# Flexible Channel Beam

Channel beam with elastic properties for deformation

• Library:
• Simscape / Multibody / Body Elements / Flexible Bodies / Beams

## Description

The Flexible Channel Beam block models a slender beam with a C-shaped cross-section, also known as a C-beam. The C-beam consists of two horizontal components, known as flanges, that are connected by one vertical component, which is called a web. The C-beam can have small and linear deformations. These deformations include extension, bending, and torsion. The block calculates the beam cross-sectional properties, such as the axial, flexural, and torsional rigidities, based on the geometry and material properties that you specify.

The geometry of the C-beam is an extrusion of its cross-section. The beam cross-section, defined in the xy-plane, is extruded along the z-axis. To define the cross-section, you can specify its dimensions in the Geometry section of the block dialog box. The figure shows a C-beam and its cross-section. The reference frame of the beam is located at the centroid of the web.

Flexible beams are assumed to be made of a homogeneous, isotropic, and linearly elastic material. You can specify the beam's density, Young’s modulus, and Poisson’s ratio or shear modulus in the Stiffness and Inertia section of the block dialog box. Additionally, this block supports two damping methods and a discretization option to increase the accuracy of the modeling. For more information, see Overview of Flexible Beams.

## Ports

### Frame

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Frame by which to connect the beam in a model. In the undeformed configuration, this frame is at half the beam length in the -z direction relative to the origin of the local reference frame.

Frame by which to connect the beam in a model. In the undeformed configuration, this frame is at half the beam length in the +z direction relative to the origin of the local reference frame.

## Parameters

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### Geometry

Distance between the outer faces of the two flanges. The ```End-to-End Height``` is also known as the beam depth.

Note

The `End-to-End Height` must be larger than the sum of the two flange thicknesses.

Distance between the two faces of the web.

Note

The `Web Thickness` must be smaller than the width of the flanges.

Distance between the two ends of the top flange.

Distance between the two faces of the top flange.

Distance between the two ends of the bottom flange.

Distance between the two faces of the bottom flange.

Extrusion length of the beam. The beam is modeled by extruding the specified cross-section along the z-axis of the local reference frame. The extrusion is symmetric about the xy-plane, with half of the beam being extruded in the negative direction of the z-axis and half in the positive direction.

### Stiffness and Inertia

Mass per unit volume of material—assumed here to be distributed uniformly throughout the beam. The default value corresponds to aluminum.

Elastic properties in terms of which to parameterize the beam. These properties are commonly available from materials databases.

Young's modulus of elasticity of the beam. The greater its value, the stronger the resistance to bending and axial deformation. The default value corresponds to aluminum.

Poisson's ratio of the beam. The value specified must be greater than or equal to `0` and smaller than `0.5`. The default value corresponds to aluminum.

Shear modulus (or modulus of rigidity) of the beam. The greater its value, the stronger the resistance to torsional deformation. The default value corresponds to aluminum.

Calculated values of the mass and stiffness sectional properties of the beam. Click Update to calculate and display those values.

The properties given include Centroid and Shear Center. The centroid is the point at which an axial force extends (or contracts) the beam without bending. The shear center is that through which a transverse force must pass to bend the beam without twisting.

The stiffness sectional properties are computed as follows:

• Axial Rigidity: EA

• Flexural Rigidity: [EIx, EIy]

• Cross Flexural Rigidity: EIxy

• Torsional Rigidity: GJ

The mass sectional properties are computed as follows:

• Mass per Unit Length: ρA

• Mass Moment of Inertia Density: [ρIx, ρIy]

• Mass Product of Inertia Density: ρIxy

• Polar Mass Moment of Inertia Density: ρIp

The equation parameters include:

• A — Cross-sectional area

• ρ — Density

• E — Young's modulus

• G — Shear modulus

• J — Torsional constant (obtained from the solution of Saint-Venant's warping partial differential equation)

The remaining parameters are the relevant moments of area of the beam. These are calculated about the axes of a centroidal frame—one aligned with the local reference frame but located with its origin at the centroid. The moments of area are:

• Ix, Iy — Centroidal second moments of area:

$\left[{I}_{x},{I}_{y}\right]=\left[\underset{A}{\int }{\left(y-{y}_{c}\right)}^{2}dA,\underset{A}{\int }{\left(x-{x}_{c}\right)}^{2}dA\right]$,

• Ixy — Centroidal product moment of area:

${I}_{xy}=\underset{A}{\int }\left(x-{x}_{c}\right)\left(y-{y}_{c}\right)dA$,

• Ip — Centroidal polar moment of area:

${I}_{P}={I}_{x}+{I}_{y}$,

where xc and yc are the coordinates of the centroid.

### Damping

Damping method to apply to the beam:

• Select `None` to model undamped beams.

• Select `Proportional` to apply the proportional (or Rayleigh) damping method. This method defines the damping matrix [C] as a linear combination of the mass matrix [M] and stiffness matrix [K]:

$\left[C\right]=\alpha \left[M\right]+\beta \left[K\right]$,

where α and β are the scalar coefficients.

• Select `Uniform Modal` to apply the uniform modal damping method. This method applies a single damping ratio to all the vibration modes of the beam. The larger the value, the faster vibrations decay.

Coefficient, α, of the mass matrix. This parameter defines damping proportional to the mass matrix [M].

#### Dependencies

To enable this parameter, set Type to `Proportional`.

Coefficient, β, of the stiffness matrix. This parameter defines damping proportional to the stiffness matrix [K].

#### Dependencies

To enable this parameter, set Type to `Proportional`.

Damping ratio, ζ, applied to all beam vibration modes in the uniform modal damping model. The larger the value, the faster beam vibrations decay.

• Use ζ = 0 to model undamped beams.

• Use ζ < 1 to model underdamped beams.

• Use ζ = 1 to model critically damped beams.

• Use ζ > 1 to model overdamped beams.

#### Dependencies

To enable this parameter, set Type to ```Uniform Modal```.

Data Types: `double`

### Discretization

Number of finite elements in the beam model. Increasing the number of elements always improves accuracy of the simulation. But practically, at some point, the increase in accuracy is negligible when there are many elements. Additionally, a higher number of elements increases the computational cost and slows down the speed of the simulation.

### Graphic

Choice of graphic used in the visualization of the beam. The graphic is by default the geometry specified for the beam. Change this parameter to `None` to eliminate this beam altogether from the model visualization.

Parameterization for specifying visual properties. Select `Simple` to specify color and opacity. Select `Advanced` to add specular highlights, ambient shadows, and self-illumination effects.

RGB color vector with red (R), green (G), and blue (B) color amounts specified on a 0–1 scale. A color picker provides an alternative interactive means of specifying a color.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Simple`.

Graphic opacity specified on a scale of 0–1. An opacity of `0` corresponds to a completely transparent graphic and an opacity of `1` to a completely opaque graphic.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Simple`.

True color under direct white light specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. An optional fourth element specifies the color opacity also on a scale of 0–1. Omitting the opacity element is equivalent to specifying a value of `1`.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Advanced`.

Color of specular highlights specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Advanced`.

Color of shadow areas in diffuse ambient light, specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Advanced`.

Surface color due to self illumination, specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Advanced`.

Sharpness of specular light reflections, specified as a scalar number on a 0–128 scale. Increase the shininess value for smaller but sharper highlights. Decrease the value for larger but smoother highlights.

#### Dependencies

To enable this parameter, set :

1. Type to `From Geometry`.

2. Visual Properties to `Advanced`.

### Frames

Select to expose the A port.

Select to expose the B port.

Click the Create button to open a pane for creating a new body-attached frame. In this pane, you can specify the name, origin, and orientation for the frame.

• To name the custom frame, click the text field of the Frame Name parameter. The name identifies the corresponding port on the beam block and in the tree view pane of the Mechanics Explorer.

• To select the Frame Origin for the custom frame, use one of the following methods:

• At Reference Frame Origin: Make the new frame origin coincident with the origin of the reference frame of the undeformed beam.

• Based on Geometric Feature: Make the new frame origin coincident with the center of the selected undeformed geometry feature. Valid features include surfaces, lines, and points. Select a feature from the visualization pane, then click Use Selected Feature to confirm the location of the origin. The name of the origin location appears in the field below this option.

• To define the orientation of the custom frame, under the Frame Axes section, select the Primary Axis and Secondary Axis of the custom frame and then specify their directions.

Use the following methods to select a vector for specifying the directions of the primary and secondary axes. The primary axis is parallel to the selected vector and constrains the remaining two axes to its normal plane. The secondary axis is parallel to the projection of the selected vector onto the normal plane.

• Along Reference Frame Axis: Selects an axis of the reference frame of the undeformed beam.

• Based on Geometric Feature: Selects the vector associated with the chosen geometry feature of the undeformed beam. Valid features include surfaces and lines. The corresponding vector is indicated by a white arrow in the visualization pane. You can select a feature from the visualization pane and then click Use Selected Feature to confirm the selection. The name of the selected feature appears in the field below this option.

Frames that you have created. `N` is a unique identifying number for each custom frame.

• Click the text field to edit the name of an existing custom frame.

• Click the Edit button to edit other aspects of the custom frame, such as origin and axes.

• Click the Delete button to delete the custom frame.

#### Dependencies

To enable this parameter, create a frame by clicking New Frame.