Net Strain Energy Density:
Net strain energy density in an element subjected to a general stress field can be obtained by adding (algebraically) the energy density because of all the stress components. That is
u = ½ [s 1 e 1+ s 2 e2 + s3 e3 ] = ½ s Te
but e = Cs
∴ u = ½ sT Cs
Eq. can, if desired, be expanded as,
