Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
12.73 If a built-up weld is to be constructed (see
Fig. 12.5), should all of it be done at once, or
should it be done a little at a time, with suffi-
cient time allowed for cooling between beads?
12.74 Describe the reasons that fatigue failure gener-
tions 2.7 and 3.8) are complex phenomena. Re-
good fatigue resistance. However, the heat af-
Fig. 12.15 on p. 749). In addition, there is a
stress concentration associated with the weld,
12.75 If the parts to be welded are preheated, is the
likelihood that porosity will form increased or
decreased? Explain.
12.76 What is the advantage of electron-beam and
laser-beam welding, as compared to arc weld-
ing?
The main advantages of these processes are as-
sociated with the very small weld zone, and the
localized energy input and small heat-affected
zone. Weld failures, especially by fatigue, oc-
welds, explain the methods by which they can
the common defects are porosity, inclusions, in-
12.78 What are the sources of weld spatter? How can
to the surface, similar to the thermal spray-
12.79 Describe the functions and characteristics of
electrodes. What functions do coatings have?
How are electrodes classified?
There are many characteristics of electrodes
and the student is encouraged to develop an
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
plosion welding.
By the student. The difference between resis-
tance seam welding and resistance spot welding
tions 12.10.1 and 12.10.2). If the nuggets over-
this chapter to make a large bolt by welding the
head to the shank? (See Fig. 6.17.) Explain the
By the student. Note that processes such as
arc welding and gas welding, as well as friction
12.84 What are the similarities and differences be-
tween a bolt and a rivet?
12.85 It is common practice to tin plate electrical ter-
minals to facilitate soldering. Why is tin a suit-
able material?
Note in Table 12.5 on p. 777 that solders that
the tin plate will be very low, thus allowing
good wetting by the solder and resulting in a
12.86 Review Table 12.3 and explain why some ma-
terials require more heat than others to melt a
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.87 Two flat copper sheets (each 1.5 mm thick) are
being spot welded by the use of a current of
7000 A and a current flow time of 0.3 s. The
H= (7000)2(0.0002)(0.3) = 2940 J
V=π
12.87, assuming that the heat generated is con-
fined to the volume of material directly between
the two electrodes and that the temperature
distribution is uniform.
= 0.53 g = 0.00053 kg. The specific heat for
copper is 385 J/kgK. Therefore, the theoretical
provided than is needed for this small volume.
Clearly, in practice, very little of the heat is con-
centrated in this small volume. A more elabo-
Problem 12.87, if the temperature should be
between 0.7 and 0.85 times the melting tem-
0.7 and 0.85 times the melting temperature on
an absolute (Kelvin) or a Celsius temperature
tion of the top piece is cut horizontally with a
sharp saw. Thus, the residual stresses will be
disturbed, and, as described in Section 2.10, the
part will undergo shape change. For this case,
compressive residual stresses. (2) If we cut this
portion with a sharp saw (so that we do not in-
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.91 The accompanying figure shows a metal sheave
that consists of two matching pieces of hot-
rolled, low-carbon-steel sheets. These two
that the electrode requires 1500 J and the alu-
minum alloy requires 1200 J to melt one gram.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.93 A shielded metal arc welding operation is tak-
ing place on carbon steel to produce a fillet weld
(see Fig. 12.21b). The desired welding speed is
around 25 mm/sec. If the power supply is 10
V, what current is needed if the weld width is
to be 7 mm?
2.45×10−5m2. For shielded metal arc welding,
9.7 J/mm3. From Eq. (12.5), the weld speed is
therefore calculated as
I=uvA
12.94 The energy applied in friction welding is given
by the formula E=IS2/C, where Iis the mo-
OD, 0.25 in. wall thickness) is welded to a flat
rial 0.25 in. deep and directly below the tube)?
12.95 In oxyacetylene, arc, and laser-beam cutting,
the processes basically involve melting of the
plate as a function of kerf. Assume that one-
half of the energy goes into the plate and one-
half goes into the blank.
The volume melted is
the specific energy required to melt the work-
only one-half of the energy goes into the blank.
= 5.29 ×10−4m3
∆T=1508ut
ρCp(5.29 ×10−4)
below for selected materials.
500
400
Al
Cu
hesive properties given in Table 12.6, estimate
the minimum and maximum tensile force that
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
25.9 MPa. These values are used in the solution
below.
and
(15)(15) = 225 mm2= 2.25 ×10−4m2.
Note that in this case, the joint is loaded
ing (see Section 6.2.4). Basically, the design
than 1.5 times the shank diameter.
magnesium, (b) copper or (c) nickel.
v=eV I
uA = (0.75)(20)(200)
(2.9)(30) = 34.5 mm/s.
(b) For the copper workpiece, we have u= 6.1
12.99 A submerged arc welding operation takes place
on 10 mm thick stainless steel, producing a butt
is 40 V at 400 A, estimate the welding speed if
a stainless steel filler wire is used.
workpiece, the unit specific energy is obtained
uA
= 12.2 mm/s
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.100 Assume that you are asked to give a quiz to stu-
dents on the contents of this chapter. Prepare
By the student. This is a challenging, open-
ended question that requires considerable focus
12.101 Design a machine that can perform friction
12.101 if one of the pieces to be welded is non-
12.103 Describe product designs that cannot be joined
not be able to support the large axial loads in-
relating to the processes described in this chap-
12.105 Review the two weld designs in Fig. 12.58a, and,
the right is capable of supporting a larger mo-
shown on the right because the strength arises
12.106 In the building of large ships, there is a need
operation for this product. Which welding pro-
of the technical literature in shipbuilding tech-
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
Oxyfuel Inexpensive;
portable.
Significant joint
distortion; weld-
p. 738), possibly
compromising
joint strength.
12.107 Examine various household products, and de-
scribe how they are joined and assembled. Ex-
cesses are used because other processes which
12.108 A major cause of erratic behavior (hardware
bugs) and failure of computer equipment is fa-
design project. Students can consider if the
12.109 Using two strips of steel 1 in. wide and 8
in. long, design and fabricate a joint that gives
class. It must be noted, however, that the thick-
ness of the strips is not given in the statement of
the problem (although the word strip generally
bolt diameter is too large, the stresses in the
rest of the cross section may be too high, caus-
12.110 Make an outline of the general guidelines for
(or cutting). Review the various publications
of the National Safety Council and other simi-
Z49.1) and describes in detail the safety pre-
cautions that must be taken. Most of the stan-
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.111 A common practice for repairing expensive bro-
ken or worn parts, such as may occur when, for
example, a fragment is broken from a forging,
By the student. Considerations are that the in-
terface between the forging and the filling may
tools to wear more rapidly. The weld may frac-
ture during machining and compromise part in-
tegrity. The weld material may have insufficient
12.112 In the roll bonding process shown in Fig. 12.28,
how would you go about ensuring that the in-
terfaces are clean and free of contaminants, so
that a good bond is developed? Explain.
By the student. The students are encouraged
12.113 Alclad stock is made from 5182 aluminum al-
12.114 Obtain a soldering iron and attempt to solder
two wires together. First, try to apply the sol-
der at the same time as you first put the solder-
By the student. This is a valuable and inex-
pensive laboratory experience, showing the im-
portance of surface tension. With cold wires,
asked to examine this phenomenon further by
placing a small piece of solder of known volume
ture of the steel. It will be noted that above a
threshold value, the solder will flow freely and
coat the surface.
12.115 Perform a literature search to determine the
properties and types of adhesives used to affix
polymer often referred to as bone cement, or
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
12.116 Using the Internet, investigate the geometry of
By the student. These heads usually present a
straight vertical surface for the screwdriver in
12.117 Obtain an expression similar to Eq. (12.6), but
for electron beam and laser welding.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.
