Case hardening (carburizing) produced globular and semi continuous carbides an undesirable brittle phase in the case microstructure
Tensile Testing:
At ATRONA we perform tensile testing on a daily
basis. Equipped with state of the art software
and three tensile testers ranging in capacity and
a machine shop to cut and machine tensile
specimens in accordance with ASTM E8/E8M
and ASTM A370 we can help you with your
routine tensile testing and certification needs. If
you have a daily or routine tensile testing/
reporting requirements - we can be your one
competitive and responsive laboratory source. Call us to inquire about the Mechanical and Tensile Testing services and programs we offer to steel companies, manufacturing companies, engineering groups, and test laboratories.
A tensile test, also known as tension test, is probably the most fundamental type of mechanical test performed on material. Tensile tests are simple, relatively inexpensive, and fully standardized. By pulling on something, you will very quickly determine how the material will react to forces being applied in tension. As the material is being pulled, you will find its strength along with how much it will elongate.
Why Perform a Tensile Test?
You can learn a lot about a substance from tensile testing. As you continue to pull on the material until it breaks, you will obtain a good, complete tensile profile. A stress-strain curve will result showing how it reacted to the forces being applied.
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.
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.
;){kind=link}