Mechanical Engineering BTEC National Engineering Specialist Units Third Edition Alan Darbyshire AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Newnes is an imprint of Elsevier Newnes is an imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP, UK 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA First edition 2003 Second edition 2008 Third edition 2010 Copyright © 2010 Alan Darbyshire, except Chapter 6 © 2010 Elsevier Ltd. All rights reserved The right of Alan Darbyshire to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (44) (0) 1865 843830; fax (44) (0) 1865 853333; email: permissions@elsevier. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress Proudly sourced and uploaded by [StormRG] ISBN: 978-0-08-096577-2 Kickass Torrents | TPB | ET | h33t For information on all Newnes publications visit our website at www.com Typeset by MPS Limited, India Printed and bound in Hong Kong, China 10 11 12 13 14 10 9 8 7 6 5 4 3 2 1 Contents Acknowledgements .vii Chapter 1 Further Mechanical Principles and Applications. 24 Rotating Systems with Uniform Angular Acceleration.
41 Moment of Inertia. 48 Centripetal Acceleration and Centripetal Force. 75 Chapter 2 Advanced Mechanical Principles and Applications. 97 Uni-axial and Complex Loading.
98 Bending in Beams. 105 Torsion in Power Transmission Shafts. 115 Resultant and Relative Velocity. 123 Plane Linkage Mechanisms.
134 Chapter 3 Applications of Mechanical Systems and Technology. 151 Lubricants and Lubrication Systems. 161 Mechanical Power Transmission Systems. 175 Plant Equipment and Systems.
201 Chapter 4 Properties and Applications of Engineering Materials. 219 Atomic Structure of Materials. 220 Material Properties and Effects of Processing. 261 Selection of Engineering Materials.
269 Chapter 5 Engineering Design. 287 Knowing How the Design Process Operates When Dealing with Customers. 288 Understanding the Impact of Legislation, Standards and Environmental and Manufacturing Constraints on the Design Function. 294 Be Able to Prepare Design Proposals That Meet the Requirements of a Product Design Specification.
303 Be Able to Produce and Present a Final Design Solution. 317 iii iv Contents Chapter 6 Electro, Pneumatic and Hydraulic Engineering Materials. 334 Legislation, Regulations and Safety Precautions. 335 Fluid Power Devices.
337 Fluid Power Principles. 363 Maintenance of Fluid Power Systems. 389 Acknowledgements Unit 6 The author and publisher would like to thank the following people for their contribution to the second edition: W Bolton for writing chapter 6 “Electro, Pneumatic and Hydraulic Systems and Devices” Mike Tooley for allowing us to adapt his chapters in Engineering A Level and Higher National Engineering for use as chapter 5 “Engineering Design” Chapter opener and cover illustrations Photo of train (chapter 1) courtesy of iStockphoto, Remus Eserblom, Image # 4619117 Photo of racing car (chapter 2) courtesy of iStockphoto, Jan Paul Schrage, Image # 4955692 Photo of turbine (chapter 3) courtesy of iStockphoto, Tomas Bercic, Image # 4056469 Photo of aircraft (chapter 4) courtesy of iStockphoto, Dan Barnes, Image # 4941515 Photo of CNC machine (chapter 5) courtesy of iStockphoto, Shawn Gearhart, Image # 1798391 Photo of robotic system (chapter 6) courtesy of iStockphoto, Paul Mckeown, Image # 5129181 v This page intentionally left blank Introduction Unit 6 Welcome to the challenging and exciting world of engineering! This book has been written to help get you through six specialist units of the revised BTEC National Certificate and Diploma awards in Engineering. It provides the essential underpinning knowledge required of a student who wishes to pursue a career in engineering.
The book has been written by a highly experienced further education lecturer, who has over 30 years of practical teaching experience, with contributions from specialist lecturers in Engineering Design and Pneumatics and Hydraulics. Throughout the book I have adopted a common format and approach with numerous student activities, examples, end of chapter review questions and key points. About the BTEC National Certificate and Diploma The BTEC National Certificate and National Diploma qualifications have long been accepted by industry as appropriate qualifications for those who are about to enter industry or who are receiving training at the early stages of employment in industry. At the same time, these qualifications have become increasingly acceptable as a means of gaining entry into higher education.
BTEC National programmes in engineering attract a very large number of registrations per annum such that there are in excess of 35,000 students currently studying these qualifications in the UK by both part-time and full-time modes of study. The BTEC National syllabus was recently reviewed and extensively updated and new programmes have been launched with effect from September 2007. The new scheme is likely to be adopted by all institutions that currently offer the programme as well as a number of others who will be offering BTEC qualifications for the first time. Many organizations have contributed to the design of the new BTEC National Engineering programme including the Qualifications and Curriculum Authority (QCA), the Engineering Council and several Sector Skills Councils (SSC).
The Engineering Council continues to view the BTEC National Certificate/Diploma as a key qualification for the sector. They also recognize that BTEC National qualifications are frequently used as a means of entry to higher education courses, such as HNC/HND programmes and Foundation Degree courses. How to use this book This book covers six of the most popular specialist units that are common to many of the BTEC Engineering programmes. Each chapter vii viii Introduction covers one unit and contains Text, Key points, Test your knowledge questions, Examples, Activities and Review questions.
The Test your knowledge questions are interspersed with the text throughout the book. These questions allow you to check your understanding of the preceding text. They also provide you with an opportunity to reflect on what you have learned and consolidate this in manageable chunks. Most Test your knowledge questions can be answered in only a few minutes and the necessary information, formulae, etc., can be gleaned from the surrounding text.
Activities, on the other hand, make excellent vehicles for gathering the necessary evidence to demonstrate that you are competent in key skills. Consequently, they normally require a significantly greater amount of time to complete. They may also require additional library or resource area research time coupled with access to computing and other information technology resources. Many tutors will use Test your knowledge questions as a means of reinforcing work done in class while Activities are more likely to be ‘set work’ for students to do outside the classroom.
Whether or not this approach is taken, it is important to be aware that this student-centred work is designed to complement a programme of lectures and tutorials based on the BTEC syllabus. those not taking a formal course) will find complete syllabus coverage in the text. The Examples not only show you how to solve simple problems but also help put the subject matter into context with typical illustrative examples. In order to successfully tackle this work you will need to have a good scientific calculator (and get to know how to use it).
Finally, here are some general points to help you with your studies: ● Allow regular time for reading – get into the habit of setting aside an hour, or two, at the weekend. Use this time to take a second look at the topics that you have covered during the week or that you may have not completely understood. ● Make notes and file these away neatly for future reference – lists of facts, definitions and formulae are particularly useful for revision! ● Look out for the inter-relationship between subjects and units – you will find many ideas and a number of themes that crop up in different places and in different units. These can often help to reinforce your understanding.
● Don’t expect to find all subjects and topics within the course equally interesting. There may be parts that, for a whole variety of reasons, don’t immediately fire your enthusiasm. There is nothing unusual in this; however, do remember that something that may not appear particularly useful now may become crucial at some point in the future! ● However difficult things seem to get – don’t be tempted to give up! Engineering is not, in itself, a difficult subject, rather it is a subject Introduction ix that demands logical thinking and an approach in which each new concept builds upon those that have gone before. ● Finally, don’t be afraid to put your new ideas into practice.
Engineering is about doing – get out there and do it! Good luck with your BTEC Engineering studies! Alan Darbyshire Trains travelling at speeds in excess of 200 kmh1 have greatly Photo courtesy of iStockphoto, Remus Eserblom, Image# 4619117 reduced the journey time to continental cities. Mechanical principles are applied in the calculation of the tractive effort required to maintain these speeds and the braking forces required to bring the trains to rest. Mechanical principles are also applied in the design of tilting mechanisms and the track infrastructure. x Chapter 1 Further Mechanical Principles and Applications T he design, manufacture and servicing of engineered products are important to the nation’s economy and well-being.
One has only to think of the information technology (IT) hardware, aircraft, motor vehicles and domestic appliances we use in everyday life to realise how reliant we have become on engineered products. A product must be fit for its purpose. It must do the job for which it was designed for a reasonable length of time and with a minimum of maintenance. The term ‘mechatronics’ is often used to describe products which contain mechanical, electrical, electronic and IT systems.
It is the aim of this chapter to broaden your knowledge of the underpinning mechanical principles which are fundamental to engineering design, manufacturing and servicing. 1 2 Further Mechanical Principles and Applications Engineering Structures CHAPTER 1 Loading systems Forces whose lines of action lie in a single plane are called coplanar forces. If the lines of action pass through a single point, the forces are said to be concurrent and the point through which they pass is called the point of concurrence (Figure 1. F1 F1 Point of concurrence F2 F2 F3 F3 Concurrent forces Non-concurrent forces Figure 1.1 Coplanar force systems A concurrent system of coplanar forces can be reduced to a single force KEY POINT acting at the point of concurrence.
This is called the resultant force. A system of concurrent coplanar forces If a body is subjected to a system of concurrent coplanar forces and is can be reduced to a single resultant force. not constrained, it will move in the direction of the resultant force. To prevent this from happening, a force must be applied which is equal and opposite to the resultant.
This balancing force, which will hold the body in a state of static equilibrium, is called the equilibrant of the system. When a body is subjected to a system of non-concurrent coplanar forces, there is a tendency for the forces not only to make it move in a particular direction, but also to make it rotate. Such a non-concurrent system can KEY POINT be reduced to a single resultant force and a resultant couple.