Dear Vladimir,<br><br>first of all thanks for your reply.<br><br>Well, defining the function as a GiNaC expression is part of my doubt, since I do not know how to represent the second-order <br>tensor E in GiNaC, and consequently, how to differentiate Psi with respect to it.<br>
<br>I've seen some classes for special tensors, like clifford, delta, etc, but it is not clear for me how to represent a second order tensor. I was guess I should use matrix and idx....but how? and how do I use diff afterwards?<br>
<br>Many thanks in advance.<br><br>Best regards,<br>Bernardo M. Rocha<br><br><br><div class="gmail_quote">2011/2/10 Vladimir V. Kisil <span dir="ltr"><<a href="mailto:kisilv@maths.leeds.ac.uk" target="_blank">kisilv@maths.leeds.ac.uk</a>></span><br>
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Dear Bernardo,<br>
<br>
>>>>> On Wed, 9 Feb 2011 10:07:51 -0200, Bernardo Rocha <<a href="mailto:bernardosk@gmail.com" target="_blank">bernardosk@gmail.com</a>> said:<br>
BMR> the strain energy function for the St. Venant-Kirchhoff<br>
BMR> material<br>
BMR> \Psi(E) = 0.5 * \lambda * (tr E)^2 + \mu E:E<br>
<br>
To start with, can you write this functions as a GiNaC expression?<br>
<br>
Best wishes,<br>
Vladimir<br>
<font color="#888888">--<br>
Vladimir V. Kisil email: <a href="mailto:kisilv@maths.leeds.ac.uk" target="_blank">kisilv@maths.leeds.ac.uk</a><br>
-- www: <a href="http://www.maths.leeds.ac.uk/%7Ekisilv/" target="_blank">http://www.maths.leeds.ac.uk/~kisilv/</a><br>
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