# Engr 45 Lb #4

The force- displacement data can be accessed below.  I’ve provided the data to you in 3 forms – a .csv file, a .xlsx file, and a google sheet.  Ignore any length/thickness information in the spreadsheets – the length and thickness can be found in part 1 of the lab on canvas.

TENSION TESTS_Lab4.csv TENSION TESTS_Lab4.xlsx ### Lab Report

Using the data collected for the four specimens, prepare a lab report with the following sections.  Upload one lab report per group as a pdf or word document.

#### Introduction

(3 points)

• Discuss the objectives of the lab
• Explain why tensile tests and hardness tests are used, what they tell us about a specimen, and why they are important.
• Describe the different specimens/materials studied in this experiment – where are these materials used in real life?

#### Procedure

You do not need to include this section in your lab report, but it is given to you here so you can see the step by step procedure

• Perform multiple Rockwell hardness tests on each specimen
• conduct the test on the wide section of the specimen to avoid damaging the specimen and affecting the results of the tensile test
• Select the correct indenter for the test (B-scale uses a 1/16 inch steel ball)
• Apply the minor load by turning the hand wheel until the small dial is facing the black dot
• Set the dial so that the large hand is facing zero
• Apply the major load by pressing down the lever
• Turn the hand lever forward to release the major load
• Read the number from the red numbers on the dial
• Perform tensile tests using the Instron universal testing machine
• Calibrate the load cell with no specimen in the tester
• Set the testing machine to conduct the test at a constant strain rate of 2.54 mm/min
• Load the specimen into the tester
• Balance the force and zero the displacement
• Start the test
• The machine will automatically stop when the specimen has been broken

#### Results and Discussion

(40 points)

• Determine the hardness of each specimen and report this in the table shown on part 1
• Calculate the stress and strain for each specimen (you do not need to submit the table of values with your lab, I just want to see your graph)
• Plot the stress-strain curve for each specimen
• Plot all four lines on one graph
• Make sure all four lines are different colors or line types
• Make sure the units on your axes are correct
• Make sure your graph has axes labels
• Using this plot, for each specimen
• Calculate the modulus of elasticity
• Determine the yield strength using a strain offset of 0.002
• Determine the ultimate tensile strength
• Approximate the ductility using percent elongation
• Compute the modulus of resilience
• Compute the toughness
• Show an example calculation for each calculation – if your calculation uses the graph, be sure to include a copy of your graph and show how you used the graph
• Put your solutions in a table that looks like the one below
• Include units in the table
• Steel 1Steel 2Steel AverageAluminum 1Aluminum 2Aluminum AverageHardnessModulus of ElasticityYield StrengthTensile StrengthPercent ElongationModulus of ResilienceToughness
• How did the properties vary between the two materials?
• Which material had a higher modulus of elasticity?  What does this mean for the elastic properties of the materials?
• Which material was more resilient?  What does it mean for a material to be more resilient than another?
• Which material was tougher?  What does it mean for a material to be tougher than another?
• Compare the value calculated for Modulus of Elasticity with the values found in the book.  Are these values different?  If so, why do you think that is?
• Compare the yield strength and tensile strength to the hardness.
• How are hardness and strength related?
• Does your data support this relationship between hardness and strength?
• Based on the properties of the steel, what kind of steel do you think was used?

#### Conclusion

(7 points)

• Discuss the results and compare them to your initial hypotheses done in the two discussions in this module
• Discuss the errors in the experiment (i.e. differences between the steel specimens)
• Were the objectives met?
• Do you have any remaining comments or questions?

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