Chapter 15 Problem 204

Nastran - Solved Step By Step

Step 1

Click on Display Settings

Step 2

Turn the grid on, turn gravity off, and set the length to millimeters in units.

Step 3

Display the edit toolbar in toolbars.

Step 4

Import both parts one at a time.

Step 5

Surprisingly when importing both parts they should automatically be positioned correctly. This will happen if the origin of the Rotating_Rod is centered along its axis (see the solidworks part, step 1), and the origin of the T_shape is located at its center.

Step 6

copy the Rotating_Rod. Notice the copy is called Copy of Rotating_Rod.

Step 7

Change the orientation of the Rotating_Rod to that shown in the picture to the left.

Step 8

Change the orientation and position of the Copy of Rotating_Rod to that shown in the picture to the left.

Step 9

The next series of steps will allow both Rods to rotate in place along their axis but not move from side to side. Change the view so that the cylindrical surface of the Rotating_Rod is visible. Then selectRevolute Joint from the drop down menu

Step 10

Select the surface of the cylinder twice (make sure to separate both points otherwise this won't work). Make sure the Split Constraint ratio button is selected then click OK.

Step 11

Next we must center both coordinate point by selecting their properties from the Object Browser.

Step 12

Center coordinate[6] by using the x, y, and z values shown in the picture to the left.

Step 13

Center coordinate[7] by using the x, y, z, and Ry values shown in the picture to the left.

Step 14

Once this is done join the constraint. (This should be the only constraint that needs the step).

Step 15

Joint this coordinate in place.

Step 16

The next step is to re-position the Rotating_Rod. Give it Rz angle of -20.

Step 17

Perform steps 9 through 16 for the cylindrical face of Copy of Rotating_Rod. Notice that after the final position is established that the constraint automatically joins correctly.

Step 18

The next step is to place constraints on the parts where the T_shape contacts the two Rods. The first constraint will also be a Revolution Joint to joint the T_shape to the Copy of Rotating_Rod.

Step 19

Place the first coordinate on the "top" face of the T_shape, and the second one on the surface of the crosspiece. (when placing the second coordinate make sure the surface of the crosspiece darkens before placing it).

Step 20

Make sure the Split Constraint ratio button is selected then click OK.

Step 21

Once this is done centering of both coordinates takes place using the same steps as mentioned previously. See the picture to the left for an example of the x, y, and z positions to use.

Step 22

Perform steps 18 through 21 for the T_shape and Rotating_Rod connection.

Step 23

To apply the angular velocity (omega) to the Copy of Rotating_Rod (Rod AC in the book) simply pace a Revolute Motor on the cylindrical surface of Rod AC.

Step 24

After centering the motor it should automatically join (appear solid).

Step 25

Let the angular velocity omega be equal to 90 degrees per second.

Step 26

The next series of steps involve measuring the angular velocity of the Rotating_Rod. After selecting the Rotating_Rod perform the following menu selections as seen in the picture to the left.

Step 27

The final result should resemble the picture to the left.

Solution

Find Omega of Rod EG

The answer given in the back of the book is shown: omega_2 = omega_1 / cos(20 degrees). When omega_1 is equal to 90 degrees per second then omega_2 equals 95.776 degrees per second. The answer given on in the figure to the left can be seen in the lower left corner of the graph. The Nastran answer is 95.8 which matches the analytical solution exactly.