Mechanical APDL Structural Analysis Guide

4.4.2.1. Modeling Hints

Both a linear constitutive model and mass must be defined. Material properties may be linear, isotropic
or anisotropic, and constant or field-dependent. Nonlinear material properties are ignored.

Only linear behavior is valid in a harmonic analysis. Nonlinear elements, if any, will be treated as linear
elements. If you include contact elements, for example, their stiffnesses are calculated based on their
initial status and are never changed. (For a prestressed full harmonic analysis, the program assumes
that the initial status of the contact elements is the status at the completion of the static prestress
analysis.) The reported nodal forces due to contact elements (FSUM,,CONT and NFORCE,CONT) are also
based on the initial configuration, which may violate equilibrium conditions.

For a full harmonic analysis, frequency-dependent elastic and damping behaviors are supported using:

• An elastic or structural damping material data table (TB and TBFIELD)


• A viscoelastic material (for more information, see Viscoelasticity in the Mechanical APDL Material Reference)


• A spring/damper element (COMBIN14)

4.4.3. Apply Loads and Obtain the Solution

In this step, you define the analysis type and options, apply loads, specify load step options, and initiate
the finite element solution. Details of how to do these tasks are explained below.

Note

Peak harmonic response occurs at forcing frequencies that match the natural frequencies of

your structure. Before obtaining the harmonic solution, you should first determine the natural

frequencies of your structure by obtaining a modal solution (as explained in Modal Analys-

is (p. 39)).

4.4.3.1. Enter the ANSYS Solution Processor

Command(s):/SOLU
GUI: Main Menu> Solution

4.4.3.2. Define the Analysis Type and Options.

ANSYS offers these options for a harmonic analysis:

Table 4.1: Analysis Types and Options

Com- GUI Path

mand

Option

New Analysis ANTYPE Main Menu> Solution> Analysis Type> New Analysis

Main Menu> Solution> Analysis Type> New Analys-

is> Harmonic

Analysis Type: Harmonic ANTYPE

Main Menu> Solution> Analysis Type> Analysis

Options

Solution Method HROPT

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Harmonic Analysis