The document discusses the deformation of solids, including definitions of stress, strain, and the processes of elastic and plastic deformation. It describes various types of stress (tensile, compressive, and shear) as well as the concept of creep in viscoelastic materials. The document also highlights the relationship between stress and strain through the elastic modulus and the conditions under which these deformations occur.

1. DEFORMATION OF SOLIDS
BY- Virendra Vaishnav
B.Pharmacy 4th Sem
Apollo College of Pharmacy, Durg

2. Deformation of Solids
 DEFORMATION- Change in size & Shape of Object
 STRESS - Force per unit area that applies to an object to deform it
 TENSILE STRESS – Tensile Force acting per unit area of the body
 COMPRESSIVE STRESS – Compressive force acting per unit area of the
body
 SHEAR STRESS – Shear force acting per unit area of the body
 TENSILE STRAIN – Ratio of incease in length to original length of Bar
 COMPRESSIVE STRAIN – Ratio of decease in length to original length of
Bar
 ELASTIC MODULUS – Ratio of (Stress to Strain)
DEFINITION-

3.  ELASTIC DEFORMATION – Process in which the material return to its
original shape when force is removed
 PLASTIC DEFORMATION – Process in which the material does not return
to its original shape when force is removed
 CREEP – Progressive , Permanent Deformation under constant load is
called Creep.

4. DEFORMATION
Change in size & Shape of the object.
When Loads are applied to body there is change in dimension.
STRESS APPLIED DEFORMATION
REMOVAL OF
STRESS
ELASTIC DEFORMATION
(Original State regain)
PLASTIC
DEFORMATION(Original
state lost)

5. ELASTIC DEFORMATION
 When a load applied or removed , no permanent deformation has occurred
 The material will return its original when force is removed .
 In Metals, ceramics, rubbers & Polymers.
 Elastic deformation in a solid can take place due to change in pressure or by an
application of force or load
 The Elasticity depend on both CHEMICAL BONDING & STRUCTURE OF SOLID
 Which takes place instaneously upon force & disappear completely on removal of
the force or load
 It obey’ s Hooke’s Law
IDEAL DEFORMATION

6. PLASTIC DEFORMATION
 The Material does not return to its original shape when force is removed
 Plastic deformation in solid does not obeys’ s Hooke’s Law
 Progressive, permanent deformation under constant load is called CREEP
FOR VISCOELASTIC MATERIALS
 Both recoverable and permanent deformationa occur together which are
dependent on time
 When force is applied to material it experience elastic, deformation followe by
plastic deformation
 Transition from elastic to plastic is characterized by yield strength of the
material

7. Force acting per unit area to an object to deform it.
Stress = Force / Area
Unit – Nm-2 or Pascal
Stress (σ)

8. There are 3 types of stress-
 DIRECT STRESS – These stress are produced under direct loading condition
Based on the type of force acting on the body it may be-:
a) TENSILE STRESS – It is defined as tensile force acting per unit area of the
body . This force produce elongation of dimension and increase in length of
the body (Ratio of change in length to original length)
b) COMPRESSIVE STRESS – It is defined as compressive force acting per unit
area area of the body. The force is applied opposite to each other and
compress the dimension of the body
c) SHEAR STRESS- Shear force acting per unit area of the body . Load is
applied on the surface of the body .Develops a resistive paralle to opposite to
direction of force applied
 INDIRECT STRESS- These stress occur due to torque produced in the body
 COMBINED STRESS- These stress are the combination of Direct & Indirect
Stress.

9. STRAIN
 Measure of amount of deformation
 If the bar length is (L) when load is applied the length will change as ( L)
 Strain = L
L
There are 3 types of strain -
 TENSILE STRAIN – Ratio of increase in length to original length of bar
 COMPRESSIVE STRESS – Ratio of decrease in length to original length of bar
 SHEAR STRAIN – Strain produced by shear force is called Shear strain

10. ELASTIC MODULUS
 Ratio of stress to strain
 Elastic modulus = Stress / Strain
 The constant of proportionality depends on the material being
deformed and the nature of the deformation is called ELASTIC
MODULUS.
 Elastic Modulus determines the amount of force required per unit
deformation
 Long elastic modulus material is difficult to deform
 Small elastic modulus is easy to deform