I'm trying to come up with a way to describe deformation on a body at each point on that body. My problem can be expressed and solved in two dimensions. Given two triangles, one being the initial shape, the other being the initial shape transformed arbitrarily :
It's evident by looking at this that points along the left edge are now more distant to each other, points along the right edge are closer, points along the bottom edge have the same distance as before, and any point inside that triangle is blend of those three states. Is there any engineering standard to describe this, for any position on the body? I've looked at stress and strain, but I'm not sure if either describe what I want. In the end, I'm trying to find a value (or possibly two? Maybe a vector?) that describe, for a tiny area, if that area is compressed or stretched after the transformation.
PS.: I'm not a mechanical engineer if that wasn't already obvious. :)