Page 26 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
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perform specific functions [3]. This book focuses on the analysis and design of universal
machine elements.
1.1.2 The Scope of Machine Design
Design is widely considered to be the central or distinguishing activity of engineering
[4]. It aims to create and execute a purposeful plan to meet commercial, industrial and
social needs. When design is discussed in mechanical engineering domain, especially
about mechanical products or machines, it is termed mechanical or machine design.
Machine design is the art of envisioning, creating and developing a brand new or
improving on an existing mechanical device for the fulfilment of human needs, with
due regard for resource conservation and environmental impact [1, 5]. It is an innova-
tive, iterative, decision making and problem-solving process involving comprehensive
utilization of scientific knowledge and creative capability. Designers are required to gen-
erate concepts and decide deterministic dimensions for devices or products from lim-
ited information, ambiguous and sometimes even partially contradictory requirements
to achieve users’ objectives while satisfying a set of specified constraints. Therefore, the
initial design is usually tentative. With more variables gradually determined, material,
geometry, as well as manufacturing and tolerance details are fine-tuned during iteration
until final optimum design is achieved [5].
Machine design generally has more than one solution. Since design is a rational
process of choosing among design alternatives [6], it greatly depends on the designer’s
knowledge, previous experience, design method and design philosophies to solve a
specific problem. Consider, for example, the design of an automobile. A large number
of models are available on the market, and all of them can fulfil the function of
transportation. The differences among them are the operation convenience, comfort,
aesthetic appearance, cost and so on. These features decide the competitiveness and
sales of products.
Analysis and design are indispensable aspects in the process of machine design. Anal-
ysis is concerned with predicting the response of an existing or a tentatively designed
machine under specified inputs, which is especially important in creative design pro-
cess; while design attempts to decide the dimensions and shapes of machines to meet
performance requirements. Integrating analysis and design skills during the design pro-
cess distinguishes an outstanding design engineer from a good one [7]. Since design is
an evolutionary process, a tentative design is firstly proposed and then analysed to see if
it satisfies the given specifications. If not, which is the usual case; the tentative design is
revised with changes involving geometry, material and loads, and is analysed again until
it satisfies the specified design requirements.
Extensive multidisciplinary skills and knowledge are employed in the design process to
convert inadequate, vague requirements into a product that is functional, safe, reliable,
manufacturable, competitive and marketable. Engineering science includes mechanics
of solids and fluids, materials science, manufacturing processes and so on. Designers are
required to use computers and graphics tools to visualize design plans. Since designers
often work collaboratively on teams, communication skills, teamwork ability and pre-
sentation skills are equally important.
To design a machine or machine element successfully, design engineers not only need
to develop competence in understanding and applying scientific knowledge, empirical