Autodesk Mechanical Material Model - Thermal Expansion - Mean or Instantaneous

[na.arno]

Dear all,

I have a question regarding the material model used in Autodesk Simulation Mechanical.

I am trying to model the stress caused by thermal expansion. I am using a custom defined material.

In the datasheet of the material i want to use i have two options;

- instantaneous coefficient of thermal expansion × 10−6 (mm/ mm/°C)

- mean coefficient of thermal expansion × 10−6 (mm/mm/°C) in going from 20°C to indicated temperature.

Can anyone tell me which one the program uses? I tried searching this and found nothing unfortunately.

Thank you in advance.

Kind Regards,

Arno

[John_Holtz]

Hi arno. Welcome to the Sim Mech forum.

What type of analysis are you performing?

• I am certain that linear stress is using the mean value. All it knows is the stress-free reference temperature and the final temperature.
• Nonlinear stress is probably using the mean value also, but I do not know for sure. I suggest that you do a test to confirm if this is true.

[na.arno]

Hi John,

Thank you for reply.

The analysis I am performing is a Non-Linear analysis (MES or Static Stress with Non-Linear material model).

Good idea, i was thinking about drawing a 2D square (100x100mm or so) and then simply adding some temperatures to it to see the outcome.

2D or 3D should not make a difference for this small experiment i guess.

Just a thought; maybe you could add this to the Autodesk Simulation Mechanical documentation? I guess there will be more users with these kind of questions.

Kind Regards 

Arno

[na.arno]

To all,

I just ran a quick test with a 2D Simulation.

I modeled a square of 100mm by 100mm constraint(single direction) at two edges perpendicular to each other and simulated a temperature rise from

20 degrees C to 600 degrees C. I set the stress free reference temperature to 20 degrees C (as in the standard i am using).

I checked that the Von Mises stresses were near zero, so the square could expand freely in all directions without constraints.

The results of the simulation were within 99.4% of the tabulated values in the material properties standard, so John was right.

Autodesk Mechanical uses the Mean Coefficient of Thermal Expansion for the Non-Linear analysis.

Arno