Unsure which dimensions to use to work out the force and strain energy here. I know that Force = yield strength * area Yield strength = 310 MPa Area, I'm unsure which radius to use. I assume 12 mm. For strain energy = (Force^2 * Length)/(2 * Area * Youngs Modulus) Unsure which length and area to use here. Best attempt I've made so far gives 42.41 J Working: F = 310 x 10^6 * pi*0.012^2 = 140,240N U = 140240^2 * 0.4 / 2 * pi*0.012^2 * 205 x 10^9 Thanks, question is below: Answer is 42.54 J.