Mechanical properties of materials

Engineers must know how solid materials respond to external forces, such as tension, compression, torsion, bending, and shear. Solid materials respond to these forces by elastic deformation (that is, the material returns to its original size and form when the external force is lifted), permanent deformation, or fracture. Time-dependent effects of external forces are creep and fatigue, which are defined below.Tension is a pulling force that acts in one direction; an example is the force in a cable holding a weight. Under tension, a material usually stretches, returning to its original length if the force does not exceed the material’s elastic limit. Under larger tensions, the material does not return completely to its original condition, and under even greater forces the material ruptures (801).