Home / Examples / Stress Analysis [Galileo] / Example 16: Harmonic Analysis of Standing Bars

Example 16: Harmonic Analysis of Standing Bars

General

Forced oscillation is applied on two standing bars with different heights. The frequency of the forced oscillation affects the vibration.
The resulting vibrations are analyzed.
Refer to Example 75: Transient Analysis of Standing Bars for the result of the transient analysis.
Unless specified in the list below, the default conditions will be applied.
The oscillation amplitude near the resonant frequency depends on the mechanical loss. Adjust the mechanical loss if needed. (See Example 50)
Obtain this session's project file. (Right-click and choose 'Save link as')

Results will vary depending on Femtet version and the PC environment.

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

Analysis Conditions

The analysis type is harmonic analysis.

Item	Settings
Solver	Stress Analysis [Galileo]
Analysis Type	Harmonic Analysis
Options	N/A

The resonant frequencies of the respective towers are 1250 Hz and 1650 Hz, which are acquired through individual analyses.

Therefore, the sweep range is around those frequencies.

The harmonic analysis is set as follows.

Tab

Setting Item

Settings

Harmonic analysis

Frequency

Minimum: 1000 [Hz]

Maximum: 2000 [Hz]

Sweep Type

Linear Step by Number of Divisions: Number of Divisions 20

Model

Two bars (TOWER) are standing on a plate (GROUND).

As a boundary condition, the displacement boundary condition (VIBE_Y) is set to the face topology
of the bottom face of GROUND to force the displacement in the Y direction.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	TOWER	001_Al *
1/Solid	TOWER	001_Al *
2/Solid	GROUND	001_Al *

* Available from the material DB

Boundary Conditions

To make the forced vibration, the displacement is set on the bottom face
of GROUND in the Y direction and the displacement in X and Z directions are fixed.

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Settings

VIBE_Y/Face

Mechanical

Displacement

Select all X/Y/Z components.

UX=UX=0.0, UY=1×10-3 [m]

This means the magnitude of Y displacement is 1[mm].