# Cylindrical Material Poling

If you attempt to pole radially a cylindrical element to get the acoustic properties, the cylinder will have to be broken into many smaller elements and individually poled.

Here's how to do it.

# Section 1: How to pole radially a cylindrical model

So, first, the model does need to be broken into smaller elements that all have their own poling direction but this can be automated to a certain extent by passing a custom coordinate system to the material.

Here's a video showing how to do that

Here's an example file with cylindrical poling implemented for a cylinder:

Download: Radial Poling Example

# Section 2: Step by step process for radial poling

Let's see step by step how to create a new cylinder poling axis and how to assign it to the material.

## Step 1- Create a new cylinder Axis

In the Axis command, add the 2 following commands:

```axis
form vctr
defn posx car2 0. 0. 0.    1.  0.  0.   0. 1. 0.
defn negx car2 0. 0. 0.   -1.  0.  0.   0. 1. 0.
defn posy car2 0. 0. 0.    0.  1.  0.   0. 0. 1.
defn negy car2 0. 0. 0.    0. -1.  0.   0. 0. 1.
defn posz car2 0. 0. 0.    0.  0.  1.   1. 0. 0.
defn negz car2 0. 0. 0.    0.  0. -1.   1. 0. 0.
form angl
defn cylnaxis cyln 0. 0. 0. 90. 0. 0.
end
```

## Step 2 - Associate this axis in the material

Find the Axis command in the material definition and modify it like this:

```axis aln cylnaxis plusr 0. 360. 120.   /* relate materials local system to global system
```

The convention used here is the following:

`axis    matname axisname option thetabeg thetaend ntheta phibeg phiend nphi`

The parameters are the following:

option: Enter PLUSR for poling in the radial direction (i.e. the z’ axis of the material coincides with the local radial direction). MINUSR for poling in the negative radial direction

thetabeg, thetaend, ntheta: ntheta orientations will be defined between thetabeg, thetaend. Theta should be input in degrees

phibeg, phiend, nphi: For spherical systems, nphi orientations will be defined between phibeg, phiend. phi should be input in degrees.

Note: For cylindrical or spherical systems, multiple materials with the same basic properties but different orientations may be automatically generated. These will be assigned names matname:1, matname:2, etc. As a shortcut, PLUSR & MINUSR map the z’ direction of the defined material to radial in AXISNAME.

# Section 3: More details

If you want to know more, check the documentation of the matr-axis command.

1. Right-click on the command axis within the matr command
2. Click on "Show-Help for matr-axis"