About Analysis Techniques

In many cases your analysis results represent a significant investment of computational effort. As a result, you will often want to reduce computation costs by utilizing results from an analysis that has already been performed. In other cases your overall analysis history will be comprised of distinct Abaqus jobs, each representing a portion of the response history of the model. Abaqus provides the following analysis continuation techniques:

• Abaqus allows you to restart an analysis, as long as you request that certain files containing model and state data be saved in the original analysis. See Restarting an Analysis.

• You can perform part of an analysis with Abaqus/Standard or Abaqus/Explicit and continue the analysis with the other product. You can transfer results from Abaqus/Standard to Abaqus/Explicit, from Abaqus/Explicit to Abaqus/Standard, and from Abaqus/Standard to Abaqus/Standard. See About Transferring Results between Abaqus Analyses.

All Abaqus models involve certain abstractions. In addition to the traditional abstractions associated with the finite element method, you can include techniques in your model to obtain more cost-effective solutions. Abaqus provides the following techniques for modeling abstractions:

• You can create substructures by grouping a number of elements together and retaining only the degrees of freedom needed to interface with adjacent structures. This technique is particularly useful when a substructure is to be reused in the same analysis, in different analyses, or by different analysts. See Using Substructures.

• You can analyze local regions of a model in greater detail and interpolate the solution results from a larger coarser global model. See About Submodeling.

• You can allow for the mathematical abstraction of model data such as mesh and material information by generating global or element matrices representing the stiffness, mass, viscous damping, structural damping, and load vectors in a model. See Generating Matrices as a Linear Analysis Step.

• You can create a three-dimensional model in Abaqus/Standard by revolving various forms of axisymmetric and three-dimensional model sectors about an axis of symmetry (see Symmetric Model Generation). You can also transfer the solution obtained in an original axisymmetric model to the new model (see Transferring Results from a Symmetric Mesh or a Partial Three-Dimensional Mesh to a Full Three-Dimensional Mesh). In addition, for models that exhibit cyclic symmetry you can extract eigenmodes and perform mode-based steady-state dynamic analysis by modeling only a single repetitive sector of the model (see Analysis of Models that Exhibit Cyclic Symmetry).

• Using the periodic media analysis technique, you can effectively model systems that are repetitive in nature, such as manufacturing processes involving conveyor belts or continuous forming operations. See Periodic Media Analysis.

• You can define a complex beam cross-section, including multiple materials and complex geometry, and automatically generate beam element cross-section properties. See Meshed Beam Cross-Sections.

• Using the extended finite element method, you can model discontinuities, such as cracks, as an enriched feature without creating a mesh to match the geometry of the discontinuity. See Modeling Discontinuities as an Enriched Feature Using the Extended Finite Element Method.

Certain analysis techniques do not fall into a general classification and are grouped here as special-purpose techniques. Abaqus provides the following special-purpose techniques:

• You can use the inertia relief technique as an inexpensive alternative to performing a full dynamic analysis on a free or partially constrained body subjected to loads derived from rigid body accelerations. See Inertia Relief.

• You can selectively remove, and later reintroduce, parts of a model. See Element and Contact Pair Removal and Reactivation.

• You can introduce small imperfections into a model, typically for postbuckling analysis. See Introducing a Geometric Imperfection into a Model.

• You can evaluate fracture performance through contour integral evaluation, through crack propagation modeling techniques, or by using line spring elements in conjunction with shell elements. See About Fracture Mechanics.

• You can model coupling between the deformation of a fluid-filled structure and the pressure exerted by a contained fluid (see About Surface-Based Fluid Cavities).

• In Abaqus/Explicit you can use the mass scaling technique to control the stable time increment and increase computational efficiency. See Mass Scaling.

• You can use selective subcycling to allow different time increments to be used for different groups of elements, which can reduce the run time for an analysis when a small region of elements in the model controls the stable time increment. See Selective Subcycling.

• You can use steady-state detection to detect the time in a quasi-static uni-directional Abaqus/Explicit simulation when a steady-state condition has been reached and then terminate the simulation. See Steady-State Detection.

Adaptivity techniques enable modification of your mesh to obtain a better solution. Abaqus provides the following adaptivity techniques:

• You can use ALE adaptive meshing to control mesh distortion or to model material loss. See About ALE Adaptive Meshing.

• You can use adaptive remeshing with Abaqus/Standard and Abaqus/CAE to iteratively improve your mesh to obtain a more accurate solution. See About Adaptive Remeshing.

• You can use mesh-to-mesh solution mapping as part of a mesh replacement strategy for distortion control. See Mesh-to-Mesh Solution Mapping.

See About Adaptivity Techniques for a comparison of the adaptivity methods.

You can use structural optimization, an iterative process that helps you refine your designs, to perform topology and shape optimization. In Abaqus/CAE you create the model to be optimized and define, configure, and execute the structural optimization. See About Structural Optimization.

You can use Abaqus/Explicit to simulate extreme deformation, up to and including fluid flow, in an Eulerian analysis. Eulerian materials can be coupled to Lagrangian structures to analyze fluid-structure interactions. See Eulerian Analysis.

Using the smoothed particle hydrodynamics technique, you can model violent free-surface fluid flow (such as wave impact) and extremely high deformation/obliteration of solid structures (such as ballistics). See Smoothed Particle Hydrodynamics.

Using the discrete element technique, you can model particulate media and perform analyses such as granular material mixing or segregation, transport, and deposition of particulate materials. See Discrete Element Method.

In Abaqus/Standard you can perform sequentially coupled multiphysics analyses when the coupling between one or more of the physical fields in a model is only important in one direction. See Sequentially Coupled Multiphysics Analyses.

You can use the co-simulation technique for run-time coupling of two Abaqus analyses or of Abaqus with third-party analysis programs to perform multiphysics simulation. See About Co-Simulation.

You can use the flexibility of user subroutines to increase the functionality of Abaqus. See User Subroutines and Utilities.

You can use design sensitivity analysis (DSA) techniques to determine sensitivities of responses with respect to specified design parameters. You can use these techniques for design studies within Abaqus/Standard or in conjunction with third-party design optimization tools. See Direct Design Sensitivity Analysis.

You can use parametric studies to perform multiple analyses in which you can systematically vary modeling parameters that you define. See Scripting Parametric Studies and Parametric Studies: Commands.

The availability of the analysis techniques provided in Abaqus is summarized in Table 1. In addition, adaptive remeshing and optimization techniques are available in Abaqus/CAE (see Adaptive Remeshing and About Structural Optimization).