Elasticity/Sample quiz4

1. What is the number of governing equations in the linear theory of elasticity ? What is the number of unknowns ?
2. The Lame-Navier equations represent the equilibrium equations in terms of displacements. Why are these equations rarely used ?
3. What are Michell's equations (use words) ? How are they different from Beltrami's equations?
4. Why do we need boundary conditions ? Can I apply full traction and displacement boundary conditions at the same point ? Do boundary conditions have to be applied at all points on the surface of a body ?
5. What is St. Venant's principle ?
6. What is the superposition principle ?
7. I have done a lot of algebra and come up with two different solutions for the same linear elasticity problem. How do I know which solution is correct ?
8. Give an example of a problem where the Betti-Rayleigh reciprocity relations can be used.

Elasticity