Multi Flexible Body Dynamics 글 편집

Multi Flexible Body Dynamics

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  MFBD (Multi Flexible Body Dynamics) in RecurDyn is a technology to analyze the dynamic behavior of systems which include both rigid bodies and flexible bodies. It combines with MBD (Multi-Body Dynamics) to analyze the motion of rigid bodies and FEM (Finite Element Method) to analyze the motion, stresses, and deformation of flexible bodies. RecurDyn’s solver combines with these two components into a single solver. This provides RecurDyn with a much faster and much more robust solver than could be achieved through co-simulation.

  Two flexible body formulations are supported in MFBD in RecurDyn. One is the method of modal synthesis, in which the deformation of a body is represented by a set of linear mode shapes obtained from an eigen analysis of the flexible body. The other is the nodal method, in which all nodal degrees of freedom are considered. The nodal method supports both nonlinear geometric deformation as well as nonlinear material formulations, such as plastic and large-strain rubber-like hyperelastic materials. RecurDyn’s powerful analysis environment combines both the modal and the nodal methods into the same solver, giving RecurDyn an incredibly robust, fast, and reliable solver.

  Furthermore, flexible body meshes can be either imported from externally created FE meshes, or the meshes can be conveniently created directly inside of RecurDyn using its built-in mesh engine. RecurDyn is the first Multi-Body Dynamics analysis code to incorporate a mesher, allowing the user great flexibility and convenience in MFBD modeling and analysis.


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- MFBD modeling and analysis highlights

  • Flex and Rflex can be used at the same time.
  • Mesh-Pre-Solve-Post (one-stop process) within RecurDyn.
  • Convenient conversion of Body type (Rigid↔Flexible).
  • Existing Joint, Force and Contact connections are preserved when the body type is converted.


MBD (Multi-Body Dynamics) Analysis

  A Multi-Body Dynamics analysis is the analysis of the motion over time of a system of rigid bodies interconnected by joints and acted on by forces, and possibly driven by user-defined motions of specific bodies in the system. The forces acting on the bodies can be inter-body forces, like springs or contact, or externally applied forces, such as gravity or a driving force. RecurDyn provides an intuitive, easy-to-use environment for modeling and analyzing Multi-Body Dynamics.


Features of MBD (Multi-Body Dynamics) Analysis in RecurDyn

  • Simple and easy to model a specified motion, force, joint, or contact.
  • Intuitive modeling and composition of mechanism elements and configurations of mechanical systems.


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MFBD (Multi Flexible Body Dynamics) Analysis

  A multi flexible body dynamics analysis is a simple extension of Multi-Body Dynamics in RecurDyn. An MFBD analysis can be composed by swapping flexible bodies for rigid ones. MFBD analysis capitalizes on the advantages of MBD analysis in RecurDyn, such as ease of modeling joints and external forces. The motion of the flexible bodies as well as the resulting stresses, strains, and deformation of these bodies can be examined directly from the results of an MFBD analysis in RecurDyn.

Features of MFBD (Multi Flexible Body Dynamics) Analysis in RecurDyn

  • Rigid and flexible bodies can be easily connected together in the same model.
  • The number of bodies to be treated as flexible can be adjusted, as well as the flexible body formulation between the modal and nodal methods. This allows for simulation time to be optimized based on the needs for fidelity in the results.
  • Boundary conditions and forces applied to the flexible parts are controlled much more naturally and much more accurately than they are using rigid bodies to estimate the forces to be applied to isolated parts in finite element analysis afterward.
  • Connections, joints, and force elements are preserved when converting a rigid body to a flexible one.
  • A rigid body in a RecurDyn model can be easily replaced with a mesh from other FE software.


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Features & Advantages


Differentiators of MFBD

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Other features of MFBD
  • 2D and 3D contacts
  • Boundary conditions can be defined for individual nodes.
  • Support for various rigid body elements (Rigid, Interpolation)
  • Support for various elements (Beam, Shell, Solid, Rigid)
  • Fast analysis using SMP support
  • Modal flexible bodies can be created by importing mesh data generated externally (ANSYS, Nastran, Design Space formats are supported).
  • Modal flexible body can be created by importing modal analysis results generated by external FEA software (ANSYS, Nastran, IDEAS, RADIOSS/OptiStruct and Simulation Mechanical are supported).


Features & Advantages


Joint Connections & Contact

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  • The same joint elements can be used to connect rigid-to-rigid, rigid-to-flexible, or flexible-to-flexible bodies in MFBD analysis.
  • Contact can be defined between rigid-to-rigid, rigid-to-flexible, or flexible-to-flexible bodies.


Self Contact

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  • RecurDyn can model self-contact between sections of the same flexible body.


Nonlinear Flexibility

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  • Simulates the load torque caused by the viscosity of the lubricating fluid acting on the differential gear train.


Accurate Loading Conditions

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  • RecurDyn is designed to model and analyze mechanical systems in addition to isolated parts. Therefore, MFBD in RecurDyn allows it to capture complex loading conditions and complex connections between bodies. RecurDyn's system-level modeling allows it to capture these conditions much more realistically and accurately than could be captured if the flexible bodies were analyzed in isolation.


Mesher

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  • RecurDyn is the first MBD software to contain a mesher. Becuase of this, it is very simple and convenient to generate MFBD analysis.
  • The mesher is very effective, even for complex geometry. The mesher supports the creation of the following element types:
    • 2-node beam (Beam2)
    • 3-node tri shell (Shell3)
    • 4-node quad shell (Shell4)
    • 4-node tetra (Solid4)
    • 5-node pyramid (Solid5)
    • 6-node wedge (Solid6)
    • 8-node hexa (Solid8)
    • 10-node tetra (Solid10)

Applications


Parking Brake

  • Toolkit Used : FFlex, Professional
  • Objective : Improve the design of a highly stressed part in an automobile parking brake system to increase its durability.
  • Modeling Methodology : The parts that have relatively high stiffness and low fatigue are modeled as rigid bodies and the highly stressed part is modeled as flexible body. Contact is used to model the connection between the flexible body and a rigid body where the most significant fatigue occurs.


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Landing Gear

  • Toolkit Used : FFlex, Professional
  • Objective : Estimate the fatigue and reliability of aircraft landing gear by analyzing its dynamic behavior as the airplane lands.
  • Modeling Methodology :The interaction of the landing gear strut and the support arms is modeled using kinematic joints, and the interaction of the inner and outer struts of the landing gear, which are both flexible bodies, is modeled using flexible-to-flexible body contact.


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Double Valve Spring

  • Toolkit Used : FFlex, Professional
  • Objective : Verify the dynamic behavior, stress, strain, and deformation of double valve spring experiencing contact between a cam and the valve assembly, which contains a double value spring.
  • Modeling Methodology : The spring is modeled as a flexible body, and self-contact is used in the double value spring to capture the interaction of the spring windings when the spring is compressed.


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Manufacturing Robot

  • Toolkit Used : FFlex, RFlex, Professional, CoLink
  • Objective : Examine the relationship between the driving torques applied at the joints of the robot arm and the contact forces between the gripper and the object.
  • Modeling Methodology : The driving torque was desired that maintained an acceptable level of contact forces acting on the object. FFlex (the nodal method) was used to model the parts in contact to capture the effect of the acceleration of the arm on the contact with the object.


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Printer

  • Toolkit Used : FFlex, RFlex, Belt, MTT3D, Professional, CoLink
  • Objective : Verify the vibration of the ribbon cable and case of an inkjet printer while printing a page when the carriage is moved by a belt drive system.
  • Modeling Methodology : The flexibility of the printer case is important to the objective, but it experiences relatively little deformation. Therefore, it is modeled using RFlex (the modal method). The ribbon cable experiences very large nonlinear geometric deformation. Therefore, it is modeled using FFlex (the nodal method). Also, the carriage drive belt is modeled as an FFlex flexible body using a shell belt and the paper is modeled as an FFlex flexible body using MTT3D.


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Paper

  • Toolkit Used : MTT3D
  • Objective : A simulation is used to predict the stacking behavior of paper as it passes through the rollers of a printer, while including the effect of air resistance on the dynamic behavior of the paper at a high feed rate (60 pages per minute) in a laser printer.
  • Modeling Methodology : The shape of the rollers is specifically designed to bend the paper laterally as the paper passes through them. This increases the longitudinal stiffness of the paper as well as increases the effect of air resistance, both of which are important to the stacking of the paper as it leaves the printer. MTT3D’s sheet shell paper elements, which are modeled using the nodal method, can accurately capture the stiffening response of the paper due to the bending imparted by the rollers.


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Wind Turbine

  • Toolkit Used : FFlex, RFlex, Professional, Gear, Bearing
  • Objective : The stresses in the blades of a windmill for wind power generation are estimated through a dynamic simulation of a windmill complete with transmission and generator assembly.
  • Modeling Methodology : The blades experience small deformation, so accurate stresses and deformation can be predicted using RFlex (the modal method). The bearings and the gears are modeled as rigid bodies, while the planet gear carrier is modeled as a FFlex body to capture the effect of the complex loading conditions it experiences.


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MFBD Solution

RecurDyn’s MFBD solution allows convenient and easy modeling of MFBD and its effective analysis. An MBD model can be easily converted to an MFBD model through the use of the RecurDyn’s AutoMesher (link). Durability analyses can be easily performed using the results of an MFBD simulation. MFBD has been directly embedded into various other toolkits as well, such as RecurDyn/MTT3D and RecurDyn/Belt.


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Modeling and Analysis Process in MFBD

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