SURFACE TENSION SHOWN BY SOLID ARROWS, INTERNAL TENSION SHOWN BY DASHED ARROWS

Where ductility is the ability of a material to deform easily upon the application of a tensile force, malleability is the ability of a metal to exhibit large deformation or plastic response when

being subjected to compressive force. Uniform compressive force causes deformation in the

manner shown in Figure 7. The material contracts axially with the force and expands laterally. Restraint due to friction at the contact faces induces axial tension on the outside. Tensile forces operate around the circumference with the lateral expansion or increasing girth. Plastic flow at the center of the material also induces tension.

Therefore, the criterion of fracture (that is, the limit of plastic deformation) for a plastic material is likely to depend on tensile rather than compressive stress. Temperature change may modify both the plastic flow mode and the fracture mode.

Figure 7 Malleable Deformation of a Cylinder Under Uniform Axial Compression