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Accelerating Links

Estimated time required: 20 min

GUI familiarity level required: Higher

MSC.ADAMS 2005 r2

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Topics CoveredTopics Covered

If you have any difficulties, import the “Accelerating_Links_shortcut.cmd” file and proceed from pg 7

If you have any difficulties, import the “Accelerating_Links_complete.cmd” file and proceed from pg 10

In this tutorial, you will learn how to:

1. Create a rotational spring with dampening

2. Create an angle measure

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Accelerating Links ProblemAccelerating Links Problem

Links A and B each weigh 8 lb, and bar C weighs 12 lb. Calculate the angle theta assumed by the links if the body to which they are pinned is given a steady horizontal acceleration a of 4 ft/sec^2.

This problem asks for the angle between the links and the accelerating body.

Problem 6/167 from J. L. Meriam and L. G. Kraige, Engineering Mechanics: Volume 2, Dynamics 3rd edition. John Wiley & Sons, Inc.

Copyright © 1992, by John Wiley & Sons, Inc. This material is used by permission of John Wiley & Sons, Inc.

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If you are successful, you should end up with a ADAMS model that illustrates the angle of a link pinned between

two moving objects.

What You Should AccomplishWhat You Should Accomplish

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Creating the ModelCreating the Model

a. Start ADAMS.

b. Create a new model. (Model Name = Accelerating_Links, Units = ips, Gravity = - Y earth)

c. Resize the working grid. (Size = X – 75i, Y – 50i, Spacing X – 1i, Y – 1i)

d. Open the Coordinate Window

e. Create main body. (box, length = 22 in, height = 3 in, depth = 1 in, Place the box on the working grid with the lower left corner at (-22, -1, 0)). Rename .Accelerating_Links.BLOCK

f. Create bar. (box, length = 22 in, height = 2 in, depth = 1 in, Place the box on the working grid with the lower left corner at (-22, -19, 0)). Rename .Accelerating_Links.BAR

g. Create Link A between points (-20, 0, 0) and (-20, -18, 0).Rename .Accelerating_Links.LINK_A

h. Create Link B between points (-2, 0, 0) and (-2, -18, 0). Rename .Accelerating_Links.LINK_B

i. Set the weight of links A and B to 8 lb each. Set the weight of BAR to 12 lb.

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Add JointsAdd Joints

a. Make revolute joints between LINK_A and the BLOCK, and between LINK_A and BAR.

b. Make spherical joints between LINK_B and the BLOCK, and between LINK_B and BAR.

c. Make a translational joint in the global X-direction between the BLOCK and ground.

d. Impose motion on the translational joint. (Tra Z,velo(time) =, f(time) = 48*time, Disp IC = 0.0).

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Add Torsional Spring DamperAdd Torsional Spring Damper

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a. Select Torsional Spring from Forces tool stack

b. Select 1 Location from Construction: pull down menu

c. Turn on KT checkbox and enter 0.0 (stiffness)

d. Turn on CT checkbox and enter 10.0 (damping)

e. Click on LINK_A.MARKER_3

b

c

d

e

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Create Angle MeasureCreate Angle Measure

a. Right light on the revolution joint between LINK_A and the BLOCK, select Joint: JOINT_1 Measure

b. Enter Theta in Measure Name text field

c. Select Ax/Ay/Az Projected Rotation from Characteristic pull down menu

d. Select Z radio button for Component

e. Click OK

a

b

c

d

e

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This is what your screen should look like whenyour model is complete

ModelModel

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Test ModelTest Model

a. Verify you model

b. Run simulation. (End Time = 50.0, Step = 500)

c. Transfer the small graph to a full plot in the ADAMS plotting screen. (right mouse button inside small plotting window)

d. Use the Display Plot Statistics tool to follow the plot curve. Observe angle measurement when the system reaches steady state.

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Theoretical Solution ADAMS solution

ResultsResults

Theoretical: Theta = 7.1 degrees

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In this tutorial you learned how to:

Topics CoveredTopics Covered

1. Create a rotational spring with dampening

2. Create an angle measure

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Best PracticesBest Practices

• Make sure correct units are set to ips and the viewing area is zoomed in or out enough to see the model. It may be helpful to set the working grid to 1 inch spacing under the Settings menu.

• Make sure gravity is turned on and set to -y Earth.

• Make sure the revolute joints are in the z direction.

• Check dimensions of the part to make sure they are correct.

• Make sure the measures are set correctly.

• Make sure the plot is displaying the correct set of results.

• Make sure there are enough output steps to allow the system to reach steady state.