Engr 45 lb #4

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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.csvPreview the document

TENSION TESTS_Lab4.xlsxPreview the document

Lab 4 google sheet (Links to an external site.)

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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