States of Stress

Mechanical Fundamentals, presents the mathematical framework for many of the chapters which follow. The concepts of combined stress and strain are reviewed and extended into three dimensions. Detailed consideration of the theories of yielding and an introduction to the concepts of plasticity.Many engineering materials are subjected to forces both during processing/fabrication and in service. When a force is applied on a solid material, it may result in translation, rotation, or deformation of that material. Aspects of material translation and rotation are dealt by engineering dynamics. We restrict ourselves here to the subject of material deformation under forces. Deformation constitutes both change in shape, distortion, and change in size/volume, dilatation. The solid material is defined such that change in their volume under applied forces in very small, thus deformation is used as synonymous to distortion.The ability of material to with stand the applied force without any deformation is expressed in two ways, i.e. strength and hardness. Strength is defined in many ways as per the design requirements, while the hardness may be defined as resistance to indentation of scratch.