Principles of Dairy Machine Design

Module 2. Dynamics

Lesson 7
WORK AND MECHANICS OF MATERIALS

7.1 Introduction

Mechanical work is the amount of energy transferred by a force acting through a distance. Like energy, it is a scalar quantity, with SI units of joules. The term work was first coined in 1826 by the French mathematician Gaspard-Gustave Coriolis.

7.2 Work

When- ever a force acts on a body and the body under goes a displacement, the work is said to be done.

As shown is figure the body on which a force ‘P’ is acting on a body moves through a distance‘s’,

Fig.7.1 Work

7.3 Mechanics of Material

It is a branch of engineering mechanics which deals with the behavior of elastic bodies (or) deformable bodies. Mechanics of materials mainly deals with the

1. Stresses
2. Strains

7.3.1 Strength

Strength is defined as the maximum internal resistance force (stress) that a material can withstand without any failure.

7.3.2 Stiffness

It is an ability of a material i.e. the resistance against the deformation.

7.3.3 Homogeneous

It is the uniform property of the material at all

7.3.4 Isotropic

It is the property of the material at any given points the properties of given material are same in all direction.

7.3.5 Orthotropic

At a point in 3 mutually perpendicular direction properties are different. An orthotropic material has two or three mutually orthogonal two fold axes of rotational symmetry so that its mechanical properties are, in general, different along each axis. Orthotropic material are thus anisotropic; their properties depend on direction in which they are measured.

7.3.6 Allotropic (or) Anisotropic

At any given point the properties are different in different directions. Any material whose physical properties depend upon direction relative to some defined axes.

Assumptions: Usually, for all engineering calculation, unless otherwise specified, following assumptions are made.

Material is assumed to be homogeneous and isotropic.

Material is assumed to be solid and continuous.

No internal forces prior to loading (self weight = 0).