| Mechanics: Stress and strain |
| Free Body Diagrams (Review) | |
| Stress | |
| Strain | |
| Deformation | |
| Hooke’s Law | |
| Stress-Strain Diagrams | |
| Design: The Safety Factor |
| Shows all external forces acting on the body | |||
| Procedure | |||
| Identify the isolated body and draw it | |||
| At all force locations draw the vectors | |||
| Supports | |||
| Connections | |||
| Contacts | |||
| Add the Weight force | |||
| Label forces with their value or a letter for unknowns | |||
| Add a coordinate system | |||
| Add geometric data (Lengths, angles, … ) | |||
| Internal Forces | |||
| Reaction to external forces | |||
| Distributed throughout volume of material | |||
| Stress | |||
| Normal stress | |||
| Acts at right angles to a selected plane | |||
| The axial direction in a rod or cable | |||
| Shear stress: stays in the selected
plane (advanced topic: Strength of materials course) |
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| Can a structure withstand the forces applied to it? | |||
| s = P/A (Pascals) | ||
| s: Average stress | ||
| P: Applied force | ||
| A: Cross section area | ||
| Tension / Compression | ||
| Strain: deformation due to stress | |||
| e = d / L | |||
| e: Normal strain | |||
| d: Change in length | |||
| L: Original (unstressed) length | |||
| Springs F = kx |
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| F: Applied Force | ||
| k: Spring constant | ||
| x: displacement | ||
| Stress-Strain s = Ee |
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| s: Stress | ||
| E: Modulus of Elasticity | ||
| e : Strain | ||
| 200 kg engine block | ||
| Cables | ||
| 0.7 m long | ||
| 4 mm diameter | ||
| E = 200 GPa | ||
| Find | ||
| Normal Stress | ||
| Axial Deformation | ||