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Introduction
The Global/Local Toolbox (GLToolBox) was created in order to facilitate
the implementation of the global/local optimization methodology.
The basic idea behind the global/local methodology is the decomposition
of an overall design problem into two levels: a global design
level and a local design level. At the global design level, an
FEM model of the complete structure is used to compute the overall
response of the structure and to assure that certain stresses
and displacements do not exceed their allowed values. At the local
design level, detailed component models are developed that allow
local stresses to be accurately computed and allow details that
are neglected by the global model to be designed. The global and
local design levels interact with each other through a local design
database and a set of interface variables.
Before the design of the overall structure begins, the detailed
local models are constructed and used to generate a series of
optimized local designs corresponding to a range of interface
variables that typically correspond to load and geometry variables.
The range of the load and geometry variables for which the database
is constructed corresponds to typical values for a realistic structure.
The results of these local optimization runs are stored in the
local design database.
Once the local database is constructed, response surface methodologies
are used to construct simple functional approximations to key
quantities in the database. These surrogate functions, which can
be evaluated very cheaply, provide important local information
to the global optimizer without having to perform computationally
expensive local analysis or local design optimization. Moreover,
once constructed, a given local design database may be used repeatedly
to perform additional vehicle design studies and could potentially
be used to design similar, but different structures. The database
can be extended and modified as needed if design requirements
change.
The tools found in Global/Local Toolbox assist the user by automating
and organizing many of the individual steps taken during the global/local
process. The integration of several tools into a single software
environment makes the specification and execution of a global/local
design problem more practical. This software implements the global/local
methodology for the specific case of a global finite element optimization
and an arbitrary user defined local analysis.
GLToolBox contains three main components, or "Tools".
These are the Local Database Tool (LDT), the Interface Definition
Tool (IDT), and the Finite Element Output Tool (FEOT). The LDT
manages the database of local designs and generates response surfaces.
The IDT visualizes the global model and provides a way to define
interface sections and define interface equations. The FEOT assembles
information from the LDT and IDT into a finite element input file.
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