ORIGINAL ARTICLE
An object-oriented approach for mechanical components
design and visualization
Mihai Dupac
Received: 29 June 2010 / Accepted: 5 April 2011
 Springer-Verlag London Limited 2011
Abstract In this paper, development of shape modeling
tools for engineering design, analysis, simulation, and
visualization is presented. The approach based on the idea
of function-based shape modeling is combined with the
power and versatility of the object-oriented programming
(OOP). An OOP code, initially developed as a teaching and
learning tool for educational use in an undergraduate
Modeling and Simulation course, to generate mechanism
components is presented. Different parametric, explicit,
and implicit functions or their combination are used to
generate mechanical components shapes. Using a blending
process, sophisticated shapes have been generated on the
graphical interface. However, the ideas and concept of the
OOP mechanical components design presented in this
paper can be applied to other application areas.
Keywords Design  Shape modeling 
OOP  Visualization
1 Introduction
Computational methods for the design, analysis, and
visualization of 3D mechanical components shapes have
become indispensable tools in engineering practice. The
importance of shape modeling in computer aided design
(CAD) or virtual prototyping has been recognized for a
long time. The idea of function-based approach to shape
modeling is that complex geometric shapes can be pro-
duced from a ‘‘small formula’’ rather than thousands of
polygons. Parametric, implicit or explicit functions and
their combinations are used to define the shapes.
Object-oriented (OO) methods have now been imple-
mented in numerous engineering applications. A Web-based
application for the design and analysis of mechanisms was
developed by Cheng and Trang [8]. The toolkit uses a
collection of OOP classes to handle mechanisms ranging
from the simple to very complex linkages. Cojocaru and
Karlsson [9] presented an OO modeling frame for simu-
lating crack propagation in a linkage mechanism, by a
generalized node release technique. An intelligent software
system, developed on the OOP basis, which can support
machine tool design was described by Woonga et al. [47].
Santos [38] discuss the design and implementation of
an OO database view mechanism, which allows the
redefinition of the structure and the behavior of the stored
objects.
Qiao [37] presents an OOP approach for the boundary
element method in 2D heat transfer analysis. Advantages of
the OOP are demonstrated for two different types of partial
differential equations. Kromera et al. [24] describe a design
implementation of a FEM multibody flexible mechanisms
code using object-oriented architecture. An OOP class
systems for finite element modeling and analysis was
suggested by Mackie [30]. Pantale et al. [33] present an OO
implementation, using the C?? language, of an explicit
finite element method (FEM) related to metal forming and
impact simulations.
Larson and Cheng [25] developed a Web-based inter-
active design package. The Web-based system was
implemented through a client/server model (applet and
CGI-based). Su et al. [42] developed an extensible Java
applet architecture applied to a computer-aided-design
M. Dupac (&)
School of Design, Engineering and Computing,
Bournemouth University, Talbot Campus,
Fern Barrow, Poole, Dorset BH12 5BB, UK
e-mail: mdupac@bournemouth.ac.uk
123
Engineering with Computers
DOI 10.1007/s00366-011-0220-3

system of several spatial linkages. A new Java approach to
computer-aided spatial linkage design was presented by
Collins et al. [10].
Web and OOP approaches give students an alternative
way to engage in learning and to have learning control in
terms of place, pace, and time. In this respect, the incor-
poration of an interactive visualization is the key in
engaging students in the exploration and discovery of
knowledge. Siemers and Fritzson [41] presented an inte-
grated visualization and simulation tool for multibody sys-
tems with detailed contact analysis. Seth et al. [40]
developed a portable VR interface (SHARP) for mechanical
assembly. The SHARP system is simulating realistic part-to-
part and hand-to-part interactions in virtual environments.
Bloomenthal [2, 3] discuss a numerical technique that
approximates an implicit surface with a polygonal repre-
sentation. Parametric with parametric, and parametric with
implicit surfaces intersection was studied by de Figueiredo
[11] using a domain decomposition method. A technique
for merging objects modeled with subdivision surfaces was
proposed by Hui and Lai [23]. A blend curve was used for
connecting the given surfaces. Parametric representations
of shapes have been discussed in [31] and are very
appropriate selections when handling complex shapes in
three dimensions.
The idea of the hybrid function-based approach and
interactive function-based shape modeling [27, 28] is to use
different mathematical functions to modeling shapes, by
defining objects by analytical formulas and by imple-
menting mathematical operators for geometry modifica-
tions. A relatively similar approach for shape modeling
applied to mechanical components generation and visual-
ization was discussed in [12] and a Web-based approach in
[13, 35]. Cartwright et al. [6] describe experiments for
designing and developing a geometrical modeler combin-
ing ideas from empirical modeling and from implicit sur-
face modeling. Another approach for shape modeling was
proposed in [16], where a system implementation for
modeling shapes using real distance functions have been
used.
In this paper, the design and implementation of a object-
oriented software for mechanism components modeling
and visualization is described. An OOP code to specifying
objects shapes is developed. The convenience and sim-
plicity of the software is illustrated through application
examples. Different implicit, explicit, and parametric
functions (or their combinations) have been used for the
modeling of the mechanical components shapes. Further-
more, different representations of surfaces such as gears,
springs, chains, rivets, and ball bearings have been gener-
ated and visualized.
Those representations aim at improving the under-
standing of engineering design through shape modeling
interactive simulation. The developing of this educational
tool has derived from the engineers’ continuing need to
understand and apply mathematical models in the design
of complex mechanical components and systems [5, 29].
The presented ideas and concepts demonstrate advanta-
ges of using this software in classroom instruction, pro-
viding valuable visualization tools to engineering
students. The examples provide students with an excel-
lent understanding of complex mechanical systems by
using graphical visualization. The considerations and
discussions in this paper may be also useful for the
advancement of computer-aided instructional tools in
other subject areas.
2 Object-oriented analysis and design strategy
2.1 Object-oriented programming process
An object-oriented approach process is an analysis and
design strategy for software development that includes
• an object-oriented analysis (OOA) phase (identifies
system requirements and specifications),
• an object-oriented design (OOD) phase (defines system
operations and modules interaction), and
• an object-oriented programming (OOP) phase (realiza-
tion of the software design).
The OOP can be regarded as a modeling approach to
software construction and development. In OOP, a soft-
ware program is regarded as a physical model, simulating
either a real or imaginary part of the world. The software,
usually structured in terms of concepts familiar to the
human, should be easier to create, understand, and
maintain.
In OOP, key concepts are modeled as user-defined
classes and are seen as the association between the data
structures and the methods that manipulate the data. More
importantly, the data structures and the manipulating
functions are regarded as ‘‘objects’’.
The classes are organized hierarchically; a new class
is defined based on an existing class by using the
inheritance mechanism. The main advantage of inheri-
tance is that the algorithms are still valid for a new
defined class (resulting in a more reusable code). An
example of a hierarchically organized Polygon class,
used in the blending process, can be visualized in
Fig. 1.
The hierarchy resulting from the repeated application of
inheritance is called the inheritance hierarchy. The new
class inherits the variables and methods of the existing
class. It may add new variables and methods of its own and
may redefine inherited methods.
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