Modal Analysis Overview

Description

Use modal analysis to calculate the natural frequencies and mode shapes of your model.

You can also see the response to the natural frequencies of your model when it is subjected to time-dependent and/or oscillatory/vibration loads by running any dynamic analysis: dynamic time, dynamic frequency, dynamic random, or dynamic shock.

Perform a modal analysis when you want Creo Simulate to calculate the following:

• natural or resonant frequencies (eigenvalues) of the model

• relative displacements of the geometry when the model is vibrating at these frequencies (modes or eigenvectors)

Typically, engineers need to know these natural frequencies for situations where the structure is exposed to excitation forces. In this case, the part may resonate and fail if the excitation frequencies coincide with the natural frequency of the structure. Even if the excitation frequency is offset from the natural frequency, it may still be close enough to produce undesirable vibrations.

In modal analysis, it is important that you accurately model the mass and stiffness distribution. Small features that are important in static stress analysis (to avoid stress concentrations) are not as important in a modal analysis.

When deciding what factors to include in your analysis, you will want to consider the following aspects of your model:

• The number of modes of vibration you want to calculate

• The frequency range you want to select

• The constraint state of your model

• Sometimes, it is also important to include the effects of prestress in an analysis—if you are, for example, studying the vibration of a structure under a tensile load. In this case, you can use prestress modal analysis.

• In most cases, symmetry conditions should be avoided in modal analysis since only the symmetric modes will be captured.

Requirements

• 0 or 1 constraint set

See Constraint and Load Sets in Structural Analyses for more information.