Tensile testing Lab Report Example | Topics and Well Written Essays - 500 words

Tensile testing - Lab Report Example Data from the test is either collected through a data acquisition system and subsequently plotted using appropriate software or plotted using an X-Y plotter. The data typically consists of the load applied to the specimen and the extension or the stress and strain (since the initial cross sectional area of the specimen and gauge length are constants both the load v extension and stress v strain graph have the same shape); a typical plot for a metallic material is shown in figure 2. Tensile specimens may have a variety of cross-sections, although rectangular or cylindrical ones tend to be more common, and may be in a machined or unmachined state. The geometry of a typical specimen is shown in Figure 3, where (note that the nomenclature may vary): The mechanical properties typically derived from a tensile test include the yield stress (or more commonly the offset proof stress), tensile strength (stress), elastic (or Young’s) modulus, percentage total extension at fracture and reduction in cross-sectional area. A more detailed explanation of the range of properties that may be determined from a test and the analysis involved may be found in BS EN ISO 6892-1:2009 and ASTM E8M. It is good practice to test to a standard such as these as they stipulate various parameters, such as the speed of testing (the rate at which the load is applied) and shape of the specimen, which may affect the results obtained, although some companies will have their own procedures that will ensure compatibility between tests within that company. Stress is usually indicated by the Greek letter ÏÆ' (sigma) or S and is the measure of the force per unit area. It has the units N.m-2 or Pa (Pascal) (megapascals, MPa, are more commonly used, these being 106 x N.m-2 (106 Pa) or N.mm-2, due to the magnitude of the values encountered). Strain is usually indicated by the Greek letter ÃŽ µ (epsilon) or e and is the amount a material