Building Flex Body Models - Kxcad.net

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16 Adams/Flex • If the existing body is a rigid body, Adams/Flex searches for the markers on the rigid body, and transfers these markers to the nodes on the replacement flexible body that are closest to the markers. If a marker is used to define joints or forces, Adams/Flex searches for interface nodes. For all other markers, it searches the entire set of nodes. • If the existing body is another flexible body, the markers are already attached to nodes. Therefore, Adams/Flex searches for the node closest to the attached node on the existing body. If the marker is attached to multiple nodes, Adams/Flex searches for the closest node for each connection. Again, if a marker is used to define joints or forces, Adams/Flex searches for interface nodes. Adams/Flex displays a Marker and Node table to let you make any changes, such as change the node to which a marker will be moved. Adams/Flex moves all markers to the replacement flexible body even if the markers have no connections. This is because you may have user-written subroutines or measures that reference the markers. By transferring all markers to flexible bodies, you ensure that all your subroutines and measures work. You can delete the markers if you want. Because Adams/Flex moves all markers, it also moves the center of mass (CM) marker. Once the marker is on the flexible body, however, it no longer indicates the CM nor does it stay coincident with the CM during a simulation. To eliminate confusion, Adams/Flex renames the CM marker from the substituted rigid body to original_rigid_cm. Note: Adams/Flex only transfers markers and any connections they define to the flexible body. It does not transfer string variables and other children of the rigid body. Overall Procedure for Replacing Rigid Bodies with Flexible Bodies To replace a rigid body with a flexible body, perform the following steps: • Select the rigid body to be replaced • Position and orient the replacement body • Transfer the connections • Replace the rigid body Each step is briefly outlined below with links to more complete procedures. Selecting the Bodies to be Replaced You can replace a rigid body with a flexible body that is already in your model or you can specify an MNF and Adams/Flex creates a new flexible body. The following explains how to specify a flexible body already in your model. To select the bodies: 1. On the screen, select the rigid body to be replaced.
2. From the Build menu, point to Flexible Bodies, and then select Rigid to Flex. Building Flex Body Models 3. Under the Alignment tab, select Flex Body, and then select a flexible body that has already been imported into your model. Position and Orient Replacement Body You use the positioning options in the Alignment tab of the Swap rigid/flexible body dialog box to move the flexible body so that it is aligned with the existing body that it is replacing. Three alignment tools are available: • Aligning center of mass of bodies • Aligning using the Precision Move dialog box • Aligning by defining three points You can use one or more of the tools to position and orient the flexible body consistently with the rigid body. Once you've used these tools, you can use the Flip about buttons to rotate the body 180° into position. Transferring the Connections You use the Connections tab on the Swap rigid body dialog box to display and transfer the connections on the rigid body to the replacement flexible body. The Connections tab displays a Marker and Node table listing the connections and how they will be transferred. It also provides options for positioning the markers relative to the attachment nodes on the replacement flexible body. You can also launch a Node Finder to search for a different node. To transfer the connections: 1. Review the list of marker connections and how Adams/Flex will transfer them to the flexible body. 2. To change the node to which the marker will be transferred, enter the new node ID in the Node ID text box, and then select Apply. Learn more. 3. If the attachment nodes are offset from the marker locations, you have three options: • Do nothing, and simply select OK as explained in the next procedure. In which case, the Adams/Solver (C++) creates a marker with an offset, while Adams/Solver (FORTRAN) automatically introduces a massless part and fixed joint pair. You are not responsible for creating dummy parts. • Move the marker to node location. Learn about this method. • Maintain any parameterization that was set up through Adams/View. Learn about this method. Replacing the Rigid Body Once you've set the alignment and connections, you can replace the existing body with the replacement flexible body. Learn about the complete procedure. 17
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