Deformation, Stress, Strain, elastic deformation, plastic deformation, creep, Direct stress, indirect stress, combined stress, Elastic Modulus, Ideal deformation, Tensile stress, compressive stress, shear stress, Viscoelatic maerials,

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