strength of material (introduction) part-1

introduction:

The strength of materials may be defined as that branch of engineering science which deals with the ability of various types of materials to resist its failure and their behavior under the action of the forces 

stress:

when some external system of forces or loads act on a body, the internal forces (equal and opposite) are set up at various sections of the body, which resist the external forces . this internal force per unit area at any section of the body is known as unit stress or simply stress. 

Mathematically,

                                    

Strain:

when a system of forces acts on a body, it undergoes some deformation. this deformation per unit length is known as unit strain or simply a strain.

Mathematically,

strain = strain it has no units

DL =extension measured in metres
L = original length measured in meters

Tensile stress or strain:

When a body is subjected to two equals and opposite axial pulls, as a result of which the body tends to extend its length, the stress, and strain induced are known as tensile stress or tensile strain.

compressive stress and strain:

when a body is subjected to two equal and opposite pushes, as a result of which the body tends to Decrease its length, the stress and strain induced is known as compressive stress and compressive strain.

Young's Modulus or Modulus of Elasticity:

Hooke's law states that when a material is loaded within elastic limit, stress is directly proportional to the strain.

Where E is a constant of proportionality and is known as young's modulus or modulus of elasticity 

Shear Stress and strain:

When a body is subjected to two equal and opposite forces, acting tangentially across the resisting section, as a result of which the body tends to shear off the section, then the stress induced is called shear stress. the corresponding strain is known as shear strain.

Mechanical Properties of Materials:

In general, all the materials used by the engineers may be classified on the basis of their physical properties, into the following four types:

1. Elastic Materials 
2. plastic Materials 
3. ductile Materials 
4. brittle   Materials 

Elastic Materials:

When materials regain its original position, on the removal of the external force, it is called an elastic material.

plastic Materials:

When a material does not regain its original position, n the removal of the external force. it is called a plastic material. 

ductile Materials:

When a material can undergo a considerable deformation without rupture (e.g. when a material can be drawn into wires) it is called ductile material.

Brittle Materials:

When a material can not undergo any deformation (like glass )and it fails y rupture, it is called a brittle material.

so, guys, it is our part-1 introduction of the(strength of material).