2012 ANSYS, Inc. March 28, 2013 1 Release 14.5

14.5 Release

Workshop 5 Harmonic Response (Fixed-Fixed Beam)

ANSYS Mechanical Linear and Nonlinear Dynamics

2012 ANSYS, Inc. March 28, 2013 2 Release 14.5

Workshop 5 - Goals

Our goal is to determine the harmonic response of a fixed-fixed beam under the influence of two harmonic forces.

The forces represent rotating machines mounted at the one-third points along the beam.

The machines rotate at 300 to 1800 RPM.

The Beam (3 m x 0.5 m x 25 mm) is made of Steel.

Constrain (Fix)

Both Ends

2012 ANSYS, Inc. March 28, 2013 3 Release 14.5

Workshop 5 Project Schematic

From the project schematic, insert a new Modal system.

we will first look at the natural frequencies and mode shapes of the system

Drop a Harmonic Response system onto the Model cell of the Modal system to share the material properties, geometry, and mesh.

note that this system will not use the modes from the Modal system

Import the Geometry file

beam.agdb

2012 ANSYS, Inc. March 28, 2013 4 Release 14.5

Workshop 5 - Preprocessing Edit the Model cell to open the Mechanical application.

verify that the material assignment is Structural Steel

2012 ANSYS, Inc. March 28, 2013 5 Release 14.5

Workshop 5 Units In Mechanical, set the following units system:

mm, kg, N, s, mV, mA Degrees RPM Celcius

2012 ANSYS, Inc. March 28, 2013 6 Release 14.5

Workshop 5 - Environment

Constrain both ends of the Beam.

Click on the Modal Branch and >Insert>Fixed Support. Switch to edge selection mode as necessary Use LMB to pick the two applicable edges. Hold to add to your selections Click Apply in the Details window

2012 ANSYS, Inc. March 28, 2013 7 Release 14.5

Workshop 5 Modal Results Solve the Modal analysis.

Create some Mode Shape Results to review the results.

note that modes 1 and 2 fall between 0 and 50 Hz

2012 ANSYS, Inc. March 28, 2013 8 Release 14.5

Workshop 5 - Preprocessing

Drag and drop the Fixed Support from the Modal branch to the Harmonic Response branch.

2012 ANSYS, Inc. March 28, 2013 9 Release 14.5

Workshop 5 - Environment

In the Harmonic Response branch, apply one force to one edge.

There are two edges imprinted on the beam face. Switch to Edge selection mode as necessary and >Insert>Force. Use LMB and drag over surface to highlight to pick the applicable edge. Click Apply in the Details window In Details, change the Defined By to Components (i.e., XYZ). Enter 250 for Y. Leave Phase Angle = 0

2012 ANSYS, Inc. March 28, 2013 10 Release 14.5

Workshop 5 - Environment

Apply another force to the other edge.

set Y Component to 250 N leave Phase Angle = 0 We will investigate the results as the phase angle between these loads

changes.

2012 ANSYS, Inc. March 28, 2013 11 Release 14.5

Workshop 5 Harmonic Response Solution

Edit the Analysis Settings.

set the Range Minimum to 0 Hz set the Range Maximum to 50 Hz set the Solution Intervals to 50 set the Constant Damping Ratio to 2%

Solve the Harmonic analysis.

2012 ANSYS, Inc. March 28, 2013 12 Release 14.5

Workshop 5 Results Insert a Deformation Frequency Response.

set the scoping to all faces on the beam set the Spatial Resolution to Use Maximum set the Orientation to Y Axis

2012 ANSYS, Inc. March 28, 2013 13 Release 14.5

Workshop 5 - Results You can also plot contours at specific frequencies.

Click RMB on the solution object and >Insert> Stress, Strain, or Deformation

This will insert the result object(s) Step thru the Details for each and specify the Geometry and other

details.

It is necessary to specify a specific frequency and phase angle.

Contours at a specific

Frequency

2012 ANSYS, Inc. March 28, 2013 14 Release 14.5

Workshop 5 Results

Return to the second harmonic force applied.

set the Phase Angle to 90 (we will try to excite different modes) resolve the Harmonic Response

2012 ANSYS, Inc. March 28, 2013 15 Release 14.5

Workshop 5 Results Return once more to the second harmonic force applied.

set the Phase Angle to 180 resolve the Harmonic Response