Solid Mechanics

1.1 What is Solid Mechanics? 

Solid mechanics is the study of the deformation and motion of solid materials under the action of forces. It is one of the fundamental applied engineering sciences, in the sense that it is used to describe, explain and predict many of the physical phenomena around us. 
Solid mechanics is a vast subject. One reason for this is the wide range of materials which falls under its ambit: steel, wood, foam, plastic, foodstuffs, textiles, concrete, biological materials, and so on. Another reason is the wide range of applications in which these materials occur. For example, the hot metal being slowly forged during the manufacture of an aircraft component will behave very differently to the metal of an automobile which crashes into a wall at high speed on a cold day.

how do you build a bridge does? which will not collapse?

1.1.1 Aspects of Solid Mechanics 

The theory of Solid Mechanics starts with the rigid body, an ideal material in which the distance between any two particles remains fixed, a good approximation in some applications. Rigid body mechanics is usually subdivided into  statics, the mechanics of materials and structures at rest, for example of a cablestayed bridge  dynamics, the study of bodies which are changing speed, for example of an accelerating and decelerating elevator Following on from statics and dynamics usually comes the topic of Mechanics of Materials (or Strength of Materials). This is the study of some elementary but very relevant deformable materials and structures, for example beams and pressure vessels. Elasticity theory is used, in which a material is assumed to undergo small deformations when loaded and, when unloaded, returns to its original shape. The theory well approximates the behaviour of most real solid materials at low loads, and the behaviour of the “engineering materials”, for example steel and concrete, right up to fairly high loads.