Performance Testing – Strength and Plasticity

3.3 Performance Testing – Strength and Plasticity

Strength: The ability of a metallic material to resist plastic deformation and fracture under external forces.

Plasticity: The ability of a metallic material to undergo permanent deformation without causing damage under external forces.

Testing method – Tensile test

Specimen preparation:

1. Sampling: Sampling from finished products or semi-finished products after heat treatment. Eccentric sampling, at 1/4 of the thread diameter. Specimen diameter according to GB/T 228.1-2010.

2. Specimen machining

3. Testing equipment

Tensile testing machine and related software

4. Test procedure

Clamp both ends of the specimen with the testing machine grips. Separate at a rate not exceeding 10 mm/min until the specimen is pulled apart. Record relevant data.

5. Test conclusions

1) Tensile strength: Rm = Fm / S0

Requirement for class 10.9 high-strength bolts: Rm ≥ 1040 Mpa

2) Yield strength:

• Upper yield strength: ReH = FeH / S0

• Lower yield strength: ReL = FeL / S0

Requirement for class 10.9 high-strength bolts: ReL ≥ 940 MPa

3) Percentage elongation after fracture A

Bring the fractured specimen pieces together tightly along a straight line.

Measure L1 using a vernier caliper.

Calculation: A = (L1 – L0) / L0

Requirement for class 10.9 high-strength bolts: A ≥ 9%

4) Percentage reduction of area Z

Bring the fractured specimen pieces together tightly along a straight line.

Measure the crosssectional diameter d1 at the fracture using a vernier caliper.

Calculation: Z = (d0 – d1) / d0

Requirement for class 10.9 high-strength bolts: Z ≥ 48%