ABSTRACT
When an applied load acts on a material it causes the material to deform, and the nature of this deformation can be described and related to its function. When the forces applied to the two ends of a material are directed away from each other, the material is said to be in tension (Fig. D3.1a) and has a tendency to extend. When the forces are directed towards each other the material is said to be in compression (Fig. D3.1b) and has a tendency to shorten. When the forces are directed along different lines of action (Fig. D3.1c) then shear is created. When torques (or twisting moments) act at each end of the material in opposite directions then torsion is created (Fig. D3.1d) causing the material to twist. Combinations of forces and torques lead to more complex types of deformation but these do not need to be considered here.
