Variational Method for a Three-dimensional Elasticity Problem

It is clear that (4.17) is equivalent to the virtual work equation and the weak form. If we recall (4.16) and set Su = v, we have 

Therefore the procedure of taking a variation is equivalent to that of calculating a directional derivative. 

2 Variational Method for a Three-dimensional Elasticity Problem 

We consider a variational method for the classical three-dimensional (3D) elasticity problem for bodies that satisfy static equilibrium. 

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