2 Values Of Young's Modulus Of Elasticity

I am currently trying to model a material (an S.M.A) with 2 values of Young’s Modulus of Elasticity at 2 different temperatures:  E=31 KN/mm^2 at T= -5C and E=79 KN/mm^2 at T= +25C.  I have a 3-D component set up to which I apply a sufficiently large force to take the material past its yield point, so that when I remove this force the component stays in its displaced shape (or very near to it).  This is carried out at a temperature of T= -5now want to apply a temperature of T= +25C.  This change in temperature and E should make the component want to revert back to its original position, but it doesn’t.  Is this a limitation of ANSYS, that a material can only have one value or each property?  Has anyone else had this problem, or can anyone offer any advice?  Thank you very much.
By the way I have the 2 values of E and yield stress set up as one material model and ANYSYS correctly plots me a graph showing this data.  Any ideas?

ADAM COOKE
STUDENT
SUSSEX UNIVERSITY
ENGLAND

Adam,

You have a simple transient thermal/stress coupled problem.  Unfortunately, I can't walk you completely throught it from this vantage point however.....perhaps I can point you in the correct direction.  You have a transient thermal event occuring.  By definition, the temperature of your component changes as a function of time.  The transient solution process allows you to build a stepped problem wherby you change the temperature from time zero to time x, y, z etc.  The solution results from the transient thermal solution are then read into the stress transient solution process having the same time steps with temperatures and body forces, if any.  Now, the other key component of this solution is to build a temperature dependant material property.  This is a simple action falling under the command "mptemp" and "mpdata".  I personally have a library of temperature dependant material properties.  As a long time user of the code I highly recommend developing these material files for yourself and use nothing but.  As you progress into daily competitive analyses, you will find that you never use a static temperature input.

Now, I know I am long on advice and short on specifics but, believe it or not, I taught myself all of the procedures for transient analyses through the ANSYS help resources.....primarily reading "Command" definitions and analyses type descriptions.  This coupled with a bit of trial and effort are necessary every time I do it again.  Seems I don't follow my own advice on occasion.  Good luck.

If I can, I will follow your thread and provide further assistance.

Cheers

Glen Hunt
ISE Incorporated