Tension Test

By Group D:

Course:

Instructor:

APPENDIX

I. ABSTRACT: page 3

II. INTRODUCTION: page 4

III. THEORY AND ANALYSIS page 5

Figure D: Example of a Stress versus Strain Curve page 7

IV. PROCEDURE: page 8

Figure A: Apparatus: page 1

Set-up Test: page 8

Starting Test: page 8

V. RESULTS page 9

Table # 1: Summarization of calculated data page 10

Table # 2: Data from MTS page 11

Table # 3: Offset line values page 12

Figure E: Stress-strain Curve page 13

VI. DISCUSSION: page 14

VII. UNCERTAINTY ANALYSIS page 16

Table #4: Summary of Uncertainty Values page 18

VIII. CONCLUSION page 19

IX. RECOMONDATIONS page 20

I. ABSTRACT:

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

II. INTRODUCTION:

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 45ÑžX 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.

III. 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 extensometer was attached to the experimental cross sectional area.

During the load application the specimen was observed and an elongation was noticed. The elongation took place in approximately 2:00 minutes up until the specimen failed under the stress applied. The analysis of the specimen showed exactly to what theory predicted. When the load was applied to the aluminum specimen it stretched a distance . Figure C. To analyze the theory at hand the change in distance made, via force was divided by the original gage length measured (7cm.). This resulted in a normal strain, which is exactly what theory predicts. See equation 1.2

L

Rearranging this for strain yields,

Similarly, as the application of the 250 KN. load continued through the aluminum specimen, its cross sectional area began to decrease over time. The depletion in cross sectional area resulted in what is known as plastic deformation.

Results that can be measured from this analysis