ANSYS Dynamics Solutions

Transcription

1 ANSYS Dynamics Solutions 11.0 RELEASE ANSYS Analysis Compression Tools Rotor Dynamics Additional tools useful for modeling rotating machinery, such as electric turbo generators, in modal, harmonic and transient dynamic analyses The design mantra "lighter, faster, stronger" is pervasive across industries from consumer electronics to space exploration. But as machines with rotating components get lighter, faster and stronger as well as spin faster, they are increasingly susceptible to selfinduced system-destroying vibrations. Customers in the rotating machinery and other industries use ANSYS software to analyze: Bending deflection of shafts Torsional oscillations Misalignments of rotor axis Balancing of rotating parts The ANSYS Family of Products The ANSYS Dynamics Solution Set ANSYS software provides extensive dynamics solution capabilities, including: Modal analysis: for calculating the natural frequencies and mode shapes of a structure Harmonic analysis: for determining the response of a structure to harmonically time-varying loads, such as those typically seen in rotating machinery Transient dynamic analysis: for determining the response of a structure to arbitrarily time-varying loads in linear and nonlinear simulation environments. The most general and comprehensive of all dynamics analysis types, transient dynamics can be subdivided into: Rigid dynamics Flexible dynamics Spectrum analysis: an extension of modal analysis for calculating stresses and strains due to a response spectrum or a power spectral density (PSD) input (random vibrations) Static analysis: often used to determine displacements, stresses, etc. under linear and nonlinear static loading conditions. Static analyses also can be used in conjunction with dynamic analyses for improved efficiencies, such as a prestressed modal simulation (as is typically done in the turbine development process). Modeling gyroscopic moment, rotor whirl and instability in multi-platen disk drive with ANSYS rotor dynamics tool set Analysis compression tools: Dynamics analyses, particularly those with extensive nonlinearities, can be computationally demanding. Therefore, additional analysis compression tools include: Rotor dynamics: useful for modeling rotating machinery, such as electric turbogenerators, in modal, harmonic and transient dynamic analyses Component modal synthesis: for breaking up a single large problem into several reduced-order problems Distributed ANSYS: for solving large models using multiple processors Variational Technology: exposed in the ANSYS DesignXplorer VT product; used to rapidly explore parametric model variations far faster than can be done when searching for an optimal configuration using traditional approaches

2 11.0 RELEASE Analysis Compression Tools High-Performance Computing The high-performance computing option of ANSYS software decreases solution time for full transient structural, static structural and modal analyses. Shown are the solution times and speedup factors for solving a 112-million degreeof-freedom modal analysis problem. Distributed ANSYS (DANSYS): solving large models using multiple processors Multiprocessing is one way to reduce analysis time. Multiprocessing computer environments (consisting of multiprocessor servers or networked workstations or clusters) may be employed to generate analysis results much more quickly. DANSYS runs equally well on both shared memory parallel (SMP) machines, such as high-end servers, and a distributed memory parallel (DMP) cluster. DANSYS supports a wide variety of analysis types including: Static linear or nonlinear analyses structural Single field thermal analyses (DOF: TEMP) Full transient analyses for single-field structural and single-field thermal analysis Modal analyses using block Lanczos and PCG _ Lanczos solutions Structural harmonic analyses Low-frequency electromagnetic analysis Coupled-field analyses including structural _ thermal, piezoresistive, electroelastic, piezoelectric, thermal _ electric, structural _ thermoelectric, thermal _ piezoelectric ANSYS Modal Analysis A modal analysis typically is used to determine the vibration characteristics (natural frequencies and mode shapes) of a structure or machine component in the design stage. It also can serve as a starting point for another more-detailed dynamic analysis, such as harmonic response or full transient dynamic analysis. Modal analysis is one of the most basic dynamic analysis types available in ANSYS software yet it can be more computationally time consuming than a typical static analysis. A reduced solver, utilizing automatically or manually selected master degreesof-freedom (DOFs), is used to drastically reduce the problem size and solution time. Multiple time-saving modal solution methods are available in ANSYS software for mode extraction from the reduced solution, such as: Block Lanczos method: typically used for large symmetric eigenvalue problems; utilizes a sparse matrix solver PCG Lanczos method: for very large symmetric eigenvalue problems (500,000+ DOFs); especially useful to obtain a solution for the lowest modes to learn how the model will behave Subspace method: for large symmetric eigenvalue problems, though in most cases the Block Lanczos method is preferred for shorter run times with equivalent accuracy Reduced (Householder) method: faster than the subspace method because it uses reduced (condensed) system matrices to calculate the solution; normally less accurate because the reduced mass matrix is approximate Unsymmetric method: used for problems with unsymmetric matrices, such as fluid structure interaction (FSI) problems Damped method: for problems in which damping cannot be ignored, such as journal bearing problems QR damped method: faster than the damped method; uses the reduced modal damped matrix to calculate complex damped frequencies Finite element representation of body-in-white model of prototype SUV as simulated with block Lanczos method modal analysis to find critical low-frequency natural vibration modes, which can cause passenger discomfort if excited

3 ANSYS Harmonic Analysis Used extensively by companies that produce rotating machinery, ANSYS harmonic analysis is employed to predict the sustained dynamic behavior of structures to consistent cyclic loading. Examples of rotating machines that produce or are subjected to harmonic loading include: Turbines Gas turbines for aircraft and power generation Steam turbines Wind turbines Water turbines Turbopumps Internal combustion engines Electric motors and generators Gas and fluid pumps Disc drives A harmonic analysis can be used to verify whether or not a machine design will successfully overcome resonance, fatigue and other harmful effects of forced vibrations. ANSYS geometry tools allow import and editing of chiller model from CAD system in preparation for rotating component analysis. Images courtesy Trane, a business of American Standard. Analysis Compression Tools ANSYS VT Accelerator TM software speeds up the solution of nonlinear structural static or transient analyses by reducing the total number of iterations for analyses not involving contact or plasticity. Additionally, the harmonic sweep feature of ANSYS VT Accelerator provides a high-performance solution for forced-frequency simulations in structural analysis over a range of user-defined frequencies. The structural material may have frequencydependent elasticity or damping. Component modal synthesis: breaking up a single large problem into several reduced-order problems saves time and processing resources; it also offers the following additional advantages: More accurate than a Guyan reduction for modal, harmonic and transient analyses The ability to include experimental results, as the substructure model need not be purely mathematical Rotordynamics investigation of rotating components of chiller assembly can be accelerated by using advanced techniques such as component mode synthesis (CMS). Chiller assembly results from modal and harmonic analyses are used to predict stability vibration characteristics of machine before an expensive prototype is produced.

4 11.0 RELEASE Analysis Compression Tools ANSYS DesignXplorer TM ANSYS DesignXplorer software, which is based on Design of Experiments (DOE), works from within the ANSYS Workbench TM environment to perform DOE analyses of any ANSYS Workbench simulation, including those with CAD parameters. DOE is not limited in the types of analyses. ANSYS DesignXplorer allows the user to study, quantify and graph various structural and thermal analysis responses on parts and assemblies. It incorporates both traditional and nontraditional optimization through a goal-driven optimization method. When coupled with ANSYS VT Accelerator software, ANSYS DesignXplorer can effectively work with structural transient analyses. ANSYS Transient Dynamic Analysis Transient dynamic analysis (sometimes called time _ history analysis) is a technique used to determine the dynamic response of a structure under the action of any general time-dependent loads. Transient dynamic analyses are used to determine the time-varying displacements, strains, stresses and forces in a structure as it responds to any combination of static and time-varying loads while simultaneously considering the effects of inertia or damping. Transient dynamic analysis in ANSYS software can be broadly classified as one of two types: Rigid dynamics: In an assembly, all parts are considered to be infinitely stiff, no mesh is required and a special solver is used to drastically reduce the amount of compu-tational resources required. The primary focus of a rigid dynamics simulation is mechanism operation, part velocities and accelerations, as well as joint forces encountered during the range of mechanism motion. The new ANSYS rigid dynamics product is used for this type of simulation. Flexible dynamics: Some or all parts of an assembly are meshed and considered flexible based on the materials from which they are made. A flexible dynamics simulation typically is done after a rigid dynamics simulation is used to verify the model setup. Flexible dynamics simulation can provide information about machine performance, such as: Will a machine or mechanism work adequately with light, more-flexible members, or will stiffer but heavier members be required? Will the forces transmitted through joints exceed the strength of the materials being used? At what rotational or translation speed will the mechanism experience plastic deformation and begin to fail? Will the mechanism s natural frequencies be excited and lead to instability? Will the repeated loading/unloading lead to fatigue and, if so, where? A flexible dynamics simulation can be performed using ANSYS Structural, ANSYS Mechanical or ANSYS Multiphysics products. Images courtesy Dale Earnhardt Inc.

5 ANSYS Random Vibration Analyses ANSYS random vibration analyses are used to determine the response of structures to random or timedependent loading conditions, such as earthquakes, wind loads, ocean wave loads, jet engine thrust, rocket motor vibrations, and more. The random vibration analysis can be much less computationally intensive than a full transient dynamic analysis while still providing design-guiding results. Types of random vibration analyses include: Response spectrum: single and multi-point base excitation in which the results of a modal analysis are used with a known spectrum to calculate the model s displacements and stresses Dynamic design analysis method (DDAM): a technique used to evaluate the shock resistance of shipboard equipment. It is similar to the response spectrum method except the loading is derived from empirical equations and shock design tables. Power spectral density: a statistical-based random vibration method in which the input load histories are specified based on a probability distribution of the loading taking that particular value. An example application is the calculation of the probable response of a sensitive automotive electronic component to the engine and drive train vibrations while the vehicle travels rapidly down a rough road. Exhaust manifold/catalytic converter assembly model utilized in PSD random vibration analysis

6 11.0 RELEASE ANSYS Static Analysis A static analysis can be a very smart first step in a dynamics simulation. Before investing in a dynamics simulation, a static analysis can be used for: Model verification, answering questions such as: Is contact set up correctly between parts of an assembly? Are the defined boundary conditions providing the expected support? Is the mesh refined in the locations of potentially significant distortion or stress concentrations? Is there an inadvertent mesh discontinuity? Do you need to model nonlinearities, which are computationally expensive, or do the static results suggest that the potential nonlinearities aren t required? Efficiently pre-loading or pre-stressing a model Apply a constant rotational velocity to a turbine, for instance, pre-stressing the entire structure including the turbine blades prior to a bird strike analysis. Apply temperature loading from a previous thermal simulation to pre-stress the model thermally in a single iteration before running a multi-iteration dynamics analysis. The ANSYS Advantage ANSYS software provides customers with a competitive advantage through: ANSYS Workbench, which provides a unified product development environment offering integration across a wide range of design processes ranging from geometry modeling and editing, meshing and pre-processing to advanced analysis (structural, thermal, electromagnetics, CFD, etc.) to robust design optimization Providing industry s broadest range of physics capability in one integrated analysis environment Advanced meshing solutions to efficiently address high-aspect ratio geometry commonly associated with complex product applications Advanced material models and contact types for simulating plastics, rubber, sliding surfaces and large deformations

7 Dynamics Functionality by Product ANSYS ANSYS ANSYS ANSYS ANSYS Multiphysics Mechanical Structural Professional Professional NLS NLT Structural Dynamic Analysis Type Modal X X X X X Spectrum X X X X X Harmonic X X X X X Random vibration X X X Structural Linear Functionality Substructuring X X X Component mode synthesis X X X Cyclic symmetry X X X X X Mode superposition X X X X X Structural Nonlinear Functionality Geometric X X X X Note 1 Material X X X X X Element X X X X X Large strain X X X X Large deflection X X X X Stress stiffening X X X X Spin softening X X X X Material Modeling Linear elasticity X X X X X Inelastic X X X X Rate-independent X X X X Rate-dependent X X X X Non-metal plasticity X X X X Shape memory alloys X X X X Cast iron X X X X Hyperelasticity (isotropic/anisotropic) X X X X Viscoplasticity and viscoelasticity X X X X Creep and swelling X X X X Material damping X X X X User materials X X X X Temperature-dependent properties X X X X X Solver Types Iterative X X X X X Sparse direct X X X X X Frontal (wavefront) X X X X X Distributed memory PCG Note 2 Note 2 Note 2 Note 2 Note 2 Distributed memory JCG Note 2 Note 2 Note 2 Note 2 Note 2 Distributed sparse (Dsparse) Note 2 Note 2 Note 2 Note 2 Note 2 Algebraic multi-grid (AMG) Note 2 Note 2 Note 2 Note 2 Note 2 General Parametric simulation X X X X X CAD parameter access Note 3 Note 3 Note 3 Note 3 Note 3 ANSYS Parametric Design Language X X X X X Design optimization Note 4 Note 4 Note 4 Note 4 Note 4 Note 1: Not available for 2-D plane and 3-D solid elements Note 2: Available in ANSYS Mechanical HPC add-on module Note 3: Available through either the ANSYS DesignModeler add-on or with ANSYS Workbench when used with a geometry interface and a parametrically supported CAD system Note 4: Available through the ANSYS DesignXplorer add-on module Note 5: Rigid dynamics is available in a separate module, ANSYS Rigid Dynamics

8 11.0 RELEASE ANSYS, Inc. Solutions ANSYS designs, develops, markets and globally supports engineering simulation solutions used to predict how product designs will behave in manufacturing and real-world environments. Its integrated, modular and extensible set of solutions addresses the needs of organizations in a wide range of industries. ANSYS solutions qualify risk, enabling organizations to know if their designs are acceptable or unacceptable not just that they will function as designed. ANSYS helps organizations achieve: Innovative and high-quality products and processes Fewer physical prototypes and test setups Faster return on investment due to reduced development time A more flexible and responsive information-based development process enabling the modification of designs at later stages of development A front-end simulation strategy that offers a superior method for bringing products to market in less time and with fewer costs About ANSYS, Inc. ANSYS, Inc., founded in 1970, develops and globally markets engineering simulation software and technologies widely used by engineers and designers across a broad spectrum of industries. The Company focuses on the development of open and flexible solutions that enable users to analyze designs directly on the desktop, providing a common platform for fast, efficient and cost-conscious product development, from design concept to final-stage testing and validation. The Company and its global network of channel partners provide sales, support and training for customers. Headquartered in Canonsburg, Pennsylvania, U.S.A., with more than 40 strategic sales locations throughout the world, ANSYS, Inc. and its subsidiaries employ approximately 1,400 people and distribute ANSYS products through a network of channel partners in over 40 countries. ANSYS, Inc. Southpointe 275 Technology Drive Canonsburg, PA U.S.A ansysinfo@ansys.com Toll Free U.S.A./Canada: Toll Free Mexico: Europe: eu.sales@ansys.com ANSYS, ANSYS Workbench, AUTODYN, CFX, FLUENT and any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarks or trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademark used under license. All other brand, product, service and feature names or trademarks are the property of their respective owners. Image Credits: Some images courtesy Aavid Thermalloy, ICT Prague and Silesian University of Technology Institute of Thermal Technology ANSYS, Inc. All Rights Reserved. Printed in U.S.A. MKT