've got a stress vs strain diagram. 

If you want specific displacements, you use NODOUT in a similar way to the stresses, as nodes are only able to give 1D values whereas ELOUT is able to plot stresses and strains. Hope this helps

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Negative Volume
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(@negativevolume)
Joined: 6 years ago

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@joneseffect Nailed it. I know this is old but for archiving:

One last important *DATABASE card is *DATABASE_EXTENT_BINARY, specifically STRFLG. This database card has a bunch of global options for outputs. If you want to output strain or look at a heatmap of strain in the Fringe Component, you need to make sure STRFLG=1. Otherwise, you will not be able to look at any strain data. 

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