Mechanical APDL Structural Analysis Guide

Figure 4.3: An Unbalanced Rotating Antenna

Plan

2 1

3 4

Frameof
Reference

Ωt

Elevation

W

Rotating

antenna

4 - pointsupport

Ω

(FrameofReference)

FZ=F
cos(Ωt- 45 °)

FZ=F
cos(Ωt- 135 °)

(FZ 3 andFZ 4 omittedforclarity)

An unbalanced rotating antenna will produce out-of-phase vertical loads at its four

support points.

Note

A harmonic analysis cannot calculate the response to multiple forcing functions acting sim-

ultaneously with different frequencies (for example, two machines with different rotating

speeds running at the same time). However, POST1 can superimpose multiple load cases to

obtain the total response.

Table 4.2: Applicable Loads in a Harmonic Analysis (p. 83) summarizes the loads applicable to a harmonic
analysis. Except for inertia loads, you can define loads either on the solid model (keypoints, lines, and
areas) or on the finite element model (nodes and elements). For a general discussion of solid-model
loads versus finite element loads, see Loading in the Basic Analysis Guide.

Table 4.2: Applicable Loads in a Harmonic Analysis

Cmd GUI Path

Family

Load Type Category

Main Menu> Solution> Define Loads> Ap-

ply> Structural> Displacement

Displacement (UX, Constraints D

UY, UZ, ROTX, ROTY,

ROTZ)

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

Performing a Harmonic Analysis