By Group D:
THEORY AND ANALYSIS
Figure D: Example of a Stress versus Strain Curve
Figure A: Apparatus:
Table # 1: Summarization of calculated data
Table # 2: Data from MTS
Table # 3: Offset line values
Figure E: Stress-strain Curve
Table #4: Summary of Uncertainty Values
The experiment was conducted to determine the specific material properties of ductile steel. Once the servo settings and interface were complete the test specimen was inserted in the MTS and load was applied. Specific behavior of the round aluminum specimen under axial load was observed. This observation was conducted while the specimen was under constant load and the results of this load brought the specimen to fracture. Figure A. The procedure included setting the MTS computer interface conversions, micro console and range cartridges. After the setting were zeroed and reference frame was found the extensometer was attached to the test specimen. The specimen was then re-measured and data was evaluated to determine the Yield Stress and Strain, Yield strength for an offset of .2% (0.002), Tensile strength, Percent elongation, Percent reduction in area, Modulus of elasticity. Some recommendations that might enhance the experiment could be 1. Timing the experiment for each stage the specimen goes through for different materials. Another suggestion might be to slow the experiment down during plastic deformation for analysis. See results section Figures B & C
The tensile test experiment of a round aluminum 6061-t651 rod and its actual results will be analyzed and compared to known theory and literature values. Background to the theory involved for the test can be found from beam design and structural designs for a variety of materials for most efficient and effective machine design. Other related experiments pertaining to stress and strain include Lab #1 Torsion test and related bibliography. The results expected were the observation of the 45¢X angle at fracture. The noticeable and calculable percent elongation and percent reduction in area of the specimen should exhibit elongation with respect to slip and show good results for modulus of elasticity. The points created from this relationship going up the linear portion of the graph also lead us to the determination of the experimental modulus of elasticity. This is seen for experimental points used in the results section and best approximations for the graph. When compared to literature values for similar aluminum specimens the percentage variations were very small, see results section, as long as the points stayed within the elastic region and below the yield strength of the specimen.
THEORY & ANALYSIS:
The steel specimen used was gage marked and axially loaded with a constant force of 250 KN. The gage marks were measured 7 cm. from the center of the test specimen. The cross sectional area was uniform throughout the 7 cm. distance. With these measurements documented the steel tensile test bar was placed an even distance between wedge grips. Figure A. In theory, as the round specimen undergoes the 250 KN. axial load a stress is created which is equal to the 250 KN. force times the average cross sectional area of the specimen. See equation 1.1
Rearranging this for stress yields,
Over each minute the 250 KN. force was applied to the test specimen for 100 mm. and strain range set to 0.15 mm/mm. To measure these phenomena an...
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