The elongation value found on metal certs relates to its ductility to the point of fracture. Certs show this as "elongation at fracture" or "elongation after fracture," depending on the test method used. These values differ from the focus of this article-uniform elongation. During a tensile test, the dogbone-shaped sample undergoes a reduction in the cross-sectional width and thickness as its length increases in tension. A stress-strain curve plots the material's response to the applied load and resulting elongation. The shape of this curve shows a peak at the maximum engineering stress, called the tensile strength. This characteristic shape results from the opposing effects of the work hardening and the reduction in cross-sectional area that occurs when the sample deforms in tension.
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