After setting up the layers the materials assignment to the surfaces of the model is very straightforward because it becomes very easy to select all the surfaces of a given layer without picking any of the other parts of the geometry. The first step in this section is the definition of the materials to be assigned, in case that they do not already exist in the material database. For this example, we are going to consider glass, with an electric permittivity εr = 4, and rubber compound for the tires, with electric permittivity εr=7 and tan(δ)=0.04. To do so, go to Materials – Add and introduce the name of the material under Material Attributes and the permittivity and/or losses values clicking on Set Parameters. Fig. 3 shows these values for the rubber compound previously mentioned. Note that it is possible to assign a certain color for the visualization of the material on the screen later. After introducing the parameters press Save.
Figure 3: Adding a new material to the database
After including both materials, it is possible to assign them to the surfaces by selecting the layer manager and mark only the “Show” checkbox of the Wheels layer. After that select all the surfaces and click on Materials – Assign. In this example, we can select the material defined by geometry, and from the drop menu picks “Rubber Compound”, configuring the thickness of the material as well. Note that for small fractions of the wavelength the thin layer approximation is adequate and a superficial mesh and simulation can be performed. Otherwise, a volumetric mesh and analysis may be necessary. Fig. 4 illustrates the procedure commented above about the material assignment.
Figure 4: Assigning a new material to the surfaces contained in a layer, with a thickness of 2mm