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The tensile test is the most fundamental mechanical test performed on steel reinforcement bars to determine their strength and ductility characteristics. The test measures the resistance of steel to a static or slowly applied force.

The key properties determined from the tensile test are:

• Yield Strength (fy): The stress at which the material begins to deform plastically
• Ultimate Tensile Strength (fu): The maximum stress the material can withstand
• Elongation: The amount of stretch before fracture, expressed as a percentage of the original gauge length

The yield strength is calculated using the formula:

Yield Strength (MPa) = Yield Load (N) / Cross-sectional Area (mm²)

The ultimate tensile strength is calculated using:

Ultimate Tensile Strength (MPa) = Maximum Load (N) / Cross-sectional Area (mm²)

Percentage elongation is calculated as:

Elongation (%) = [(Final Gauge Length - Original Gauge Length) / Original Gauge Length] × 100

As per IS 1786:2008, steel reinforcement bars are classified based on their yield strength:

• Fe 250: Minimum yield strength of 250 MPa
• Fe 415: Minimum yield strength of 415 MPa
• Fe 500: Minimum yield strength of 500 MPa
• Fe 550: Minimum yield strength of 550 MPa
• Fe 600: Minimum yield strength of 600 MPa

• Universal testing machine
• Extensometer
• Vernier caliper
• Steel bar samples

1. Measure the diameter of the steel bar at several points using a vernier caliper and calculate the average diameter.
2. Mark the gauge length (typically 5 times the diameter) on the bar.
3. Mount the specimen in the universal testing machine, ensuring proper alignment.
4. Attach the extensometer to measure elongation if required.
5. Apply the load gradually at a rate of 10-15 MPa per second.
6. Record the yield load (the point where the load stops increasing linearly with elongation).
7. Continue loading until the specimen fractures.
8. Record the maximum load and the elongation at fracture.
9. Remove the specimen and measure the final gauge length.
10. Calculate the yield strength, ultimate tensile strength, and percentage elongation.

The tensile test results for the steel reinforcement bars are as follows:

• Average yield strength: 528.0 MPa
• Average ultimate tensile strength: 679.8 MPa
• Average elongation: 12.8%

As per IS 1786:2008, these results meet the requirements for Fe 500 grade steel (minimum yield strength of 500 MPa).

The tensile test conducted on the steel reinforcement bars showed satisfactory results with an average yield strength of 528.0 MPa, ultimate tensile strength of 679.8 MPa, and elongation of 12.8%, meeting the requirements for Fe 500 grade steel as per IS 1786:2008.

• Ensure proper alignment of the specimen in the testing machine to avoid eccentric loading.
• Measure the diameter accurately at several points to get a representative value.
• Apply the load gradually at the specified rate.
• Record the yield load carefully as it marks the transition from elastic to plastic deformation.
• Handle the extensometer carefully to avoid damage.
• Measure the final gauge length immediately after fracture.