Strength of Materials

Strength of Materials: the study of material under load

Why are nails made of steel? Boats of fiberglass? Beer cans of aluminum? Why heat treat steel? How do I make my design stiffer? Stronger? Cheaper? To correctly select materials for your project you must understand the mechanical properties of your choices. Students will observe tensile testing to failure of mild steel, high strength steel, 6061 aluminum, ash (wood), Delrin (acetal plastic) and fiberglass/epoxy. The stress/strain curve of each material will be displayed in real time. In the process students will learn what tensile strength, yield strength and modulus of elasticity are and measure them for all 6 materials. All the material properties will be graphed to compare the results so they can answer these questions:

1. What material has the highest strength per pound? Per square inch? Per dollar?
2. What material has the greatest stiffness per pound?
3. Will heat treating a steel part make it stiffer?
4. What is the difference between brittle and ductile failures and when does it matter?

Finally using the data collected the class will calculate the fatigue life of a shaft under fully reversed loading and then test it to destruction to verify their calculations.