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Design and development of an expert advisor for general purpose finite element modeling of 2-dimensional structures

By BP Naganarayana, SA Virupaksha and Gangan Prathap

Abstract

Finite element analysis of many engineering systems is13; practiced more as an art than science. It involves high level expertise (analytical as welt as heuristic) regarding problem modelling (e.g problem specification, choosing appropriate type of elements etc.), optimal mesh design for achieving the specified accuracy (e.g. initial mesh selection, adaptive mesh refinement),selection of appropriate type of analysis and solution routines and, finally, diagnosis of the finite element solutions. Very13; often such expertise is highly dispersed and is not available at a single place with a singl expert. The design of an expert system, which makes the necessary expertise .available to a novice to perform the same job in the absence of trained experts, becomes an attractive proposition.13; In this report a simple knowledge based expert advisor has been developed for General purpose finite element modelling of 2-D structures. Modelling any problem requires expertise in selecting and/or development of optimal theopetical basis (e.g. plate theories, shell theories etc.) and type of elements to be used. Considerable knowledge regarding topological configuration and material constitution of the structure, boundary conditions and loading environment is required for this purpose.13; Expert systems are interactive computer programs based on13; heuristics, incorporating judgement, rules of thumb, intuition and expertise to provide knowledgeable advice about a variety of tasks. The main issues involved in building such specialized interactive programs can be broadly classified as (1) identifying the relevant design. knowledge, (2) providing a formalism for representing and processing such knowledge and (3) synthesis of expertise for the course of action required.13; The knowledge required for the present task is identified and acquired through domain experts and published literature. The domain knowledge, thus acquired, is represented using production rules. The problem dependent knowledge is generated and represented using the concepts of semantic nets and frames. The acquisition module for the problem dependent knowledge is made user friendly using the screen help menus with graphic environment wherever it is necessary. The knowledge is represented using both conventional and fuzzy logic depending on the type of knowledge. The inference mechanism for processing the knowledge is built in the program using mainly forward reasoning strategy. Finally the knowledge that is processed is evaluated and appropriate expert advise is offered for general purpose finite element modelling of two dimensional structures.13; In this report only general linear hexahedral structures are considered for analysis. The validity of the program is thoroughly investigated by solving several problems

Topics: Structural Mechanics
Publisher: National Aerospace Laboratories
Year: 1993
OAI identifier: oai:nal-ir.nal.res.in:1697
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