Mechanical APDL Structural Analysis Guide

3.7.1. An Example Modal Analysis (GUI Method)

3.7.2. An Example Modal Analysis (Command or Bat ch Method)

3.7.3. Brake Squeal (Prestressed Modal) Analysis

3.7.4. Reuse of Jobname.MODESYM in QRDAMP eigensolver

3.7.5. Calculate the Complex Mode Contribution Coefficients (CMCC)

3.7.6. Where to Find Other Modal Analysis Examples

3.7.1. An Example Modal Analysis (GUI Method)

In this example, you perform a modal analysis on the wing of a model plane to demonstrat e the wing's
modal degrees of freedom.

3.7.1.1. Problem Description

This is a modal analysis of a wing of a model plane. The wing is of uniform configuration along its
length, and its cross-sectional area is defined to be a straight line and a spline, as shown. It is held fixed
to the body on one end and hangs freely at the other. The objective of the problem is to demonstrate
the wing's modal degrees of freedom.

3.7.1.2. Problem Specifications

The dimensions of the wing are shown in the problem sketch. The wing is made of low density poly-
ethylene with the following values:

Young's modulus = 38x10^3 psi

Poisson's ratio = .3

Density = 8.3e-5 lb-sec^2 /in^4

3.7.1.3. Problem Sketch

Figure 3.1: Diagram of a Model Airplane Wing

x

y

2 "

10 "

A

Slope= 0 .25

B

C

D

z E

B(2,0,0)

C(2.3,.2,0)

D(1.9,.45,0)

E(1,.25,0)

The detailed step-by-step procedure for this example, Modal Analysis of a Model Airplane Wing, is in-
cluded in the Modal Tutorial.

3.7.2. An Example Modal Analysis (Command or Batch Method)

You can perform the example modal analysis of a model airplane wing using the commands shown
below instead of GUI choices. Items prefaced with an exclamation point (!) are comments.

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Modal Analysis Examples