AERO214 Axial Loading

docx

School

Texas A&M University *

*We aren’t endorsed by this school

Course

214

Subject

Mechanical Engineering

Date

Dec 6, 2023

Type

docx

Pages

Uploaded by MasterWorld12545

Tension Test INTRODUCTION Tensile testing is performed on materials to ascertain important mechanical properties like Young’s modulus, tensile strength, yield strength, ductility and fracture strength. The fundamental purpose of a tensile test is to determine the deformation response of a given material under a specified load. This information is critical in the design of load carrying structural members. Tensile tests are performed with specimens of various geometries. Often, a specimen with a circular or flat rectangular cross section is used. In this laboratory experiment, we will be using a flat rectangular configuration. OBJECTIVES • To understand how a tensile test is performed and how to obtain the relevant material properties • To determine the following properties for given metallic specimens (Aluminum 6061, 316 Stainless Steel, and 1018 Carbon Steel) using a uniaxial tensile test: Young’s modulus, E Yield strength, σ Tensile strength, Strain to failure Lab-Specific Information Each lab group will conduct the experimental portion for the entirety of the lab, examining the response of each of the three samples to tensile loading. Each group will be responsible for writing a lab report due two weeks after the date the lab was conducted. Axial Loading: This lab examines the elastic and plastic deformation of an axially-loaded material to failure. Three separate materials are examined in this work. Each lab group is responsible for developing stress-strain curves to obtain a deeper understanding of constitutive relationships, strain hardening, strength, and failure. THEORY  Inputs: F  Measured Outputs: ∆ L  Calculated Outputs: ε , E  Known Parameters: A, L, For a rod with gage length L with both ends fully constrained (no translational or rotational movement allowed), the applied force can be converted to stress by dividing the applied load by the cross-sectional area: L

σ = F A The axial strain ε can be obtained – correlating the change in length of the sample ( ∆ L ) to the original gage length. ε = ∆ L L The sample geometry shown in the shape is referred to as a dog bone sample. We use the gage length (measured from the beginning of curvature of the sample) rather than the total length in calculating the strain. This is because the deformation scales inversely with cross-sectional area: The two “heads” of the sample experience much less strain than the gage length, and the strain in the heads is considered to be negligible. A COUPLE OF KEY TERMS The modulus of elasticity : also known as the young’s modulus – can be obtained for an elastic response of the material. E = σ ε Elastic modulus does not use data from the plastic regime or failure regime of the stress-strain curve. Gage Length: constant-radius section of experimental sample. Necking: visible reduction in cross-sectional area in a sample at the point where failure is imminent. Strain to failure: The maximum strain that the sample can take right before rupture. Yield stress: The minimum stress required for the solid to undergo plastic deformation. Energy to failure: The energy per unit volume of the material required to break the sample. It is equal to the area under the stress-strain curve.

TEST PROCEDURE This lab examines three separate materials:  Aluminum 2024  Aluminum 6061  ASTM-A36 Carbon Steel For each material, begin by obtain the gage length and cross-sectional dimensions of each sample. Each sample will be loaded to fracture in the INSTRON tensile testing apparatus, seen below: Figure 1: Instron Test Apparatus The test methods for each of the tests below have already been programmed into the INSTRON Bluehill software package. These methods will automatically output the force and deformation data to an excel sheet, with a separate sheet for each run, which you can email to yourself for data analysis. Aluminum 6061 and 316 Stainless Samples ONLY: Loading to Fracture 1. Position your sample in the test apparatus, zeroing the force and deformation gages or readings 2. Log in to the computer with your TAMU ID and password, then access the data folder on the desktop window. Each run will store data to this folder. Open the Instron software package on the desktop window. Upon opening, enter the userID and password provided by the TA.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

3. Upon opening the Instron software package, select the test tab. Select the first of the two 214 tensile test methods. Figure 2: Method Selection 4. Ensure that the travel limits are set correctly for starting the test – make sure you have the slides positioned so the sample can be loaded to failure, as well as positioned in the test apparatus. Set the lower limit just below the start position. Use the jog up and jog down buttons on the physical controller on the right side of the test apparatus to position the grips and insert the test sample. 5. Double-check with the TA to ensure your operator inputs are correct. Click zero displacement, then balance force. This should position the sample in a zero-force state where the sample is gripped but not loaded, as seen below. 6. Hit start once the sample is in a zero-force state. The method will continue applying load and measuring the deformation and applied force at regular increments. This method will also pause periodically for you to observe the sample, requiring manual input to continue after the sample state has been observed. 7. Once you see necking occur, carefully observe sample failure over the next few mm of deformation and note how the force vs deformation data changes as well as the visual effects on the sample. 8. Once fracture occurs, observe the fracture interface and record notes on it. 9. Record the length immediately prior to failure, or if possible, place the fractured pieces together and use to measure the final gage length. Figure 3: Slide Limits Figure 4: Gripped Sample

1018 Carbon Sample ONLY: Strain Hardening 1. Repeat steps 1-6 from the first two samples but change the test method to the second 214 214 test method. This method will examine strain hardening, where you will load a material to the point where plastic deformation occurs, unload the material to a zero-force state, then re-load to failure. 2. When the sample reaches 13kN of force, the method will unload the sample, recording force vs deflection to a zero-force state. ( A/N – your length will NOT go back to zero, you have permanently deformed the sample via plastic deformation!) 3. Note the new initial length of the sample. This is the new ‘base’ length of the plastically deformed, strain-hardened sample. 4. Continue execution of the method: the sample will be resubjected to an applied load until fracture occurs. Note how the response of the material is different compared to the elastic loading regime from earlier.

REPORTING REQUIREMENTS Lab Content (50 Points)  For each material, plot stress vs strain for each of the tests conducted. For the steel sample, plot stress vs strain for the initial loading, the unloading, and the re-loading to failure, and clearly identify each. (10 points)  For each material, determine the modulus of elasticity using only the linear-elastic portion of the graph. Keep track of units, and either show in graphs or calculations how your modulus was obtained. Calculate the uncertainty of the modulus (7.5 points)  What does an R 2 value represent for linear regression? Define and explain your elastic regime, plastic regime, and failure regime for each plot, as well as your yield and ultimate strengths (7.5 points)  Briefly comment on what the boundary conditions for this test setup would be, and draw a free body diagram for the test (5 points)  Compare the calculated values of modulus of elasticity (with uncertainty) to those from the literature and comment on the accuracy of the results. (5 points)  Calculate and record the yield strength, tensile strength, fracture stress, ductility, and toughness for all specimens. Compare this to published data. Calculate uncertainty for each value and report results with correct significant figures (10 points)  Show sample calculations for all the data in steps 5 and 6 for one of the samples in an appendix. Clearly state the equations used for each calculation and show step-by-step calculations. (10 points)  Discuss how strain hardening affected the material properties of the steel sample, clearly showing how plastically deforming the material impacted properties such as elasticity, yield strength, and ductility. (5 points) Lab Report (50 points) Title Page: (2.5 points)  The cover page should provide the following information: Report Title, Report Authors (Team Number, UINs, and Team Leader(s) if any for the report), Date Conducted, Date Submitted.  Templates are available through Texas A&M Table of Contents: (2.5 points)  Includes and hyperlinks all sections of the report – for each section you should have intro, abstract, conclusions, and all other sections listed.  Includes and hyperlinks figures, tables, and appendices Abstract: (7.5 points)

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

 This summarizes (1) what the purpose of the lab is, (2) what concepts are covered, (3) what was done in the lab, (4) what results were obtained (include quantitative information!), and (5) why these results are important.  Your report should be written such that someone who has not done the lab or who does not have prior knowledge of the lab should be able to understand what you did, why you did it, what data you obtained, and why it matters! Introduction: (10 points)  This section details the motivation, background, and theory of the lab.  Make sure you clearly explain the motivation for the experiment – why does it matter? Why does it have value? What is the background of the lab? Why are you conducting this lab?  Make sure you adequately summarize the experiment here! This is separate from the experimental procedure, which is a step-by-step writeup of the steps you took.  Make sure you clearly define all equations, terms, and variables. All of these should be defined! Experimental Procedure: (5 points)  This section is a step-by-step writeup of the experimental procedure you used to conduct the lab  This must be in your own words! Data and Results: (10 points)  This section is primarily tables – both of the raw data (which can be placed in an appendix, and probably should be for most labs for readability!) and the calculated data. This section will also include the lab content requested for each lab.  Make sure your data is readable and directly included (no google sheets links). If you directly import handwritten data, be very careful that your work is legible and is as clear as typed work would be.  Include uncertainty and track your significant figures!  Be careful with figure formatting – units, titles, error bars, axes, etc. This matters significantly when it comes to good reports! Discussion and Conclusions ( 10 points)  Discussion: discuss the results obtained – do they seem reasonable? Are there any calculations where you know your results are likely inaccurate? Do any figures need axes, uncertainty, or any content explained? o How closely do your calculated results line up to theory or expected results? o What were the likely causes of error in your calculated results? Don’t just say human error, need detail here! Discussion and Conclusions (2.5 points)

 Highlight important results. Include your conclusions on the lab and your results. Discuss positive aspects of the lab (what went well, what worked) and any things that should be changed for next semester or next lab.