ENGI 7706/7934: Finite Element Analysis

Abaqus CAE Tutorial 4: Mode-based Dynamic Analysis ___________________________________________________________

A simple machine is shown below. The machine is subject to dynamic

excitation. As a preliminary analysis perform free vibration analysis to

obtain 30 vibration modes and their natural frequencies. The machine

has a fixed bottom and a few constraints at the top. The material is steel

(Density: 7800kg/m3, E=210,000 MPa, ν=0.3).

Analysis Steps 1. In the model tree double click on the “Parts” node (or right click on “parts” and select Create) 2. In the Create Part dialog box name the part and a. Select “3D” b. Select “Deformable” c. Select “Solid” d. Set approximate size = 200 e. Click “Continue…”

3. Create the geometry shown below. (50

20)

4. Enter the base extrusion depth = 25

5. Create solid: Extrude, select a plane for the extrusion.

6. a. Sketch the cylinder on the plane.: The center of the circle is (0, 5), the radius is 3.

b. Linear pattern: Use linear pattern to create two other circles.

b. Enter the extrusion depth: 6. Done.

7. Double click on the “Materials” node in the model tree a. Name the new material as “Steel” b. Click on the “General” tab, define the density of steel. c. Click on the “Mechanical” tab, Elasticity, Elastic. Define Young’s Modulus and Poisson’s Ratio.

8. Double click on the “Sections” node in the model tree a. Name the section “Machine” and select “Solid” for the category and “Homogeneous” for the type b. Click “Continue…” c. Leave the section integration set to “During Analysis” d. Select the material created above (Steel) e. Click “OK”

9. Assign section select “assign section” in the red box shown below a. Select the entire geometry in the viewport and press Enter b. Select the section created above (Machine) c. Click “OK”

10. Expand the “Assembly” node in the model tree and then double click on“Instances” a. Select “Dependent” for the instance type b. Click “OK”

11. Double click on the “Steps” node in the model tree a. Name the step, set the procedure to “Linear Pertubation”, and select “Frequency” b. Click “Continue…” c. Eigensolver: Lanczos. Number of eigenvalue requested: 30. d. Click “OK”

12. Expand the Field Output Requests node in the model tree, and then double click

on F‐Output‐1 (F‐Output‐1 was automatically generated when creating the step)

a. check the variables “U” b. Click “OK”

14. Double click on the “BCs” node in the model tree a. To create boundary condition on the top and bottom: Select the top surface: U1=U2=U3=0 Select the bottom surface: U1=U2=U3=UR1=UR2=UR3=0. b. Click “Continue…”

15. In the model tree double click on “Mesh” for the part. a. In the toolbox area click on the “Global seeds”, assign global seed size to 2.

b. Create partition: Select “Partition cell: Extend face”.

c. Create Mesh controls: Select “Hex-dominated” shape, Techique: “Sweep”, Algorithm: “Advanced”.

d. Mesh the part.

16. Create and run the job.

17. View the results of first 30 modes.