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Introduction to Mechanical Engineering Design 5
Design is a communication-intensive activity in which both words and pictures are
used, and written and oral forms are employed. Engineers have to communicate effec-
tively and work with people of many disciplines. These are important skills, and an
engineer’s success depends on them.
A designer’s personal resources of creativeness, communicative ability, and problem-
solving skill are intertwined with the knowledge of technology and first principles.
Engineering tools (such as mathematics, statistics, computers, graphics, and languages)
are combined to produce a plan that, when carried out, produces a product that is func-
tional, safe, reliable, competitive, usable, manufacturable, and marketable, regardless
of who builds it or who uses it.

1–2 Mechanical Engineering Design
Mechanical engineers are associated with the production and processing of energy and
with providing the means of production, the tools of transportation, and the techniques
of automation. The skill and knowledge base are extensive. Among the disciplinary
bases are mechanics of solids and fluids, mass and momentum transport, manufactur-
ing processes, and electrical and information theory. Mechanical engineering design
involves all the disciplines of mechanical engineering.
Real problems resist compartmentalization. A simple journal bearing involves fluid
flow, heat transfer, friction, energy transport, material selection, thermomechanical
treatments, statistical descriptions, and so on. A building is environmentally controlled.
The heating, ventilation, and air-conditioning considerations are sufficiently specialized
that some speak of heating, ventilating, and air-conditioning design as if it is separate
and distinct from mechanical engineering design. Similarly, internal-combustion engine
design, turbomachinery design, and jet-engine design are sometimes considered dis-
crete entities. Here, the leading string of words preceding the word design is merely a
product descriptor. Similarly, there are phrases such as machine design, machine-element
design, machine-component design, systems design, and fluid-power design. All of
these phrases are somewhat more focused examples of mechanical engineering design.
They all draw on the same bodies of knowledge, are similarly organized, and require
similar skills.

1–3 Phases and Interactions of the Design Process

What is the design process? How does it begin? Does the engineer simply sit down at
a desk with a blank sheet of paper and jot down some ideas? What happens next? What
factors influence or control the decisions that have to be made? Finally, how does the
design process end?
The complete design process, from start to finish, is often outlined as in Fig. 1–1.
The process begins with an identification of a need and a decision to do something
about it. After many iterations, the process ends with the presentation of the plans
for satisfying the need. Depending on the nature of the design task, several design
phases may be repeated throughout the life of the product, from inception to termi-
nation. In the next several subsections, we shall examine these steps in the design
process in detail.
Identification of need generally starts the design process. Recognition of the need
and phrasing the need often constitute a highly creative act, because the need may be
only a vague discontent, a feeling of uneasiness, or a sensing that something is not right.
The need is often not evident at all; recognition can be triggered by a particular adverse