Table of contents  
Metal's Property, Stress and Strain  
Stress  
Strain  
True Stress and True Strain  
Hooke's Law  
Properties of Materials  
Elongation 
Stress and Strain is the first topic in Strength of Materials which consist of various types of stresses, strains and different properties of materials which are important while working on them.
When a material is subjected to an external force, a resisting force is set up in the component. The internal resistance force per unit area acting on a material is called the stress at a point. It is a tensor quantity having unit of N/m^{2 }or Pascal.
Stress = Force/Area
Force(F) is expressed in Newton (N) and A, original area, in square meters (m^{2}), the stress σ will be expresses in N/m^{2}. This unit is called Pascal (Pa).
It is the deformation produced in the material due to simple stress. It usually represents the displacement between particles in the body relative to a reference length.
StressStrain Relationship
Comparison of engineering stress and the true stressstrain curves shown below:
The true stressstrain curve is also known as the flow curve.
Where K is the strength coefficient
According to Hooke’s law the stress is directly proportional to strain i.e. normal stress (σ) ∝ normal strain (ε) and shearing stress ( ζ ) ∝ shearing strain ( γ ).
σ = Eε and ζ = γG
The coefficient E is called the modulus of elasticity i.e. its resistance to elastic strain. The coefficient
G is called the shear modulus of elasticity or modulus of rigidity.
Some properties of materials which judge the strength of materials are given below:
A prismatic bar loaded in tension by an axial force P
For a prismatic bar loaded in tension by an axial force P. The elongation of the bar can be determined as δ=PL/AE
2 videos122 docs55 tests

1. What are the properties of metals related to stress and strain? 
2. What is the difference between stress and strain in materials? 
3. How is true stress and true strain different from conventional stress and strain measurements? 
4. What is Hooke's Law and how does it relate to the properties of materials? 
5. How do properties of materials such as elongation affect their behavior under stress and strain? 
2 videos122 docs55 tests


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