Poisson Effect
Poisson's Ratio
A measure of the Poisson effect, the tendency of a material to expand in directions perpendicular to the direction of compression. Named after Siméon Poisson, it quantifies the relationship between lateral strain and axial strain.
Formula
ν = -ε_lateral / ε_axial
Units
Dimensionless
Range
-1.0 to 0.5
Stable Materials
0.0 to 0.5
Auxetic Materials
Negative values
Key Properties
Elastic Properties| Property | Value | Description |
|---|---|---|
| Theoretical Limits | -1.0 to 0.5 | Thermodynamic constraints |
| Stable Materials | 0.0 to 0.5 | Most engineering materials |
| Auxetic Materials | < 0 | Negative Poisson's ratio |
Crystal Structure
Metals & Alloys
Most metals exhibit Poisson's ratio values between 0.25 and 0.35, with approximately 0.3 being the most common. This is due to the atomic bonding characteristics and crystal structures of metallic materials.
Formula
ν_metal ≈ 0.3
Units
Dimensionless
Common Metal Values
Common Values| Material | Poisson's Ratio | Structure |
|---|---|---|
| Steel | 0.27 - 0.30 | BCC/FCC |
| Aluminum | 0.32 - 0.35 | FCC |
| Copper | 0.33 - 0.36 | FCC |
| Titanium | 0.30 - 0.34 | HCP |
| Cast Iron | 0.21 - 0.26 | BCC |
Material Behavior
Other Materials
Poisson's ratio varies significantly across different material classes. Polymers, ceramics, and biological materials exhibit unique values based on their molecular structure and bonding mechanisms.
Formula
ν = -ε_lateral / ε_axial
Units
Dimensionless
Material Classes
Different Behaviors| Material | Poisson's Ratio | Behavior |
|---|---|---|
| Rubber | 0.49 - 0.50 | Near incompressible |
| Glass | 0.18 - 0.24 | Brittle |
| Cork | ~0.00 | Zero lateral strain |
| Auxetic Foam | -0.10 to -0.80 | Negative ratio |
| Concrete | 0.10 - 0.20 | Brittle |