Rigid Dynamic Analysis in Workbench

Transcription

1 Rigid Dynamic Analysis in Workbench 1-1

2 Introduction Rigid Dynamic Analysis: Calculates dynamic response of an assembly of rigid bodies. Can be used to study the kinematics of an assembly. Bodies are linked via joints and springs. 1-2

3 Rigid Dynamics Inputs and outputs are forces, moments, displacements, velocities and accelerations. All parts are assumed rigid (no stress/strain). Viscous damping is accounted for via spring definitions. 1-3

4 Rigid Dynamic Setup Solid geometry is used to define the model (no multibody parts). Parts are considered rigid so density is the only required material property. To begin a rigid dynamic analysis parts must have their stiffness behavior flagged as rigid. 1-4

5 D. Joint Types There are 9 available joint types in Simulation: Fixed Joint Revolute Joint Cylindrical Joint Translational Joint Slot Joint Universal Joint Spherical Joint Planar Joint General Joint Remember, joint DOF are with respect to the joint s reference coordinate system. Examples follow

6 Dynamics Joint Types Revolute Cylindrical Spherical Planer Universal Translational Slot 1-6

7 Joint Types Revolute Joint: Constrained DOF: UX, UY, UX, ROTX, ROTY Fixed Free 1-7

8 Joint Types Cylindrical Joint: Constrained DOF: UX, UY, ROTX, ROTY Fixed Free 1-8

9 Joint Types Translational Joint: Constrained DOF: UX, UZ, ROTX, ROTY, ROTZ Free Fixed 1-9

10 Joint Types Slot Joint: Constrained DOF: UY, UZ Free Fixed 1-10

11 Joint Types Universal Joint: Constrained DOF: UX, UY, UZ, ROTY Free Fixed 1-11

12 Joint Types Spherical Joint: Constrained DOF: UX, UY, UZ Free Fixed 1-12

13 Joint Types Planar Joint: Constrained DOF: UZ, ROTX, ROTY Free Fixed 1-13

14 Joint Types Fixed Joint: Constrained DOF: All General Joint: Constrained DOF: Fixed All, Free X, Free Y, Free Z, Free All General joints allow configurations not covered by the basic joints shown on the previous pages. A free body must be linked to ground using a general BTG joint with Free All specified (recall that all bodies must be defined such that a path to ground exists via joints). 1-14

15 Springs Springs can be added from the BTG or BTB menus. In BTG a reference CS is used to locate the ground location. 1-15

16 Rigid Dynamic Solution Setup From the New Analysis menu choose Rigid Dynamic. The Analysis Setting branch contains the controls for setting up the analysis: Number of steps Time step controls Output controls Solver tolerances Note, additional steps are generally used when loads are applied or removed or when load histories undergo abrupt changes. 1-16

17 Rigid Dynamic Solution Setup For rigid dynamic analysis only inertial loads (acceleration and/or gravity) are used. No loads or supports are used as in flexible body analyses. Joint conditions are used to apply all other loads as constants or time varying using tabular or functional definitions. Once inserted each joint in the model is available via the drop down list in the joint condition details. 1-17

18 Joint Conditions Joint conditions can be defined as constant, tabular or as a function. Tabular data can be input in the table in Simulation or in the Engineering Data application. Once entered in Simulation the data can be saved to the ED application. 1-18

19 Joint Conditions Functional joint conditions can be entered in the details or defined in the ED application. From the EDA choose to Insert New Load History. Select the appropriate type and indicate the data is in the form of a function. 1-19

20 Joint Conditions Various mathematical functions and arithmetic operators can be used to construct functions using time as an independent variable. The function is displayed in function and graphical formats. Can type in functions or choose to insert them. 1-20

21 Rigid Dynamic Postprocessing Results available from rigid dynamic analyses are deformations, velocities, accelerations and various probe results. As with other analysis types results may be scoped to entire assemblies or to individual parts, surfaces, edges or points. 1-21

22 Rigid Dynamic Postprocessing Rigid dynamic results are graphical, tabular or animations. 1-22

23 Rigid Dynamic Demonstration Body to Ground Fixed Body to Body Revolute Body to Body Translational Body to Ground Revolute Body to Body Revolute 1-23

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25 Lecture Workbench Simulation Flexible Dynamic Analysis 1-25

26 Introduction If inertial effects are significant, the use of static structural analyses is not sufficient in determining the dynamic response of a system Flexible dynamic analysis in Workbench Simulation 11.0 provides users with the ability to determine the dynamic response of the system under any type of time-varying loads. Unlike rigid dynamic analyses, bodies can be either rigid or flexible. For flexible bodies, nonlinear materials can be included, and stresses and strains can be output. Flexible dynamic analysis is also known as time-history analysis or transient structural analysis. Assembly shown here is from an Autodesk Inventor sample model 1-26

27 Dynamics From Rigid to Flexible Step 1 - Add Flexible Dynamics Analysis to solution leg of tree 1-27

28 Dynamics From Rigid to Flexible Step 2 - Change part definition from Rigid to Flexible 1-28

29 Dynamics From Rigid to Flexible Step 3 - Preview Flexible Part Mesh 1-29

30 Dynamics From Rigid to Flexible Step 4 - Set Analysis Options for time step etc. and solve 1-30

31 Loads and Supports For flexible bodies, any type of load or support can be applied For rigid bodies, acceleration load and joint conditions are available Multiple Steps are supported for load histories: Similar to the static case, user can easily define multiple steps As shown below, loads, supports, and joints may be deactivated or activated at any step simply by right-clicking on the Timeline. This gives the user flexibility in the load definition. 1-31

32 Postprocessing Probe Results The Probe tool has also been enhanced at 11.0 to include more results, including Energy, Reactions, Joint results, and Spring results After a Probe result is added, the Timeline and Tabular Data views show the values. From the Tabular Data view, the user can check/uncheck the columns to show what will be displayed in the Timeline A New Chart and Table can also be added to create customized charts and tables for output purposes. 1-32

33 Flexible Dynamic Demonstration 1-33

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