8
Determine the first two natural frequencies of the micro-electromechanical system
(MEMS) cantilever beam shown here using the built-up beam feature. The beam crosssection is made of three layers of aluminum embedded in silicon and the beam length is
100
 m. All dimensions and properties are in

MKSV units.
1.
Start ANSYS 5.7 with the default jobname (file).
2.
Create a rectangle that is 2
 m across and 3.5
 m in height and symmetrical about the origin.
3.
Set the element edge length on all lines to be 0.5
 m.
4.
Write the area as a custom section to a file, name the file
“beam.SECT”.
5.
Clear the database.
6.
Edit the custom section by modifying the aluminum elements to reference material number 2.
7.
Input the file “beam.inp”.
8.
Read in the section mesh “builtup.SECT” as section ID number 1.
9.
Do an element plot to see the resulting beam crosssection mesh.
10.
Solve the modal analysis.
11.
List the Results Summary.
12.
Exit ANSYS.
ANSYS 5.7 New Features Workshop Supplement 8-1

1.
Start ANSYS 5.7 with the default jobname (file).
2.
Create a rectangle that is 2
 m across and 3.5
 m in height and symmetrical about the origin.
Click on:
 Main Menu > Preprocessor > -Modeling- Create > -Areas- Rectangle
> By Dimensions
X1 = -1
X2 = 1
Y1 = -1.75
Y2 = 1.75
[OK]
Or issue:
/PREP7
RECTNG,-1.0,1.0,-1.75,1.75
3.
Set the element edge length on all lines to be 0.5
 m.
Click on:
 Main Menu > Preprocessor > Size Cntrls > -Lines- All Lines
SIZE = 0.5
[OK]
Or issue:
LESIZE,ALL,0.5
4.
Write the area as a custom section to a file, name the file “beam.SECT”.
Click on:
 Main Menu > Preprocessor > Sections > -Beam- Custom Sectns >
Write from Areas
Read the Note that comes up, then click [Close]
In the “Select areas” window, click [Pick All]
FILE = beam.SECT
[OK]
5.
Clear the database.
Click on:
 Utility Menu > File > Clear & Start New
[OK]
Answer [Yes] to the verification question
Or issue:
FINISH
/CLEAR
8-2 ANSYS 5.7 New Features Workshop Supplement

6.
Edit the custom section by modifying the aluminum elements to reference material number 2.
Click on:
 Main Menu > Preprocessor > Sections > -Beam-
Custom Sectns > Edit/Built-up
Select [Edit Custom]
FILE = beam.SECT
[OK]
Select [Modify Material]
Pick the aluminum elements (shown below)
[OK]
MAT = 2
[OK]
Select [Save ]
FILE = built-up.SECT
[OK]
Select [Finish]
ANSYS 5.7 New Features Workshop Supplement 8-3

7.
Input the file “beam.inp”.
Click on:
 Utility Menu > File > Read Input From beam.inp
[OK]
Or issue:
/INPUT,beam,inp
NOTE: This input file creates the cantilever beam model using BEAM188 elements, defines the material properties, and specifies the modal analysis solution options.
8.
Read in the section mesh “built-up.SECT” as section ID number 1.
Click on:
 Main Menu > Preprocessor > Sections > -Beam- Custom Sectns > Read
Sect Mesh
Section ID number = 1
Section Name = built-up
FILE = [built-up.SECT]
[OK]
Or issue:
SECTYPE,1,BEAM,MESH,built-up
SECOFFSET,CENT
SECREAD,built-up,SECT,,MESH
9.
Do an element plot to see the resulting beam cross-section mesh.
Click on:
 Utility Menu > Plot > Elements
Or issue:
EPLOT
8-4 ANSYS 5.7 New Features Workshop Supplement

10.
Solve the modal analysis.
Click on:
 Main Menu > Solution > -Solve- Current LS
[OK]
Or issue:
/SOLUTION
SOLVE
11.
List the Results Summary.
Click on:
 Main Menu > General Postproc > Results Summary
Or issue:
/POST1
SET,LIST
12.
Exit ANSYS.
Click on:
 Main Menu > File > Exit
Choose Quit – No Save!
[OK]
Or issue:
FINISH
/EXIT,NOSAVE
ANSYS 5.7 New Features Workshop Supplement 8-5

8-6 ANSYS 5.7 New Features Workshop Supplement