02 Mechanical Engineering

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2

MECHANICAL ENGINEERING

The aim of this chapter is to introduce mechan-

ical engineering and its interrelationships to

mechanical design. Defining mechanical engineer-

ing is itself a challenge. Some people hold the

opinion that it should not suffer the indignity of a

definition, as this would invariably set bounds on

the activity. Nevertheless, it is considered here

that the subject of definition should be explored

as this serves the purpose of introducing some

vital concepts and setting the context and the

interrelationships with the topics considered in

this book.

2.1 Introduction

A brief look at the publicity material for the world's larger bodies representing mechanical

engineers and mechanical engineering, such as the Institution of Mechanical Engineers (about 80000 members) and the American Society of Mechanical Engineers (about 125 000 members),

will reveal that mechanical engineering relates to

activities including:

9 Aerospace

9 Automobiles

9 Rail

9 Shipping

9 Power generation

9 Mining

9 White goods

9 Sports

9 Agriculture

9 Manufacture/production

9 Military hardware The above activities involve a challenge. Take the

automobile, for example, which comprises a power

plant, fuel storage, a form of support (traditionally

wheels and suspension), a skin, furniture and

entertainment systems.Which aspects relate to the

activity of the mechanical engineer? The engine, a typical example of which is illustrated in Figure

2.1, is invariably controlled by a microprocessor-

based engine management system as only this can

currently perform the necessary monitoring and

control functions to maintain acceptable emissions

standards. Where do the mechanical engineer's

responsibilities start and end and how should the

interaction with software experts and electronic

Figure 2.1 An engine from the Mondeo. (Figure courtesy of Ford Motor Co.)

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and control engineers occur? Should in fact just one individual undertake all the tasks associated with producing a functioning engine? The answer to this last question lies in the complexity of the task and the timescales involved. It is unlikely that

any one individual has all the necessary skills and

furthermore, the timescales demanded in industry

to fulfil profit objectives and changes in available

technology usually preclude an individual working

in isolation from being effective.

Taking another example from the aerospace

sector using Airbus Industrie's A380 illustrated in

Figures 2.2 to 2.4.The design work here was not

Figure 2.2 The Airbus A380. (Figure courtesy of Airbus Industrie.) only divided across overlapping disciplines, but

across countries and cultural divides.Wings were designed and made in the United Kingdom, the fuselage in France, cabin interior and seats in

Business

Economy

First

Ii ! iI Economy

Freight or underfloor passenger activities

Figure 2.4 Cabin options for the A380. (Figure courtesy of Airbus Industrie.)

Figure 2.3 Exploded view of the A380. (Figure courtesy of Airbus Industrie.)

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Germany and the assembly undertaken in France. To give an idea of the complexity of the task

involved, psychologists can be involved in deter-

mining the layout of cockpit design in order to

advise on human-machine interactions.

Mechanical engineers can choose to limit their

activity to items they perceive to be inherently

mechanical, such as gearboxes, clutches and internal

combustion engines. If this is the case then some

form of deception has invariably occurred, as it is

next to impossible to isolate a mechanism or

component entirely and thereby decouple it from

its relationship to other factors and influences.

Devices of a mechanical nature can be considered

to be those involving relative motion, stressed

components and prime movers amongst many

others.This limitation, however, is too constraining

for today's products where added value is a key

consideration as exemplified by the variety in

white goods, such as vacuum cleaners and dish-

washers available in any electrical hardware store.

Instead the mechanical engineer needs to be a

master of his own discipline and also have skills and

awareness of many related disciplines. This need is

reflected in the demands of accrediting bodies for

first degrees such as the Institution of Mechanical Engineers.A typical requirement is for an interdis- ciplinary education followed up by continuing pro-

fessional development where the engineer covers the fundamentals of his primary profession in

depth and breadth accompanied by courses that widen the perspective, such as studies in materials, electronics, software, management, etc.