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Data file display
The data (.dat) file contains information about the model definition generated by the analysis input file processor. You can control the amount of output generated by the analysis input file processor; see “Controlling the amount of analysis input file processor information written to the data file” in “Output,” Section 4.1.1, for details. In particular, you can specify whether or not the original input (.inp) file is echoed to the data file (by default, it is not).
In the case of parametric input this file will generally contain a number of parameter, parameter dependence table, and parameter shape variation definitions, as well as a number of instances. To verify the definition of parametric input, you can create a modified version of the original input file showing the parameters and their values (this file is named job-name.par). You can also create the job-name.pes file, which is the modified version of the original input file that is free of parameter and parameter dependence table definitions, as well as instances.
Input File Usage:
Use the following option to print the contents of the job-name.par file to the data file:
*PREPRINT, PARVALUES=YES
Use the following option to print the contents of the job-name.pes file to the data file:
*PREPRINT, PARSUBSTITUTION=YES
Additional reference
• Lutz, M., and D. Ascher, Learning Python, O’Reilly & Associates, Inc., 1999.
2. Spatial Modeling
Node definition 2.1
Element definition 2.2
Surface definition 2.3
Rigid body definition 2.4
Integrated output section definition 2.5
Mass adjustment 2.6
Nonstructural mass definition 2.7
Distribution definition 2.8
Display body definition 2.9
Assembly definition 2.10
Matrix definition 2.11
Probability density function 2.12
2.1 Node definition
• “Node definition,” Section 2.1.1
• “Parametric shape variation,” Section 2.1.2
• “Nodal thicknesses,” Section 2.1.3
• “Normal definitions at nodes,” Section 2.1.4
• “Transformed coordinate systems,” Section 2.1.5
• “Adjusting nodal coordinates,” Section 2.1.6
2.1.1 NODE DEFINITION
Products: Abaqus/Standard Abaqus/Explicit
References
• *NCOPY
• *NFILL
• *NGEN
• *NMAP
• *NODE
• *NSET
• *SYSTEM
Overview
This section describes the methods for defining nodes in an Abaqus input file. In a preprocessor such as Abaqus/CAE, you define the model geometry rather than the nodes and elements; when you mesh the geometry, the preprocessor automatically creates the nodes and elements needed for analysis. Although the concepts discussed in this section apply in general to the node definitions in the input file that is created by Abaqus/CAE, the methods and techniques described here apply only if you are creating the input file manually.
Node definition consists of:
• assigning a node number to the node;
• optionally specifying a local coordinate system in which to define nodes;
• defining individual nodes by specifying their coordinates;
• grouping nodes into node sets;
• creating nodes from existing nodes by generating them incrementally, by copying existing nodes, or by filling in nodes between the bounds of a region; and
• mapping a set of nodes from one coordinate system to another.
If any node is specified more than once, the last specification given is used.
Abaqus will eliminate all unnecessary nodes before proceeding with the analysis. This feature is useful because it allows points to be defined as nodes for mesh generation purposes only.
Assigning a node number to the node
Each individual node must have a numeric label called the node number, which is assigned when the node is defined. The node number must be a positive integer, and the maximum node number allowed is 999999999 (for information on integer input, see “Input syntax rules,” Section 1.2.1). The nodes do not need to be numbered continuously.
An Abaqus model can be defined in terms of an assembly of part instances (see “Defining an assembly,” Section 2.10.1). In such a model all nodes must belong to either a part, part instance, or, in the case of reference nodes, to the assembly. Node numbers must be unique within a part, part instance, or the assembly; but they can be repeated in different parts or part instances.
Specifying a local coordinate system in which to define nodes
Sometimes it is convenient to define nodal coordinates in a local coordinate system and then transform these coordinates to the global coordinate system. You can define a nodal coordinate system; Abaqus will translate and rotate the local ( X ^ { 1 } , Y ^ { 1 } , \dot { Z ^ { 1 } } ) coordinate values into the global coordinate system. The transformation is done immediately after input and will be applied to all nodal coordinates entered or generated after the nodal coordinate system is defined.
The transformation affects only the input of nodal coordinates in node definitions. Nodal coordinate system definitions cannot be used
• for applying loads and boundary conditions—see “Transformed coordinate systems,” Section 2.1.5, instead; or
• for output of components of stress, strain, and element section forces—see “Orientations,” Section 2.2.5, instead.
In addition to defining nodal coordinate systems, you can define individual nodes or node sets in local rectangular, cylindrical, or spherical systems (see “Specifying a local coordinate system for the nodal coordinates”). If a nodal coordinate system is in effect and you specify a local coordinate system for a particular node or node set definition, the input coordinates are first transformed according to the local system specified in the node definition and then according to the nodal coordinate system.
Defining the nodal coordinate system
You set up the coordinate system specification by specifying the global coordinates of three points in the local system: the origin of the local system (point a in Figure 2.1.1–1), a point on the local X ^ { 1 } -axis (point b in Figure 2.1.1–1), and a point in the ( X ^ { 1 } , Y ^ { 1 } ) plane of the local system on (or near) the local Y ^ { 1 } -axis (point c in Figure 2.1.1–1).
text_image
Z Y X (global)
text_image
Z¹ Y¹ a c b X¹ (local)
Figure 2.1.1–1 Nodal coordinate system.
If only one point (the origin) is given, Abaqus assumes that you need a translation only. If only two points are given, the direction of the -axis will be the same as that of the Z-axis; that is, the X ^ { \bar { 1 } } -axis will be projected onto the plane.
To change the nodal coordinate system that is in effect, define another nodal coordinate system; to revert to input in the global coordinate system, use a nodal coordinate system definition without any associated data.
Input File Usage:
Use the following option to define a nodal coordinate system:
*SYSTEM
X _ {a}, Y _ {a}, Z _ {a}, X _ {b}, Y _ {b}, Z _ {b}
X _ {c}, Y _ {c}, Z _ {c}
For example, in the following input, nodes 1 through 3 are defined in the first nodal coordinate system, nodes 4 and 5 are defined in the second nodal coordinate system, and nodes 6 and 7 are defined in the global coordinate system:
*SYSTEM
0, 0, 0, 5, 5, 5
*NODE
1, 0, 0, 1
2, 0, 0, 2
3, 0, 1, 2
*SYSTEM
2, 3, 4
*NODE
4, 0, 0, 1
5, 1, 4, 0
*SYSTEM
*NODE
6, 1, 0, 1
7, 0, 4, 2
Defining a nodal coordinate system within part definitions
When you define a nodal coordinate system within a part (or part instance) definition, it is in effect only within that part (or part instance) definition. Nodes defined in other parts are not affected.
You specify the local ( X ^ { 1 } , Y ^ { 1 } , Z ^ { 1 } ) coordinate values relative to the part coordinate system, which subsequently may be translated and/or rotated according to the positioning data given for the instance (see “Defining an assembly,” Section 2.10.1).
Defining individual nodes by specifying their coordinates
You can define individual nodes by specifying the node number and the coordinates that define the node. Abaqus uses a right-handed, rectangular Cartesian coordinate system for all nodes except for
axisymmetric models, when the coordinates of the nodes must be given as the radial and axial positions. For more information about direction definitions, see “Conventions,” Section 1.2.2.
In a model defined in terms of an assembly of part instances, give nodal coordinates in the local coordinate system of the part (or part instance). See “Defining an assembly,” Section 2.10.1.
Input File Usage: *NODE
Reading node definitions from a file
Node definitions can be read into Abaqus from an alternate file. The syntax of such file names is described in “Input syntax rules,” Section 1.2.1.
Input File Usage: *NODE, INPUT=file_name
Specifying a local coordinate system for the nodal coordinates
You can specify that a local rectangular Cartesian, cylindrical, or spherical coordinate system be used for a particular node definition. These coordinate systems are shown in Figure 2.1.1–2.
text_image
Z (X,Y,Z) Y X
Rectangular Cartesian (default)
text_image
Z (R,θ,Z) Y R θ X
Cylindrical (θ and φ are given in degrees)
text_image
Z (R,θ,φ) φ θ Y X
Spherical
Figure 2.1.1–2 Coordinate systems.