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7. Terminate the test. 8. REMOVE the extensometer and specimen according to the instruction of the TA. 9. SAVE the experimental data for analysis. 10. Collect the two pieces and make sure the broken ends do not rub together, since you will need them for microscopy. Examine the fracture surface on the two pieces. Identify the area for crack growth (flat area) and ductile fracture (shearing). Measure the crack length from the fractured specimen. This length may be greater than that measured before the test Results: Engineering stress and strain: Strain Ultimate Tensile Stress: 50974.51525psiThis number was derived by looking for the maximum ‘y’ value on the plot Fy maximum yield stress (roughly) = 42ksi. This number was approximated by using the offset method on the plot. The intersection between the parallel line from the point (0, 0) and the x value 0.002 came out to be roughly 42ksi. Slope = Modulus of Elasticity: 10,000ksi This number was calculated using the slope function available on Microsoft excel for the plot that we had grafted
Slope = 10722519psi The real value of E for Aluminum is roughly 10,000ksi which is, with a small room of error very close tothe number that we calculated which 10722519psi was True Stress and strain: One sample of aluminum was used to find the true stress and the true strain encountered during a tensile test, and to compare both to the engineering stress and the engineering strain. The engineering stress and strain does not account for the change in cross sectional area, and only accounts for the axial strain in the sample. The true stress and strain account for the change in cross sectional area, and therefore the true stress is higher than the engineering stress. The true strain is also greater than the engineering strain due to strains in the transverse direction along the gage of the sample.

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Strain The true stress at the point of maximum load (where the ultimate tensile strength occurs) for the 6061- T6 aluminum sample had a value of 404.9 MPa, compared to a maximum tensile strength of 376.6 MPa. The true strain at this point had a value of 0.0723 m/m, compared to an engineering strain of 0.0750 m/m. The maximum true stress at fracture was 561.5 MPa, with a strain of 0.765 m/m. At fracture, the engineering stress was 261.3 MPa, with a strain of 0.182 m/m. Discussion: The modulus of resilience and the modulus of toughness are important values in determining the energy that a material can absorb before yielding and before fracture. The modulus of resilience is the area under the engineering stress-strain curve up until the yield, and corresponds to the energy per unit volume that a material can absorb before it yields. The 6061-T6 aluminum had the highest modulus of resilience. The aluminum had the highest resilience due to the high yield strength, and the low modulus of elasticity. . The low modulus of elasticity ensured that the aluminum was strained more before yielding, allowing it to absorb more energy.
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