Definition of stress state
The stress state is that when an object is subjected to a force, the magnitude and direction of its internal stress not only change with the orientation of the section, but also not necessarily the same at each point on the same section. Countless sections with different orientations can be made through a point in the object. Among them, three cross sections that are perpendicular to each other must be selected. Only normal stress acts on it and the shear stress is equal to zero. The stress at a point expressed by these three sections, This is called the stress state at this point.