An ABAQUS model is composed of several components that together describe the physical problem to be analyzed and the results to be obtained. At minimum the model consists of the following information: geometry, element section properties, material data, loads and boundary conditions, analysis type, and output requests.
Geometry
Finite elements, nodes, and rigid bodies define the basic geometry of the model. Each element in the model represents a discrete portion of the physical structure, which is, in turn, represented by many interconnected elements. Elements are connected to one another by shared nodes. The coordinates of the nodes and the connectivity of the elements—that is, which nodes belong to which elements—comprise the model geometry. The collection of all the elements and nodes in a model is called the mesh. Generally, the mesh will be only an approximation of the structure's actual geometry.
The element type, shape, and location, as well as the overall number of elements used in the mesh, affect the results obtained from a simulation. The greater the mesh density (i.e., the greater the number of elements in the mesh), the more accurate the results. As the mesh density increases, the analysis results converge to a unique solution (except in rare cases), and the computer time required for the analysis increases. The solution from the numerical model is generally an approximation to the solution of the physical problem being simulated. The extent of the approximations made in the model's geometry, material behavior, boundary conditions, and loading determines how well the numerical simulation matches the physical problem.
Element section properties
The geometry of many elements in ABAQUS/Explicit is not defined completely by the nodal coordinates. For example, the layers of a composite shell or the dimensions of an I-beam section are not defined by the nodes of the element. Such additional geometric data are defined as physical properties of the element and are necessary to define the model geometry completely. Chapter 4, “Finite Elements and Rigid Bodies,” describes the necessary section properties for each element type.
Material data
Material properties for all elements must be specified. The validity of results from ABAQUS/Explicit is limited by the quality of the material data.
Loads and boundary conditions
ABAQUS/Explicit provides a variety of loading options, the most common of which include:
point loads;
pressure loads on surfaces;
body forces, such as the force of gravity; and
thermal loads.
Boundary conditions are used to constrain portions of the model to remain fixed (zero displacements) or to move by a prescribed amount (nonzero displacements).
Analysis type
The most common type of simulation performed in ABAQUS/Explicit is an explicit dynamic analysis, where the dynamic response of a structure to the applied loads is obtained. Fully coupled thermal stress analyses, which simulate the coupled thermal-mechanical response of a body, and annealing analyses, which simulate the relaxation of stresses and plastic strains that occurs as metals are heated to a high temperature, can also be performed in ABAQUS/Explicit. Only explicit dynamic analyses are discussed in this guide.
Output requests
A finite element analysis can generate a large amount of output. Making use of the variety of available output options, you can request only the output necessary for you to interpret the results adequately.