{"id":397893,"date":"2024-12-18T17:29:37","date_gmt":"2024-12-18T17:29:37","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/397893\/"},"modified":"2024-12-18T17:29:37","modified_gmt":"2024-12-18T17:29:37","slug":"397893","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/397893\/","title":{"rendered":"Reply To: Cross-coupled stiffness elements in LS-DYNA"},"content":{"rendered":"<p>&lt;p&gt;Hello Simon,&lt;\/p&gt;&lt;p&gt;I found the following in our knowledge database:&lt;\/p&gt;&lt;p&gt;&#8221;&lt;\/p&gt;<\/p>\n<pre>Superelements are not appropriate for bodies undergoing finite rotations.  \nFor that case, one could employ flexible rigid bodies (*part_modes)\"&lt;br&gt;&lt;br&gt;One developer told me: \"&lt;span data-teams=\"true\"&gt;We are working on extending it to large rotations, underway.\"&lt;br&gt;&lt;br&gt;And here is more information from our knowledge database:&lt;br&gt;&lt;br&gt;\"A \"flexible rigid body\" saves cpu time by approximating response using mode superposition.\nThe basic procedure is to first compute normal modes (*control_implicit_eigenvalue) and\/or\nconstraint or attachment modes (*control_implicit_modes) of a deformable body.\nThen in a subsequent explicit analysis, you approximate that deformable body as a\n\"flexible rigid body\" via the command *part_modes.\n\nHere are links to papers describing the procedure and examples:\nhttp:\/\/ftp.lstc.com\/anonymous\/outgoing\/jday\/Session_12-1.pdf\nhttp:\/\/ftp.lstc.com\/anonymous\/outgoing\/jday\/flexrb.pdf\nhttp:\/\/ftp.lstc.com\/anonymous\/outgoing\/jday\/Bitzenbauer.pdf\nThe first two are essentially the same paper.\n\nExample input (rather old, I'm afraid) is in http:\/\/ftp.lstc.com\/anonymous\/outgoing\/jday\/flexrb_example.tar\"&lt;br&gt;&lt;br&gt;You will find a regular super element example here:&lt;br&gt;&lt;br&gt;http:\/\/ftp.lstc.com\/anonymous\/outgoing\/support\/EXAMPLES\/superel_inertia_matrix.tar&lt;br&gt;&lt;br&gt;&lt;br&gt;Let me know if this helps or not.&lt;br&gt;&lt;br&gt;&lt;br&gt;Reno.&lt;\/span&gt;<\/pre>\n","protected":false},"template":"","class_list":["post-397893","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"acf":[],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/397893","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/reply"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/397893\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=397893"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}