Stress-displacement curve

MartinaC

Hi everyone,

I am simulating tensile tests with welded samples. I am using NLQS analysis in Optistruct, according to the eBook Introduction to Non Linear Finite Element Analysis using Optistruct.

 

My problem is that the stress-displacement curve after the simulation shows stresses which value is higher than the ultimate stress imposed with the TABLES1.

How is it possible? Why the stress-displacement curve does not become flat? Does it have any meaning?

 

Bests

Martina

Rahul Rajan_21763

Can you please share the settings you defined in MATS1 card?

MartinaC

Of course. I attach elso the TABLES1. I imposed the strains between 0 and 1 because shown in the eBook. The real material has maximum total strain equal to 0.3.

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

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

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

Rahul Rajan_21763

So you are using true stress/strain curve & set up for MATS1 looks ok to me.To understand your issue in detail, we want some more information related to your model.(.out/.fem/.h3d file)

 

Simon Križnik

Hi,

Altair Forum User said:

My problem is that the stress-displacement curve after the simulation shows stresses which value is higher than the ultimate stress imposed with the TABLES1.

How is it possible? Why the stress-displacement curve does not become flat? Does it have any meaning?

 

If the deformations go past the values defined in the table, the curve is extrapolated linearly (the slope is taken from the last two data points defined). I think Optistruct does not support rupture (failure), but Radioss does. 

MartinaC

Thank you very much. I modified the stress-strain input curve and it worked!

MartinaC

Here the files, if you can find a different solution for my problem. The .h3d is too heavy to be uploaded here.

Unable to find an attachment - read this blog