Where is the subject stored?

What is the Strain Energy Stored?

• Hey, So I'm giving this question on a homework sheet and it's totally confused me: A steel bar with cross-section 60mm by 30mm and length 0.6m is subject to an axial tensile load of 210GPa, what is the strain energy stored in the bar? I've learned stress and strain and I have no idea how to put this together, I know strain is E/L but where does that come into this? Any help would be hugely appreciated thanks

• Answer:

  Let me start from a simple beginning to make you understand the problem. The strain energy stored in an extensible material is simply equal to half the product of force and the extension (recall that mechanical energy or work is force multiplied by distance) On a Force-extension graph, the area under the graph (within the limits of elasticity) is the elastic strain energy. Thus, strain energy U = Fxe/2 In the problem, you were given F = 210GPa but e was not given. Recall that Young's modulus, E = stress/strain Stress = Force/Area Strain = e/L Thus, E = FL/Ae which gives e = FL/AE Finally, you get U = F^2L/(2AE) [A= cross-sectional area, E is the Young's modulus of steel (get that from a text), L is length] Do the calculation.