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Vaibhav25

Quasistatic analysis of metal honeycomb

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14 minutes ago, gopal_rathore said:

Hi,

You need to take material properties of material i.e a fresh sample . If you have reference graph of it mark the yield point and strain value on graph. Make this as your point on graph by making strain zero and keeping the yield value as it is

 

This part how to do with my curve i'm not getting can you help me.  And should I define any strain rate for MAT 36. I donno the rate. 

stress vs strain (al-3003).xlsx

 

 

 

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Hi 

I created the curve and imported it to radioss. And the trend of the graph is important right? Or do units matter here? 

Because for my graph stress is in mpa and strain in terms of 10^3.

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Hi

The analysis which I'm doing is explicit radioss right? Is that correct for quasi static analysis? 

Or should I use implicit card for radioss? If so how do I use implicit card. 

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Hi,

Unit consistency is very important during analysis. The material will behave as per the trend in the graph and unit consistency is required else all the results will jumble up. 

I'm not sure about the strain values in your curve ie it shows 10^3. It's represented normally in %. Please cross check the same.

 

You can do this simulation with explicit approach. Since it involves high deformation and contacts it may be tougher for the implicit run to converge, and so please continue the explicit approach.

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Hi i ran using MAT36 the intial compression is happening but after sometime the material is getting squeezed.

 

 Earlier i tried with MAT2 but that loops came out from side. And MAT2 those parameters hardening parameters(b,c etc) im not getting in the net to define.

5ad0a1d454ed9_Screenshot(13).thumb.png.868f6603eaacd396ecd851f7752e9fe3.png

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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.

 

 

 

joneycomb_deformation.avi

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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:

5ae2d9354ee2f_Screenshot(37).thumb.png.9b8d83b24bcdda99b936a33b1b22be82.png

 

case2:

5ae2d93c88c15_Screenshot(38).thumb.png.2cab2ccb1bbe7a56ecf7ec95956392b3.png

 

 

 

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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.

 

1.PNG

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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.

 

5ae6af16c6d3b_Screenshot(41)_LI.thumb.jpg.d03bddc7fdd23e4e572955ac36c9773b.jpg

 

 

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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.

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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On 4/30/2018 at 6:14 PM, Vaibhav25 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. 

honey_2mm_1.hm

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