Quasistatic analysis of metal honeycomb
Answers
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Hi,
Please share animation file of it. Also data for comparison with experimental testing like Force vs displacement curve, final deformed shape in experimental testing etc. Also check unit consistency .
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ok im sending the files.
Animation file:
Experiment files:
<?xml version="1.0" encoding="UTF-8"?>
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I'm trying again but same result with what ever yield stress graph I try.
For MAT 36. The geometry starts folding in from the edges after sometime.
Units is Mpa for stress by default i gave it as Mpa only.
Please help
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hi.
I am getting good deformation when using MAT 36 material but not getting the correct graph for force vs deflection.
I defined the curve for yield by taking the stress-strain values from start.
when I am defining it from yield the deformation is wrong that is material squeezes.
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Hi,
For /MAT/LAW36 the material plasticity is calculated based on the post yield curve user provides. And from my understanding, based on your above inputs the issue seems to be with the material parameters provided. You can cross check and ensure values are correct.
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Hi.
case 1:
This time I got the correct trend for the graph by taking the values from elastic to plastic region in MAT 36.
But the main problem is the y-axis values of the graph. That is the force values are very less in terms of Newtons, not , matching with the experiment.
case 2:
And when I'm doing the same analysis with the values from yield to plastic for MAT 36 I'm not getting the correct graph but the y-axis values in terms of newtons are matching with my experiment.
I'm attaching the screenshot of the first case and second case.
case1:
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case2:
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Hi,
Please share the snapshot of the material card and the stress-strain curves also.
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Ok.
Material card:
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The full true stress-strain curve and yield to plastic is attached in the excel sheet. The curve is clearly explained in SHEET 2.
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Hi,
For the true stress-strain curve update the curve as shown in the image below. If you have multiple curves with strain rate dependency also update as below.
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Hi.
I have already defined the curve in the material card. i Have defined it under fct_iD and the name is yield. What you said in the above post is also same but the difference is you are getting the option under N_func. Whereas i am not getting any option after i select N_funs as 1. In place of that i am defining it in the next option that is fct_iD which you can see in my attached screenshot.
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Hi,
How many curves you are defining?. Seems like 2 with strain rate from the excel sheet, but in the above image only one curve is updated.
Can you please clarify on this.
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Hi.
I am defining only one curve, In the excel sheet i just have divided one(Same) curve into three parts that is 1) FULL stress-strain(till plastic) 2) Yield to plastic using two methods which are 1. by directly taking x-axis point corresponding to 0.2%strain and the other taking the x-axis point by drawing a line parallel to the elastic limit till it touches the curve.
Basically, I'm just defining one curve at a time. I'm trying for only one strain rate.
In one case with the full stress-strain curve and in the other one the curve from yield to plastic these two I'm doing separately and these results I posted earlier and said about the nature of the graphs.
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Hi,
Try modelling one with post yield values for the stress-strain curve and without any strain rate and please update the nature of the graph.
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Hi.
The following are the results obtained by taking the curve from yield to plastic.
Deformation:
Graph: F vs d.
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Hi.
I feel that this haphazard deformation has got something to do with the bonding. Because during the deformation process the elements are starting to fail from the corners and the hexagon itself is getting deformed instead of getting compressed and this happens only when I take the curve from yield to plastic.
But when I take the curve from elastic to plastic range the deformation is absolutely correct and the trend of the graph also correct but the problem is in the magnitude of the force which is very less in terms of 900N and I require the magnitude in terms of 15000N.
With the yield to plastic case the deformation is bad but the graph I get a good magnitude of force but very high that is 40000N.
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Altair Forum User said:
But when I take the curve from elastic to plastic range the deformation is absolutely correct and the trend of the graph also correct but the problem is in the magnitude of the force which is very less in terms of 900N and I require the magnitude in terms of 15000N.
With the yield to plastic case the deformation is bad but the graph I get a good magnitude of force but very high that is 40000N.
I think this is because of the curve that is used.
Is it possible to share both the files?
Please use the file transfer link in my signature to share the model file
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Hi.
The full true stress-strain curve and yield to plastic is attached in the excel sheet. The curve is clearly explained in SHEET 2 of the excel file attached.
I took 1st and 3rd values table from sheet2 for elastic and yield respectively in the two models (hm) sent to your Dropbox.
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Hi.
I have done the meshing again this time i have set the correct criteria and the mesh is 99% correct. I have set all the conditions and contacts and also bcs_x for the anvil. But the anvil is also deforming again.
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Altair Forum User said:
Hi Prakash thanks for the reply.
In this graph the force values that is the interface/contact force is coming close to my experimental values. But again if you see the deformation in the structure the elements at the top are getting distorted. why is that. What was the run time you gave? and you used imposed displacement only?
And one thing this time the elements are not folding inside like the previous one which is good.
And how were you able to get this graph.
Thanks again.
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I will share the modified model with you.
I had to stop the run in between as it is taking time and resource of my machine.
I did use the model shared by you as it is except changes are done in the curve.
Please correlate the model dimensions and deformation pattern and compare at the end of the analysis.
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hi.
Iam trying to do the analysis with a rigid wall this time.
But the problem is no deformation is taking place how much ever time i give and velocity. Mass i gave same as anvil.
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Hi.
Here I'm sharing the pic.
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Hi.
Ya here is the model.
<?xml version="1.0" encoding="UTF-8"?>
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Hi Vaibhav,
How do you come up with the velocity?
Can you increase the velocity and check if that helps?
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Hi.
I tried by giving a velocity of 100mm/sec. Very negligible deformation is happening and it looks like the rigid wall is moving to and fro as in the h3D file the deformation contour is coming and going.
I am attaching the h3D file. The analysis not complete but still attaching.
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