1. Introduction
In engineering, the selection of materials depends on their properties and how they behave under different conditions.
Material testing is done to determine these properties and ensure the material is suitable for a specific application.
Key idea:
Properties define behavior; testing verifies performance.
2. Classification of Material Properties
Material properties are broadly classified into:
- Mechanical properties
- Physical properties
- Thermal properties
- Electrical properties
- Chemical properties
3. Mechanical Properties of Materials
Mechanical properties describe how a material behaves under applied forces or loads.
(a) Strength
- Ability to resist applied force without failure
- Types:
- Tensile strength
- Compressive strength
- Shear strength
(b) Elasticity
- Ability to regain original shape after removal of load
- Measured by Young’s Modulus
(c) Plasticity
- Ability to undergo permanent deformation without rupture
(d) Ductility
- Ability to be drawn into wires
- Measured by % elongation
(e) Malleability
- Ability to be hammered into sheets
(f) Toughness
- Ability to absorb energy before fracture
(g) Hardness
- Resistance to wear, indentation, or scratching
(h) Brittleness
- Tendency to fracture without deformation
(i) Stiffness
- Resistance to deformation
(j) Fatigue
- Failure under repeated or cyclic loading
(k) Creep
- Slow deformation under constant load over time
4. Physical Properties
- Density
- Porosity
- Color and appearance
- Crystal structure
5. Thermal Properties
- Thermal conductivity
- Thermal expansion
- Specific heat
6. Electrical Properties
- Electrical conductivity
- Resistivity
- Dielectric strength
7. Chemical Properties
- Corrosion resistance
- Oxidation resistance
- Chemical stability
8. Testing of Materials
Material testing is done to evaluate the properties and behavior under different conditions.
9. Types of Material Testing
(A) Destructive Testing
Material is damaged or destroyed during testing.
1. Tensile Test
4
- Measures strength, ductility, elasticity
- Produces stress-strain curve
Key results:
- Yield strength
- Ultimate strength
- Young’s modulus
2. Compression Test
4
- Measures compressive strength
- Used for brittle materials (concrete, cast iron)
3. Hardness Test
4
Types:
- Brinell
- Rockwell
- Vickers
4. Impact Test
4
- Measures toughness
- Types:
- Charpy test
- Izod test
5. Fatigue Test
4
- Determines life under cyclic loading
- Produces S-N curve
6. Creep Test
4
- Measures deformation over time at high temperature
- Important for turbines and boilers
(B) Non-Destructive Testing (NDT)
Material is not damaged.
1. Ultrasonic Testing (UT)
4
- Detects internal flaws using sound waves
2. Radiographic Testing (RT)
4
- Uses X-rays or gamma rays
- Detects internal defects
3. Magnetic Particle Testing (MPT)
4
- Detects surface cracks in ferromagnetic materials
4. Dye Penetrant Testing (DPT)
4
- Detects surface defects using dye
10. Importance of Material Testing
- Ensures safety and reliability
- Helps in material selection
- Detects defects
- Improves quality control