Mae244tesile Test and Impact Testlab-1B.1

MAE244Tesile Test and Impact TestLab-1b.1

Tensile Test and Impact Test

Introduction

Material characterization of conventional metals and advanced materials such as fibrous composites is of fundamental importance. Standardized tests are performed regularly in industry to validate quality control and product reliability. The tensile test is a basic test for determining elastic constants, such as Young's Modulus and Poisson's ratio, strengths such as yield strength and ultimate tensile strength, as well as ductility such as uniform elongation and elongation to failure. The impact test is a common test for evaluating the toughness of materials. This experiment will be performed to demonstrate common methods used in material characterization.

Objectives

To learn the operation of modern tensile and impact testing equipment. To conduct tensile tests on ductile and brittle materials, aluminum and Plexiglas, and to perform impact tests, both for characterizing the toughness properties of engineering materials, and for analyzing the factors, criteria and results that define the process of shock absorption during impact.

Equipment

Tensile Test –

Instron electromechanical testing machine (1125 Lb capacity), aluminum and plexiglas tensile specimens, clip gage extensometer, micrometer.

Impact Test -

Sonntag Universal Impact Machine (240 ft-lb capability), steel and plastic impact specimens, wrench and specimen holder, ruler.

Procedure

Tensile test

The following provides a step by step guide to running a modern materials testing machine. The series IX software is a data acquisition and control software for the Instron 4411 testing machine. READ and follow the instructions carefully.

Initial tests will be run using the cardboard specimens. After each student is comfortable performing a test with the cardboard, the aluminum and plexiglas specimens will be tested.

Power-up and Familiarization

1.Power-up the Instron test machine and the PC next to it.

2.Double-Click the “Instron” icon in the windows menu to start the test software.

Specimen preparation, Extensometer Attachment, Calibrations and Limits

3. Take the dimensions (thickness and width) of the test specimen and record on your data sheet.

4. Insert specimen into the upper grip and firmly tighten grip. Do not over-tighten. Make sure that the specimen is aligned in the upper grip. Misalignment can cause non uniform stress distribution due to bending and incorrect and premature failure patterns. Position the specimen approximately 1 inch into the grip before tightening.

5. Using appropriately sized specimen clips, attach the extensometer to the specimen as demonstrated by the instructor (Note that the extensometer is attached to the unloaded, or un-gripped specimen, so that strain induced by the gripping force is accounted for ).

6.If, needed, lower upper grip using the crosshead jog control

7.Calibrate the load cell by pressing Load/Cal, wait for 1000 on screen and press enter, wait until the light is off.

8.Calibrate the extensometer by pressing strain/Cal, wait for 100 (100 % strain) on screen, and press enter, wait until the light is off.

9. Press the “GL Reset” (gage length reset) button. This establishes a zero for the test.

10. Firmly attach it to the other end of the specimen paying attention to specimen alignment.

1. Check to see that maximum load is set at 1000 Lbs. While the minimum load is set at –10

Lbs.

12.Press the IEEE button so that it is lit. This returns control to the computer.

At this point the test machine, data acquisition and test specimen are ready for testing. If you are conducting multiple tests on the same material, skip to step 14.

Test Sequence

13.On the ‘Home Screen’, press the ‘Test’ icon. This is done only once for a series of tests (i.e. for several specimens of one material type that will be averaged together). When separate tests are conducted (e.g. aluminum, plexiglas) there will be two separate ‘tests’ run.

14.The software will prompt you for a filename to store the raw data. Type the filename

mae53A1.mrd (A1 is your group name)

Choose "OK". It is "OK" to overwrite this file. A window will then display information regarding test method and sample ID. If everything looks ok, choose "OK". (see note above pertaining to different test).

15. Choose Test Method as "65 MAE53", then "OK".

1. The test screen will appear. Choose "setup" in "Graph" menu.

1. Take off "Auto scale" and input the right X-Y scales for the specimen, then "OK".

MaterialX scale maxY scale Max

Aluminum-5 to 20%0 to 60,000 psi

Plexiglas0 to 4%0 to 10,000 psi

1. Choose "Start Test" on the test screen, input the specimen dimensions: width and thickness.

19.The screen will indicate that the test is starting, choose "OK".

20.The test will begin and you will see the stress-strain data on the screen ‘live’. When the test is completed, the stress-strain plot will automatically resize to fit the data.

21.To remove the specimen, push the IEEE button (LED light goes OUT) to return control back to the test machine.

22.Carefully remove the extensometer, place it back on the holder and then remove the specimen from the grips.

23. Press the yellow return button [RTN] to move the specimen grip back to initial position.

24. Write down the test results reported on the computer screen.

25. Select "End Sample" and wait for printing graph is aborted by "cancel".

36. Select "Continue", then on the "report to" screen, select "none", then "OK".

Each student should perform a test with the cardboard specimens. To Run another test, return to step 15 and repeat the test sequence.

Aluminum and Plexiglas Specimens

Raw test data for aluminum and Plexiglas test specimens will be analyzed in the lab report. Raw data from the test will be recorded and saved on a file for the analysis. The students should also record screen calculation values (max stress, strain, modulus, etc.) for comparison with home calculations using the raw data. In running the tests, consider the following differences:

• extensometer test clips will need to be changed to accomodate thinner specimens.
• The displacement rate should be set at 0.1 in/min.
• Data file names will be different for each test. Assume the following

Aluminum:ALUMX(e.g.ALUMTB)

PlexiglasPLEXX

where X corresponds to your group number (e.g. A, B, ...)

Data Retrieval

Once the tests are completed, you can replay the test, modify raw data or create output files for manipulation outside the Instron software environment (which is what we intend to do). This requires some rather tedious footwork, so pay attention here to avoid error. Your data exists in ‘Instron’ format, so it must be converted to ASCII format for you to read and write in EXCEL or other spreadsheet packages.

1. Under the main menu of the Instron software, select “Utilities”

1. Choose ‘raw data’ and then ‘display raw data’. Type in the sample ID (filename of tests), then click "F10".

1. To create the ASCII file, select ‘file’ from the raw data menu followed by ‘create ASCII file’.

1. In the menu window that appears, double click on the ‘header’ and select ‘Raw Data’. This puts test in formation and raw data on the output file, select "F10" to create the ASCII file.

1. When finished, select "quit" and return to the Utilities screen. Select "home screen" back to Home Screen.
2. Click "Exit" to MS Windows

1. Use file manager on Main Group to find the file. The file name will appear as ‘filename.mad’ (Do not select the filename.mrd which has the Instron format) and can be found using the path ‘Instron/s9/data’.
2. Double click the filename to show the ASCII file window, make sure get the right data file.

1. Save the data from the two tests on a floppy disk.
2. Close the file manager window, close the windows to MS-DOS.
3. Shut down the computer and the Instron machine.

Data Format:

The data on the disk will appear in three columns: increment number, displacement, or L (in inches) and load in Lbs.. You will need to convert the data to stress and strain for analysis and plotting:

stress = load(Lbs)/cross section area (units = Lbs/in2 or psi)

strain = L (inches)/gauge length (= 2 inches)(units = in /in)

Impact Test -

ATTENTION!!This experiment involves high-speed motion objects that may cause injury under improper actions. Follow the TA’s instructions. Do not play with the pendulum.

Procedures for the IZOD impact Experiment

Set-up Sequence

1. Move up the hammer of the pendulum to the 240 ft-lb position, so that the indicator arm is pointing to zero.
2. Without any specimen mounted, release the pendulum, and record the reading of the indicator arm (in ft-lb).
3. Repeat steps 1 and 2 until the calibration is consistent.
4. Repeat steps 1 and 2 for the 100 ft-lb position.

Impact Test

1. Rest the hammer on a steel block away from the vertical position.
2. Use the wrench to mount the steel specimen on the specimen holder. Make sure that the notch is just above the top of the holder.
3. Move up the hammer of the pendulum to the 240 ft-lb position with the indicator arm pointing to zero.
4. Release the pendulum, and record the reading of the indicator arm (in ft-lb)..
5. Repeat steps 5 to 8 for the plastic specimen. The pendulum must set at 100 ft-lb position in order to test plastic specimen.

Impact Energy

1. Move up the hammer of the pendulum to the 240 ft-lb position, so that the indicator arm is pointing to zero. Measure the height of hammer at this position.
2. Move the hammer of the pendulum to the other side until the indicator arm points the reading of steel specimen test. Measure the height of hammer at this position.
3. Repeat steps 10and 11 for plastic specimen.

Report (Discussion items indicated in italics)

Tensile Test –

1. Convert the experimental data to stress versus strain diagrams.
2. Determine the Young's Modulus (slope of linear portion of the curve), yield stress (defined by 0.2% offset) and ultimate stress for both materials and tabulate. Compare experimentally determined values with the expected values in a table and discuss the accuracy of the comparisons.
3. Report the total strain before rupture for each material and compare with textbook value in a table. Qualitatively discuss the type of failure (i.e. the appearance of the fracture). Also, discuss the ductility of the specimen in terms of the total strain before rupture. Which material has the highest elongation at failure?
4. Estimate the material toughness for both materials and compare these with calculations made by the test software. Can brittle material and ductile materials have the same toughness?

Impact Test -

1. Compare the measured values of the impact energy with those calculated from the heights of the hammer at the two limits of its swing motion. Determine the weight of hammer. Are the data consistent across the different methods?
2. Qualitatively discuss the type of failure (i.e. the appearance of the fracture).

AluminumPlexiglas