Problem: Using MD ADAMS, Find the minimum inclination that will ensure that a crate slides off an inclined plane, the plane has dimensions of 50 in. by 8 in. by 2 in and the crate has dimensions of 12 in. by 8 in. by 4 in. and has a mass of 100 lbs. The coefficient of static friction (μs) is 0.3 and the coefficient of dynamic friction (μd) is 0.25 and gravity is 32.2 ft/sec2. Note: If you need assistance on a step, just click on it for more information. Note: Click on images to enlarge.

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1) Click on Create a new model.

2) Under Start in, browse to the folder where you want to save your model.

3) Type the name of the new Model name as inclined_plane and click OK.

4)Make sure that the Gravity is set to Earth Normal (-Global Y) and the Units is set to IPS - inch, lbm, lbf, s, deg.

1) From the Settings menu, select Working Grid.

2)Set Spacing to 1 in. in the x and y direction.

3) Make sure that the working grid is oriented along the Global XY direction (default setting when you open Adams/View). The Set Orientation pull-down menu allows you to choose Global XY, YZ, XZ, or custom orientation. Click Apply and OK.

1) To create the plane, click on the Rigid Body: Box icon.

2) Make sure On Ground is selected and enter (50 in) for the Length, (3 in) for the Width, and (8 in) for the Depth. Also make sure that the Length, Width, and Depth are all checked. Then click on the center of the coordinate plane to create the plane.

3) Pan so that the right end of the plane is visible. To create the crate, click on the Rigid Body: Box icon.

4) Make sure New Part is selected and enter (12 in) for the Length, (4 in) for the Width, and (8 in) for the Depth. Also make sure that the Length, Width, and Depth are all checked. Then position the crate near the end of the ramp as shown.

1) Right-click on the large box (plane), point to Block: BOX_1, and then select Rename.

2) Enter Ramp, under New Name, and click Apply and OK.

3) Right-click on the smaller box (Crate), point to Block: BOX_2, and then select Rename.

4) Enter Crate, under New Name, and click Apply and OK.

5) Enter the mass of the crate by right-clicking on crate and going to Part:Crate, and then selecting Modify.

6) Set Define Mass By to User Input and in the Mass text box, enter 100 lbm. Click Apply and OK.

1) On the file tree to the left, under Bodies>ground right click MARKER _1 and select modify.

2) Under Orientation, input 15.0, 0.0, 0.0 click Apply and OK.

3) Rotate the view so that the Z axis of MARKER_1 is visible (left side of plane). Under the Move tool stack, select the Align & Rotate tool.

4) Under Angle, input 15 and press Enter. Then click on the crate to select it as the object that will be rotated.

5) Now select the Z-axis of MARKER_1 (MARKER_1.Z) as the axis of rotation. It may be easier to rotate the view slightly to select the Z-axis.

1) Click on Connectors in the toolbar and select “Create a Translational Joint” from Joints.

2) Then Select 2 Bodies- 1 Location and Pick Geometry Feature.

3) Then proceed to select the bodies to be constrained by clicking on the crate, then the ramp.

4) Then for location choose Crate.MARKER_2 and then MARKER_2.X with the vector point up the ramp.

1) Right-click on the crate and go to Part:Crate and then Measure.

2) Under Characteristic select CM acceleration, under Component select X.

3) Under Represent coordinates in: right-click in the gray area and select Marker, then Guesses and then MARKER_1. Alternatively, you can select Pick and then select MARKER_1 in the geometry, which is the corner point at the bottom of the ramp. Click OK.

1) To verify the mechanism, simulate the model by clicking on the "Gear" icon for 1 second and 50 steps.

2) Find the value of the crate's constant acceleration and verify it by checking Without friction in the Closed-form solution in the Analytical Solution tab below and making sure the values match.

1) Display the joint's modify dialog box by right-clicking on the translational joint and pointing to Joint:JOINT_1, and then select Modify.

2) In the lower right corner of the Modify dialog box, select the Friction tool.

3) Fill in the coefficients of friction (0.3 for the coefficient of static friction and 0.25 for the coefficient of dynamic friction) and leave the remaining friction parameters at their default values.

4) In the Input Forces to Friction section, clear the selection of Bending Moment and Torsional Moment. Click OK on both windows.

5) Simulate the model and note if the create slides off the ramp.

6) Then right-click on the curve in the stripchart, and then select Save Curve.

1) From the Build menu, select Group and New.

2) Make a group, named rotated_objects, containing: the crate, the joint, and all of the geometry on the ramp (including the markers but not the ground), by right clicking in the Objects In Group text box and going to All and then Browse.

3) This should bring up the Database Navigator, here select the Crate, MARKER_1, MARKER_4 and JOINT_1 (hold CTRL to select multiple entities) and then click OK on both boxes.

4) Now you can rotate the group, by going to the Main Toolbox, and from the Move tool stack, select the Precision Move tool .

5) In the text box to the right of Relocate the, enter the group name, rotated_objects. Then click OK on the Database Navigator window.

6) Set the menus in the second row to About the and marker.

7) In the text box to the right of these menus, enter MARKER_1. The Precision Move tool rotates objects in increments about a specified axis of the marker you just selected.

8) In the "Plus/Minus" text box, enter 5.

9) Select the Z-axis box. Note that you can select the axis box (X, Y, or Z) to rotate a group to the desired orientation. Now, click Close.

1) Simulate the model and note of the crate slides off the ramp. For an end time of 0.5 seconds, verify that the create acceleration vs. time graph matches the adjoining figure.

2) Through trial and error, find the approximate angle at which the crate starts to slide off the ramp. Save the curve in the graph plot and compare your results using ADAMS/PostProcessor.

    • MD ADAMS Simulation Results:
    • At θ = 15°, a = 0
    • At θ = 20°, a = -41.35 in/sec2.
    • Max Angle for Crate to Slip (θmax) = 16.8°. a = -19.19 in/sec2.