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5 THERMO-MECHANICAL BEHAVIOUR OF THE TRIAXIAL WOVEN FABRIC (TWF) COMPOSITE IN PIPELINE REPAIR 5.1 Introduction The previous chapters have discussed a complete methodology to assess the integrity of the pipeline system especially in quantifying the level of the reinforcement provided the repair in the elastic working region. However, the integrity of bonding between the reinforced material (i.e. steel) and reinforcing material (i.e. composite) is not only subjected to pressure only but also temperature (heating). In this chapter, the heating that influences the thermal expansion of these two materials was studied. According to Palmer and Paisley (2000), the difference in thermal expansion coefficient between the composite (repair) and the steel may have a detrimental effect on the composite to pipe (shell) bond and will certainly introduce significant changes to the internal stresses of the composite on heating. Avram (2001) demonstrates that the CTE mismatch between the composite patch and repaired structure plays an important role in the success of the repair. The closer the CTE's match, the greater the repair life because of less residual thermal stresses in the repair. Fouladi et al. (2010) in their study also agree that the difference in CTE of the patch material and the aluminium fuselage plays an important role in patching effectiveness. In the composite-based pipeline repair industry for example, if the CTE of the composite based pipeline repair is known, then operators will be in a better position to evaluate how well their composite repairs behave in terms of linear and circumferential expansions under different working temperatures. According to Gedeon (2001), the temperature range of the produced oil and gas under extreme conditions can be expected to be a maximum of 110°C. Therefore the design of the pipeline system should be based on 120°C. Any safe design should be able to include this eventuality in the 168
consideration for the selection of material and maintenance. Therefore, this preventive measure will ensure both the reliability and durability of the composite repair as planned. 5.2 Objectives The main objectives of this chapter are; 1. To study the internal thermal strain behaviour across the through thickness of the composite repair, and the stresses resulted from this expansion along with their effect on the SCF. 2. To determine and predict shear strain and shear angle values in the composite repair due to heating effect using a new approach. 3. To develop a simple and cost effective method in measuring the CTE measurement and prove as one of the acceptable CTE measurement techniques. 5.3 Techniques to Measure the Coefficient of Thermal Expansion (CTE) To determine the CTE, two physical quantities (displacement and temperature) must be measured on a sample that is undergoing a thermal cycle (ASM International, 2002). There are several thermal analysis techniques in which the property of a sample is measured while the sample is subjected to a controlled temperature programme, for example Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Thermomechanical Analysis (TMA) and Dynamic Mechanical Analysis (DMA) (Chawla, 1998) and Dilatometer. All these techniques have different approaches. For example, if the Dilatometer is used, the difference in expansion between a rod made from the test material and a matching length of quartz or vitreous silica is compared 169
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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
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Figure 3.24: Finding the hoop stres
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Table 3.8: The effect of repair len
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four up to 18 layers. In this study
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hoop and axial stress concentration
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Table 3.11: Predicted Elastic Const
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Table 3.13: Axial Stress v/s L/W ra
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Hoop Stress (MPa) Figure 3.3: Hoop
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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
Page 181 and 182: Table 4.4: Study at the defect area
Page 187: 14.25% in hoop strain and 23.5% in
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
Page 223 and 224: Bucinell, R. B. (2001), Calculating
Page 225 and 226: Proceedings of OMAE'01 20th Interna
Page 227 and 228: Greenwood, R. (2002), UKOPA Pipelin
Page 229 and 230: Kotrechko, S. A., Krasovskii, A. Y.
Page 231 and 232: Mousavi, S. E., Xiao, H. and Sukuma
Page 233 and 234: Raju, I. S. and Newman, J. C. (1986
Page 235 and 236: Tennyson, R. C. and Mufti, A. A. (2
Page 237 and 238: 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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