11-1
Connecting Rod
BASIC ANALYSIS
11
11-2
Connecting Rod
Connecting Rod
11-3
Model Description:
1
1
Z
Y
X
BASIC ANALYSIS
This example will demonstrate some of MSC/NASTRAN for Window’s (MSC/N4W) solid modeling capabilities. We will start by reading in a neutral file that contains the base curves we will use
to build the solid. These curves were created in MSC/N4W and you could build this model from
scratch in MSC/N4W, but to save time and get right to the solid modeling we have provided the
curves for you.
11-4
Connecting Rod
Exercise Procedure:
1. Start up MSC/NASTRAN for Windows 3.0 and begin to create a new model.
Start MSC/N4W by double-clicking on the MSC/N4W icon. When the Open Model File dialog box
appears; choose New Model.
Open Model File:
New Model
Then File/Import/FEMAP Neutral menu should be selected to import the geometry.
File/Import/FEMAP Neutral...
Navigate to the mscn4w--\examples directory and select mconrod.NEU.
File Name:
mconrod.NEU
Open
Accept the default values in the Neutral File Read Options dialog box.
OK
2. Customize the display to better view the model.
Autoscale the model with Ctrl-A.
View/Rotate...
Dimetric
Mag..
Fill View
OK
The geometry you read in from the neutral file contains all the existing curves and boundaries you
will need to form the solid model. As I said before, this geometry was all created in MSC/N4W and
is not hard to duplicate but those commands are covered in other examples.
Connecting Rod
11-5
Your display should look like this.
E
BASIC ANALYSIS
D
B
A
C
F
G
3. Extrude the Beam.
Extrude the boundary surface to form the solid.
Geometry/Solid/Extrude...
Boundary...
ID:
< Select the Boundary Surface A
shown in the above diagram
(Surface 8) >
OK
Note: On your display, the surface normal vector will appear. Choose the appropriate directional,
positive or negative, button so that the vector is pointing in the Positive Z direction.
Direction:
l Negative (verify with above
comments)
Length:
l To Depth
OK
0.5
11-6
Connecting Rod
OK
Geometry/Solid/Slice...
ID:
< Select the solid just created
(Solid 1) >
OK
We need to change the snap mode to point. Do this by either pressing the right mouse button in the
graphics window, and then clicking the Point option under Snap To, or using the toolbar Snap To
Point icon.
or
Connecting Rod
11-7
K
H
J
M
L
Choose Point H, J, and K(in the diagram above) for Base, Point1, and Point 2 respectively. Then
subtract 0.05 from H and J and 0.1 from K in the z-coordinate.
Base:
X:
XPT(27)
Y:
YPT(27)
Z:
ZPT(27)-0.05
Point 1:
X:
XPT(31)
Y:
YPT(31)
Z:
ZPT(31)-0.05
Point 2:
X:
XPT(23)
Y:
YPT(23)
Z:
ZPT(23)-0.1
OK
Slice the larger solid once more.
Geometry/Solid/Slice...
ID:
OK
< Select the larger solid (Solid 1) >
BASIC ANALYSIS
N
11-8
Connecting Rod
Choose Point L, M, and N (in the diagram on the previous page) for Base, Point1, and Point 2
respectively. Then add 0.05 to L and M and 0.1 to N in the z-coordinate.
Base:
X:
XPT(33)
Y:
YPT(33)
Z:
ZPT(33)+0.05
Point 1:
X:
XPT(28)
Y:
YPT(28)
Z:
ZPT(28)+0.05
Point 2:
X:
XPT(5)
Y:
YPT(5)
Z:
ZPT(5)+0.1
OK
Delete the two slivers on the top and bottom of the beam.
Delete/Geometry/Solid...
Select the top and bottom solids (Solid 2 and 3).
OK
Yes
4. Remove Material from the Beam.
We want to turn this part of our solid into something more like an I-beam instead of a block. To do
this we will remove material by extruding boundaries into the top and bottom of the beam.
Geometry/Solid/Extrude...
Boundary...
ID:
OK
< Select the boundary surface B
shown in the diagram on page 5.
(Surface 9) >
Connecting Rod
11-9
Note: Choose the appropriate directional button so that the vector is pointing in the Negative Z
direction.
l Remove - Hole
Direction:
l Positive
Length:
l To Depth
0.175
OK
Geometry/Solid/Extrude...
Boundary...
ID:
< Select the boundary surface C
shown in the diagram on page 5.
(Surface 10) >
OK
Material:
l Remove - Hole
Direction:
l Negative
Length:
l To Depth
OK
0.175
BASIC ANALYSIS
Material:
11-10
Connecting Rod
5. Forming the Small End of the Rod.
Geometry/Solid/Extrude...
Boundary...
ID:
< Select the boundary surface E
shown in the diagram on page 5.
(Surface 12) >
OK
Note: Choose the appropriate directional button so that the vector is pointing in
the Positive Z direction (Towards the Beam).
Material:
l Add - Protrusion
Direction:
l Positive
Length:
l To Depth
0.5
OK
Geometry/Solid/Extrude...
Boundary...
ID:
< Select the boundary surface D
shown in the diagram on page 5.
(Surface 11) >
OK
Material:
l Remove - Hole
Direction:
l Positive
Length:
l Thru All
Connecting Rod
11-11
BASIC ANALYSIS
OK
6. Forming the Big End of the Rod.
Geometry/Solid/Extrude...
Boundary...
ID:
< Select the boundary surface F
shown in the diagram on page 5.
(Surface 13) >
OK
Note: Choose the appropriate directional button so that the vector is pointing in the Positive Z
direction (towards the beam).
Material:
l Add - Protrusion
Direction:
l Positive
Length:
l To Depth
OK
Geometry/Solid/Extrude...
0.5
11-12
Connecting Rod
Boundary...
ID:
< Select the boundary surface G
shown in the diagram on page 5.
(Surface 14) >
OK
Material:
l Remove - Hole
Direction:
l Positive
Length:
l Thru All
OK
Now, split the big end in half. You can use the same method we used before to slice the beam.
However, lets use another approach.
Geometry/Solid/Slice...
ID:
< Select the solid (Solid 1) >
OK
Split the solid into two parts by slicing with a coordinate plane.
Methods ^
CSys Plane
The cutting plane will be the YZ plane, which is perpendicular to the flat face of the solid tube. We
will cut the solid tube in two equal parts by cutting through the center [5, 0, 0].
Base:
Direction:
X:
5
Y:
0
Z:
0
l Negative
l YZ Plane
Note: The positive and negative cutting direction will determine which solid retains the original
Solid ID. We will be consistent with the exercise and keep the larger portion of the solid as Solid 1.
Connecting Rod
11-13
BASIC ANALYSIS
OK
Delete/Geometry/Solid...
Select the disconnected half of the big end (Solid 4).
OK
Yes
7. View the model as Solid.
From the tollbar select the View Style icon quick button, select Solid.
11-14
Connecting Rod
The resulting solid model should look as follow:
8. Prepare the Small End for Load on Surface.
We only want to load the bottom half of the small end of the rod, but currently it is split side to side.
We will update the surfaces with a parametric curve at the midpoint of these two surfaces to split
the inside of the small end into quarters. This will allow us to put a load on the two quarters of the
bottom part of the small end.
Choose Geometry/Curve - From Surface/Update Surfaces if it is not already checked.
Geometry/Curve - From Surface/Update Surfaces...
This is so that the curves created on the surface will split the surface.
Geometry/Curve - From Surface/Parametric Curve...
Select one of the inner surfaces of the small end (Surface 47 or 48). We will do the same for the
surface you did not pick later.
OK
Methods ^
Midpoint
Connecting Rod
11-15
Select one of the arcs of the surface you picked (Curve 98 or 102).
OK
OK
Repeat for the other surface of the small end that you did not pick before (Surface 48 and
Curve 99).
Cancel
9. Adding loads on Geometry.
We will add a slightly angled force on the lower half of the small end to simulate the piston pushing
down on the rod.
Model/Load/On Surface...
Title:
Loads
OK
Select the two quarter surfaces of the small end that are near the beam portion of the rod (the
two surfaces are outlined by the bold curves shown below).
OK
(highlight)
Force Per Area
BASIC ANALYSIS
U Direction
11-16
Connecting Rod
FX
787
FY
138
OK
Cancel
This corresponds to a force/area of 800 at an angle of 10 degrees with the X-axis.
10. Adding Constraints on Geometry.
Constraints on surfaces are always relative to the global coordinate system and can only be fixed,
pinned or have no rotations.
Model/Constraint/On Surface...
Title:
Constraints
OK
Select the two quarter surfaces on the inside of the big end (Surface 55 and 56).
OK
DOF:
OK
l Fixed
Connecting Rod
11-17
Cancel
The default values MSC/N4W calculated for this model are fine. Feel free to experiment with different mesh sizes to become familiar with the meshing process.
Mesh/Geometry/Solid...
OK
Since no material has been created MSC/N4W prompts you to make one. You can enter in values
or press the Load button to bring up the material library.
Load...
The material library shipped with MSC/N4W contains material properties using English and metric
units. You can create your own materials and store them in this library or create your own library.
Make sure that you select a material with English units for this example.
Library Entry:
7075-T651 Al Plate .25-.5
Note:
Remember, there are no units in MSC/N4W. All dimensions must be kept consistent with the unit system you use to define your material properties. Always
make sure this is correct from the beginning because there is no way to correct
inconsistencies in units once the model is built.
OK
OK
OK
When the meshing completes the model will be ready for analysis.
The model should look like the one shown on the front page of this exercise.
BASIC ANALYSIS
11. Meshing the Solid.
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Connecting Rod