Stress Strain Diagram
The most important test of a
material’s mechanical response
is the tensile test
Stress (σ) = F/A
Strain (ε) = x/L
X= change in length
L= Original length
Yield point is the point at which the material will have an appreciable elongation or yielding
without any increase in load.
Ultimate Strength: The maximum ordinate in the stress-strain diagram is the ultimate strength or
tensile strength.
Hook’s Law
According to Hook’s law,
“Within the elastic limit the force (stress) applied is proportional to the strain
produced”. The material will regain its original shape and size after removal of the
stress.
σαε
σ = Eε or E= σ/ε
E= Modulus of Elasticity or Young’s modulus
It is also the measure of stiffness of a material. It is tensor quantity.
True stress (F/A) vs. Engineering Stress (F/Ao)
Definitions- Mechanical properties
• Ductility
• Ability of a material to undergo permanent deformation without breaking
• Resilience
• the capacity of a material to absorb energy when it is deformed elastically and the upon unloading to have this
energy recovered.
• Hardness
• Resistance to abrasion or resistance to localized plastic deformation
• Ultimate tensile strength (UTS)
• The maximum stress a material withstands when subjected to an applied load
• Toughness
• Different in several contexts: This describes the way a material reacts under sudden impacts