CONTACTS AND MODAL FORCES Section 7 CONTACTS AND MODAL FORCES

CONTACTS AND MODAL FORCES What’s in this section: Contact with Flexible Bodies Modal Applied Force and Preloaded Flexible Bodies

CONTACT WITH FLEXIBLE BODIES Adams 2005r2 began supporting points on flexible bodies Point to plane Point to curve The point can exist on the flexible body, but the plane or curve cannot. Adams/Solver (C++) supports several points defined in a contact. Adams/Solver (FORTAN) supports only one point in a contact. For other contact pairs, you must use your own modeling tricks or the built-in contact primitives. Use dummy parts and the Adams/View built-in contact pairs: Curve to plane Curve to curve (for example, circle to circle) Sphere to plane (see Creating the contact forces) Solid to solid Note: Spheres will solve faster than other solids. Write your own user-written forces. Don’t forget that the flexible body must be the action body.

CONTACT WITH FLEXIBLE BODIES Flexible body contact using modal formulation (C++ Solver only) Flex body to solid (flex body must be the action body) Flex body to flex body Adams 2010 began supporting shell elements in MNF for contact modeling in flexible body contact . Flex Edge to Curve Flex Edge to Flex Edge Flex Edge to Plane Setup just like rigid body contact Main Toolbox > Force Pallette > Contact The Contact Create dialog will show the Flex Body to Solid and Flex Body to Flex Body options. Geometry used for contact detection is extracted from the mnf. Both solid elements and shell elements are supported

CONTACT WITH FLEXIBLE BODIES Additional Limitations Lists of flexible bodies, edges, curves, and/or planes are not supported. Restitution method not supported, use IMPACT method instead. Parasolid contact library only, no support for the RAPID geometry library The flexible body edges participating in contact must be planar (2d). Contact between planar (2D shell element) flexible bodies should be defined using the free edges of the shells. For more information, refer below SimCompanion article: AFL-008: Flexible Body Contact Using Modal Formulation http://simcompanion.mscsoftware.com/infocenter/index?page=content&id=KB8018094 AFL-011: Shell Element Support for Flexible Body Contact http://simcompanion.mscsoftware.com/infocenter/index?page=content&id=KB8018471 Lists of flexible bodies, edges, curves, and/or planes are not supported. However, you can make as many individual contacts as you like, referencing a given flexible body for each individual contact. Flexible body contact is only supported with the default CONTACT_GEOMETRY_LIBRARY. Specifying PREFERENCES/CONTACT_GEOMETRY_LIBRARY = PARASOLIDS will cause an error message The flexible body edges participating in contact must be planar (2d). The Solver will report an error message when the IEDGE and/or the JEDGE in a flex contact is not planar. Contact between planar (2D shell element) flexible bodies should be defined using the free edges of the shells. The Flex-Body to Flex-Body contact pair (using both IFLEX and JFLEX arguments) is intended for 3D contacts and cannot be used with planar (2D shell element) flexible bodies.

MODAL APPLIED FORCE AND PRELOADED FLEXIBLE BODIES In Adams/Flex you can accept exported finite element load cases as part of your flexible body definition and optionally apply them in Adams using the MFORCE element Possibilities: Easily define distributed loads using FEM facilities and efficiently apply them in Adams Combine multiple load cases, scaling them with functions of time and response Thermal loads Flutter analysis

MODAL APPLIED FORCE AND PRELOADED FLEXIBLE BODIES Adams/PostProcessor features: When you define MFORCEs for your flexible bodies, you can display the force magnitudes in Adams/PostProcessor The force magnitudes are displayed in Cartesian coordinates Color contour and vector plots: Let you determine the scale of the MFORCEs Allow you to verify that the MFORCE is set up correctly Help you in debugging your models Note: These options must be selected for each flexible body in either the Modify Flexible Body dialog box in Adams/View or in the property editor in Adams/PostProcessor. Modal forces of the various modes are denoted by FQ. The sum of FQ on all the modes equals the applied force.

MODAL APPLIED FORCE AND PRELOADED FLEXIBLE BODIES Additionally, Adams/Flex lets you define preloaded flexible bodies Possibilities: Simplify modeling by defining flexible bodies that have a natural deformed shape. Example: assemble valve springs or other assemblies. Account for stress stiffening, for example in spinning systems or taut strings. Linearize non-linear finite element models about a deformed state. Example: finite element tire models. Notes: A preload cannot contain a global resultant force. No body should have a tendency to accelerate itself. A preloaded flexible body pushes or pulls on its surroundings and recoils unless the preload is maintained.

MODAL APPLIED FORCE AND PRELOADED FLEXIBLE BODIES Availability Currently not all FEA programs that support Adams/Flex have added support for modal loads and preloads. The following table lists the FEA vendors and available MNF functionality. For the most current version of this chart, see SimCompanion article KB8015076 at: http://simcompanion.mscsoftware.com/infocenter/index?page=content&id=KB8015076 Workaround: Add applied loads and preloads to existing mnf files using the MNFLOAD tool in Adams/Flex Toolkit. adams2012 flextk mnfload input.mnf output.mnf loadfile [threshold] threshold:If specified, modes with frequency less than threshold are considered as rigid modes. FEA Vendors Offering MNF Generation http://simcompanion.mscsoftware.com/infocenter/index?page=content&id=KB8015076 Old KB article http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1-KB9474.

exercises Perform Workshop 7 “Using Contacts and Modal Force” in your exercise workbook.