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How to set dt with curve?

Altair Forum User

When I do the non-linear quasi-static analysis.

I use the dt=0.002 and I open the EXPERTNL = AUTO

But when I saw the result of the outfile the dt just became 0.01 ( zoomed in five times )

Here has 3 problems:

1. Can I modify the zoomed Magnification? like it can zoom to 10 times or more. So it can be the 0.04 for the max.

2. Can I give a curve to define the dt of solver?

If I know it is good converged at 0-0.5 sec, I can use the dt for large. (Like dt=0.5)

And I know it is converged hard in 0.6-1 sec, I want the dt for small. (Like dt = 0.1)

Can I do this?!

At the last question,

3. Can I output the pretension force for the time to force curve?

I know we can set Global_Output_Request > PRETBOLT to see the pretension force.

But it just can see the result of pretension force. I want to see the process how it applied force on the bolt.

Unable to find an attachment - read this blog

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Altair Forum User

Hi @LKZ

Fixed time points is available with TSTEPNL using TABDLEDi which is only valid with NLGEOM analysis type.

You can also use NLADAPT with DIRECT = YES which adopts Adopt fixed time increment. In case of divergence, the run will stop immediately.

Altair Forum User

But it just can see the result of pretension force. I want to see the process how it applied force on the bolt.

Have you tried to plot in HyperGraph?

Altair Forum User

@Prakash Pagadala Thanks to your apply!

At your first reply I have tried this and how should I modify?!

If I set this I can't set NLPARM?

image.png.5734f5e3c36e3158729e9ea79178a826.png

At the second reply I don't know how to set

I have opened the Hypergraph2D

<?xml version="1.0" encoding="UTF-8"?>

Unable to find an attachment - read this blog

Altair Forum User

At your first reply I have tried this and how should I modify?!

Activate TSTEPNLX and use FIXTID which uses a TABLEDi card where X is the fixed time points.

As said, you can also use NLADAPT when you are using NLADAPT but this way you cannot control using user time step table.

Altair Forum User

@Prakash Pagadala Thanks to your apply!

I have the file of preten

Do you know how can I draw it in HyperGraph?!

Here I have tried to draw but it can't show the time to pretension load curve

My time is 1 sec and force is plused to 6000 N

<?xml version="1.0" encoding="UTF-8"?>

Really thanks to you.

Altair Forum User

@Prakash Pagadala

Do you know what is my error of the HyperGraph 2D of pretension?

I can't plot the time to pretension curve.

Altair Forum User

Hi @LKZ

Unfortunately, .pret file doesn't pret force Vs time.

I am checking on this. I will get back to you soon.

Altair Forum User

@Prakash Pagadala Really thanks to you!

And I want to ask where to set the TABLEDi because I want to set the iteration with curve.

I will use the TSTEPNL>TSTEPNX>TOUT>FIXTID.

Or do you have example file?

Altair Forum User

Create a load collector with card image tableD1

Altair Forum User

@Prakash Pagadala I have set the example file.

Does I set this correctly?

I have set the TABLED1 and TSTEPNL

I want 0-0.8 sec to solved with dt = 0.003, 0.8-0.9 sec to solved with dt = 0.002 and 0.9-1 sec to solved with dt = 0.001.

Unable to find an attachment - read this blog

Altair Forum User

Hi @LKZ

Activate TSTEPNLX and use FIXTID which uses a TABLEDi card where X is the fixed time points.

As said, you can also use NLADAPT when you are using NLADAPT but this way you cannot control using user time step table.

As said before, TSTEPNL is only vaild for NLGEOM and doesn't work with NLSTAT

Altair Forum User

@Prakash Pagadala I got it.

So I just can modify the NLADAPT to adjust my max load dt.

Because I am doing the NLSTAT.

At another question, do you know how to plot the pretension curve?

Really thanks for your help.

Altair Forum User

Hi @LKZ

I think @Rahul R replied to the same question regarding pretension curve in another post.

You can use NLADAPT but this will not allow the freedom to use user-specified timestep. This feature to have user-specific timestep for NLSTAT large displacement is under development.

Altair Forum User

@Prakash Pagadala I have saw the @Rahul R replied me at another article.

Thanks for you two applied .

So the NLADAPT can set in the small displacement analysis, right?

Because I am doing the small displacement analysis.

Altair Forum User

@LKZ

All parameters, except NOPCL, on the NLADAPT Bulk Data Entry, are applicable only to Large Displacement Nonlinear Quasi-static Analysis and Nonlinear Direct Transient Analysis. NOPCL can be used in Nonlinear Small Displacement Quasi-stati Nonlinear Analysis

Altair Forum User

@Prakash Pagadala Thanks to your apply!

I have read the explanation at help.

image.png.6fa1f8e803125db3af6f0dc3783a2061.png

How does it mean ? Because at my out file it only amplify 5 times.

image.png.7d9213be8b265cc9ee4e19e3706b4599.png

I set it to 10, I think it should amplify 10 times.

For example here my dt = 0.001, so if I set the instruction to 10. It should be 0.01 if my model convergence successfully.

Altair Forum User

NOCPL has nothing to do with timestep.

As said in one of my previous replies, it is DIRECT YES which uses fixed time increment.

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

@Prakash Pagadala

My problem is small displacement problem

Here is my file :

Unable to find an attachment - read this blog

Altair Forum User

OK, with small displacement all NLADAPT parameters will be ignored except NOPCL which affects the Number of grids allowed to have open-close contact status change.

Altair Forum User

@Prakash Pagadala

So the NOPCL is not to change the dt amplify value ?