Procedures for Tensile Tests

2018-07-13 10:28:00
The Industrial Revolution produced many new materials, but without methods for testing these materials engineers would build structures and hope the materials were strong enough to withstand the forces on them. Building collapses or explosions were some of the first methods used to determine strength of materials. The Little Giant, designed and patented in 1880 by Tinius Olsen, a Norwegian immigrant living in Philadelphia, was one of the first machines to perform tensile testing.

Tensile testing subjects a sample to a controlled tension until catastrophic failure. This tests the strength of a material and how much tension it can withstand until it fails, or how much a sample can be elongated before it reaches its breaking point.

For isotropic materials, or materials that are uniform in all axes, the most common tensile test procedure is the uniaxial tension test, which measures tensile test across one distinct axis of the sample. The test report can be used to determine such parameters as Young's Modulus, yield strength, ultimate strength, elongation at break, and Poisson's ratio for a sample material. Types of tensile tests include adhesion/bond strength, crimp join pull-off force, peel, and tear resistance. The ASTM Standard for tensile testing has clear instructions for how to follow each of these procedures.

Tensile strength indicates how safe the material is for a certain application and shows the integrity of that material. It can also indicate batch quality and consistency in manufacture. Higher tensile strength indicates the material can be subjected to greater tension before deformation and/or failure.

Tensile test samples are generally formed so that they have an enlarged upper and lower part, called shoulders, which are gripped by the tensile testing machine. These samples are known as tensile bars. The middle, known as the gage section, is more narrow and this is where deformation and failure occur during the test. Depending on the sample, it may be gripped by wedges, screwed into threads, or held by other methods, ensuring there is no slippage of the sample during testing.

The quality of the sample is a factor in obtaining accurate results. The sample must be representative of the material as whole in order to produce useful results. Therefore, samples must be clearly identified in terms of its source and location in relation to the larger body it came from, along with the date and time the sample was obtained. Care must be taken to ensure the sample represents the whole material as accurately as possible, meaning it has undergone the same treatments and is oriented in the same way as the larger material, recreating the larger material as much as possible.

TensileMill CNC offers high quality machines for preparing tensile samples. Their tensile sample preparation equipment can produce both flat and round specimens, and their process is streamlined so that even with no machining experience, tensile samples can be produced with ease. The CNC Machines are designed to create multiple specimens at one time with stacking capabilities for even faster sample preparation. Please contact us today for a quote.
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