ABSTRACT
The critical point is reached when the circle touches the brittle fracture strength line, and the material fails in a brittle manner. Wear life equations usually include symbols that represent material properties. In metallic materials, deformation leads to changes in material temperature. During reversible plastic deformation under tensile stress results in temperature decrease as a result of material volume increase. Under compressive stress and resulting volume reduction during elastic deformation, temperature will increase. Residual stresses imposed by any means will cause distortion of the entire part and have a significant effect on the fatigue life of solids. Most materials are nonlinearly elastic and irreversible to some extent in their stress–strain behavior, though not to the same extent as soft polymers. In elementary mechanics one is introduced to the tensile testing of materials. The Griffith criterion states that brittle fracture results from tensile (normal) stresses predominantly, although compressive stresses impose shear stresses which also produce brittle failure.
