Continuous medium. Cartesian tensors. Deformation, displacement and strain tensor. Compatibility conditions. Enternal and internal forces. Stress tensor. Principal stresses, invariants and stress deviator. Mohrís circle. Constitutive theory. Laws of mechanics. Equilibrium. Linear elasticity. Isotropy. Navierís equations. Uniqueness of solution. Plane stress and plane strain problems. Variational principles. Plasticity theory. Yield criteria. Stability postulates. General theory of plane strain for perfectly plastic materials.