ABSTRACT
Strain is a local property, and the values of each strain component may change dramatically within a material. There are some special coordinate system orientations that will allow us to understand key facts about a stress or strain state. The more general way to think about this is that positive normal stress arises when the force component acting on an area has the same direction as the normal to that area. Negative stress results when the force component is acting in a direction opposite to the area’s normal. Problems in plane strain occur when there is reason to believe there is no appreciable variation or deformation in a direction. In such instances, the movement of any point is likely to be very small in that direction. The chapter describes how a two-dimensional problem is formulated in the theory of elasticity.
