1. What is Testing of materials?

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

Tensile testing is a destructive mechanical test used to determine the behavior of a material when subjected to a gradually increasing tensile (pulling) load until failure. It is one of the most common tests performed to evaluate the mechanical properties of metals, plastics, and other engineering materials.

Objective of Tensile Testing

Determine the strength of a material.
Measure its ability to deform under load.
Evaluate its ductility and toughness.
Verify compliance with material specifications and standards.

Principle

A standardized test specimen is gripped in a Universal Testing Machine (UTM) and subjected to a continuously increasing tensile load. The machine records the applied load and corresponding elongation until the specimen fractures.

Mechanical Properties Obtained

1. Yield Strength (YS)

The stress at which a material begins to deform plastically.

2. Ultimate Tensile Strength (UTS)

The maximum stress the material can withstand before necking occurs.

3. Breaking Strength

The stress corresponding to fracture of the specimen.

4. Percentage Elongation

A measure of ductility. $\% \text{Elongation} = \frac{L_f – L_0}{L_0} \times 100$

Where:

$L_0$ = Original gauge length
$L_f$ = Final gauge length

5. Percentage Reduction in Area

Another measure of ductility. $\% \text{Reduction in Area} = \frac{A_0 – A_f}{A_0} \times 100$