Tensile, Compression & Flexure Testing

The capacity of a material to withstand a static load can be determined by testing that material in tension or compression.

In tensile test the sample is elongated due to an applied load, and the load necessary to produce a given elongation is measured as a dependent variable.

Engineering Stress, σ, is defined as the ratio of the load on the sample, P, to the original cross-sectional area, Ao:

σ = P/Ao (1)

Engineering strain, ε, is defined as the ratio of the change in the length of the sample, Δl, to its original length lo:

ε = Δl/lo (2)

The material during stress passes through different stages, the material is said to be in elastic limit if after load is removed it regains its original shape. The material is said to have passed its elastic limit when the load is sufficient to initiate plastic or nonrecoverable deformation. With further elongation, the engineering stress increases and the material is said to be work harden or strain harden. The stress reaches a maximum at the ultimate tensile strength, at which the area specimen starts to reduce as load required to continue elongate the specimen as it continues to reduce. After neck formation engineering stress decreases with further increase in strain until the sample fractures.

The relation between stress and strain within the elastic limit is described by Hooke’s law

∑ = Ε*ε (3)

Where E is a constant for particular material, known as Young’s Modulus.

During elastic deformation there is a slight change in volume of a metal; during plastic deformation there is no change in volume

AoLo = AiLi (4)

Where Ao and Lo are initial area and length and Ai and Li are final.

At ITS Tensile testing can be carried out up-to a load of 400,000 lbs. We also have sophisticated Extensometers for strain rate measurements and we use Clip-gages to record CTOD values.

Some of the standards utilized at ITS for Tensile testing are given below:

ASTM TESTING CAPABILITIES
A 370	Standard for Test Methods and Definitions for Mechanical Testing of Steel Products.
E-8	Standard Test Methods For Tension Testing of Metallic Materials.
E-8M	Standard Test Methods For Tension Testing of Metallic Material (Metric).
E-9	Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature.
E-21	Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials.
E-111	Standard Test Method for Young's Modulus, Tangent Modulus and Chord Modulus.
E-132	Standard Test Method for Poisson's Ratio at Room Temperature.
E-139	Standard Test Methods for Conducting Creep, Creep-Rupture and Stress-Rupture Tests of Metallic Materials.
E-143	Standard Test Method for Shear Modulus at Room Temperature.
E-209	Standard Practice for Compression Tests of Metallic Materials at Elevated Temperatures with Conventional or Rapid Heating Rates and Strain Rates.
E-238	Standard Test Method for Pin-Type Bearing Test of Metallic Materials.
E-292	Standard Test Methods for Conducting Time-for-Rupture Notch Tension Tests of Materials.
E-345	Standard Test Methods of Tension Testing of Metallic Foil.
E-517	Standard Test Method for Plastic Strain Ratio r for Sheet Metal.
E-646	Standard Test Method for Tensile Strain-Hardening Exponents (n-Values) of Metallic Sheet Materials.
E-606	Standard Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners, Washers and Rivets.
E-1875	Standard Test Method for Dynamic Young's Modulus, Shear Modulus and Poisson's Ratio by Sonic Resonance.
E-1876	Standard Test Method for Dynamic Young's Modulus, Shear Modulus and Poisson's Ratio by Impulse Excitation of Vibration