Finding Modes of a Cantilever Beam in NX 7.0

Dr. Singh

Starting NX 7.0

Start>EAS Applications>Engineering Apps>NX 7.0.

New Model

New>Model. Change Units to Inches. New File Name>Name>’Beam.prt’ and Folder to your M-

drive. Click OK.

Sketching Geometry

Select the Sketch icon. Select Planar Face as the X-Z axis> OK. Green arrows should appear as shown above.

Sketching Geometry

Select the Rectangle tool. Sketch a rectangle at the origin with

width= 3” and height= .25”.

Extruding

Click the Finish Sketch icon. Click the Extrude icon. Select Curve>select the sketch. Direction>Reverse Direction. Limits>End Distance>24 in. Select OK.

Advanced Simulation

Start icon>Advanced Simulation.

Advanced Simulation

Simulation Navigator>Right-click beam.prt >New FEM and Simulation.

When New FEM and Simulation window appears, select OK.

Advanced Simulation

Change Solution Type to SEMODES 103- Response Simulation.

Click OK.

Meshing

Under Simulation File View, select beam_fem1 and click 3D Tetrahedral.

Meshing

Select Bodies: select the beam. Mesh Parameters>Element

Size>Automatic Element Size icon. Click OK.

Material Properties

Click on the Material Properties icon. Select the beam and Aluminum_6061. Click OK.

Advanced Simulation

Reselect beam_sim1.sim. Under Solution 1, right-click

Subcase- Dynamics and select Edit.

Advanced Simulation

Under Subcase- Dynamics>Output Request, click the Create Modeling Object icon.

Advanced Simulation

Under the Displacement tab, check the box next to Enable DISPLACEMENT Request.

Click OK.

Advanced Simulation

Under Lanczos Method, click the Create Modeling Object icon.

Advanced Simulation

Change the Number of Desired Modes to 10. Click OK.

Click Constraint Type pull-down bar and select Fixed Constraint.

Apply this to the left face of the beam. Click OK.

Advanced Simulation

Right-click Solution 1 and click Solve. When the window appears, click OK. Wait until the Analysis Job Monitor lists the solution as

‘Completed’.

Advanced Simulation

In the Post Processing Navigator, right-click Solution 1 and click Load.

Click the plus sign to expand the solution.

Results

Click on the plus sign next to each mode to expand.

Double click Displacement- Nodal to view displacement results.

Mode 1 Mode 2

Mode 5

Interpreting Results

Different types of modes can occur- for example, Mode 4 is a torsional mode.

Since we are only interested in bending modes, our first three modes will be Mode 1, Mode 2, and Mode 5.

Mode 4

Interpreting Results

If you are having difficulty distinguishing which type of mode is occurring, try rotating the beam to view from the constrained end.

Bending modes will displace up and down, lateral from side to side, and torsional in a twisting motion.

Bending Lateral Torsional

Interpreting Results

The values of Modes 1, 2, and 5 should approximately be:

Frequency (Hz)

Mode 1 14.09

Mode 2 88.19

Mode 5 247.1

Animation

To animate results, double-click Displacement-Nodal for any mode and click the Animation icon.

Adjust Synchronized frame delay and Number of frames.

Check the box next to Full-cycle to see the full modal cycle.

Click the Next Mode/Iteration icon to see the next mode.