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General Structural Tips (24 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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Calculating effective Coefficient of Thermal Expansion [PDF]
  Bill Bulat (CSI)
  Tips on how to define coefficient of thermal expansion and converting that material data to format that ANSYS can use.
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Average Rating: 9.8 (44 votes)  
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CERIG vs RBE3, RIGID184 [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Constraint equations provide many useful features in ANSYS, such as tying together dissimilar meshes, representing parts of the system not explicitly modeled, or distributing loads. Two automated methods of generating constraint equations are the CERIG and RBE3 commands. Because there is often confusion over their use, this memo hopes to provide some information on differences between the two methods.
"Constraint equations in ANSYS are linear, so they are not valid for large-rotation analyses. RIGID184 is a beta element in version 6.1 which provides rigid link/beam capabilities, valid for large-rotation problems. The latter part of this memo will cover some details of this undocumented feature, available in 6.1."

(Week 19, week of 07/08/02.)
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Average Rating: 9.9 (69 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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Different Methods of Connecting Parts Together [PDF]
  Sean Harvey (CSI)
  Connecting Parts - A study of Continuous Mesh versus Bonded Contact versus Constraint Equations.
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Average Rating: 9.4 (61 votes)  
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Elastic Foundation Stiffness
  Sheldon Imaoka (ANSYS, Inc.)
  Short explanation of what elastic foundation stiffness (SURF154) is and how to calculate the resulting stiffness for non-planar cases. In Workbench Mechanical, this feature is referred to as an "Elastic Support".
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Average Rating: 9.3 (7 votes)  
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Manual Calculation of Strain Energy Density [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Output of elastic, plastic, and creep strain energy densities (SEND) was introduced in ANSYS 6.0, although this is limited to 18x elements in nonlinear analyses. Users whose models include core elements with plasticity and creep may also wish to obtain these quantities, and this memo hopes to review this procedure."
(Week 22, week of 12/22/02.)
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Average Rating: 10.0 (19 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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Performance of SOLID92 vs. Degenerate SOLID95
  Sheldon Imaoka (CSI)
  Discussion on why there are differences in run times of SOLID92 and the degenerate tetrahedra form of SOLID95. (From XANSYS posting)
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Average Rating: 7.3 (13 votes)  
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Pressure Load Macro [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "In ANSYS, pressure loading via the SFx family of commands allows users to apply a force per unit area in a direction normal to the surface. Structural surface effect elements SURF153 and SURF154 extend pressure loading capabilities by allowing users to specify normal, tangential, or arbitrary distributed loading. In fact, for an arbitrary ‘distributed loading vector,’ the full or projected area may be used, with or without the tangential component of load. This type of loading can be useful in mimicking a bearing load (include tangential component) or wind loading (no tangential component), to name a couple of examples.
"Because of the fact that the vector-type of pressure loading can be based on full or projected area, with or without the tangential component, trying to determine an appropriate value for the loading can be cumbersome. The author has written a simple macro which can be used as an example in utilizing surface effects more effectively by allowing the user to specify the total force instead of pressure – the macro calculates the appropriate pressure value to be applied on the surface effect elements."

(Week 27, week of 07/04/04.)
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Average Rating: 8.9 (18 votes)  
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Review of Anisotropy, Yield Criteria, Failure Criteria [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "This memo hopes to serve as a review of the basics of anisotropy, yield criteria, failure criteria, and the ANSYS procedure related to these topics."
(Week 15, week of 01/21/02.)
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Average Rating: 8.8 (20 votes)  
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SOLID92 and EMAT Files
  Sheldon Imaoka (CSI)
  Discussion on when EMAT files are written when using SOLID92. Preventing writing of EMAT files to disk may decrease overall solution times on some hardware. (From XANSYS posting)
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Average Rating: 10.0 (3 votes)  
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Sparse Solver (Memory and Performance Information)
  Gene Poole (ANSYS, Inc.)
  Discussion on memory requirements and performance of the sparse solver in ANSYS. (From XANSYS posting)
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Average Rating: 8.8 (4 votes)  
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Sparse vs. PCG Solvers
  Gene Poole (ANSYS, Inc.)
  Thorough discussion on the differences in performance between sparse and PCG solvers.
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Average Rating: 6.9 (8 votes)  
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Spatially-Varying Pressure Loading in Workbench Simulation [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Workbench Simulation 11.0 allows users not only to apply constant pressure loads or force vectors per unit area but also to utilize hydrostatic pressure loads and line pressure loads (force per unit length), and these can be defined as a function of time. Moreover, fluid pressures can be mapped from a steady-state or transient ANSYS CFX solution.
Despite these options, there may be situations where a user may want to import a predefined, spatially-varying pressure field from an external text file. This can be accomplished through the use of a “Commands” object and APDL tables, which this memo will introduce."

(Week 38, week of 07/01/07.)
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Average Rating: 8.4 (19 votes)  
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Structural Beam Elements Overview [PDF]
  Sheldon Imaoka (CSI)
  An overview of beam elements available in ANSYS, including the new BEAM188/189 elements and differences between thin and thick beams.
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Average Rating: 8.8 (17 votes)  
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Structural Shell Elements Overview [PDF]
  Sheldon Imaoka (CSI)
  Overview of structural shell elements in ANSYS, including differences between thin and thick shells, drilling DOF, etc.
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Average Rating: 9.2 (20 votes)  
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Structural Surface Effect Elements Intro [PDF]
  Sheldon Imaoka (CSI)
  Introduction to structural surface effect elements (SURF153/154).
BOLTLOAD input file
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Average Rating: 8.6 (7 votes)  
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Structural surface Effect Elements, General Overview
  Sheldon Imaoka (ANSYS, Inc.)
  An overview presentation and example workshop on structural surface effect elements. This is an old presentation I did at ANSYS 5.6.1, so if you use later versions of ANSYS, some of the menus and dialog boxes may have changed.
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Average Rating: 9.5 (11 votes)  
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Thermal-stress analyses using SHELL57 and SHELL93
  Sheldon Imaoka (CSI)
  Tips on performing thermal-stress analyses of shells, including temperature effects of SHELL93 and compatibility with SHELL57. (From XANSYS posting)
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Average Rating: 8.8 (20 votes)  
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Unsymmetric MATRIX27
  Sheldon Imaoka (ANSYS, Inc.)
  There have been changes between ANSYS 10.0 and 11.0 regarding MATRIX27 unsymmetric input via real constants. This describes the change and provides a visual representation of the matrix input.
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Average Rating: 10.0 (2 votes)  
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User-Defined Failure Criteria with USERFC [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "The FC command provides users with the ability to predict first-ply failure using maximum strain, maximum stress, or Tsai-wu failure criteria. In ANSYS 12.0.1, users can also take advantage of the userfc subroutine to define up to nine different criteria.
This memo reviews the userfc subroutine, and a sample implementation of the Hashin criterion is included."

(Week 54, week of 10/11/09)
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Average Rating: 9.5 (10 votes)  
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Using PSOLVE [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  Although most often used for large-deflection prestressed modal analyses, PSOLVE has other applications which make it attractive to use, especially for large models.

PSOLVE can be used for the following situations:

  • Precise mass calculations
  • Detailed listing of contact pair information
  • Evaluation of tabular boundary conditions and loads

Since PSOLVE is a partial solution (namely, calculation of element matrices), it is usually much faster than performing an actual solution. Hence, the user may obtain any (or all) of the above three types of information prior to running an actual analysis, which can be a valuable way of verifying model input and settings prior to solution.

(Week 20, week of 07/14/02.)
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Average Rating: 8.1 (21 votes)  
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Visualizing structural matrices in ANSYS using APDL
  Aaron Acton (ANSYS, Inc.)
  "This article presents a method of visualizing structural matrices used in finite-element analysis using ANSYS and the ANSYS Parametric Design Language (APDL). The information is intended to provide some insight into the nature of structural matrices used in finite-element codes. Some terms used in sparse-matrix arithmetic are discussed, and methods for calculating certain quantities are provided. A test model is constructed to demonstrate how the stiff ness, mass, and damping matrices may be visualized for various systems. The eff ect of element shape, element type (including superelements), element reordering, and equation reordering on structural matrices is briefly investigated."
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Average Rating: 9.3 (15 votes)  
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