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Hoop Stress (MPa) 95 93 91 89 87 85 83 81 79 77 75 0 1 2 3 4 5 6 7 8 Figure 3.30: Hoop Stress versus L/W Ratio (2 different materials) From Figure 3.30, as the length of composite repair <strong>an</strong>d ply thickness increase, the hoop stress that is measured in the centre of the notch root of the steel pipe model decreases until the minimum value is reached at 80.64 MPa (i.e. referring to carbon epoxy with 18 plies). Most of the repaired pipes with variable plies have reached their minimum stresses as the composite repair length is around 160 mm except for carbon epoxy with four plies where, at this length, the maximum hoop stress occurs. However, a further increase in length of the composite repair of each variable ply, gradually increases the hoop stress. Hence, from the graph, the optimum length of repair for the defect width of 40 mm is 160 mm. L/W Ratio Table 3.13 summarises the axial stress results against the ratio of repair length to notch length. Likewise, the phenomenon of the hoop stress distribution, as shown in Figure 3.30, occurs in the axial stress distribution but at a smaller magnitude, as referred to in Figure 3.31. The minimum axial stress that has been recorded for 18 plies of carbon epoxy composite at a length of 160 mm is 34.75 MPa. 110 4 Plies Glass/Epoxy 4 Plies Carbon/Epoxy 8 Plies Glass/Epoxy 8 Plies Carbon/Epoxy 12 Plies Glass/Epoxy 12 Plies Carbon/Epoxy 18 Plies Glass/Epoxy 18 Plies Carbon/Epoxy
Table 3.13: Axial Stress v/s L/W ratio (defect length, W= 40 mm) Length of Repair (L) 50 mm 80 mm 120 mm 160 mm 200 mm 240 mm 280 mm 290 mm Length of Notch (W) 40 mm L/W ratio 1.25 2 3 4 5 6 7 7.25 Material Ply Carbon Axial Stress (MPa) Epoxy Carbon 4 Plies 41.39 39.78 39.98 42.9 42.3 42.04 42.19 46.38 Epoxy Carbon 8 Plies 41.32 38.56 38 38.29 38.38 39.15 41.23 43.59 Epoxy Carbon 12 Plies 37.96 37.74 35.83 36.68 36.71 37.49 39.23 42.02 Epoxy 18 Plies 37.11 37.31 35.45 34.75 36.25 35.9 36.41 38.07 Glass Epoxy 4 Plies 44.2 44.56 44.65 45.82 45.67 45.42 45.26 49.88 Glass Epoxy 8 Plies 42.35 42 41.39 41.61 41.78 42.69 43.34 46.44 Glass Epoxy 12 Plies 39.6 40.16 38.78 39.53 39.68 40.59 41.83 45.32 Glass Epoxy 18 Plies 39.27 38.93 37.77 37.23 38.63 39.03 40.33 42.78 Axial Stress (MPa) 55 50 45 40 35 30 0 1 2 3 4 5 6 7 8 L/W Ratio Figure 3.2: Axial Stress versus L/W Ratio (2 different materials) 111 4 Plies Glass/Epoxy 4 Plies Carbon/Epoxy 8 Plies Glass/Epoxy 8 Plies Carbon/Epoxy 12 Plies Glass/Epoxy 12 Plies Carbon/Epoxy
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CRANFIELD UNIVERSITY MAHADI ABD MUR
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ABSTRACT One of the most common pro
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TABLE OF CONTENTS ABSTRACT ........
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3.7.1 Introduction ................
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5.6 Summary and Conclusions .......
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Figure 3.1: Schematic diagram of th
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Figure 5.4: The average temperature
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NOMENCLATURES ACFM Alternating Curr
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1 INTRODUCTION One of the most comm
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1.1 Objectives Knowing this backgro
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The methodology of this integrated
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Chapter 6 contains the summary and
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period of the major part of the exi
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Figure 2.2: Reported interest in de
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Figure 2.4: Dent damage caused by v
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presented current practices, recent
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Energy Workforce Sdn Bhd (2011) cla
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available provides real time detect
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2.3.3 Reliability Analysis of Infor
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Figure 2.9: Pipeline failure probab
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2.3.3.1 NDT Reliability and POD cur
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increase in the yield limit of stee
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the SCC assessment in their integri
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Manufacturers such as Walkers Techn
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Company L.P, 2005); Aquawrap ® pro
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monitoring, inspection, and damage
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2.6.2 Aims of Structural Health Mon
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Figure 2.16: Application fields and
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egistered by the piezoelectric sens
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discretization error. Round-off err
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notches and Neuber‘s is better fo
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maximum local stress at discontinui
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De Carvalho (2005) concludes that t
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accurate simulation of loading espe
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Based on the above facts, the opera
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3 FINITE ELEMENT ANALYSIS (FEA) IN
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Figure 3.2: Schematic diagram of th
Page 79 and 80: In this modelling work (i.e. compos
Page 81 and 82: This partition toolset also helps u
Page 83 and 84: Figure 3.6: Mesh control using Swee
Page 85 and 86: Figure 3.7: Schematic representatio
Page 87 and 88: discretization. Therefore, in this
Page 89 and 90: According to Staten et al. (2010b),
Page 91 and 92: 3.5 The influence of pressure on th
Page 93 and 94: each pressure value remains constan
Page 95 and 96: Axial Stress, σa (S22) was referre
Page 97 and 98: Figure 3.14 shows a graph of analyt
Page 99 and 100: the notch defect is found to be in
Page 101 and 102: One of the contributions of this st
Page 103 and 104: Table 3.4: Convergence tests on var
Page 105 and 106: Figures 3.16 and 3.17 show that the
Page 107 and 108: Figure 3.20 shows that as the relat
Page 109 and 110: 3.7.4 Concluding Remarks A biaxial
Page 111 and 112: yarns change and lateral contact be
Page 113 and 114: For predicting E2 and Gl2, a number
Page 115 and 116: Where: Ar = weight of one sheet of
Page 117 and 118: Where; The Stiffness matrix is trad
Page 119 and 120: simulations for the hoop strain at
Page 121 and 122: Figure 3.24: Finding the hoop stres
Page 123 and 124: Table 3.8: The effect of repair len
Page 125 and 126: four up to 18 layers. In this study
Page 127 and 128: hoop and axial stress concentration
Page 129: Table 3.11: Predicted Elastic Const
Page 133 and 134: Hoop Stress (MPa) Figure 3.3: Hoop
Page 135 and 136: However, Frost (2008) and Alexander
Page 137 and 138: Table 3.17: Ratio of Axial Stress N
Page 139 and 140: axial load (e.g. buried pipelines t
Page 141 and 142: 3.10 Numerical Strain Analysis of C
Page 143 and 144: Figure 3.36 shows the contours befo
Page 145 and 146: Stress Concentration Factor 2 1.8 1
Page 147 and 148: In fact, for Notch 40 with 18 plies
Page 149 and 150: this second approach (i.e. the expe
Page 151 and 152: 4.2.2 Strain Gauge Selection and Cr
Page 153 and 154: Finally, a method used to calculate
Page 155 and 156: Where, and are the maximum and mini
Page 157 and 158: should be between 20 and 28 bar and
Page 159 and 160: welded weld neck flange at both end
Page 161 and 162: Figure 4.7: Sensor and heating elem
Page 163 and 164: Figure 4.9: A summary of data acqui
Page 165 and 166: One of the objectives of doing this
Page 167 and 168: Figure 4.14: A schematic diagram of
Page 169 and 170: Table 4.1: Strain gauge readings at
Page 171 and 172: microstrain 3.00E-04 2.50E-04 2.00E
Page 173 and 174: However, the axial load transfer is
Page 175 and 176: Mircostrain 500 450 400 350 300 250
Page 177 and 178: Since the defect is not a flat notc
Page 179 and 180: Again, the epoxy resin plays a sign
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Table 4.4: Study at the defect area
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Mircostrain 300 250 200 150 100 50
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Mircostrain 600 500 400 300 200 100
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14.25% in hoop strain and 23.5% in
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consideration for the selection of
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5.4 Methodology of Thermal Expansio
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Figure 5.1: Some preventive measure
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5.4.1 The Fundamentals of the Therm
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5.5 Analysis of Results 5.5.1 The t
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Thermal Output (strain ) 0.0002 0.0
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(Strain ,ε) Figure 5.12: Coefficie
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(Strain ,ε) 0.0002 0.00018 0.00016
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Table 5.1: The strain readings afte
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maximum shear strain increase as th
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The above results show that shear s
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shear strains becomes more stable a
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for future safe design and operatio
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has been fully cured. Poor surface
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6.3 Primary PhD Achievements The ea
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In Chapter 5, the CTE was determine
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ASM International (2002), "Thermal
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Bucinell, R. B. (2001), Calculating
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Proceedings of OMAE'01 20th Interna
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Greenwood, R. (2002), UKOPA Pipelin
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Kotrechko, S. A., Krasovskii, A. Y.
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Mousavi, S. E., Xiao, H. and Sukuma
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Raju, I. S. and Newman, J. C. (1986
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Tennyson, R. C. and Mufti, A. A. (2
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Xue, L., Widera, G. E. O. and Sang,
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General Technical Specifications: T
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Photos of the Design and Build of t
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Composite Installation Process usin
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APPENDIX 3 - STRAIN GAUGE INSTALLAT
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Figure 7: Mylar tape was stuck onto
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Figure 19: Repeating the above proc
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2) Electrical Insulation Test Resul
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