ANSYS Rigid Dynamics Features
ANSYS Rigid Dynamics provides a complete array of joint types, loads, contact conditions and special elements, allowing quick creation of accurate virtual prototypes of mechanical systems. If geometric or material nonlinearities are important considerations, rigid body models are easily extended to include flexibility, large deformation and nonlinear constitutive models. Since multibody dynamics solutions are supported in the ANSYS Workbench environment, engineers can leverage a fully parametric, persistent modeling environment and a rich set of design exploration tools to optimize their designs for motion, strength and durability requirements.
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ANSYS Rigid Dynamics software supports a complete set of joint types to connect both flexible and rigid bodies. A joint is an idealized constraint on the relative movement between two bodies. Standard joint types include:
Most joint types support optional “stops” that restrict the joint’s relative degree(s) of freedom within a specified range. The software also supports a general joint type, which provides selective restriction of relative degrees of freedom. For more complex constraints, a unique constraint editor is available that allows definition of custom constraint equations.
Beyond kinematic constraints, bodies can be connected with bushings and springs whose stiffness and damping characteristics can be expressed with constants, expressions or tabular data. Force, moment and fixed displacement conditions are also available and can vary as a function of time. All joint and force elements are persistent to geometric variations and can be parameterized.
An automatic joint creation capability facilitates connecting parts in complex assemblies. Once the assembly has been imported, this feature automatically defines joints between parts. Joint definitions can be modified, options specified, and additional joints can be manually defined. Each joint is easily identified with graphical tools provided by the ANSYS Workbench platform. Once the joints are created and fully defined, ANSYS Rigid Dynamics software calculates the total number of free degrees of freedom. If the model is overconstrained, offending joints are clearly identified with options to remove the redundant constraints.
ANSYS Rigid Dynamics technology provides several tools to verify the assembly of complex models. A configuration option helps to explore the motion of the assembly using simple mouse movements. Activating the configure option starts the ANSYS Rigid Dynamic solver for real-time interactive part manipulation within the constraint manifold. This tool enables fast and simple discovery of unexpected motion from incorrectly specified joints. Additional tools are available to help identify and repair over-constrained models.
Rigid body dynamics if often used to assess the kinematics and dynamics of mechanical systems. However, increasing demand for material reduction and faster operational speeds may require simulation fidelity beyond the reach of rigid body assumptions. In these cases, ANSYS Rigid Dynamic models can be converted to a fully or partially flexible model in a few mouse clicks without having to transfer data to and from third-party software components. Flexibility can be modeled in the linear range. Alternately, geometric and material nonlinearities can be enabled to capture large deformation, stress stiffening, and plasticity, among other solid continuum phenomena.
Robust and efficient numerical methods are paramount for rigid body dynamics simulations, which often require the solution of highly nonlinear equations over thousands of time steps. ANSYS Rigid Dynamics software leverages a highly compact and efficient formation of the system’s governing equations of motion, then uses advanced numerical integration algorithms to advance the solution with the largest possible time steps while controlling numerical stability. This is vital for models containing multiple inputs with measured time histories.
Beyond kinematic and dynamic requirements, mechanical systems must be designed to transfer loads and to reliably operate under a range of conditions. To meet these design challenges, ANSYS software provides powerful post-processing capabilities to investigate the component’s internal stress and to verify that the component or assembly is operating within various failure criteria. For flexible components, internal stress and strain states are readily obtained from multibody dynamic analysis. For rigid components, ANSYS software transfers external and inertia loads to a static structural analysis to recover the quasi-static stress state. In either case, a variety of visualization tools — such as contour plotting, probing, cut planes and path plots — lead to a complete understanding of a component’s internal stresses.
Traditionally, mechanical systems are designed using dedicated analysis tools along with engineering experience and intuition. Such an ad hoc approach rarely leads to an optimal design because the engineer does not explore a sufficient number of alternatives. What’s required is a systematic and logical approach to mechanical design. Fortunately, ANSYS delivers ANSYS Rigid Dynamics technology in the ANSYS Workbench environment, which provides a full range of parametric and design analysis capabilities. Parametric variations of CAD parameters, material properties, joint locations and loading conditions enable engineers to easily explore the design space with what-if studies. Alternatively, the power of parametric analysis can be leveraged using ANSYS DesignXplorer to drive design of experiments, goal-driven optimization or min/max search or to even perform Six Sigma analysis to investigate design robustness.
At the foundation of the ANSYS Rigid Dynamics is the ANSYS Workbench platform, which assembles a full range of physics with key enabling technologies for bidirectional CAD connectivity, geometry creation and meshing. Within this environment, engineering teams can design and assess mechanical systems for all dynamic performance objectives. Analysts can conduct a complete set of dynamic simulations on the same model, including multibody dynamics, implicit nonlinear dynamics, explicit dynamics, modal analysis, harmonic analysis and random vibration. ANSYS Workbench enables engineering teams to achieve their simulation objectives faster and smarter without error-prone file transfers between disparate CAE solutions.
Contact is fundamental for most mechanical system simulations, and its accurate modeling is paramount for many applications. ANSYS Rigid Dynamics software includes a general 3-D contact capability for intermittent and persistent contact between rigid bodies. Automatic contact detection and state-of-the-art algorithms allow for fast and accurate solutions. If the contacting parts are flexible, there’s no problem: Enlist the implicit finite element solver to compute the solution.