# Strength of Materials Diploma Study Materials N Scheme – Unit 2

### Strength of Materials Diploma Study Materials N Scheme

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Subject : Strength of Materials

Three Marks

Scheme: N                                          Department: Mechanical Engineering

Unit – 2 Deformation of Metals

1. Define Stress and Strain

Stress is defined as a force applied per unit area

Stress = Load / Area Unit N / mm2

Strain is the amount of deformation experienced by the body in the direction of force applied, divided by the initial dimensions of the body.

Strain = Change in Length / Original Length

1. What are the classification of force system?
• Tensile force
• Compressive Force
• Torsional force
• Bending Force
• Shear force
1. State Hook’s law

Hooks Law states that when the material is loaded within the elastic limit the stress is directly proportional to the strain

Hooke’s law = Stress α Strain

Stress / Strain = Constant

1. Define Young’s Modulus

The ratio between stress and strain in tension or compression is called young’s modulus

1. Define factor of safety

The ratio between ultimate or yield stress and working or allowable stress is called factor of safety

Factor of safety = Ultimate stress / Working load

1. Define Poisson’s ratio

When the material is loaded within the elastic limit, the ration of lateral strain to linear strain is called poisson’s ratio

Poison ratio is denoted by 1/m

1. What is a composite bar?

A composite bar is made of two (or) more different materials in such a way that they extend or contract

Note:

• Strain of each material is same
• The sum of load taken by the individual material is equal to the applied load
1. Define Temperature stress

The stress induced in the body due to the change in temperature of the body is called temperature stress.

1. Define Proof of Resilience

The Maximum strain energy that can be stored in a body without undergoing permanent deformation is called proof of resilience.

1. What is modulus of resilience?

The Maximum energy that can be stored in a body per unit volume is called modulus of resilience.

1. Define Resilience.

The work must be done on the member to produce deformation against the internal resistance offered by the body. This work done is stored in the body is called Strain energy

1. What are the type of Load applications due to stresses?
2. State the relationship between E & K

E = 3K (1 – 2/M)

1. State the relationship between E & N

E = 2N (1+1/M)

1. Define Tensile stress

When a body is subjected to two equal and opposite axial pulls, the body tends to increase in length. The resistance offered by each and every cross section to the increase in length is called tensile stress. The corresponding strain is called tensile strain.

1. What is Compressive stress.

When a body is subjected to equal and opposite pushes, the body tends to shorten in its length and subsequently the thickness or diameter increases

1. Define Shear Stress

When a body is subjected to two equal and opposite forces acting tangentially across the resisting section, the the stress induced is known as shear stress

1. What is bending stress?

When a beam is subjected to a system of transverse loads the beam bends and the internal resistance is setup in the material. This internal resistance is called bending stress

1. Define Torsional Stress.

When a shaft is subjected to equal and opposite end couples whose axes coincide with the axis of shaft, the stress induced is called torsional stress.

1. Define Longitudinal Strain

Whenever a single force or system of force acts on a body it undergoes some deformation. This deformation per unit length is called Linear Strain

1. Define Working Stress.

The ratio between ultimate or yield stress and factor of safety is called Working stress

1. What is Modulus of rigidity.

The ratio between shear stress & shear strain is called Modulus of rigidity or shear modulus.

It is denoted by C or G or N

1. Define Volumetric strain

When a body is subjected to system of force, it undergoes some changes in its dimensions, which will cause changes in its volume. The ratio of change in volume to the original volume is known as volumetric strain

Volumetric strain = change in volume / original volume

1. What is Bulk Modulus?

When a body is subjected to three mutually perpendicular stresses of equal intensity , the ratio of direct stress to the corresponding volumetric strain is called Bulk Modulus.

Bulk Modulus = Direct stress / Volumetric strain 