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TENSILE TESTING LAB

Tensile Testing Lab

DETERMINE THE TENSILE PROPERTIES OF RAW MATERIALS, COMPONENTS AND ASSEMBLIES.

You can learn a lot about a material from tensile testing. As you continue to pull on the material until it breaks, you obtain a complete tensile profile with a Stress Strain Curve showing how it reacted to the forces being applied. This data can be used to determine the strength and ductility of a material, determine batch quality, or assure compliance with provided mill certs or industry standards.

QAI’s team of experts performs tensile testing for various industries on a large variety of components and raw materials utilizing state of the art software and multiple tensile testers ranging in load capacity with various load cells and extensometers. Part shape and size hardly matter with our extensive sample preparation capabilities. Our machine shop has equipment ranging from small high speed diamond saws to double column band saws with carbide blades, as well as mills, and lathes (manual and CNC), for fast, expert machining of tensile of both full-size and sub-size samples per ASTM A370, E8/E8M.

PRINCIPLES FOR ANALYZING TENSILE PROPERTIES:

HOOKE’S LAW: For most tensile testing of materials, you will notice that in the initial portion of the test, the relationship between the applied force, or load, and the elongation the specimen exhibits is linear. In this linear region, the line obeys the relationship defined as “Hooke’s Law” where the ratio of stress to strain is a constant, or E is the slope of the line in this region where stress (σ) is proportional to strain (ε) and is called the Modulus of Elasticity or Young’s Modulus.

MODULUS OF ELASTICITY: The modulus of elasticity is a measure of the stiffness of the material, but it only applies in the linear region of the curve. If a specimen is loaded within this linear region, the material will return to its exact same condition if the load is removed. At the point that the curve is no longer linear and deviates from the straight-line relationship, Hooke’s Law no longer applies and some permanent deformation occurs in the specimen. This point is called the “elastic limit.” From this point on in the tensile test, the material reacts plastically to any further increase in load or stress. It will not return to its original, unstressed condition if the load were removed.

A sample Stress Strain Curve.

YIELD STRENGTH: A value called “yield strength” of a material is defined as the stress applied to the material at which plastic deformation starts to occur while the material is loaded. Offset Method & Elongation For some materials (e.g., metals and plastics) the departure from the linear elastic region cannot be easily identified. Therefore, an offset method to determine the yield strength of the material tested is allowed. These methods are discussed in ASTM E8/E8M (metals) and D638 (plastics). An offset is specified as a % of strain (for metals, usually 0.2% from E8/E8M and sometimes for plastics a value of 2% is used). The stress (R) that is determined from the intersection point “r” when the line of the linear elastic region (with slope equal to Modulus of Elasticity) is drawn from the offset “m” becomes the “Yield Strength by the Off Set Method”. Elongation of the material after final rupture is then evaluated by extensometers registering the final length of the specimen and subtracting the initial length then dividing by the initial length multiplied by 100 to get the percentage of elongation.

If you are a steel mill looking for a lab that can handle multiple tests daily or a heat treater looking to certify heat treat lots, we can meet your tensile testing requirements and deadlines at affordable prices.