Hi all, I've been trying to understand how to calculate the elastic energy of a deformed object. For example, if I have a box, and I push on it and it deforms, how can I calculate this deformation energy? I don't know much about elasticity, but I have read a little about strain energy and find the following equation promising: http://en.wikipedia.org/wiki/Strain_energy However, I keep coming across different types of strain tensors, and principle strain, and shear strain, and all kinds of things, and I just don't know how to put it together. I would imagine that you simply take a lot of dot products between forces and displacements, but I don't know how to take care of this with these tensors and such. So for the box example, could you help me understand how I could go about calculating this energy? Thanks!