Why test reinforcing steel
- Concrete performs well in compression, while reinforcing steel supplies tensile and flexural capacity.
- Tensile testing verifies steel mechanical properties and supports comparison of batches with the applicable specification.
Stress-strain response
- In the elastic region, deformation is approximately reversible; its slope represents elastic modulus.
- At yield, plastic deformation begins. Strain hardening, maximum load, localized necking, and fracture may follow.
- Tensile strength and final elongation describe different properties: maximum resistance and deformation capacity.
Test procedure
- Measure and mark the gauge length, check diameter or section, and grip the specimen with compatible jaws.
- Apply axial load under control and measure force and strain using the extensometry method required.
- Record fracture mode and location; a break at the grip or outside the valid region may invalidate a result.
Reporting and safety
- Report yield strength or specified proof strength, maximum tensile strength, elongation, and the control method used.
- Steel can fragment at failure. Use guards and follow the current standard for rate, extensometer, and specimen validity.
Stress-strain curve
- Engineering stress: σ = F/A0, with axial force F and original cross-sectional area A0.
- Engineering strain: ε = ΔL/L0, where L0 is extensometer gauge length. Elastic modulus in the linear range is E = Δσ/Δε.
- Elongation after fracture: A% = 100 · (Lf − L0)/L0, measured after fitting the broken pieces together. The percentage depends on gauge length.
- Reduction of area: Z% = 100 · (A0 − Af)/A0, where Af is the minimum final area at the fracture.
- For steel comparisons, keep the required geometry and gauge length; report yield strength, maximum strength, elongation, and reduction of area separately.
Educational reference guide. Check the current standard, calculation assumptions, and project specification before applying a procedure or acceptance criterion.