Saturday, October 27, 2012

Tensile Property Testing

Testing of tensile properties is probably the most widely used short-term mechanical test of all. This is because it is relatively easy to perform, gives reasonably reproducible results and yields a great deal of information. From this test one can obtain not only tensile strength, but also elongation and modulus.

Tensile properties are determined by stretching a test specimen at a constant rate. The resulting stress (or load applied) is measured an recorded as a function of strain (or elongation). The stress and strain are defined mathematically by:

Stress=     Load applied on specimen
                 Cross-section area of specimen

      Strain=    Increase in length of specimen
                                                          Original length of specimen

                                      Modulus=  Stress
                                                      Strain

Tensile strength is the maximum tensile stree which a material is capable of supporting. It is calculated from the maximum load carried during the tensile test and the original cross-sectional area of the specimen. If the tensile strength occurs at the sample's yield point, this stress is designated as the tensile strength at yield. if it occurs at the sample's break point, it is then designted the tensile strength at break 

The percentage of elongation at break is the ratio, expressed in percentage, of the extension (change in gauge length) at break point to the original gauge length multiplied by 100.

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