Description
Prerequisites
Course Content
MATERIALS
Mechanical Properties:
- Properties can be visualized on a stress-strain (force-displacement) curve.
- Stress- force applied over an area [Pa]
$$
\sigma = \dfrac{F}{A_o}
$$
- Strain- change in length compared to an object’s original length [unitless]
$$
\epsilon = \dfrac{\delta L}{L}
$$
- Modulus (stiffness)- factor that relates stress to strain; slope in the elastic region of the stress-strain curve [Pa]
$$
E = \dfrac{\sigma}{\epsilon}
$$
- Ductility- max displacement before breaking [m]
- Toughness- energy required to break a material; the area under the stress-strain curve before the breaking point
The three defining properties of a material are yield strength, modulus, and ductility.
Three Basic Materials:
| Material |
Strength |
Modulus |
Ductility |
Conductivity |
Melting Point |
Bonding |
| Metals |
High |
High |
High |
High |
Middle |
Metallic |
| Polymers |
Low |
Low |
Varies |
Low |
Low |
Covalent |
| Ceramics |
High (compression) |
Higher |
Low |
Low |
High |
Covalent/ionic |