Mechanics of Solids

Solid mechanics (also known as mechanics of solids) is the branch of Continuum Mechanics that studies the behavior of solid materials, especially their motion and deformation under the action of forces, temperature changes, phase changes and other external or internal agents. The application of the principles of mechanics to bulk matter is conventionally divided into the mechanics of fluids and the mechanics of solids. The entire subject is often called continuum mechanics.

Solid mechanics is also defined as a branch of applied mechanics that deals with behaviours of solid bodies subjected to various types of loadings. Solid mechanics is concerned with the stressing, deformation and failure of solid materials and structures.

The various bodies on which engineers are interested to apply laws of mechanics may be classified as Solids and Fluids.

Solids

The bodies which do not change their shape or size appreciably when the forces are applied are termed as solids. It can support normal forces.

Example: stone, steel, concrete etc.

Fluids

The bodies which change their shape or size appreciably even when small forces are applied are termed as fluids.

Example : water, gases etc.

History 

Solid mechanics developed in the outpouring of mathematical and physical studies by the Newton laws of motion. The need to understand and control the fracture of solids in structural member seems to have been a first motivation. Leonardo da Vinci sketched in his notebooks a possible test of the tensile strength of a wire. Galileo had investigated the breaking loads of rods under tension and concluded that the load was independent of length and proportional to the cross section area, this being a first step toward a concept of stress. He also investigated the breaking loads on beams that were suspended horizontally from a wall into which they were built.

Solid mechanics is usually subdivided into further two streams i.e Mechanics of rigid bodies or simply Mechanics and Mechanics of deformable solids. 

Rigid body 

Rigid bodies do not deform (stretch, compress or bend) when subjected to external loads. Rigid body is basically defined as a body where changes in the distance between any two of its points are negligible.

In actuality, no physical body is completely rigid, but most bodies deform so little that this deformation has a minimal impact on the analysis. For this reason, we usually assume that bodies in the statics and dynamics are rigid. 

Deformable body 

Deformable bodies deform (stretch, compress or bend) when subjected to external loads. Deformable body is basically defined as a body where changes in the distance between any two of its points could not be neglected.