# Subspace-based steady-state dynamic analysis

 A subspace-based steady-state dynamic analysis: is used to calculate the steady-state dynamic linearized response of a system to harmonic excitation; is based on projection of the steady-state dynamic equations on a subspace of selected modes of the undamped system; is a linear perturbation procedure; provides a cost-effective way to include frequency-dependent effects (such as frequency-dependent damping and viscoelastic effects) in the model; allows for nonsymmetric stiffness; requires that an eigenfrequency extraction procedure be performed prior to the steady-state dynamic analysis; can use the high-performance SIM software architecture (see Using the SIM architecture for modal superposition dynamic analyses); is an alternative to direct-solution steady-state dynamic analysis, in which the system's response is calculated in terms of the physical degrees of freedom of the model; can include computation of acoustic contribution factors to help determine the major contributors to acoustic noise; is computationally cheaper than direct-solution steady-state dynamics but more expensive than mode-based steady-state dynamics; is less accurate than direct-solution steady-state analysis, in particular if significant material damping or viscoelasticity with a high loss modulus is present; and is able to bias the excitation frequencies toward the values that generate a response peak. The following topics are discussed:
 Related Topics Defining an analysis General and perturbation procedures About dynamic analysis procedures Direct-solution steady-state dynamic analysis Natural frequency extraction Mode-based steady-state dynamic analysis In Other Guides *STEADY STATE DYNAMICS Configuring a subspace-based steady-state dynamic analysis

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