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`NU MARK Ex.1039 p.1
`
`NU MARK Ex.1039 p.1
`
`

`

`Library of Congress Cataloging-in-Publication Data
`
`Speck, James A
`Mechanical fastening, joining, and assembly I James A Speck.
`p. cm. -
`(Mechanical engineering : 109)
`Includes index.
`ISBN 0~8247-9835-X (alk. paper)
`1. Fasteners. 2. Joints (Engineering) 3. Assembling machines.
`II. Series: Mechanical engineering (Marcel Dekker, Inc.)
`I. Title.
`; 109.
`TJ1320.S65 1997
`621.8'8-dc21
`
`96-52021
`CIP
`
`The publisher offers discounts on this book when ordered in bulk quantities.
`For more information, write to Special Sales/Professional Marketing at the
`address below.
`
`This book is printed on acid-free paper.
`
`Copyright© 1997 by MARCEL DEKKER, INC. All Rights Reserved.
`
`Neither this book nor any part may be reproduced or transmitted in any form
`or by any means, electronic or mechanical, including photocopying, micro(cid:173)
`filming, and recording, or by any information storage and retrieval system,
`without permission in writing from the publisher.
`
`MARCEL DEKKER, INC.
`270 Madison Avenue, New York, New York 10016
`
`Current printing (last digit):
`10 9 8 7 6 5 4 3 2 l
`
`PRJNTED IN THE UNITED STATES OF AMERICA
`
`NU MARK Ex.1039 p.2
`
`

`

`1
`FASTENER FUNCTIONS AND ASSEMBLY TESTING
`
`1.1 THE FASTENER DESIGN ROLE
`
`Fasteners are used in applications for strength, appearance and reusability.
`Considering them in reverse order, reusability is often a consideration since many
`assemblies may need to be taken apart for maintenance, service and repair. In even
`some moderate volume assemblies, it may be desirable by either some percentage
`of the target market, or the product manufacturer, if not both, to have the ability at
`some time after manufacturing assembly to disassemble. Even for those products
`which have only a remote possibility of ever needing disassembly for service or
`repair, there is no way of knowing which of them will need to be disassembled. If
`only one in a thousand needs reusability in its fasteners, for whatever purpose, the
`reusability of the fastenings is a design requirement. Since knowing which 1 % will
`require reusability is not possible during assembly, it is a requirement for all of the
`assemblies produced during the production run.
`Fasteners play an appearance role in the market acceptance or lack of
`acceptance of their respective products. Although, when asked, many purchasers
`will state that economic or technical features of a product were a prime purchasing
`decision factor, it cannot be refuted that style and appearance are much larger
`factors in what we choose to buy than many of us would care to admit.
`Fastener appearance can function as a visible sign of robustness as in the
`exposed, high strength fasteners in a piece of industrial machinery. ln this manner,
`they can give visual assurance to customers and prospects of product strength,
`durability and value. Conversely, fasteners can be designed «out of view," a design
`trend. which is popular now in consmner durable goods, especially autos and
`appliances. This well tailored, sleek appearance makes a strong visual statement of
`thoughtful design, seamless assembly and a general up-to-date, modern
`appearance. These two and numerous other fastener "looks" ebb and flow in
`popularity. But the assembly designer and manufacturer ignores them at their risk.
`At the most basic level, fasteners are used because of their strength,
`especially their holding strength in the assembly. As fasteners come "out of the
`box" they make available potential holding power. Holding power is the key
`
`NU MARK Ex.1039 p.3
`
`

`

`Appendix C
`SOME FREQUENT FASTENER QUESTIONS AND ANSWERS
`
`Question:
`
`When is an application a good one for threaded fasteners?
`
`Answer:
`
`Threaded fasteners are most useful '>vhen there is a need for reusability
`that has some frequency. For example, changing the wheels on an
`automobile makes good application of machine screw threads. Threads
`would not be as useful on the exterior trim molding, which may be held on
`with snap on clips or adhesive. When reusability is a possibility, the
`frequency of reuse is uncertain or infrequent enough to not require the
`high reusability of threaded fasteners.
`
`Question:
`
`What is hydrogen embrittlement and how does it occur in fasteners?
`
`Answer:
`
`Hydrogen embrittlement is a metallurgical phenomenon which makes
`steel fasteners brittle and easily fractured under load. It is the result of
`hydrogen accumulating in fasteners, usually during electroplating. An
`example would be an alloy steel tension fastener, through hardened to
`HRc 40 and cleaned or zinc plated in a plating process generating
`excessive amounts of hydrogen gas as a by product. The hydrogen
`migrates to the highly stressed areas of the fastener. During tensioning, the
`molecules of hydrogen attach themselves to the grains of steel composed
`of atomic iron, carbon, manganese and the other alloying elements, taking
`away the space which normally allows the fastener grains to flex under
`load and remain somewhat ductile. Instead, the grains boundaries develop
`cracks which grow quickly under load and result in the fastener fracturing,
`sometimes catastrophically.
`
`Hydrogen embrittlement can be controlled by three steps. First, the
`cleaning and plating processes should be selected, controlled and
`monitored. Electroless nickel is not known to be hydrogen embrittling
`while zinc plating is .. The plating process should have adequate
`process controls for current density, which is a contributing factor to
`excessive hydrogen generation. Second, all heat treated and electroplated
`fasteners should be baked at a minimum of 375 degrees Fahrenheit, for at
`least three hours in a temperature controlled oven within l hour of plating.
`
`230
`
`NU MARK Ex.1039 p.4
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`