Stress

Introduction

In all engineering construction, the component parts of a structure or a machine must be assigned definite physical sizes; such parts must be properly proportioned to resist the actual or probable forces that may be imposed upon them. Thus, the walls of a pressure vessel must be of adequate strength to withstand the internal pressure; the floors of a building must be sufficiently strong for their intended purpose; the shaft of a machine must be of adequate size to carry the required torque; a wing of an sir plane must safely withstand the aerodynamic loads that may come upon it in takeoff, flight, and landing.

Likewise, the parts of a composite structure must be rigid enough so as not to deflect or “sag” excessively when in operation under the imposed loads. A floor of a building may be strong enough but yet may deflect excessively. Which in some instances may cause misalignment of manufacturing equipment, or in other cases result in the cracking of a plaster ceiling attached underneath. Also a member may be so thin or slender that, upon being subjected to compressive loading, it will collapse through buckling. The ability to determine the maximum load that a slender column can carry before buckling occurs of the safe level of vacuum that can be maintained by a vessel is of great practical importance.

In engineering practice, such requirements must be met with the minimum expenditure of a given material. Aside from cost, at times as in the design of satellites the feasibility and success of mechanics of materials, or the strength of materials, as it has been traditionally called, involves analytical methods for determining the strength, stiffness and stability of the various load-carrying members. Alternately, the subject may be called the mechanics of solid deformable bodies, or simply mechanics of solids.