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Structural Dynamics Tips (22 entries)
 
22x Coupled-Field Elements [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "The 22x direct coupled-field elements (PLANE223, SOLID226-227) provide a wide array of material behavior for multiphysics applications - these include piezoelectricity, piezoresistivity, thermoelasticity, and thermoelectricity. This memo hopes to introduce some of the pertinent features of these elements."
(Week 34, week of 06/11/06.)
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Average Rating: 8.9 (37 votes)  
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Basics on Structural Damping (Addendum) [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Since ANSYS 5.6, there have been numerous enhancements as well as facets of the software program that have changed, including treatment of damping. This article is meant to serve as an addendum to Section 6 of the authorís "Structural Damping" memo, which was written in October, 2000."
(Week 46, week of 04/27/08)
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Average Rating: 10.0 (4 votes)  
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Basics on Structural Damping [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  This is an old document I wrote a while ago on damping which I sometimes use. Although written back at version 5.6, it is still applicable at version 7.0.
"Damping is required in many dynamic applications, yet because there are many ways to include it, there is often confusion regarding the implementation of damping in ANSYS. This memo hopes to provide a general summary of the representation of damping available in ANSYS."
(Week 21, week of 11/25/02.)
See also Addendum to "Basics on Structural Damping" memo.
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Average Rating: 9.2 (52 votes)  
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Clustering Results Around Peaks for Full-Harmonic Analyses in ANSYS
  Aaron Acton (ANSYS, Inc.)
  "This article presents a method for obtaining full harmonic solutions clustered around potential peak responses. Full harmonic analyses provide exact solutions, typically calculated at equally spaced intervals over the desired frequency range. Mode-superposition analyses, however, provide approximate solutions, but can be clustered around potential resonant peaks. The hybrid method discussed in this article uses a modal solution to determine natural frequencies, which are then used to calculate clusters of points surrounding those frequencies. Full harmonic solutions can then be performed at these clustered points. Examples and input les are provided in order to utilize this method."
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Average Rating: 10.0 (3 votes)  
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Converting pressures to nodal forces [PDF]
  Sheldon Imaoka (CSI)
  Tip on converting element pressures to nodal forces. This can be useful for mode superposition methods where LVSCALE may not be suitable.
SI_P2F Macro and test input file.
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Average Rating: 8.1 (32 votes)  
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Converting Prony Series to Frequency Domain
  Sheldon Imaoka (ANSYS, Inc.)
  Simple example showing how to convert Prony series for viscoelasticity from time domain to frequency domain. This is to convert TB,PRONY to TB,ELASTIC/SDAMP for use in harmonic response analyses.
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Average Rating: 10.0 (7 votes)  
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Differences Between Implicit and Explicit Dynamics
  Sheldon Imaoka (ANSYS, Inc.)
  Discussion of the differences between implicit and explicit dynamics. (Differences between regular ANSYS and ANSYS/LS-DYNA)
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Average Rating: 8.1 (39 votes)  
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Example harmonic analysis using the large mass method [PDF]
  David Haberman (CSI)
  Step-by-step instructions on performing an example harmonic analysis using the large mass method.
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Average Rating: 8.4 (22 votes)  
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Introduction to the Residual Vector Method [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "The residual vector method can improve the accuracy of mode-superposition harmonic response or transient analyses, especially when the high-frequency content of the structure is excited. This memo provides details on how users can take advantage of this analysis technique introduced in ANSYS 11.0."
(Week 45, week of 04/20/08)
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Average Rating: 10.0 (3 votes)  
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Modal Cyclic Symmetry Enhancements at 6.0 [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "At ANSYS 6.0, the modal cyclic symmetry procedure has been significantly improved. New commands, CYCLIC and CYCOPT, replace the older CYCGEN and CYCSOL macros and provide more flexibility and ease-of-use."
(Week 12, week of 12/31/01.)
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Average Rating: 7.1 (12 votes)  
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Multiframe Restarts [PDF]
  Sean Harvey (CSI)
  Memo covering the multiframe restart capability (RESCON) in ANSYS.
Accompanying input file
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Average Rating: 4.5 (10 votes)  
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Options for ADAMS.MAC
  Sheldon Imaoka (ANSYS, Inc.)
  The ADAMS.MAC macro enables ANSYS users to generate MNFs for flexible bodies for use in ADAMS. The user can set an environment variable MDI_MNFWRITE_OPTIONS that can reduce the size of the MNF, as well as provide other options also available through the ADAMS/Flex Toolkit The temporary directory where the MNF is written can also be specified by the user.
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Average Rating: 10.0 (3 votes)  
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Postprocessing Harmonic Results [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "In harmonic analyses, due to the fact that results may not be in phase, postprocessing quantities of interest can pose a challenge. Users may need to review non-sinusoidal results, such as equivalent stresses, at different locations, so accounting for phase information may be required.
This memo hopes to cover some of the more important points regarding postprocessing structural harmonic analysis results in both the General and Time-History Postprocessors."

(Week 30, week of 07/17/05.)
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Average Rating: 10.0 (22 votes)  
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PSD Calculation Efficiency [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "A very common use of PSD analyses is to look at the response of a system under a single base excitation, such as the case with many aerospace and civil applications. The default PSD settings are very general in nature and may consequently be inefficient for such a situation. This memo hopes to outline some ways in which the user may obtain more efficient PSD solutions for the specific instance of single base excitation with relatively flat spectrum (although some techniques may be extrapolated for other cases)."
…An older doc I recently reanimated and updated…
(Week 25, week of 06/13/04.)
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Average Rating: 9.2 (13 votes)  
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PSD Postprocessing [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "PSD, or random vibration, analyses present some interesting challenges in postprocessing due to the nature of the assumptions related to the analysis. This memo hopes to address some of these items, including evaluation of derived stresses and calculation of response power spectral density."
…An older doc I recently reanimated and updated…
(Week 26, week of 06/27/04.)
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Average Rating: 9.6 (13 votes)  
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PSD Postprocessing of Relative Displacement [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "PSD users may wish to determine the relative 1-sigma results between two points. This memo covers three methods to perform this operation, in hopes that it will give users more familiarity with PSD postprocessing in ANSYS."
(Week 53, week of 03/07/09)
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Average Rating: 10.0 (5 votes)  
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PSD results and RSYS
  Sheldon Imaoka (ANSYS, Inc.)
  Some tips on postprocessing random vibration analyses - specifically, RSYS,SOLU and PSD results as well as cases with rotated nodes.
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Average Rating: 10.0 (2 votes)  
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QR Damped and Unsymmetric Stiffness [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "There have been significant enhancements to the QR Damped eigenvalue extraction method in the past several releases of ANSYS. At 8.0, the capability of including unsymmetric damping [C] matrix was introduced, along with support of damping defined via the DMPRAT and MDAMP commands.
ANSYS 8.1, the material-based constant damping ratio MP,DMPR allowed users to specify constant damping ratios per material ID in mode-superposition harmonic analyses, when used with the QRDAMP eigensolver. With the release of 9.0, QRDAMP also supports unsymmetric stiffness [K] matrix, output of complex eigenvectors, and the use of the PSOLVE command. This memo hopes to cover the use of QR Damped eigenvalue extraction method in friction problems, where an unsymmetric stiffness [K] matrix may be present. An example of this type of problem is brake squeal analyses, where the combination of ANSYS 17x contact elements and the QRDAMP eigensolver provide an easy-to-use, efficient means of determining unstable modes."

(Week 29, week of 01/09/05.)
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Average Rating: 9.4 (16 votes)  
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QR Damped Modal Analysis [PDF]
  Sheldon Imaoka (CSI)
  Presentation on different damped eigenvalue extraction methods in ANSYS, focusing on the newer QR Damped method.
Input files in zip format
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Average Rating: 10.0 (10 votes)  
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Random Vibration Analysis of a Circuit Board [PDF]
  Sean Harvey (CSI)
  Example of random vibration analysis of a circuit board in ANSYS.
Input files in zip format
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Average Rating: 9.8 (48 votes)  
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Sine sweep simulation [PDF]
  David Haberman (CSI)
  Discussion on harmonic sweeps, either via the direct displacement method or the large mass method.
Direct displacement method example input file and Large mass method example input file
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Average Rating: 8.4 (25 votes)  
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Using CMS in Workbench Simulation [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "At Workbench 11.0, the ANSYS Rigid Dynamics add-on module enables users to model complex kinematic assemblies, whereby system-level performance as well as accurate force loading on components can be obtained.
Although the parts in the assembly may initially be considered rigid, an interesting, related method is the use of component mode synthesis (CMS) to account for the flexibility of parts. This memo will attempt to cover a way in which users can incorporate CMS in their multibody analyses in Workbench Simulation."

[For version 12.0, use supplied "cms_use_v12.mac" instead of "cms_use.mac" - courtesy of D. Creech.]
(Week 37, week of 05/27/07.)
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Average Rating: 9.8 (28 votes)  
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