Damping (Simcenter Samcef)

Damping is energy dissipation in a structure. In the Simcenter Samcef environment, you can set proportional damping options in physical property tables. This allows you to set damping options for groups of elements. If you are setting up a dynamic response analysis (linear transient or linear harmonic), you can additionally set structural (Rayleigh) damping and modal damping at the solution level.

Proportional damping

In proportional damping, the damping matrix is proportional to the mass and stiffness matrices. You can set the following types of physical damping:

• Viscous (or non-modal) damping is proportional to velocity and is caused by viscous effects, such as in a shock absorber.You define both the stiffness proportionality factor (Viscous Stiffness Factor (ALPHA)) and the mass proportionality factor (Viscous Mass Factor (BETA)) values.You can define Viscous Stiffness Factor (ALPHA) as constant or variable.**Viscous Stiffness Factor (ALPHA)**Supported analysis typeConstantDynamic response analysis (linear transient or linear harmonic)Variable as a function of time or frequencyNonlinear analysisNote: To define Viscous Stiffness Factor (ALPHA) as a function of time or frequency, create a table field with the independent domain set to frequency or time.

• Hysteretic (or structural) damping is proportional to displacement and is caused by external friction, such as from slippage in structural joints, or by the internal friction related to the properties of the material. You can set: A stiffness hysteretic damping (Hysteretic Stiffness Factor) when you define the Hysteretic Stiffness Factor (HYST) value.A flexibility hysteretic damping (Hysteretic Flexibility Factor) when you define the Hysteretic Flexibility Factor (IHYST) value.

Critical damping

For a dynamic response analysis (linear transient or linear harmonic), you can additionally set the following critical damping options to make the ratio per element lower than the critical value that you set.

• Viscous Damping Ratio by Element (VDA)

• Hysteretic Damping Ratio per Element (HDA)

For information on the damping equations, see Diagonal Damping and Critical Damping Ratio per Element in the Dynamic response Simcenter Samcef solver documentation.

Global damping for dynamic response analyses

In addition to the proportional and critical damping that you can define for groups of elements at the mesh collector level, you can also select structural (Rayleigh) damping and modal damping at the solution level. This lets you set damping that applies to all components of a model, and then set proportional damping to areas of the model that require different or additional damping.

• Structural dampingYou can set structural (Rayleigh) damping regardless of whether you enable Modal Superposition. Rayleigh damping is defined by two coefficients—one for stiffness and one for mass.

• Modal dampingYou can set modal damping only when you enable Modal Superposition. The modal damping is optionally defined by a formula or table field of modes and corresponding critical damping rates, and a scale factor.

• Superposed structural and modal damping.You can superpose structural (Rayleigh) damping and modal damping only when you enable Modal Superposition.For information on superposing structural and modal damping, see Superpose damping in a dynamic response analysis.

For more information on these damping options, see the Solver Parameters page in the Solver Parameters page or Solver Parameters page.

For more information on the damping options you can set on the elements (physical properties), see the .AMO command in the Simcenter Samcef solver documentation.

For information on accessing physical properties so you can set proportional and critical damping options, see Define physical properties.

For a list of the physical properties that are supported by the damping options, see Physical and element properties support (Simcenter Samcef).

Look up more details

Axisymmetric Solid (structural) / Plane Stress / Plane Strain physical property dialog boxes (Simcenter Samcef)

Physical and element properties support (Simcenter Samcef)

Predefined Laminate Physical Property dialog box (Simcenter Samcef)

Solid dialog box (Simcenter Samcef)

Thin Shell dialog box (Simcenter Samcef)

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Damping (Simcenter Samcef), Simcenter 3D 2021.1 Series

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