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Unformatted text preview: Mechanical Properties of Materials In Tension by Patrick McAdams Laboratory Section AA, Tuesday 2:30 p.m., January 30, 2007 Daniel Flores Date of Laboratory: February 5, 2007 Report Submitted to: Jiangyu Li EXECUTIVE SUMMARY Three samples of four materials underwent tensile strain until fracture. These materials were 1018 steel, 6061-T6 aluminum, polycarbonate, and polymethylmethacrylate (PMMA). The tensile test was done using a 5585H Instron tensile test machine. During these tests, stress and strain was measured every tenth of a second. Using these stresses and strains, engineeringstress vs. engineering strain curves were created for each sample. With these curves, modulus of elasticity, yield strength, ultimate tensile strength, strain at fracture, modulus of resilience, and modulus of toughness were determined. From the strain at fracture, the ductility was looked at qualitatively for the materials. Steel, aluminum, and polycarbonate were observed to be ductile and, as a result, experienced necking and large strains after yielding. PMMA, however, fractured with no little change in its cross-sectional area and had little strain at fracture. All mechanical properties found agreed with literature values, except the yield strengths and ultimate tensile strengths for steel and aluminum. It was determined that this was due to cold-working on the samples. All of the mechanical properties were determined using the engineering stress vs. engineering strain curves, but in order to get an idea of the true stress and true strain within the sample, change in cross-sectional area must be taken into consideration. This change in area increases the stress within the material. This true stress vs. true strain plot can also be approximated after yielding using a constitutive power relation. This was demonstrated as the percent difference in stress at 0.1% and 1%, both before yielding, to be 67.51% and 8.07%. At 5%, after yielding, however, the percent difference in stress was 0.90%. This demonstrates the validity of the power relationship. OBJECTIVES This laboratory is meant to demonstrate credibility to many of the mechanical properties used day to day by engineers. This laboratory will also give better understanding of these properties and their assumptions. When designing, an understanding of material properties and their implications is imperative to the design process. The simple tensile test that will be performed will reveal many of the mechanical properties including modulus of elasticity, yield strength, ultimate tensile strength, modulus of resilience, and modulus of toughness. These properties will allow for a deeper understanding when designing with material specifications as parameters....
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This note was uploaded on 04/08/2008 for the course ME 354 taught by Professor Jiangyuli during the Winter '07 term at University of Washington.
- Winter '07