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# MIME 1650 Laboratory 5

By Eddie Andrews,2014-01-20 02:14
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MIME 1650 Laboratory 5

MIME 1650 Laboratory 5

Tensile and Compression Tests

Objective

The student should learn to use Universal Testing Machine to perform tensile and

compression test of materials. A deeper understanding of stress-strain diagram is

expected as well.

Agenda

-Introduction to Universal Testing Machine

-Review of stress-strain curves

-Laboratory procedure

Instron Universal Testing Machine

Fig. 1 Instron universal testing machine [1]

Stress-Strain Curve (see text book pp. 132 pp. 150)

Proportional Limit

In Figs 2 and 3 it will be noted that, up to a certain stress, the strain is directly

proportional to the stress. The stress at which this proportionality ceases to exist is

known as the proportional limit.

Young’s Modulus (or Modulus or Elasticity)

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Up to the proportional limit, the material obeys Hooke’s law, which states that stress is directly proportional to strain. The proportionality constant, or ratio of stress to strain in

this region, is known as Young’s modulus or the modulus of elasticity.

Fig. 2 The Stress-strain curve for an aluminum alloy

Fig. 3 The Stress-strain curve for carbon steel

Elastic Limit

The maximum stress for which truly elastic behavior exists is called the elastic limit.

Permanent Set (or Plastic Deformation)

Elongation beyond the elastic limit becomes unrecoverable and is known as permanent set or plastic deformation.

Yield Point

Beyond the elastic limit, increases in strain do not require proportionate increases in

stress. In some materials, a point may be reached where additional strain occurs without

any increase in stress, this point being known as the yield point or yield-point stress.

Ultimate Strength (or Tensile Strength)

In the tensile test, however, a point is reached where the drop in the area with increased

strain dominates the increase in strength and the overall load-bearing capacity peaks and

begins to diminish, as in Figure 2 and Figure 3. The value of this point on the stress-train

curve is known as the ultimate strength or tensile strength of the material.

Breaking Strength (or Fracture Strength)

If straining is continued far enough, the tensile specimen will ultimately fracture. The

stress at which this occurs is called the breaking strength or fracture strength.

Safety Precautions

? Wear safety glasses all times

? Close the glass lid after mounting the specimen.

? Do not stand behind the test machine.

? If something goes wrong, there are three different ways to stop the test.

? The emergency stop button.

? Control panel stop button.

? Software stop button shown as in the small icon respectively.

Experimental Procedure:

A. Initial Measurements

1. (Tensile Test) Measure the diameter and gauge length of the Al-Alloy

sample and the width and thickness of the steel sheet tensile sample and the

nylon (non-transparent plastic) and acrylic (transparent plastic) samples.

Mark lines to show the gauge length on the samples.

2. (Compression Test) Measure the width and length of the compression

sample Wood Block.

B. Tensile Test ( Al bar, Steel sheet, Plastics)

1. Turn on the power to the computer first and then Instron Machine.

2. Open the Bluehill 2 software using the shortcut on the desktop. The Home

Screen of Bluehill interface will be showing. The Home Screen is going to

be your main access point for all the features of Bluehill software.

3. Before running a test the load transducer must be calibrated. Once the

Bluehill2 software appears on the screen, there are couple transducers

shown on the right hand corner of the screen. Click on the Load Cell icon

shown on the right. Transducer Setup dialog box pops up. Hit on

Calibrate button. When warning dialog box pops up click on OK. Then

load must be balanced by hitting on Balance button in same dialog box.

After balancing the load press Done button to exit the dialog box. 4. To mount the sample in between the grips of the test machine grips can be

controlled by the up and down button on the control panel. Tighten the

jaws no more than necessary. Lose jaws might cause slippage and very

tight jaws might also yield wrong results.

5. On Home Screen just click on Test button. 6. The Create a New Sample screen will be displayed. In this screen

methods already saved in the computer will be selected for specific test

samples. There are four Tension Tests that are going to be performed in

this lab.

7. In the New Sample view there is a list of methods have recently been used.

For aluminum bar sample tests select the method file called

aluminum.im_tens, for the rectangular steel specimen select the method file

called rectangular_steel.im_tens, for acrylic (transparent plastic) select the

method file called transparent_plastic.im_tens, and similarly for nylon

(non-transparent plastic) select the method file called non-

transparent_plastic.im_tens. The method file at the top of the list is

highlighted. On the right, the preview pane shows the important

parameters of the highlighted method.

8. Choose a method and click Next button to proceed. 9. Second step of Create a Sample screen asks you to type a file name for

your sample. Type your group number and the name of the specimen that

you are testing, for example group1_rectangular_steel click Browse to

find your section folder and hit Save. There are going to be fourteen

folders for each section and sections are going to be split up according to

availability of the test specimens. Then click Next to continue.

10. The first screen of the prompted test is the reminder of calibration. If

calibration is not done, the specimen must be unmounted and Step: 3 must

be followed for calibration. If calibration has already been done click

Next to continue. (If you are not sure whether the calibration has been

11. The second screen of the prompted test is the Before Specimen section.

Here the prompt and input controls require you to enter some information

about the specimen. Default values for the specimen will show in the

inputs. This data is not required to be changed. Click Next to continue.

12. Before the Test prompt screen will appear. Please make sure the specimen

is properly installed in the test machine. Keep clear of the machine and

make sure no student is close by. Everybody MUST wear safety glasses.

The softkeys at the top of the screen is set to be Reset Gauge Length and

Balance Load button, respectively. First reset the gauge length pressing on

Reset Gauge Length key, and then hit the Load Balance. At this screen

the Next button is grayed out. On the other hand Start button is enabled. If

everything is ready click the Start button to start the test. 13. The workspace screen displays. Progress of test can be viewed here. The

stress vs. strain curve can be observed growing and autosizing as the test

progresses. Once the test is complete, the workspace will still be showing

for students to examine it. After examined the graph and results click on

Next to proceed.

14. Finishing screen will be displayed. In this screen click on the Finish

Sample button. The software will save your file in selected directory.

Then a dialog box appears asking if another sample is going to be tested

using same test parameters. Click on No in that dialog box. Once again

Create a Sample screen will display.

15. Then let the next group of students run the same test starting from Step: 4.

16. Last lab section of the day should close to software; turn off Instron

Machine and computer.

C. Compression Test (Wood). You will be performing compression tests on two

wood samples. First with the load applied parallel to the grain and then with

the load perpendicular to the grain.

1. Turn on power computer first and then Instron Machine.

2. Open the Bluehill 2 software which has a shortcut on desktop. Home Screen

of Bluehill interface will be showing. Home Screen is going to be your main

access point for all the features of Bluehill software.

3. Before running a test the load transducer must be calibrated. Once the

Bluehill2 software appears on the screen, there are couple transducers shown

on the right hand corner of the screen. Click on the Load Cell icon shown on

the right. Transducer Setup dialog box pops up. Hit on Calibrate button.

When warning dialog box pops up click on OK. Then load must be balanced

by hitting on Balance button in same dialog box. After balancing the load

press Done button to exit the dialog box.

4. To mount the sample in between the grips of the test machine grips can be

controlled by the up and down button on the control panel. Tighten the jaws

no more than necessary. Lose jaws might cause slippage and very tight jaws

might cause initial bending both of which yield wrong results.

5. On Home Screen just click on Test button.

6. The Create a New Sample screen will be displayed. In this screen methods

already saved in the computer will be selected for specific test samples. There

are four Tension Tests that are going to be held in the lab.

7. In the New Sample view there is a list of methods have recently been used.

For wood prism sample tests select the method file called wood.im_com. The

method file at the top of the list is highlighted. On the right, Preview pane

shows the important parameters of the highlighted method.

8. Prompt in this screen requests you to choose a method and click Next button

to proceed.

9. Second step of Create a Sample screen asks you to type a file name for your

sample. Type your group number and the name of the specimen that you are

testing, like group1_wood click Browse to find your section folder and hit

Save. There is going to be fourteen folders for each section and sections are

going to be split up according to availability of the test specimens. Then click

Next to continue.

10. The first screen of the prompted test is the reminder of calibration. If

calibration is not done, the specimen must be dismounted and Step: 3 must be

followed for calibration. If calibration has already been done click Next to

continue.

11. The second screen of the prompted test is the Before Specimen section. Here

the prompt and input controls require you to enter some information about the

specimen. Default values for the specimen will show in the inputs. This data

is not required to be changed. Then click Next to continue. 12. Before the Test prompt screen will appear. Please make sure the specimen is

properly installed in the test machine. Keep clear of the machine and make

sure no student is close by. Everybody MUST wear safety glasses. The

softkeys at the top of the screen is set to be Reset Gauge Length and Balance

Load button, respectively. First reset the gauge length pressing on Reset

Gauge Length key, and then hit the Load Balance. At this screen the Next

button is grayed out. On the other hand Start button is enabled. If everything is

ready click the Start button to start the test.

13. The workspace screen displays. Progress of test can be viewed here. The

stress vs. strain curve can be observed growing and autosizing as the test

progress. Once the test is complete, the workspace will still be showing for

students to examine it. After examined the graph and results click on Next to

proceed.

14. Finishing screen comes out. In this screen click on the Finish Sample button.

The software will save your file in selected directory. Then a dialog box

appears asking if another sample is going to be tested using same test

parameters. Click on No in that dialog box. Once again Create a Sample

screen will display.

15. Then let next group of students run the same test starting from Step: 4.

16. Last lab section of the day should close to software; turn off Instron Machine

and computer.

D. Draw Stress-strain curve for each sample

1. Open data file in ‘MS Excel’. The data will be in two columns: Displacement

2. In Excel, use the extension and load data to compute strain and stress using

the initial sample dimensions you measured.

Report Requirements

1. Can you determine whether the testing material is ductile or brittle from observing

the shape of the cross section after tensile test? How?

2. Describe the shape and surface of the cross section after tensile test.

3. What is stress? How does it differ from load or force?

4. What is strain? How it is normally expressed?

5. Is strain proportional to stress at all stress levels?

6. What is the significance of the modulus of elasticity of a material to a designer? 7. What is the yield point? Do all materials exhibit the yield point phenomenon? For

those cases in which the material changes from elastic to plastic behavior is not

easily detected, how is the yield point determined?

8. What factors should be considered to determine whether a tension or compression

test is used to evaluate a material property?

9. Describe the morphology of the fractured specimens.

10. Draw the load displacement and stress-strain curves obtained in each experiment.

11. What is the percentage elongation at fracture for the aluminum and steel samples?

Data Sheet

Tensile Test for aluminum tensile specimen

Material of Specimen Diameter Before D (in.)

After d (in.)

2Cross-Sectional Area Before A (in.) 0

2After A’ (in.) Length Before L (in.) 0

After L’ (in.) Upper Yield Point Load P (lb.) y

2Yield Strength = P/ A (lb./in.) y 0

Max.(Ultimate) Load Load P (lb.) u2Point Tensile Strength = P/ A(lb./in.) u 0

Elongation = L’ L (in.) 0

% of Elongation = (L’ L) / L × 100 (%) 0 0

% of Area Reduction = (A A’) / A × 100 (%) 0 0

Breaking (Fracture) Load P (lb.) z

2Point Breaking Strength = P/ A(lb./in.) z 0

Tensile Test for Sheet tensile specimen

Material of Specimen Width Before W (in.) 0

After W’ (in.) Thickness Before T (in.) 0

After T’ (in.)

2Cross-Sectional Area Before A (in.) 0

2After A’ (in.) Length Before L (in.) 0

After L’ (in.) Upper Yield Point Load P (lb.) y2Yield Strength = P/ A (lb./in.) y 0

Max.(Ultimate) Load Load P (lb.) u2Point Tensile Strength = P/ A(lb./in.) u 0

Elongation = L’ L (in.) 0

% of Elongation = (L’ L) / L × 100 (%) 0 0

% of Area Reduction = (A A’) / A × 100 (%) 0 0

Breaking (Fracture) Load P (lb.) z

2Point Breaking Strength = P/ A(lb./in.) z 0

Tensile Test for nylon specimen

Material of Specimen Diameter Before D (in.)

After d (in.)

2Cross-Sectional Area Before A (in.) 02After A’ (in.) Length Before L (in.) 0

After L’ (in.) Upper Yield Point Load P (lb.) y

2Yield Strength = P/ A (lb./in.) y 0

Max.(Ultimate) Load Load P (lb.) u2Point Tensile Strength = P/ A(lb./in.) u 0

Elongation = L’ L (in.) 0

% of Elongation = (L’ L) / L × 100 (%) 0 0

% of Area Reduction = (A A’) / A × 100 (%) 0 0

Breaking (Fracture) Load P (lb.) z

2Point Breaking Strength = P/ A(lb./in.) z 0

Tensile Test for acrylic specimen

Material of Specimen Width Before W (in.) 0

After W’ (in.) Thickness Before T (in.) 0

After T’ (in.)

2Cross-Sectional Area Before A (in.) 02After A’ (in.) Length Before L (in.) 0

After L’ (in.) Upper Yield Point Load P (lb.) y

2Yield Strength = P/ A (lb./in.) y 0

Max.(Ultimate) Load Load P (lb.) u2Point Tensile Strength = P/ A(lb./in.) u 0

Elongation = L’ L (in.) 0

% of Elongation = (L’ L) / L × 100 (%) 0 0

% of Area Reduction = (A A’) / A × 100 (%) 0 0

Breaking (Fracture) Load P (lb.) z

2Point Breaking Strength = P/ A(lb./in.) z 0

Material of Specimen Compression Test

Before Width (W) (in.) 0

Length (L) (in.) 0

2Cross-sectional Area (A) (in.) 0

After Width (W’) (in.)

Length (L’) (in.)

2Cross-sectional Area (A’) (in.) Max.(Ultimate) Load P (lb.) m

2Compression Strength = P/ A(lb./in.) m 0

% of Compression (Length) = (L’ L) / L × 100 (%) 0 0

References

[1] http://www.instron.us/wa/products/universal_material/5560.aspx [2] All small iconic pictures are taken from documentations supplied by Instron at

purchase.

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