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Make the specimen to geometric standards.
Measure the specimen in 3 places in the gauge section and report average thickness and width to 3 sig figs. Determine the specimen area as A = w × h. Record the average area in units of mm2 (in.2 ).
Set speed of testing to effect a nearly constant strain rate in the gage section. (If strain control is not available on the testing machine, this may be approximated by repeated monitoring and adjusting of the rate of force application to maintain a nearly constant strain rate). The strain rate should be selected so as to produce failure within 1 to 10 min.
Determining modulus of elasticity, at least one specimen per like sample should be evaluated with back-to-back axial transducers to evaluate the percent bending using the equation below, at the average axial strain checkpoint value (the mid range of the appropriate chord modulus strain range) shown in Table 3.
Calculate the ultimate tensile strength using Eq 5 below. Report the results to three significant figures. If the tensile modulus is to be calculated, determine the tensile stress at each required data point using Eq 6 also below.
If tensile modulus or ultimate tensile strain is to be calculated, and material response is being determined by an extensometer, determine the tensile strain from the indicated displacement at each required data point using Eq 7 and report the results to three significant figures.
Tensile Chord Modulus of Elasticity—Select the appropriate chord modulus strain range from Table 3. Calculate the tensile chord modulus of elasticity from the stress-strain data using Eq 8 below. If data is not available at the exact strain range end points (as often occurs with digital data), use the closest available data point.
8. Poisson’s Ratio By Chord Method—Select the appropriate chord modulus longitudinal strain range from Table 3 above. Determine (by plotting or otherwise) the transverse strain (measured perpendicular to the applied force), εt , at each of the two longitudinal strains (measured parallel to the applied force), εl , strain range end points. If data is not available at the exact strain range end points (as often occurs with digital data), use the closest available data point. Calculate Poisson’s ratio by Eq 9, below, and report to three significant figures. Also report the strain range used.
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