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Technical Overview
tuned by each hardware vendor for optimum performance on their machines.
The degree of freedom set present in the assembled matrix at any given time is known as the wavefront, which expands and contracts as degrees of freedom are introduced to and deleted from the matrix.
After the wavefront has passed through all the elements
and the response of each degree of freedom has been
computed, postprocessing can be used to display integrated results for the entire model.
As an alternative to the default frontal solver, the
user can activate either of two iterative solvers, which
provide faster solution times and utilize less computer
resources in analyzing large models. In almost all analyses, the software is faced with solving a series of linear
simultaneous equations. Direct solvers, such as the
frontal solver, calculate exact solutions for a set of linear simultaneous equations, while iterative solvers iterate to approximate solutions.
The ANSYS program includes three iterative
equation solvers: a highly efficient solver, known as the
PowerSolver, which is a Preconditioned Conjugate
Gradient (PCG) solver, the Jacobi Conjugate Gradient
(JCG) solver, and the Incomplete Cholesky Conjugate
Gradient (ICCG) solver. Having access to three different
solvers enables ANSYS users to maximize productivity by
choosing the most appropriate solver for a particular
problem. The frontal solver is very efficient for small to
moderate-sized problems, while an iterative solver is
generally preferable for large, complex problems.
The PowerSolver represents a significant technological breakthrough because it transcends the limitations of prior iterative solvers. This solver is extremely
reliable and accurate, with a preconditioner specialized
for finite elements. It is the only iterative solver that can
handle constraint equations and shell elements. The
PowerSolver is a new level of technology that permits
analysis of complex problems on desktop workstations,
providing order of magnitude faster solution times and
significant disk savings for large, complicated problems.
The PowerSolver is applicable to both h- and p-element
analyses and may also be used as an option in subspace
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iteration modal analysis. Additionally, for linear analyses
with higher order planar or tetrahedron elements, a
superfast option exists that cuts another factor of two in
run times and disk space requirements.
The iterative solver can be used to provide more
efficient solutions to field problems (including
acoustic, heat transfer, and electromagnetic field problems) and other large analyses having symmetric,
sparse, positive, and definite matrices.
An explicit solver, ANSYS/LS-DYNA, is also available. The explicit solver allows users to efficiently perform
dynamic analyses including general, high-speed, largestrain, impact/contact problems; crash-worthiness simulation; failure analysis; and material forming processes
including metal, glass, and plastic. ANSYS/LS-DYNA
solves highly nonlinear structural problems. The explicit
solution method is accomplished without the formation
of a stiffness matrix and is ideally suited to problems of
short duration involving contact, large deformations, and
nonlinear materials. ANSYS/LS-DYNA consists of the
combination of ANSYS pre and postprocessing, specifically customized for LS-DYNA3D, and solution of
the problem by the LS-DYNA3D explicit solver from
Livermore Software Technology Corporation (LSTC).
Structural
Static Analysis
The structural static analysis capabilities in the ANSYS
program are used to determine the displacements,
stresses, strains, and forces that occur in a structure or
component as a result of applied loads (Figures 12 and
13). Static analysis is appropriate for solving problems
in which the time-dependent effects of inertia and
damping do not significantly affect the structure’s
response. This analysis type can be used for many applications, such as determining the stress intensities in fillets of mechanical components or predicting the stresses
in a structure resulting from a temperature distribution.
Most mechanical and structural engineers are
familiar with this type of analysis and have probably