ws05-1 vnd101, workshop 05 msc.visualnastran 4d exercise workbook staircase demonstration

WS05-1VND101, Workshop 05

MSC.visualNastran 4D

Exercise Workbook

Staircase Demonstration


ObjectivesThis exercise will introduce some of the basic features of visualNastran Desktop 4D.

You will create a simple dynamic system: a ball rolling off the top of a staircase.

The concepts emphasized with this demonstration are the:

definition and positioning of bodies

the application of the automatically applied constraints

friction and restitution coefficient

Capture critical information regarding this simulation through the measurements of the key variables.


Exercise Overview Setup Create Staircase Assigning Staircase Properties Test Run Simulation Body Placement Precisely Positioning Body Through Keyboard Entries Create a Ball Assign the Properties of the Ball Confirm that the Position of the Ball is Correct Test Run Simulation Simulation: Animation Define Collisions Measure the Ball’s Angular Velocity


I - Set Up the Workspace

Launch visualNastran 4DMSC.visualNastran 4D starts and presents a blank document window. (Figure 1)

Define Simulation Settings1) Click on the Display Settings button in the toolbar

or select the World pull-down menu and choose Display Settings.

A folder of tables like that shown on the left side of Figure 2 appears.

Units2) Pick the Units tab under the Display Settings tree

and choose “SI (degrees)”. (Figure 2)

Figure 1 Drawing Window

Toolbar

Object Manager Tabs

Global Axis

Playback Controls

Connections Window

Properties List

Figure 2 Display Settings - Units


Grid Settings3) Still in the “Settings” dialog box, click on the Grid

tab under the Display Settings tree.

A Grid Settings table appears. (Figure 3)

4) Check “Show Grid” in the “Grid” area.

5) Check the “Snap to Grid” option.

6) Uncheck the “Automatic Sizes” option.

7) Set “Extents” to “10” m and “Snap” to “1” m, then click the “Close” button. (Figure 3)

Modify View8) Select View All from the View pull-down menu or

click the View All button from the toolbar.

The simulation window should now look like Figure 4. Notice that common commands have “hot keys” labeled in the pull-down menu. In this case, the “hot key” is V to View All.

Figure 3 Modifying Grid Setting


Figure 4 View All



9) Use the Rotate Around tool or the arrow keys to adjust your view on the grid such that it appears like that shown in Figure 5.

The “hot key” for this tool is F4.

Notice the edit grid fans out from the origin 10 units along each side of XY plane. This grid defines the area upon which you sketch the body’s profile. These profiles are then extruded to complete the figure. In short, the grid is a visual tool and helps define the general size of the bodies created.

Grid Extents determines the overall dimension of the grid by setting the length of each side as shown in Figure 5. Grid Snap, on the other hand, helps you by snapping line segment endpoints to the grid at precise intervals. This helps speed up the drawing process.

Figure 5 Grid Snap

10 m


II - Create Staircase

We will extrude a staircase from its profile drawn on the edit grid. Then after assigning some properties, we will re-position it for the demonstration.

10) Pick the Extruded Polygon tool from the toolbar.

11) Left-click once at the World Origin.

To draw the staircase profile, begin at the origin of the global coordinate system. As you move the cursor you should notice that you are drawing a green line.

12) Complete first line segment by moving cursor 9 increments along the X-axis of the World Coordinate System and left clicking to define the other endpoint of this line segment.

Again, as you move the cursor, another line segment is drawn which emanates from the end point of the previous line segment. Apply the same procedure to complete the line segment.

13) Continue defining line segments in this way to create the staircase profile. (Figure 6)

14) Complete the staircase profile by double-clicking on the final endpoint of the final line segment.

The final endpoint is the World Origin in this case.

15) Move the mouse forward to extrude shape and complete the extrusion with a single left mouse click. (Figure 7)

Extrude to an arbitrary thickness, we will assign the extruded dimension through the properties window of this body in the next section.

Figure 6 Properties of body - Position

Figure 7 Extrusion of Staircase


III - Assign Staircase Properties

16) Open the “Properties” dialog box by locating the mouse anywhere over the staircase and double-clicking the mouse.

This opens the “Properties” dialog box for the staircase as is shown in Figure 8. The staircase is referred to as a body[1]. Notice that body[1] is listed and highlighted in two of the left-hand window screens. The top window is called the Object List and the middle one is the Connections List. Throughout the training course, we will make use of these lists and you will find them to be very helpful. Our next step is to give body[1] a name.

17) Pick the Appearance tab in the “Properties” dialog box. (Figure 8)

18) Type in “Staircase” in the “Name” field and click “Apply”. (Figure 8)

19) Pick the Geometry tab and assign “3” m to Height (Z).

Also verify that the width and length of the staircase is 9 m. (Figure 9)

20) Click the “Apply” and “Close” buttons.

In the simulation window, notice that the staircase has been widened to 3 meters in the z-direction.

Figure 9 Modify Geometry

Figure 8 Appearance Window


IV - Test Run Simulation

21) Click the arrow button next to the button with the sphere on it.

22) In the pull-down menu, click on the wire sphere.

This option, also called “wire frame”, will change the bodies in the simulation window to a wire frame.

23) Select the staircase by locating the mouse anywhere over the staircase and clicking the left mouse button.

When the staircase is the selected object, it appears in bolder lines and an additional coordinate system is visible. (Figure 10)

24) Run the simulation by clicking the “Run” button in the Playback Controls.

Notice that the staircase falls downward off the screen due to gravity. The gravity is on by default and acts on all bodies. We will soon anchor the body such that it does not move.

25) Stop and reset the simulation by clicking the “Stop” button, then the “Reset” button.

Figure 10 Wireframe Mode


V - Body Placement

Figure 12 Drag Z tool

The staircase needs to be positioned appropriately and then anchored to the background.

Positioning Body through Mouse Drags26) Select the “Drag” tool from the Edit toolbar.

27) Locate mouse over the staircase and hold left mouse button down as you drag it to a new location.

Move the staircase around to become familiar with the “Drag” tool. Notice that the repositioning of the body occurs parallel to the edit plane. While holding down the mouse, notice the curser symbol. (Figure 11)

28) Release left mouse button when the staircase is positioned appropriately.

Locate the body in an arbitrary position for now. We will precisely locate it in the next section.

29) Pick the “Drag Z” tool from the Edit toolbar.

30) Locate mouse over the staircase and hold left mouse button down as you drag it to a new location.

Notice that the repositioning of the body is along the direction normal to the edit plane. While holding the mouse down, notice curser symbol. (Figure 12)

31) Release the left mouse button when the staircase is positioned appropriately.

Again, just choose an arbitrary location for now.

Figure 11 Drag tool


V - Body PlacementPrecisely Positioning Body Through Keyboard Entries

32) Open the “Properties” dialog box by locating the mouse on the word “Staircase” appearing in the Object List windowand double click the left mouse button.

This is an alternative way of opening the “Properties” dialog box. Essentially, all objects can be selected through either the viewing area, the object list, or the connections list.

33) Select the Position tab, which is labeled Pos.

The Position table appears. (Figure 13)

34) Assign the “Staircase” the position X=0, Y=0, and Z=0. (Figure 13)

This locates the origin of the reference coordinate system of the staircase relative to the world coordinate system. You will notice that the staircase is moved such that its own reference coordinate system is coincident with the World Coordinate System as is shown in Figure 14.

Figure 14 Position of Staircase

Figure 13 Position of Staircase


V - Body Placement

Figure 16 Body and World Coordinate System

35) Rotate the “Staircase” such that it is aligned properly relative to the downward direction of gravity by assigning Ry = -90. (Figure 15)

This rotates the staircase 90 degrees about the y-axis of its own reference coordinate system. The staircase should now appear as is shown in Figure 16.

36) To fix the staircase to the background, check the “Fixed” box of the Position tab of the” Properties” dialog box. (Figure 15)

To check this box, locate mouse over the box and click the left mouse button.

37) Click the “Close” button in the “Properties” dialog box.

If you prefer not to have a grid, pick the Display Settings button in the toolbar and go to the Grid tab. Uncheck “Show Grid” and close the menu.

Figure 15 Rotate Staircase


VI - Test Run Simulation

38) Click the “Run” button.

Notice that the staircase does not fall. It is fixed to the background. (Figure 17)

39) Stop and reset the simulation by picking the “Stop” button and “Reset” button.

Figure 17 Run Simulation


VII - Create a Ball

40) Choose the Sphere tool from the toolbar.

41) Click the left mouse button anywhere on the edit grid to define the center of the sphere.

42) Drag the mouse to adjust the radius to an arbitrary size.

Once you move the mouse, an orange ball increases or decreases in size.

43) Click the left mouse button to complete the sphere.

We will now go through the same steps to name, position, and size this sphere as we did with the staircase.

Figure 18 Creating the Ball


VIII - Assign Ball Properties

44) Double-click on the sphere to open the “Properties” dialog box for the sphere.

45) Go to the Sphere tab of the “Properties” dialog box, assign the sphere a radius of “1 m”. (Figure 19)

46) Name the sphere “Ball” through the Appearance tab.

In other words, go to the Appearance tab and type in “Ball” in the name field.

47) Pick the Position tab and set the “Ball’s” coordinates at X=0, Y=0, and Z=12. (Figure 20)

Use the Pan and Zoom tools to view the ball’s placement. (Figure 21) Notice that the reference coordinate system is located at its center of mass (CM). This is the case for all bodies not extruded from a polygon.

48) Click the “Close” button.

Figure 21 Positioning the ball Figure 20 Position Tab

Figure 19 Sphere Tab


IX - Confirm Position of Ball

49) Click on the arrow next to Perspective View button, and in the pull-down menu, pick the Isometric View button. Refer to the toolbar above.

The Isometric View mode is useful for simplifying views to appear 2-dimensional. Because all lines converge to horizon points in the perspective mode, the standard front, top and right side views may appear distorted and lack the clarity offered by the isometric view mode.

50) Press the “X” key.This should modify your view such that you are staring down the x-axis. This view is defined as the front view. (Figure 22)

If you haven’t turned off the “Show Grid” option, go to the Display Settings dialog box, click on the Grid option, and uncheck “Show Grid.

51) Press the “Z” key.This should modify your view such that you are staring down the z-axis. This view is defined as the top view. (Figure 23)

Figure 22 Side View

Figure 23 Top View


X - Test Run Simulation

52) Modify the view to fully-shaded mode by selecting the arrow next to the Wireframe button and picking the solid sphere.

53) Use viewing tools to adjust view to resemble the view shown in Figure 24.

54) Run the simulation.

You will notice that the ball penetrates through the surface of the staircase. (Figure 25) MSC.visualNastran applies automatic collision detection only between bodies defined to collide. In the next section we will define the collision between the ball and staircase.

55) Stop and Reset the simulation.

Figure 25 Running Simulation

Figure 24 Shaded Mode


XI - Simulation Animation

Since our goal is to construct a useful dynamic model, we should choose a convenient animation speed.

56) Click the Simulation Settings tool and pick the Integration tab.

57) Change the “Animation Frame Rate” to 10 frames per second and click Apply.

The Integration tab is shown in Figure 26. This means the simulation will play at 10 frames per second. Its reciprocal, the length of each frame, will adjust automatically.


Figure 26 Animation Frame Rate


XII - Define Collisions

Unlike the “gravity” setting which is ON by default, “collision” is set at OFF. In the next step, we will set collisions between the staircase and the ball.

59) Select both bodies.

There are multiple ways of selecting bodies. You can hold down the “Ctrl” key and click on both bodies in the workspace. An alternative way is holding down the “Ctrl” key and selecting both objects in the Object List.

60) Right click on either body to open a pop-up menu and pick Collide. (Figure 27)

61) Run the simulation.

Now, the body bounces on the top of the stairs. In order to get the ball to do more than just bounce, we have to give it a spin. A closer look reveals that we need to establish an angular velocity about its X-axis.

Figure 28 shows the simulation after 2 seconds. The ball is stationary.

62) Stop and reset the simulation.

Figure 27 Set Bodies to Collide

Figure 28 Running Simulation


XIII - Add Rotational Velocity

63) Double click the “Ball” and select the Velocity tab in the “Properties” dialog box.

64) Assign an angular velocity of “-100” degrees/second to the Wx component. (Figure 29)


66) Run the simulation again.

The ball falls down the staircase this time. (Figure 30)

67) Stop and reset the simulation.

Figure 29 Assigning Velocity to the ball

Figure 30 Running the Simulation


XIV - Measure Ball Velocities

You can take measurements frame by frame or over the entire course of events with just a few simple commands. Here we will plot the ball’s angular velocity as it bounces down the stairway.

68) Select the “Ball” either from the workspace or the object list.

An orange box will appear around the “Ball” to indicate it’s selected.

69) From the Insert pull-down menu, go to Meter>Angular Velocity.

Click “OK” in the Tiling Options menu. (Figure 31)

The screen should now look like Figure 32.

Figure 32 Angular Velocity Measurement

Figure 31 Tiling Options


XIV - Measure Ball Velocities

70) Run the simulation until the “Ball” drops off the “Staircase”. (Figure 33)

71) Run it again, frame by frame: use the arrow buttons at the bottom right of the screen. Notice the plot within the meter window.

You can also position the simulation to a point by sliding the tape player control tab at the bottom.

The Position Tracking feature is often helpful in understanding simulation events. It is activated from the Properties dialog box.

72) Hit “Reset” to bring the “Ball” back to its starting position.

73) Open the “Ball’s” “Properties” dialog box and under the Appearance tab, place a check next to “Track”. (Figure 34)

74) Accept the number of frames to track and close the “Properties” dialog box.

75) Run the simulation again.

Notice that you can pan, zoom, and rotate the model as the simulation proceeds.

Figure 34 Appearance Tab

Figure 33 Run Simulation with Meter


Figure 35 Tracking the ball

ws05-1 vnd101, workshop 05 msc.visualnastran 4d exercise workbook staircase demonstration

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