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Table 4.2: Strain gauge readings at all locations Mircostrain Location and Strain Values (Microstrain) Type of Strain 0 layer 2 Layers 4 Layers 6 Layers 8 Layers S1-Hoop Strain 276.42 257.53 266 260.8 252.8 S1-Axial Strain 86 80 79.45 83.37 78.46 S2 - Hoop Strain 401.14 407.17 400.48 383.07 380.12 S2 - Axial Strain 363.41 335.29 310.88 305.58 287.65 S3-Hoop Strain 440.82 429.87 406.28 398.42 378.04 S3-Axial Strain 285.77 268.26 239.43 224.47 218.62 S4 - Hoop Strain 278.28 276.08 274.43 266.76 255.16 S4 - Axial Strain 68.38 72.3 67.82 70.8 66.13 S5 - Hoop Strain 479.77 396.87 380.71 368.72 356.86 S5 - Axial Strain 301.86 326.47 297.14 301.02 284.8 S6 - Hoop Strain 427.03 476 476.3 476.3 477.64 S6 - Axial Strain 334.7 301.18 302.52 302.52 280.02 600 500 400 300 200 100 0 Figure 4.19: The load transfer behaviour at different positions on the steel (testing pressure at 50 bar) 152 0 layer 2 Layers 4 Layers 6 Layers 8 Layers
However, the axial load transfer is slightly different. At S1 which is close to the stress riser (i.e. welding joint flange), the axial strain at the zero layer (i.e. 86 microstrain) is higher than at S4 (i.e. 68.38 microstrain) which is away from the notch defect and welding joint. This shows that the axial strain at S1 is not only the function of internal pressure but also the discontinuity or geometry of the structure. The axial load transfer from the non-repaired (i.e. zero layer) to fully repaired (i.e. eight layers) is more effective at S1 where the improvement of load transfer is 8.7% higher than at S4 which is only 3.29%. Finally, the difference in the axial strain readings at S1 and S4 after eight layers has been reduced from 20.49% to 15.71%. Strain distributions at defect locations such as at S2, S3 and S5 shows a significant load transfer from 0 to 8 layers of the composite repair and this is further discussed at the end of this section. A strain distribution can also be seen at location S6, where location and orientation of the rectangular strain gauge are similar to S3 except that at this location no repair has been done. At the zero layer, the strain readings at S3 and S6 are very close to each other with an error of 3.12% only. The reason for this is mainly attributed to machining error at the defect shape and depth of both locations. Interestingly, when the adjacent location (i.e. S3) is wrapped with two layers of composite, the hoop strain reading at S6 tends to increase instead of remaining constant. When the number of layers is increased from two to eight layers, the hoop strain readings remain steady and almost constant but higher than the reading at the zero layer. This shows that one side (i.e. S3) is under compression due to the effect of the composite repair and at the other end is under tension (i.e. S6) due to the unrepaired defect surface. However, the axial strain finally decreases when S3 has been fully repaired with 8 layers of composite. This shows that the effect of the composite repair not only reduces the axial strain values at the repaired area but also the adjacent (non- repaired) area as well. 153
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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
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In this modelling work (i.e. compos
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This partition toolset also helps u
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Figure 3.6: Mesh control using Swee
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Figure 3.7: Schematic representatio
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discretization. Therefore, in this
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According to Staten et al. (2010b),
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3.5 The influence of pressure on th
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each pressure value remains constan
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Axial Stress, σa (S22) was referre
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Figure 3.14 shows a graph of analyt
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the notch defect is found to be in
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One of the contributions of this st
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Table 3.4: Convergence tests on var
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Figures 3.16 and 3.17 show that the
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Figure 3.20 shows that as the relat
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3.7.4 Concluding Remarks A biaxial
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yarns change and lateral contact be
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For predicting E2 and Gl2, a number
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Where: Ar = weight of one sheet of
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Where; The Stiffness matrix is trad
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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 and 130: Table 3.11: Predicted Elastic Const
Page 131 and 132: Table 3.13: Axial Stress v/s L/W ra
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: microstrain 3.00E-04 2.50E-04 2.00E
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
Page 181 and 182: Table 4.4: Study at the defect area
Page 187 and 188: 14.25% in hoop strain and 23.5% in
Page 189 and 190: consideration for the selection of
Page 191 and 192: 5.4 Methodology of Thermal Expansio
Page 193 and 194: Figure 5.1: Some preventive measure
Page 195 and 196: 5.4.1 The Fundamentals of the Therm
Page 197 and 198: 5.5 Analysis of Results 5.5.1 The t
Page 199 and 200: Thermal Output (strain ) 0.0002 0.0
Page 201 and 202: (Strain ,ε) Figure 5.12: Coefficie
Page 203 and 204: (Strain ,ε) 0.0002 0.00018 0.00016
Page 205 and 206: Table 5.1: The strain readings afte
Page 207 and 208: maximum shear strain increase as th
Page 209 and 210: The above results show that shear s
Page 211 and 212: shear strains becomes more stable a
Page 213 and 214: for future safe design and operatio
Page 215 and 216: has been fully cured. Poor surface
Page 217 and 218: 6.3 Primary PhD Achievements The ea
Page 219 and 220: In Chapter 5, the CTE was determine
Page 221 and 222: 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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