Lecture1 Basics

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Introduction to ABAQUS/Standard and ABAQUS/Explicit Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc. Lecture 1 Defining an ABAQUS Model

Transcript of Lecture1 Basics

Lecture 1Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Lecture 1
Defining an
ABAQUS Model
Introduction
Details of an ABAQUS Input File
ABAQUS Input Conventions
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction to ABAQUS/Standard and ABAQUS/Explicit
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Introduction
Founded in 1978.
Offices and representatives throughout the industrialized world.
Sole activities are the development and the support of simulation software for the analysis of engineering problems.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Course preliminaries
This course introduces ABAQUS; basic knowledge of finite element analysis is assumed.
This course introduces concepts in a manner that gives users a working knowledge of ABAQUS as quickly as possible—the lecture notes do not attempt to cover all the details of ABAQUS completely.
There are several sources for additional information on the topics presented in this course:
HKS Home Page (available via the Internet at www.abaqus.com).
ABAQUS documentation—all usage details are covered in the user’s manuals.
Extensive library of lecture notes developed by HKS on particular topics (a list is available at www.abaqus.com).
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
ABAQUS/CAE
Intuitive and consistent user interface throughout the system.
Based on the concepts of parts and assemblies of part instances, which are common to many CAD systems.
Parts can be created within ABAQUS/CAE or imported from other systems as geometry (to be meshed in ABAQUS/CAE) or as meshes.
Built-in feature-based parametric modeling system for creating parts.
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Introduction
ABAQUS/Standard’s capabilities:
Introduction
Thermo-electrical
Introduction
Transient response via modal superposition
Steady-state response resulting from harmonic loading
Includes alternative “subspace projection” method for efficient analysis of large models with frequency-dependent properties (like damping)
Response spectrum analysis
Introduction
Fully coupled thermo-mechanical analysis
Automatic adaptive meshing allows the robust solution of highly nonlinear problems
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Can solve for true static equilibrium in structural simulations.
Provides a large number of capabilities for analyzing many different types of problems, including many nonstructural applications.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
ABAQUS/Explicit
Solves highly discontinuous high-speed dynamic problems efficiently.
Does not require as much disk space as ABAQUS/Standard for larger problems.
Contact calculations are easier with ABAQUS/Explicit. Applications such as quasi-static metal forming simulations are easier.
Provides an adaptive meshing capability.
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Introduction
Available with ABAQUS/CAE or as a stand-alone product
Can be used to visualize ABAQUS results whether or not the model was created in ABAQUS/CAE
Provides efficient visualization of large models
Contour plot of an aluminum wheel hitting a curb in ABAQUS/Viewer
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Documentation
Unless otherwise indicated, all documentation is available both online and in print.
User’s Manuals
ABAQUS Example Problems Manual
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Advanced lecture notes on various topics (print only)
Tutorials
Getting Started with ABAQUS/Standard: Keywords Version (online)
Getting Started with ABAQUS/Explicit (online)
HKS Home Page
Introduction
Introduction to the analysis modules and interactive postprocessing.
Details of using ABAQUS to solve a variety of structural analysis problems:
Linear Static Analysis
Workshop 1: Basic Input and Output—analysis of forces on a
connecting lug
Nonlinear Finite Element Analysis
Workshop 2: Nonlinear Statics—large deformation analysis of a skew plate
Simulations with Several Analysis Steps
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Contact among Multiple Bodies
Workshop 3: Contact—contact analysis of a plate clamped and displaced by rigid dies
Linear and Nonlinear Dynamic Analysis
Workshop 4: Dynamics—frequency analysis and implicit and explicit free vibration analysis of a cantilever beam
High-Speed Dynamics in ABAQUS/Explicit
Workshop 5: Contact with ABAQUS/Explicit—dynamic crushing of a square energy-absorbing tube
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Introduction
Quasi-Static Combined Analysis in ABAQUS/Standard and ABAQUS/Explicit
Workshop 6: Quasi-Static and Import Analysis—deep drawing of a can bottom, including springback
Nonstructural applications—such as heat transfer, soils consolidation, and acoustics—are not discussed.
All ABAQUS analysis techniques use the same framework.
The knowledge gained in this course will help in learning to use ABAQUS for other applications.
Introduction to ABAQUS/Standard and ABAQUS/Explicit
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Components of an ABAQUS Model
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Components of an ABAQUS Model
The ABAQUS analysis modules run as batch programs. The primary input to the analysis modules is an input file, which contains options from element, material, procedure, and loading libraries.
These options can be combined in any reasonable way, allowing a tremendous variety of problems to be modeled.
The input file is divided into two parts: model data and history data.
Model data Geometric options—nodes, elements
Material options
Components of an ABAQUS Model
Model data—define the physical model
Discretized model geometry—nodes,elements
Components of an ABAQUS Model
Model data
Fixed constraints
Initial conditions
Components of an ABAQUS Model
History data—specify what happens to the model
Types of analysis procedures—static, dynamic, soil, heat transfer, etc.
Loadings
ENCASTRE
X-symmetry
Y-symmetry
Components of an ABAQUS Model
History subdivided into analysis steps
Steps are convenient subdivisions in an analysis history.
Different steps can contain different analysis procedures—for example, static followed by dynamic.
Distinction between general and linear perturbation steps:
General steps define a sequence of events that follow one another.
The state of the model at the end of the previous general step provides the initial conditions for the start of the next step. This is needed for any history-dependent analysis.
Linear perturbation steps provide the linear response about the base state, which is the state at the end of the most recent general step.
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Components of an ABAQUS Model
Example: bow and arrow simulation
Step 1: String the bow
Step 2: Pull back on the bow string
Step 3: Linear perturbation step to extract the natural frequencies of the system—
has no effect on subsequent steps
Step 4: Release the arrow
Step 1 = pretension
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Details of an ABAQUS Input File
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Details of an ABAQUS Input File
Option blocks
All data are defined in “option blocks” that describe specific aspects of the problem definition, such as an element definition, etc. Together the option blocks build the model.
Node option block
Each option block begins with a keyword line.
Data lines, if needed, follow the keyword line.
Comment lines, starting with **, can be included anywhere.
All input lines have a limit of 256 characters.
Names can be up to 80 characters long and must begin with a letter. For example, the following would be a permissible name:
nodes_at_the_top_of_the_block_next_to_the_gasket
Keyword lines
Begin with a single * followed directly by the name of the option.
May include a combination of required and optional parameters, along with their values, separated by commas.
Example: A material option block defines a set of material properties.
keyword
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Details of an ABAQUS Input File
Data lines
Define the bulk data for a given option; for example, element definitions.
A keyword line may have many data lines associated with it.
Example: An element option block defines elements by specifying the element type, the element numbers, and the nodal connectivity.
*ELEMENT, TYPE=B21
560, 101, 102
564, 102, 103
572, 103, 104
element numbers
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Details of an ABAQUS Input File
Example: The elastic material option block defines the type of elasticity model as well as the elastic material properties.
*ELASTIC, TYPE=ISOTROPIC
200.0E4, 0.3, 20.0
150.0E3, 0.35, 400.0
Ordering of option blocks
Each option block belongs in either the model data or the history data—one or the other —as specified in the user’s manual.
The ordering within the model data or history data is arbitrary, except for a few cases.
Examples:
*HEADING must be the first option in the input file.
*ELASTIC, *DENSITY, and *PLASTIC are suboptions of *MATERIAL. As such, they must follow *MATERIAL directly. Suboptions have no name references of their own.
*STATIC, *DYNAMIC, and *FREQUENCY must follow *STEP to specify the analysis procedure for the step.
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Details of an ABAQUS Input File
Node sets and element sets
Used for efficient cross referencing.
Allow you to refer to a set all at once instead of each node or element individually.
Node set TOPNODES contains nodes 101,102, ...
Boundary condition applied to all nodes in node set TOPNODES.
Example: Node sets
*NODE, NSET=TOPNODES
Example: Element sets
560, 101, 102,
564, 102, 103
ELSET=SEATPOST
0.12, 0.004
pipe radius
wall thickness
These beam cross-section properties apply to all elements in element set SEATPOST.
Element set SEATPOST contains elements 560, 564, ...
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Details of an ABAQUS Input File
Including data from other files
ABAQUS reads data from an include file as if the data were directly in the ABAQUS input file.
An include file can include any portion of an input file and can contain references to other include files.
Data must be in the same format as required for input file data—all rules that apply to input file syntax apply to data from included files.
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Details of an ABAQUS Input File
Example: Input file referencing an include file
*HEADING
*NODE, NSET=TOPNODES
560, 101, 102,
564, 102, 103
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ABAQUS Input Conventions
ABAQUS Input Conventions
In general, ABAQUS uses no inherent set of units.
The exception is ABAQUS/Safe, which uses a built-in set of units.
It is the user’s responsibility to use consistent units.
Example:
etc.
ABAQUS Input Conventions
Time measures
ABAQUS keeps track of both total time in an analysis and step time for each analysis step.
Time is physically meaningful for some analysis procedures, such as transient dynamics.
Time is not physically meaningful for some procedures. In rate-independent, static procedures “time” is just a convenient, monotonically increasing measure for incrementing loads.
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ABAQUS Input Conventions
The default is a rectangular Cartesian system.
Specify an alternative system using *SYSTEM or *NODE, SYSTEM=[RECTANGULAR | CYLINDRICAL | SPHERICAL].
Do not affect loading or output because automatically converted internally to the global rectangular Cartesian system.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
ABAQUS Input Conventions
The default is a rectangular Cartesian system.
Specify an alternative system using the *TRANSFORM option.
These directions do not rotate with the material in large-displacement analyses.
Example: Boundary conditions on a skew edge.
Use *TRANSFORM on these nodes with YSYMM boundary conditions
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ABAQUS Input Conventions
For material point directions (directions associated with each element’s material or integration points).
Affect input: Anisotropic material directions.
Affect output: Stress/strain output directions.
The default depends on the element type.
Solid elements use a global rectangular Cartesian system.
Shell and membrane elements use a projection of the global Cartesian system onto the surface.
Default material directions for shell and membrane elements
Default material directions for solid elements
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ABAQUS Input Conventions
Specify a local material coordinate system using the *ORIENTATION option.
These directions rotate with the material in large-displacement analyses.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
ABAQUS Input Conventions
Degrees of freedom
Available nodal degrees of freedom depend on the element type.
Each degree of freedom is labeled with a number: 1=x-displacement, 2=y-displacement, ..., 11=temperature.
Introduction to ABAQUS/Standard and ABAQUS/Explicit
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
ABAQUS Output
ABAQUS Output
Four types of output are available:
Neutral binary output can be written to the output database (.odb) file using the *OUTPUT option and related suboptions.
Printed output can be written to the printed output (.dat) file.
This is available only for ABAQUS/Standard.
Restart output can be written to the restart (.res) file using the *RESTART option for the purpose of conducting restart analyses (discussed in Lecture 4).
Results (.fil) file output can be written for third-party postprocessing.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
ABAQUS Output
Output to the output database file
The output database file is used by ABAQUS/Viewer. An application programming interface (API) is available in Python and C++ to use for external postprocessing (e.g., to add data to display in ABAQUS/Viewer).
Two types of output data: field and history data.
Field data is used for model plots (deformed, contour, etc.):
*OUTPUT, FIELD
which output is written.
*OUTPUT, HISTORY
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
ABAQUS Output
The VARIABLE=PRESELECT parameter is optional for either history or field output. It indicates that the default output variables will be written to the output database.
Additional output variables can be selected using any of the following suboptions of *OUTPUT:
*NODE OUTPUT
*ELEMENT OUTPUT
*ENERGY OUTPUT
*CONTACT OUTPUT
ABAQUS Output
Output to the printed output file
These options allow tabular data to be written to an ASCII file that can be read with a text editor.
These options are available only for ABAQUS/Standard.
Syntax:
ABAQUS Output
Output to the restart file
If a simulation stops prematurely, the restart data can be used to start the simulation from some intermediate point without repeating any calculations.
*RESTART, WRITE
Output to the results file
The results file can be used by third-party postprocessors.
*FILE OUTPUT (This option required for ABAQUS/Explicit only.)
*NODE FILE
*ENERGY FILE
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Example: Cantilever Beam Model
Example: Cantilever Beam Model
boundary conditions
node number
element number
point load
Model data
*NODE
1, 1, 3
50.0, 5.0
*MATERIAL, NAME=MAT1
This line will appear on each page of output.
elastic option block
Example: Cantilever Beam Model
The history data end with the last *END STEP option.
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Example: Cantilever Beam Model
1, 1, 3
50.0, 5.0
2.0E5, 0.3
The property reference *BEAM SECTION associates the element set BEAMS with the material definition MAT1.
The option can also provide geometric information. In this case the
cross-section type is rectangular (RECT); the width is 50.0; and the height is 5.0.
All elements in a model must have an appropriate property reference. Solid elements reference *SOLID SECTION; shell elements reference *SHELL SECTION; etc.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Example: Cantilever Beam Model
Definition for an isotropic linear elastic material
ABAQUS interprets the options following a *MATERIAL option as part of the same material option block until the next *MATERIAL option or the next nonmaterial property option, such as the *NODE option, is encountered.
Options such as *ELASTIC are called suboptions and must be used in conjunction with the *MATERIAL option.
Poisson’s ratio
Example: Cantilever Beam Model
1, 1, 6
Fixed boundary condition constraints are applied to active degrees of freedom.
Prescribed nonzero boundary conditions can be included only in the history data.
ABAQUS activates only the necessary degrees of freedom at a node. Thus, for this two-dimensional example with only degrees of freedom 1, 2, and 6 active, the following are equivalent input data:
1, 1, 2
1, 6, 6
1, ENCASTRE
The batch preprocessor will issue a warning about inactive degrees of freedom.
node or node set
range of degrees of freedom or type of BC (pinned, encastre, symmetry, antisymmetry)
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Example: Cantilever Beam Model
*STATIC
The *STEP option block can include a title of any length.
The procedure definition must be the first option after *STEP.
Begins the history data.
Specifies a static analysis procedure.
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Example: Cantilever Beam Model
Definition of a concentrated load in the global negative 2-direction:
*CLOAD
Many distributed loadings are also available, including surface pressure, body forces, centrifugal and Coriolis loads, etc.
node or node set
Example: Cantilever Beam Model
U,
In this case we have requested field output of a preselected set of the most commonly used output variables.
We have also requested history output of displacements for the previously defined node set END.
Since history output is usually requested at relatively high frequencies, the sets should be as small as possible.
Each output request includes a FREQUENCY parameter. If the analysis requires many increments, the FREQUENCY parameter specifies how often results will be written to the requested file.
output to the output database file
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Example: Cantilever Beam Model
*EL PRINT, FREQUENCY=10
U
Tabular output is printed to the data (.dat) file for visual inspection using the *EL PRINT option.
In this case we have requested output of the stress (S) and strain (E) components.
Binary output is written to the legacy ABAQUS results file for postprocessing in other postprocessors using the *NODE FILE option.
In this case we have requested output of the displacement (U) components.
Printed output to the data file
Output to the results file
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Example: Cantilever Beam Model
Each analysis step ends with the *END STEP option.
The final option in the input file is the *END STEP option for the final analysis step.
ends the analysis step
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Parts and Assemblies
Parts and Assemblies
The input file can be defined in terms of parts, part instances, and an assembly.
An ABAQUS model uses the same terminology in the input file as in ABAQUS/CAE.
Future enhancements to ABAQUS will take advantage of the concept of parts and assemblies.
Provides an inherent means of referring to distinct regions of the model. The user need not define separate sets for this purpose.
Allows reuse of part definitions, which is valuable for creating large, complex models.
Labels—node and element numbers, set names—need be unique only within the level in which they are defined.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Parts and Assemblies
Defining parts
A part is defined by using the *PART and *END PART options, which must appear outside of the assembly definition. Each part must have a unique name.
Defining part instances
A part instance is defined by using the *INSTANCE and *END INSTANCE options within the assembly definition. Each part instance must have a unique name.
Defining an assembly
The assembly is defined by using the *ASSEMBLY and *END ASSEMBLY options. Only one assembly can be defined in a model.
Additional sets and surfaces, as well as constraints and rigid body definitions, must appear in the assembly definition.
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Parts and Assemblies
<positioning data>
*END INSTANCE
<positioning data>
*END INSTANCE
*NSET, NSET=Output
Parts and Assemblies
Part: Tire
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Workshop 1: Basic Input and Output
Copyright 2001 Hibbitt, Karlsson & Sorensen, Inc.
Workshop 1: Basic Input and Output
Workshop tasks
Open the online documentation, and search for useful information.
Use the online documentation to determine the syntax for various options.
Add some details to an existing input file to complete the model of a connecting lug.
50 Mpa pressure load
30 kN/(2 × 0.015m × 0.02m)
Submit analyses a few different ways (datacheck only, complete analysis, interactive, and batch submission).
View the results using ABAQUS/Viewer.