Stress Strain Work Sheet - Gears EdS
Stress Strain Work Sheet
Materials deform under loads. Deformation means they change shape. It is possible to experimentally determine the proportional relationship between the load (stress) in psi) and the amount of deformation (strain) in inches.
In this experiment you will create a graph that illustrates the stress/strain proportionality as well as define the elastic limit and breaking strength of a monofilament fishing line.
Directions
Research Strength of materials terms and concepts. Click here to navigate to a website that offers clear explanations of strength of materials terms.
Create a stress/strain graph for a monofilament fishing line similar to the line used to attach the projectile to the trebuchet throwing arm.
Stress is calculated using this simple algebraic formula:
Stress = Load (lbs)/ Area (square inches)
Strain = The amount of elongation due to stress
Modulus of Elasticity (E) = Stress/Strain
Additional necessary formulas
Area of a Circle = [pic]
1. Suspend a lightweight monofilament fishing line so that it hangs about 48” above the floor.
2. Drill 2 small (1/8”) holes at the top (opposite quadrants) of a coffee can and attach a coat hanger to the holes on the coffee handle to make a handle similar to a paint can.
3. Attach the coffee can to the fishing line.
4. Measure the diameter of the fishing line using the dial calipers. Calculate the cross sectional area of the fishing line.
5. Measure the height of the coffee can above the floor. Measurements should be accurate to 1/16” or 1.5 mm. Record this measurement.
6. Weight out 1/8 lb of water and pour the water into the coffee can.
7. Measure the change in height of the coffee can above the floor caused by the stretching of the fishing line in response to the added mass of water it supports.
8. Calculate the stress acting on the fishing line (See worksheet). Record this value each time water (weight) is added to the coffee can.
9. Repeat steps 4 through 6 until the fishing line breaks.
10. Graph the results of the experiment using the Stress Strain Worksheet.
Stress vs. Strain Graph
The blue graph is offered as an example of a stress vs. strain graph. It is not necessarily the graph profile you will obtain in your experiment.
Lbs/in2
-----------------------
Stress
Lbs/
Strain
(" length inches)
Note: Experimentally determine the correct range for the graph. Another idea is to use a spreadsheet program to create a graph from the experimental dat∆ length inches)
Note: Experimentally determine the correct range for the graph. Another idea is to use a spreadsheet program to create a graph from the experimental data you obtain.
Use the graph above to plot the experimental data you obtain or use a spreadsheet to create a graph from the data and measurements you obtain.
Proportional Limit
Elastic Limit
Yield Point
Ultimate Strength
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