Document Type

Thesis

Date of Degree

Fall 2015

Degree Name

MS (Master of Science)

Degree In

Mechanical Engineering

First Advisor

Jia Lu

Abstract

Non-uniform rational basis spline (NURBS) is a geometric language which has been commonly used in computer graphics and Computer Aided Design over years, due to its great flexibility and precision for handling modeled shapes. In computer-aided design, NURBS has become part of industry standards. In most CAD programs every solid model is described by NURBS and stored in NURBS data structure. Recently, the geometric basis function of NURBS is directly used in analysis, leading to the birth of a new area of computational mechanics called isogeometric analysis (IGA). Compared with the traditional finite element analysis, IGA eliminates the disconnection between analysis and design at the geometric level, showing superiority on efficiency and accuracy over the traditional finite element method.

This thesis focuses on the development of an IGA preprocessor for converting an original CAD model (2D-NURBS model) to an ASG (analysis suited geometry) model. ASG means models with mesh quality suitable for analysis. Core technologies utilized during the development include the well-developed NURBS algorithm of knot insertion and knot removal, and a self-developed technology of constructing and utilizing “multi-patch tree”. The developed IGA preprocessor is utilized to process a body armour model consisting of multiple NURBS patches with overly dense meshes. After the processing, the output model has a relatively reasonable elements distribution; the uniformity of the mesh across presumably contact patch boundaries is rebuilt.

Public Abstract

In garment design field now-a-days, the traditional manual methods of designing and clothing construction have been taken by digital technologies, most designing and clothing construction tasks are completed by utilizing a varies of CAD/CAM programs. With the assistance of CAD software, designer can “sew” cloth patters together, and watch the try-on effect by putting them on a virtual model before actually making a real prototype.

NURBS is de-facto industrial standard for geometric description in most CAD programs. Consequently, the constructed cloth models are always represented by NURBS; 2D NURBS patch models are commonly utilized in cloth modeling. This thesis focuses on the development of an IGA preprocessor for converting an original cloth model (2D-NURBS model) to a model that suits for cloth simulation. Core technologies utilized during the development include the well-developed NURBS algorithm of knot insertion and knot removal, and a self-developed technology of constructing and utilizing “multi-patch tree”. The developed IGA preprocessor is utilized to process a body armour model consisting of multiple NURBS patches with overly dense meshes. After the processing, the output model to some extent becomes an analysis-ready model with some key factors satisfied.

Keywords

publicabstract

Pages

ix, 86 pages

Bibliography

Includes bibliographical references (pages 84-86).

Copyright

Copyright 2015 Zhiyu Sun

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