Tension (or tensile) test is a popular method of studying the short-term mechanical behavior (strength and ductility) of a material under quasi-static uniaxial tensile state of stress. This test provides important design data for load-bearing components. Tension test involves stretching of an appropriately designed tensile specimen under monotonic uniaxial tensile loading condition. Generally, a constant displace­ment rate is used during the test. The load and sample elongation are measured simultaneously using load cells and strain gage/LVDT (linear variable differential transformer), respectively. Figure 5.2 shows a schematic of a basic tensile tester.

The test generally uses a standard specimen size shown in Figure 5.3. But for irradiated materials (considering the induced radioactivity among other factors), the use of the subsize tensile specimens is quite common. One important thing to observe is that the transition region between the gauge length and the shoulders is smooth so that stress concentration effect does not set in creating flaws. It is gener­ally recognized that in order to compare elongation measurements with a good approximation in different sized specimens, the specimens must be geometrically similar. In this regard, Barba’s law (1880), which states that І0Д/A0 (L0 is the gauge length and A0 is the cross-sectional area) needs to be a constant, is useful. In the United States, І0Д/A0 is taken as ~4.5 for round specimens. The relevant ASTM standard for tension testing is E8 (standard test method for tension testing of metallic materials).