# Convert Load Deformation (Extension) Data to Stress-Strain Curve

I am trying to manipulate some data that were obtained from a three point load experiment on a porcine tibia.

I would like to obtain a stress-strain curve for the various specimens; however, the only data that was given from the Instron three-point loading set up was Load (N) vs Deformation/Extension (mm).

My question is: how do you convert the Load vs Deformation curve to a Stress-Strain curve?

4. Formula for bending stress is $\sigma = -\frac{M\cdot y }{I}$ which is called flexure formula M is moment, y is distance from neutral axis and I is area moment of inertia.
5. Strain is $\varepsilon = \frac{y}{\rho }$ where $\rho$ is radius of curvature. A simple presantation is here (PDF)