Lecture 14: Stiffness and complaince matrices for Plane Stress, Plane Strain and Axisymmetric models

3D models are simplified to 2D models under plane stress, plane strain and axisymmetric conditions. In this video, I introduce the assumptions and conditions for each type of 2D model. I also present the stiffness and compliance matrices for each case.
1. Plane stress condition: (a) Stresses must be acting on x-y plane, (b) One dimension must be smaller than the other two dimensions Example: thin plate
2. Plane strain condition: (a) Strains must be acting on x-y plane, or in other word: displacements in x, y must be only function of x and y, and the displacement in z direction must be neglegible (b) One dimension must be larger than the other two dimensions Example: thick plate, long pipe, dam cross section
3. Axisymmetric: Displacement, stresses and strains must not depend on circumferential coordinate,
Example: a disk under uniform pressure