Gen. Principles and Concepts

STRENGTH OF MATERIALSINTRODUCTION LECTURE SLIDES Week 1

What is Strength of Materials?  Materials?  • Statics is the study of forces acting in equilibrium

on rigid bodies. •  “Bodies” are solid objects, like steel cables, gear

teeth, timber beams, and axle shafts (no liquids or gases); • “rigid” means the bodies do not stretch, bend, or

twist; and “equilibrium” means the rigid bodies are not accelerating. • Most problems in a Statics textbook also assume

the rigid bodies are stationary.

What is Strength of Materials?  Materials?  • In Strength of Materials, Materials, we keep the

assumptions assumptio ns of bodies in equilibrium, but we drop the “rigid” assumption. • Real cables stretch under tension, real floor  joists bend bend when when you walk walk across a wood wood floor, and real axle shafts twist under torsional load.

What is Strength of Materials?  Materials?  • Statics, is essentially force analysis: the

determination of the total internal forces produced in members of a structural framework by externally applied loads. • Statics in itself is not the design of any

member, but it is a first step leading to structural design.

What is Strength of Materials?  Materials?  • The primary objective for a course of study in

strength (mechanics) of materials is the development of the relationship between the loads applied to a non rigid body and the resulting internal forces and deformations induced in the body. • These internal forces, together with predetermined

allowable unit stresses stresses (usually  (usually expressed in pounds per square inch), are then used to determine the size of a structural element required to safely resist the externally externally applied  applied loads. • This forms the basis of structural design.