Aluminium Design and Construction John Dwight

More documents

Recommendations

Info

Type 4 fillers The advantage of these, when used for welding 1xxx, 3xxx or 6xxx-series material, is their ability to prevent cracking. The normally preferred version is 4043A (�5% Si). When crack control is paramount, as in a highly restrained joint, the 4047A (�12% Si) filler may be specified instead, but with some loss in corrosion resistance. Type 4 fillers provide no protection against cracking when employed for welding parent metal containing over 2% Mg, and are therefore unsuitable for use with most 5xxx and 7xxx materials. Type 5 fillers When a joint is to be made in 7xxx-series alloy or the strongest form of 5xxx (such as 5083), and the prime requirement is weld-metal strength, the best filler alloy is 5556A (or equivalent). For other 5xxx-series parent alloys, the precise choice of filler tends to be less critical. As a general rule, the filler composition should broadly match that of the parent metal. A lower amount of magnesium will produce a weaker weld, whereas a more highly alloyed filler may lead to trouble in potentially corrosive environments. 3.3.5 Weld inspection The required amount of inspection at a welded joint depends on the level of weld quality that the designer wants to achieve, and BS.8118 recognizes three such levels [9]. 1. Minimum quality. This is acceptable when the force transmitted by the joint under factored loading is not more than one-third of its factored static resistance, and fatigue is not a factor. 2. Normal quality is called for in non-fatigue situations when the transmitted force is too high for minimum quality to be allowed, or under fatigue conditions when the required fatigue class is 20 or below. 3. Fatigue quality applies when fatigue is a factor in the design of the joint, and the required fatigue class is 24 or over. Table 3.2 Filler wire types for welding dissimilar parent alloys Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
For welds of minimum or fatigue quality, the designer must indicate the quality level on the drawing. Where no such information is given, the fabricator assumes that normal quality applies. For fatigue quality joints the drawing should include the Fat-number and also an arrow showing the direction of the fluctuating stress. As explained in Section 12.7, the Fat-number defines the required fatigue class (24, 29, 35, 42 or 50), which may be less than the highest class possible for the detail concerned. The following is a summary of the main types of inspection method that are available for aluminium welds: 1. Visual inspection before welding (surface condition, preparation, alignment, fit-up, etc); 2. Visual inspection after welding (weld geometry, profile discon-tinuities, alignment, etc); 3. Non-destructive testing (NDT), which aims at checking all surface and sub-surface defects (cracks, porosity, inclusions etc): dye penetrant testing; ultrasonic testing; radiography. 4. Taking macro-sections from separate test-pieces, which are welded at the same time and properly represent the technique and conditions in the production joint. British Standard BS.8118 provides comprehensive tables stating which inspection methods are needed when, and also the recommended acceptance levels for different kinds of defect. The amount of inspection called for depends on the required quality level, the type and orientation of the weld, and the Fat-number (when relevant). Minimum quality welds only have to be visually inspected. Dye penetrant tests are generally required for normal or fatigue quality, with ultrasonics or radiography being necessary as well at transversely loaded butts. Macros are required only for fatigue-quality welds of higher Fat-number. 3.4 FRICTION-STIR WELDING 3.4.1 The process The friction-stir (FS) process is a solid-phase welding process, invented in 1991 at the TWI (formerly The Welding Institute), near Cambridge, UK. [10]. It has been developed in the first place for welding aluminium, where it is set to become an accepted technique along with MIG and TIG, and at the time of writing it is being exploited commercially in several countries [11]. Possible extension of the FS process to steel poses a Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
Page 1 and 2:
Aluminium Design and Construction C
Page 3 and 4:
First published 1999 by E & FN Spon
Page 5 and 6:
2.2.1 Rolling mill practice 2.2.2 P
Page 7 and 8:
5 Limit state design and limiting s
Page 9 and 10:
8.2.6 Use of interpolation for semi
Page 11 and 12:
10.3.2 Inertias for a section with
Page 13 and 14:
Preface Aluminium is easily the sec
Page 15 and 16: List of symbols The following symbo
Page 17 and 18: uu, vv principal axes w effective s
Page 19 and 20: 1.1.3 The industrial metal It is on
Page 21 and 22: where A is the section area (mm 2 )
Page 23 and 24: 1.3.1. The good points about alumin
Page 25 and 26: Deflection Because of the lower mod
Page 27 and 28: 1.4.4 Establishment of the alloys I
Page 29 and 30: 1.5.2 New technology Most of alumin
Page 31 and 32: large span, where self-weight is a
Page 33 and 34: These tend to be in all-aluminium c
Page 35 and 36: Close-up of the M-dec system, which
Page 37 and 38: Aluminium glazing system for commer
Page 39 and 40: Nat West Media Centre, Lords Cricke
Page 41 and 42: The main requirements for the produ
Page 43 and 44: in which t and w are in mm. These a
Page 45 and 46: Figure 2.1 Extrusion process (direc
Page 47 and 48: Figure 2.2 Typical extrusion die. t
Page 49 and 50: Figure 2.6 ‘Semi-hollow’ profil
Page 51 and 52: especially the stronger alloys in t
Page 53 and 54: Figure 2.9 Conventional profiles. 2
Page 55 and 56: 2.4 TUBES By tubes we mean hollow s
Page 57 and 58: CHAPTER 3 Fabrication 3.1 PREPARATI
Page 59 and 60: Figure 3.1 Alternative designs for
Page 61 and 62: Figure 3.2 Thread insert. a coil-sp
Page 63 and 64: 3.3 ARC WELDING 3.3.1 Use of arc we
Page 65: adjusted. The technique is claimed
Page 69 and 70: Figure 3.5 Friction-stir welding: s
Page 71 and 72: are, and the designer/fabricator mu
Page 73 and 74: cartridge, and mixing takes place a
Page 75 and 76: 3.7.4 Painting Alloys having durabi
Page 77 and 78: Where a range is given, as for the
Page 79 and 80: will be only slightly above that fo
Page 81 and 82: heating the metal to a temperature
Page 83 and 84: Table 4.4 Characteristics of differ
Page 85 and 86: softening in the heat-affected zone
Page 87 and 88: 60 alloys, are: BSEN.485 plate and
Page 89 and 90: Firure 4.3 Nominal composition and
Page 91 and 92: popular alloys in the series are: 6
Page 93 and 94: Figure 4.6 Variation of tensile str
Page 95 and 96: undercarriages of aircraft. They ar
Page 97 and 98: Figure 4.11 Minimum stress-strain c
Page 99 and 100: AC.51400 This is another non-heat-t
Page 101 and 102: times that of the actual pits) prod
Page 103 and 104: The severity of bimetallic corrosio
Page 105 and 106: Nominal loading. Nominal loads are
Page 107 and 108: 2. Material factor (� m ). In the
Page 109 and 110: design does not, because stress at
Page 111 and 112: Table 5.2 Summary of limiting stres
Page 113 and 114: Figure 5.4 Plastic strain at workin
Page 115 and 116: example, a reduced value might be t
Page 117 and 118:
The parameter � depends purely on
Page 119 and 120:
CHAPTER 6 Heat-affected zone soften
Page 121 and 122:
area of softening. With 7xxx-type m
Page 123 and 124:
Figure 6.3 Typical hardness plots a
Page 125 and 126:
6.4 SEVERITY OF HAZ SOFTENING 6.4.1
Page 127 and 128:
Figure 6.6 Categories of welded joi
Page 129 and 130:
Figure 6.10 One-inch rule, extent o
Page 131 and 132:
e allowed for in design by replacin
Page 133 and 134:
Figure 6.13 Predicted area (A z ) o
Page 135 and 136:
Figure 6.15 Overlapping HAZs. nomin
Page 137 and 138:
In determining A zp , an appropriat
Page 139 and 140:
failure plane in the HAZ, close to
Page 141 and 142:
With MIG welding, an electrode-posi
Page 143 and 144:
CHAPTER 7 Plate elements in compres
Page 145 and 146:
(a) Compression member elements The
Page 147 and 148:
Table 7.1 Classification of element
Page 149 and 150:
Figure 7.4 Slender internal element
Page 151 and 152:
Figure 7.7 shows curves of � ° p
Page 153 and 154:
(7.9a) (7.9b) The strain gradient c
Page 155 and 156:
(through the centroid) for ß S . F
Page 157 and 158:
Figure 7.13 Outstands under strain-
Page 159 and 160:
Figure 7.15 Reinforced elements. Th
Page 161 and 162:
Figure 7.18 Stiffener location for
Page 163 and 164:
Figure 7.20 Slender reinforced inte
Page 165 and 166:
CHAPTER 8 Beams 8.1 GENERAL APPROAC
Page 167 and 168:
8.2.2 Section classification The di
Page 169 and 170:
that for the gross section. It woul
Page 171 and 172:
the usual manner. Line 1 in the fig
Page 173 and 174:
1. Fully compact sections. The limi
Page 175 and 176:
Figure 8.8 Transverse and longitudi
Page 177 and 178:
8.3.4 Shear resistance of bars and
Page 179 and 180:
Figure 8.12 Tension-field action. i
Page 181 and 182:
Figure 8.14 Moment/shear interactio
Page 183 and 184:
depending on the estimated degree o
Page 185 and 186:
where a is the stiffener spacing an
Page 187 and 188:
plates (if fitted), p v =limiting m
Page 189 and 190:
ending moment diagram. Two cases ar
Page 191 and 192:
Figure 8.23 Sections covered in Tab
Page 193 and 194:
where: I yy , I vv =inertia about m
Page 195 and 196:
post (Section 8.6.4) or by some oth
Page 197 and 198:
Figure 8.26 Components of deflectio
Page 199 and 200:
9.1.2 Classification of the cross-s
Page 201 and 202:
hole. Alternatively, it might fail
Page 203 and 204:
Figure 9.2 Limiting stress p b for
Page 205 and 206:
The determination of l involves a c
Page 207 and 208:
Figure 9.6 Monosymmetric section. I
Page 209 and 210:
Figure 9.9 Limiting stress p b for
Page 211 and 212:
where s=� s /� t s =slenderness
Page 213 and 214:
Figure 9.11 Type-R sections covered
Page 215 and 216:
Figure 9.14 Four standardized profi
Page 217 and 218:
9.7.2 Secondary bending in trusses
Page 219 and 220:
Table 9.5 Necessary checks for memb
Page 221 and 222:
Figure 9.18 Axial load with biaxial
Page 223 and 224:
1. Tension members. The localized f
Page 225 and 226:
Figure 10.1 Symmetric plastic bendi
Page 227 and 228:
We now turn to monosymmetric sectio
Page 229 and 230:
distance of its centroid from the n
Page 231 and 232:
Figure 10.6 Elements of sections. I
Page 233 and 234:
10.3.3 Product of inertia The produ
Page 235 and 236:
Usually the conditions are such as
Page 237 and 238:
Table 10.2 Torsion constant. Factor
Page 239 and 240:
Figure 10.12 Warping. Conventional
Page 241 and 242:
where b, t=element width and thickn
Page 243 and 244:
10.5.3 Evaluation of warping When t
Page 245 and 246:
For sections where the position of
Page 247 and 248:
(10.31) where: e=distance that S li
Page 249 and 250:
10.5.9 Asymmetric sections Before s
Page 251 and 252:
CHAPTER 11 Joints This chapter cons
Page 253 and 254:
the use of limiting stresses taken
Page 255 and 256:
and the summation is made for all t
Page 257 and 258:
Figure 11.3 Interaction diagram for
Page 259 and 260:
k in order to give a fair compariso
Page 261 and 262:
3. The design is satisfactory if fo
Page 263 and 264:
When the method of surface preparat
Page 265 and 266:
11.3.3 Weld force arising In many c
Page 267 and 268:
Table 11.6 Limiting stress p w (N/m
Page 269 and 270:
where p a =limiting stress for unwe
Page 271 and 272:
Figure 11.11 Interaction diagram fo
Page 273 and 274:
Manufacturers of structural adhesiv
Page 275 and 276:
11.4.6 Creep Shear strength figures
Page 277 and 278:
Figure 11.15 Effect of glue-line th
Page 279 and 280:
Table 11.7 and Figure 11.17 provide
Page 281 and 282:
11.4.11 Resistance calculations for
Page 283 and 284:
high value reflects the various unc
Page 285 and 286:
therefore usually presented in term
Page 287 and 288:
For example: The loading spectrum i
Page 289 and 290:
act on the structure. However, BS.8
Page 291 and 292:
Figure 12.4 Crack propagation: (a)
Page 293 and 294:
12.5 CLASSIFICATION OF DETAILS 12.5
Page 295 and 296:
i.e. a joint extending in the same
Page 297 and 298:
when the design life is low or when
Page 299 and 300:
Methods (2) and (3) are difficult t
Page 301:
it reverts to line 1. The slope s o
show all

Aluminium Design and Construction John Dwight

Create successful ePaper yourself

Delete template?

Save as template?