CST2013: Material Parameters: default - General

Modeling: MaterialsNew/EditNew MaterialGeneral

Edit Object Properties (navigation tree: Materials:material1PropertiesGeneral)

This is a dialog page of the Material Parameters dialog box.

In this dialog page the main material properties can be defined. These are  the electromagnetic properties as well as thermal properties and  the visualization specification of the material.

General properties frame

This frame shows different settings depending on the chosen  Type.

The Type setting will also influence what property pages will be shown in the material parameter dialog.

Material name:

Displays the material name or offers the possibility to define the name of a new material. Please note: For the background material the name cannot be modified.

Material folder:

Displays the material folder name. You can either choose a material folder from the select list, or create a new one by typing the name of it.

Type PEC:

Perfect electrically conducting.

Coated Material...: This button will open a dialog box which offers the possibility of defining coating materials for the actual material.

Type Normal:

Material with relative permittivity epsilon and relative permeability mue.

For the "Default" and the "High Frequency" material sets electric and magnetic losses as well as dispersion models may optionally be defined on the following "Conductivity" and "Dispersion" pages.

For "Low Frequency" material sets, the electric conductivity can be defined in the "Conductivity" page.

Epsilon / Mue: Settings for the relative permittivity and relative permeability .

Please note: When defined by parameters, Epsilon and Mue can be used with sensitivity analysis (see Sensitivity Analysis for more information).

Type Anisotropic:

Identical to the normal material type, but enabling the input of diagonal anisotropic material values.

Note that this option is not available for magnetic gyrotropic dispersion and neither for LF tetrahedral simulations.

Epsilon (x/y/z) / Mue (x/y/z): In these  fields, you may enter the anisotropic values for the relative permittivity epsilon and relative permeability mue.

Please note: The labels might differ depending on the coordinate representation chosen in the Coordinates frame.

Type Lossy metal:

For good (but not perfect) electric conductors, this type simulates the associated solids by use of a one-dimensional surface impedance model. It should be noted that this model is physically reasonable only when the conductivity is so high that the dielectric and polarization effects within the material could be deemed negligible. This condition is represented by the equation (), where sigma is the material conductivity.

In this situation it can be demonstrated that the electric fields will penetrate the material only for in a very tiny layer, whose thickness (usually referred as "skin depth") is represented by the following formula

As shown by the formula, the skin depth effect is mainly an high frequency phenomenon. The higher the frequency, the better is the corresponding approximation. Thus, to take low frequencies into account, the material should be modeled applying a normal type in connection with an electric conductivity . For broadband simulations, the frequency range should be split up into two intervals. The lossy metal material is determined by the input of an electric conductivity and permeability value.

Electric conductivity / Mue: In these  fields, you may enter the electric conductivity and the relative permeability mue that describe the lossy metal.

Coated Material...: This button will open a dialog box which offers the possibility of defining coating materials for the actual material.

Please note: Defining parameters for electric conductivity/mue then they can be used with sensitivity analysis (see Sensitivity Analysis for more information).

Type Nonlinear:  (not applicable to HF simulations)

For nonlinear materials a nonlinear permeability   is defined by means of a magnetic H-B curve in the Nonlinear frame.

The nonlinear material type is only available for the "Default" and the "Low Frequency" material sets.

The Mue value in the General frame will be ignored by all solvers which support nonlinear materials. Some other solvers interpret nonlinear materials like Normal materials with the relative permeability Mue specified in the General frame.

Type Corrugated wall: (not applicable to LF simulations)

A corrugated wall is a planar surface with a periodically repeated rectangular corrugation with a certain depth, gap width, and a small tooth width.

When truly modeling these surfaces, the mesh would end up with a very high number of mesh cells to represent all details. However, in many cases, such as S-Parameter calculations, the exact field solution inside the corrugation is not of interest. Then it is sufficient to replace the real corrugation by a appropriate material with the same macroscopic properties. Much like the lossy metal, a surface impedance model is used to relate fields on the corrugated wall surface. The conditions where this model is valid are described in the Material Overview.

This type of material is available only for the transient solver and the tetrahedral frequency domain (only for the "Default" and the "High Frequency" material set).

Corrugation depth, gap width, tooth width: Here, specific dimensions of the rectangular corrugation can be defined.

Type Ohmic sheet: (not applicable to LF simulations)

A surface impedance model is used to relate fields on the ohmic sheet surface.

This type of material is available for the transient solver, the tetrahedral frequency domain and the integral equation solvers (only for the "Default" and the "High Frequency" material set.)

Resistance / Reactance / Reference freq: The complex impedance of the sheet (real and imaginary) and the reference frequency where the impedance is defined or measured. The unit is Ohm, which in the context of Ohmic Sheets is also referred to as "Ohm per square", abbreviated "Ohm-sq" in the dialog box. The "per square" refers to a DC measurement with a voltage applied across a material sample, the cross section of which is a square (stationary current with homogeneous electric field). In case the reference frequency will not be provided, the center value of the frequency simulation range will be automatically assumed.

The TLM solver Ohmic sheet model is not translucent - the fields on one side of the surface cannot pass through to the other side. This means that even for an infinitely thin object the two resistances presented to fields on each side are independent. For example consider an infinitely thin sheet of 5mm by 5mm with 250 Ohm-sq. The Transient solver will see a lumped resistor from one edge to the opposite edge of 250 Ohms and the TLM solver will see two lumped resistors of 250 Ohms in parallel, giving a total impedance across the gap of 125 Ohms.

Frequency domain solvers may assume and compute a constant (i.e. frequency independent) complex impedance for the Ohmic sheet. This constant model may be generally "non-physical" (due to the so called Kramers&endash;Kronig relations) and may lead to "non-causal" effects. Therefore, for the transient solver, a first order (Debye) model of the impedance will be assumed which exactly interpolates the user given impedance in correspondence of the reference frequency.

Coated Material...: This button will open a dialog box which offers the possibility of defining coating materials for the actual material.

Surface impedance (table): (not applicable to LF simulations)

Surface impedances relate the tangential electric and magnetic fields on surfaces of bodies (solids or sheets) to which this material has been assigned. The effect of field inside bodies is described by equivalent currents on the surface of those bodies.

Tabulated surface impedance models (only available for the transient solver and the general purpose frequency domain solver with tetrahedral mesh) are given in form of a table with their resistance and reactance tabulated versus frequency.

The frequency domain solver may compute a model directly driven by the user defined impedance. It should be noted anyway that, depending on the user data, this model may lead to some "non-physical" or "non-causal" behavior. For instance, possibly due to uncertainty or measurement errors, the so called Kramers&endash;Kronig relations could not be fulfilled. Therefore for the time domain simulation a rational fitting of the data will be performed, assuming a superposition of first or second order pole terms. A more detailed description of the model can be found in Material Overview (HF) and Tabulated Surface Impedance dialog.

Tensor formula: (not applicable to LF simulations)

This material type is only available for the general purpose frequency domain solver with tetrahedral mesh. It can be created and customized by Visual Basic (VBA) language only. See the VBA online help for the Material Object.

The complex relative permittivity and permeability tensors for this material type are given by formulas, with the frequency f in Hz being variable. An alignment vector can be specified to transform the tensors (rotation.) The material type therefore allows to use custom material models which are not yet covered by the material types mentioned above.

Thin panel: (not applicable to LF simulations)

This is a sheet-material consisting of one or more layers of 'normal' material, and is specified by listing the thickness and material of each constituent layer. The layer-materials may be dispersive and may have such high conductivity that there are many skin-depths in the layer thickness. It is thus possible to represent metallized films though the metal must be specified as a high-conductivity 'normal' material rather than as a 'lossy metal'. Unlike panels of 'lossy metal', thin panels are always penetrable to electromagnetic fields.

Each layer within the thin panel is modelled as a number of finer subsidiary layers, so that the frequency dependence of the skin-depth and wavelength is reproduced. The model is one-dimensional; it correctly represents reflection and transmission normal to the surface, but cannot  trap waves travelling over the surface or between the laminations.

Only bodies consisting of surfaces with no thickness should be specified as being thin panels. The actual thickness of the panel is taken as an electric parameter (along with the permittivity, permeability and conductivity etc.), from the layer-list, and is disregarded as a geometric property.

Thin panel materials consisting of an asymmetric sandwich of laminations may only be attached to a body having two distinct faces (an orientable manifold; not a m?bius strip and not a body with fins). The faces of the body must be distinguished by attaching a local coordiante basis to any one point in its surface, with the 'w-vector' pointing from the 'back' (first layer) to 'front' (last layer) sides. No such restrictions or requirement apply when the thin panel material is symmetric.

Suitable applications for thin panels include carbon-fibre panels on vehicles, carbon-loaded and metal-sputtered surfaces of dielectric bodies, and radome covers over horns and antennas. If penetration through the panel may be neglected, then metal sheets should be used instead.

The computer resources required to model thin panels are proportional to the number of cell faces covered with the panel (or roughly to the total area of panel), and to the number of skin-depths in the thickness of the panel (at the maximum model frequency). If thin panels are specified which are very many skin-depths thick, then the computer memory usage and run-time can become excessive. Since the penetration through many skin-depths is likely to be negligible, metal panels should be used instead (or a lower maximum frequency specified).

Moreover, this is only supported by the TLM solver and other solvers consider it as a normal material by ignoring the layers.

Only available for the "Default" and the "High Frequency" material sets and not applicable to Low Frequency simulations.

Layers...: This button will open a dialog box  which offers the possibility of defining coating materials for the actual material.

Wire mesh: (not applicable to LF simulations)

Wire mesh is a material that is typically used for electromagnetic shielding and is often sandwiches between other materials in a laminate structure..

A wire mesh can only be used on thin sheet objects, but it cannot be directly applied to a sheet object. Instead the wire mesh must first be created and then attached as a layer of a Thin panel material, and then that Thin panel material can be attached to the sheet object. Moreover, wire mesh material  is only supported by the TLM solver.

Only available for the "Default" and the "High Frequency" material sets and not applicable to Low Frequency simulations.

Shielded cable: (not applicable to LF simulations)

Shielded cables are widely used in industrial applications in order to suppress unwanted crosstalk effects between neighboring wires.

A typical shielded cable is the coaxial cable with an inner wire and a concentric outer screen.

Only thin wires can wear this material type. Moreover, this is only supported by the TLM solver.

Only available for the "Default" and the "High Frequency" material sets and not applicable to Low Frequency simulations.

Temp. dependent:

This material type allows to define temperature dependencies for the relative permittivity , relative permeability , and/or electric conductivity . In other respects this material type is synonymous with Normal. Button Properties... opens the dialog Temperature Dependent Materials.

Coordinates frame

Use local solid coordinates: Specifies whether the given material settings are to be interpreted in global coordinates or relative to local solid coordinates. By default, global coordinate settings are considered. The advantage of local solid coordinates is that if the material is applied to multiple solids the material orientation does not change when single solids are transformed.

Representation: Defines the type of the coordinate system in which the material settings are given. By default, all material settings are interpreted in Cartesian coordinates (x/y/z or u/v/w depending on the reference coordinate system). It is also possible to prescribe settings (like permeability, permittivity or conductivity) in cylindrical or spherical coordinates. To this end, the same commands are used (e.g. EpsilonX/EpsilonY/EpsilonZ), but they are interpreted as (R/phi/z) or (r/theta/phi), respectively.

For cylindrical coordinates (R,phi,z), the first component means the radial direction, where the radius R is the distance to the z/w axis. The second component prescribes the angular direction, where the azimuth phi is the angle to the x-z-plane (u-w-plane). The third component is the longitudinal direction and coincides with the Cartesian z/w component.

For spherical coordinates (r,theta,phi), the radius r specifies the distance to the origin, theta is the inclination (zenith angle) measured from the z-axis, and phi is the azimuth (angle to the x-z-plane/u-w-plane).
 

Please note: Coordinate settings are meaningful, in particular, for anisotropic materials and will be ignored for other material types. Furthermore, local solid and non-Cartesian coordinate settings are relevant only for tetrahedral solvers.

Color frame

This section allows you to specify how the corresponding solids are visualized.

Draw as wireframe:

Displays all solids associated with this material as wireframes.

Draw reflective surface:

Display all solids associated with this material using reflective surfaces (usually applied to metallic surfaces).

Allow outline display:

Determine whether outlines are allowed to be drawn for solids belonging to this material. The actual visibility of outlines also depends on the setting of the global outline state as well as the current selection. If this option is unchecked, outlines will never be drawn for the corresponding solids.

Draw outline for transparent shapes:

Determine whether outlines are also displayed when the corresponding solids are drawn transparently.

Color bar:

Click here to change the material color.

Transparency slider:

 This slider displays all associated solids in a transparent mode from 0 to 100 per cent.

Add to Material Library

Selecting this check box will open the dialog 'Add to Material Library' after pushing the OK button. (This button is NOT available for the background material)

Copy Properties from Material

Use this button to copy the material settings from another material.  (This button is ONLY available for the background material)