# PoissonRatio¶

Type: | 2-Tensor, or section |
---|---|

Range: | [v_1, …, v_9] |

Default: | -/- |

Appearance: | optional |

Specifies the Poisson ratio of a mechanical body. When a body is stretched, the Poisson ratio describes the ratio of contraction in the plane perpendicular to the direction of applied strain to the extension in direction of applied strain. The Poisson ratio is dimensionless.

A constant Poisson ratio can be defined by assigning a rank-2 tensor:

```
Material {
# defines a constant Poisson ratio
PoissonRatio =
[..., ..., ...
..., ..., ...
..., ..., ...]
}
```

Assign a scalar for an isotropic Poisson ratio.

For more general cases, the Poisson ratio may be given as a section in order to deal with space, time, and parameter dependent definitions:

```
# define the Poisson ratio as a section
PoissonRatio {
Python {...}
...
}
```

Field definitions within the section `PoissonRatio`

are summed up. Consult the subsequent sections to see which types of field definitions are allowed.

Note

Setting the Poisson ratio together with the Young modulus, see YoungModulus, will implicitly define a stiffness matrix. For details, we refer to Stiffness.