http://imechanica.org/node/2609 Comments for "Is negative strain energy density possible?" en http://imechanica.org/node/2609 <p>I have a question that has troubled me for quite a while. Any kind of help would be greatly appreciated. I am computing the strain-energy density in a elastic solid when wave passes through. The formula I use is U=[I1^2+2(1+v)I2]/(2E), where U is the strain-energy density, I1 and I2 the first and second principal stress invariants, v poisson&#39;s ratio=0.3, E the Young&#39;s modulus. Since I1^2 must be positive, I2 might be negative behind the wave front. U might be negative. However, the textbook and many papers I ran into, says strain-energy density must be positive. Is it possible strain-energy density negative? What would the physical meaning of the negative strain-energy density be &nbsp;if it exits?</p> <p>&nbsp;Thank you for reading.</p> <p>Jacky&nbsp;</p> <br class="clear" /> http://imechanica.org/node/2609#comments strain energy density Wed, 23 Jan 2008 12:27:09 -0500 JackyLuo 2609 at http://imechanica.org