Tensile Testing Procedures:
- Measure the cross-sectional area (Thickness and Width) of the specimens by using the caliper.
- Load the specimen to the equipment.
- Clamp the specimen tightly by the upper clamp
- Lower the specimen to the bottom clamp slowly and tighten it by hand
- Activate the specimen protection
- Set all the reading to zero
- Execute the test
- Get the data, fill in the following table and plot the graph of Stress vs. Strain using Excel.
- Remove the specimen.
Compare all the three curves in one frame of axes and discuss about the differences.
*The three graphs includes Aluminum-Copper alloy bar, Polyethylene and Polystyrene.
The Polystyrene takes the longest to snap, followed by Polyethylene and then by Aluminum-Copper alloy bar.
For Aluminum-Copper alloy bar:
•Rank 1st in Stiffness
•Rank 2nd in Ductility
•Rank 2nd in Stiffness
•Rank 3rd in Ductility
•Rank 3rd in Stiffness
•Rank 1st in Ductility
Why are there variations in mechanical properties of materials of the same type?
There are different density and atom bonds in the materials. Density and Atom bonds will affect their mechanical properties even though they are of the same type.
Why differences exist in mechanical properties of different materials?
Atom bonds. How the atom bonds and the amount of atoms actually affects the mechanical properties.
What is the major difference between polymer and metals in terms of mechanical behavior?
The Modulus of Elasticity, Ultimate Tensile Strength, Ductility and Toughness.
MSE 2 - Scanning Electron Microscope (SEM)
Outcome of project:
To learn how to use a Scanning Electron Microscope and using it to find out the composition of materials.
Procedures (to be done in software):
1) Vent the column and insert specimen
2) Pump down (evacuate)
3) Select accelerating voltage, spot size and working distance
4) Turn on high voltage
5) Select load current (3-5kv for polymers and 15kv for metals and ceremics)
6) Turn up filament slowly (touch the orange bar)
7) Select TV rate
8) Adjust the image and save
1) What do you think may be caused if there is too much moisture on the specimen?
The moisture will either be sucked out of the specimen together with the air in the chamber or float around in the vacuum, obstructing the user's view of the specimen.
2) Why can't we heat the filament too fast?
Since the temperature inside the vacuum is very low, heating the filament up at a fast rate will cause it to shatter due to thermal shock. This happens when an object, for example a glass, is quickly heated up from a low temperature to a higher temperature at a fast rate. This will different rate of expansion between the glass' layers will then cause it to shatter, similar to the filament if it is heated too fast.
Aim: To fabricate fibre-reinforced composites.
1) Take 6 pieces of the fibre matt.
2)Pour 20 grams of hardener solution and 30 grams of epoxy in a styrofoam cup and mix the solution for 2-3 minutes
3)Arrange the plastic sheet, teflon sheet and tissue paper in the following way:
-> Plastic sheet
->Fibre + epoxy
4)Put the first fiber matt on the Teflon sheet
5)Pour a small amount of the solution on the fibre matt and spread it on its surface
6)Quickly put the second fiber matt on top of the first fiber matt
7)Pour some of the solution on the second fiber surface
8)Repeat steps 6-7 for the rest of the fibre matts
9)Quickly cover the fiber matt with Teflon sheet, tissue paper and plastic sheet as shown in the arrangement in step 3
10)Put on some weight on the finished product and leave it for 1-2 hours.