Aluminium Design and Construction John Dwight

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Table 11.8 Properties of a selected one-component epoxy adhesive Figure 11.18 One-component Araldite adhesive AV.119: (a) curing time t and shear strength (at 23°C) as functions of the curing temperature Tc ; (b) variation of shear strength � � with ambient temperature T after 30 min cure at 150°C. Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
11.4.11 Resistance calculations for bonded joints Resistance calculations are needed in the earlier stages of design, even when a bonded joint is going to be eventually validated by testing. Such calculations pose problems because: 1. The stress transmitted by the adhesive is non-uniform, with peak values at critical points. 2. The adhesives used with aluminium are not generally ductile enough to allow redistribution of these peak stresses. 3. The shear strengths quoted for adhesives are only typical. Also they are based on the standard lap-test which is not ideal (Section 11.4.6). When a joint is to be checked by calculation, the basic requirement is that the peak shear stress q1 transmitted by the adhesive, under factored loading, should satisfy: (11.26) where p v is the limiting shear stress for the adhesive and � m the material factor. The determination of suitable values for the three quantities involved is considered below. (a) Stress arising (q1 ) The load transmitted by a bonded joint can be transverse or longitudinal, or a combination thereof. In each case, the adhesive is stressed in shear. The mean value q of the shear stress in the adhesive can usually be found using conventional engineering formulae. But this is not the same as the peak value q1 which is what matters. Figure 11.19(a) shows the typical stress variation in a simple lap joint with peak stresses at the ends. For a simple joint of this kind, the difference between q1 and q is considerable and not to be ignored, since the adhesives used are not generally ductile enough to allow full redistribution to occur. One outcome of this is that little advantage is gained by increasing the length l of such a joint beyond a certain point. The situation can be improved by tapering the aluminium, which reduces the peakiness of the stress pattern (Figure 11.19(b)). Modifying the joint in such a way can reduce the peak stress to a value much closer to the mean, provided the taper is correctly designed. The determination of q1 and the design of the taper (if used) is typically achieved by employing an elastic finite-element program, although a simpler analysis is possible in some cases. An essential input to such calculations is the shear-flexibility of the adhesive, which is a function of its shear modulus G and the glue-line thickness tg . In assuming a suitable value for the latter, it is important to realize that the ‘peakiness’ of the Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
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Aluminium Design and Construction C
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First published 1999 by E & FN Spon
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2.2.1 Rolling mill practice 2.2.2 P
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5 Limit state design and limiting s
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8.2.6 Use of interpolation for semi
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10.3.2 Inertias for a section with
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Preface Aluminium is easily the sec
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List of symbols The following symbo
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uu, vv principal axes w effective s
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1.1.3 The industrial metal It is on
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where A is the section area (mm 2 )
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1.3.1. The good points about alumin
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Deflection Because of the lower mod
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1.4.4 Establishment of the alloys I
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1.5.2 New technology Most of alumin
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large span, where self-weight is a
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These tend to be in all-aluminium c
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Close-up of the M-dec system, which
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Aluminium glazing system for commer
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Nat West Media Centre, Lords Cricke
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The main requirements for the produ
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in which t and w are in mm. These a
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Figure 2.1 Extrusion process (direc
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Figure 2.2 Typical extrusion die. t
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Figure 2.6 ‘Semi-hollow’ profil
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especially the stronger alloys in t
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Figure 2.9 Conventional profiles. 2
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2.4 TUBES By tubes we mean hollow s
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CHAPTER 3 Fabrication 3.1 PREPARATI
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Figure 3.1 Alternative designs for
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Figure 3.2 Thread insert. a coil-sp
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3.3 ARC WELDING 3.3.1 Use of arc we
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adjusted. The technique is claimed
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For welds of minimum or fatigue qua
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Figure 3.5 Friction-stir welding: s
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are, and the designer/fabricator mu
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cartridge, and mixing takes place a
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3.7.4 Painting Alloys having durabi
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Where a range is given, as for the
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will be only slightly above that fo
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heating the metal to a temperature
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Table 4.4 Characteristics of differ
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softening in the heat-affected zone
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60 alloys, are: BSEN.485 plate and
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Firure 4.3 Nominal composition and
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popular alloys in the series are: 6
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Figure 4.6 Variation of tensile str
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undercarriages of aircraft. They ar
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Figure 4.11 Minimum stress-strain c
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AC.51400 This is another non-heat-t
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times that of the actual pits) prod
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The severity of bimetallic corrosio
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Nominal loading. Nominal loads are
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2. Material factor (� m ). In the
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design does not, because stress at
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Table 5.2 Summary of limiting stres
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Figure 5.4 Plastic strain at workin
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example, a reduced value might be t
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The parameter � depends purely on
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CHAPTER 6 Heat-affected zone soften
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area of softening. With 7xxx-type m
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Figure 6.3 Typical hardness plots a
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6.4 SEVERITY OF HAZ SOFTENING 6.4.1
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Figure 6.6 Categories of welded joi
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Figure 6.10 One-inch rule, extent o
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e allowed for in design by replacin
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Figure 6.13 Predicted area (A z ) o
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Figure 6.15 Overlapping HAZs. nomin
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In determining A zp , an appropriat
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failure plane in the HAZ, close to
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With MIG welding, an electrode-posi
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CHAPTER 7 Plate elements in compres
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(a) Compression member elements The
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Table 7.1 Classification of element
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Figure 7.4 Slender internal element
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Figure 7.7 shows curves of � ° p
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(7.9a) (7.9b) The strain gradient c
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(through the centroid) for ß S . F
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Figure 7.13 Outstands under strain-
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Figure 7.15 Reinforced elements. Th
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Figure 7.18 Stiffener location for
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Figure 7.20 Slender reinforced inte
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CHAPTER 8 Beams 8.1 GENERAL APPROAC
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8.2.2 Section classification The di
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that for the gross section. It woul
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the usual manner. Line 1 in the fig
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1. Fully compact sections. The limi
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Figure 8.8 Transverse and longitudi
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8.3.4 Shear resistance of bars and
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Figure 8.12 Tension-field action. i
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Figure 8.14 Moment/shear interactio
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depending on the estimated degree o
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where a is the stiffener spacing an
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plates (if fitted), p v =limiting m
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ending moment diagram. Two cases ar
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Figure 8.23 Sections covered in Tab
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where: I yy , I vv =inertia about m
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post (Section 8.6.4) or by some oth
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Figure 8.26 Components of deflectio
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9.1.2 Classification of the cross-s
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hole. Alternatively, it might fail
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Figure 9.2 Limiting stress p b for
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The determination of l involves a c
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Figure 9.6 Monosymmetric section. I
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Figure 9.9 Limiting stress p b for
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where s=� s /� t s =slenderness
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Figure 9.11 Type-R sections covered
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Figure 9.14 Four standardized profi
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9.7.2 Secondary bending in trusses
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Table 9.5 Necessary checks for memb
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Figure 9.18 Axial load with biaxial
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1. Tension members. The localized f
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Figure 10.1 Symmetric plastic bendi
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We now turn to monosymmetric sectio
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Page 233 and 234: 10.3.3 Product of inertia The produ
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Page 237 and 238: Table 10.2 Torsion constant. Factor
Page 239 and 240: Figure 10.12 Warping. Conventional
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Page 243 and 244: 10.5.3 Evaluation of warping When t
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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
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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
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Page 275 and 276: 11.4.6 Creep Shear strength figures
Page 277 and 278: Figure 11.15 Effect of glue-line th
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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
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Aluminium Design and Construction John Dwight

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