These stresses are shown in figure 1-19. It is the stress of stretching an object or pulling at its ends. An elevator control cable is in additional tension when the pilot moves the control column. Tension is the resistance to pulling apart or stretching, produced by two forces pulling in opposite directions along the same straight line. If forces acting on an aircraft move toward each other to squeeze the material, the stress is called compression.
Compression is the opposite of tension.
Compression is the resistance to crushing, produced by two forces pushing toward each other in the same straight line. While an airplane is on the ground, the landing gear struts are under a constant compression stress. Cutting a piece of paper with a pair of scissors is an example of shearing action. Shear in an aircraft structure is a stress exerted when two pieces of fastened material tend to separate. Shear stress is the outcome of sliding one part over the other in opposite directions.