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efinement is often not a fully automatic procedure and user-controlled adjustments are required in order to generate better meshing, and it relies on the approximation properties of (mapped) polynomials. Therefore, Fries and Belytschko (2010) point out that an alternative to remeshing is to enrich the approximation space of the FEM so that these non-smooth solution properties are accounted for correctly, and independent of the mesh, and this is the path chosen in the XFEM. As a result, simple fixed meshes can be used throughout the simulation so that mesh construction and maintenance are reduced to a minimum and to enrich a polynomial approximation space such that non-smooth solutions can be modelled independent of the mesh. Alternatively to the technique of Fries and Belytschko (2010), Compere et al. (2010) propose improved mesh adaption using local mesh modifications. They understand that the remeshing technique normally removes the existing mesh and replaces it with an adapted one. However, they identify two problems with the current remeshing technique: 1) It introduces a lot of numerical diffusion in the mesh-to-mesh interpolation procedure 2) It is difficult to be applied when the computation is done in parallel. Therefore, in order to satisfy a prescribed mesh field size and maximise mesh quality, they have developed the open source Mesh Adaptation Library (Madlib) that describes a new code repositioning algorithm which combines a standard global node repositioning with local mesh modifications. Although this technique can improve the efficiency of the CPU time and memory consumption, these Madlib tools and algorithms are only suitable for adapting the tetrahedral meshes. 3.4.4 Artificial constraints In the composite-based pipeline repair modelling, the composite wraps and the solid pipeline that are subjected to biaxial loading are inappropriate for 2D 66
discretization. Therefore, in this study, they were modelled by 3D elements instead. The Triaxial Woven Fibre (TWF) composites were meshed with continuum shell elements (SC8R). These elements enabled capturing 3D geometry and consequently improved accuracy in contact problems. Pipe and repair compounds were modelled by solid C3D8 elements. As both continuum shell and solid elements have only a translational degree of freedom, coupling at the interface of the face layer and core elements was achieved by sharing the same interface nodes, thereby eliminating the need for kinematic constraints. According to Smojver and Ivancevic, (2010), in order to correctly transfer rotational degrees of freedom at the interface of 3D and conventional shell elements, appropriate coupling constraints need to be provided at the interface of different element types. This kinematic coupling constraint was achieved by tie surface-based constraints which were imposed on the nodes at the joint line of the continuum shells and solid elements. The methods that describe the above explanations are illustrated in Figures 3.8, 3.9, and 3.10. Without these artificial constraints such as tie and rigid body constraints, results cannot be generated successfully (ABAQUS Inc and DS, 2007). Figure 3.8: The first tie constraint between pipe and epoxy compound 67
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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
Page 35 and 36: presented current practices, recent
Page 37 and 38: Energy Workforce Sdn Bhd (2011) cla
Page 39 and 40: available provides real time detect
Page 41 and 42: 2.3.3 Reliability Analysis of Infor
Page 43 and 44: Figure 2.9: Pipeline failure probab
Page 45 and 46: 2.3.3.1 NDT Reliability and POD cur
Page 47 and 48: increase in the yield limit of stee
Page 49 and 50: the SCC assessment in their integri
Page 51 and 52: Manufacturers such as Walkers Techn
Page 53 and 54: Company L.P, 2005); Aquawrap ® pro
Page 55 and 56: monitoring, inspection, and damage
Page 57 and 58: 2.6.2 Aims of Structural Health Mon
Page 59 and 60: Figure 2.16: Application fields and
Page 61 and 62: egistered by the piezoelectric sens
Page 63 and 64: discretization error. Round-off err
Page 65 and 66: notches and Neuber‘s is better fo
Page 67 and 68: maximum local stress at discontinui
Page 69 and 70: De Carvalho (2005) concludes that t
Page 71 and 72: accurate simulation of loading espe
Page 73 and 74: Based on the above facts, the opera
Page 75 and 76: 3 FINITE ELEMENT ANALYSIS (FEA) IN
Page 77 and 78: 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: Figure 3.7: Schematic representatio
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 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
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Table 3.17: Ratio of Axial Stress N
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axial load (e.g. buried pipelines t
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3.10 Numerical Strain Analysis of C
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Figure 3.36 shows the contours befo
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Stress Concentration Factor 2 1.8 1
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In fact, for Notch 40 with 18 plies
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this second approach (i.e. the expe
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4.2.2 Strain Gauge Selection and Cr
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Finally, a method used to calculate
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Where, and are the maximum and mini
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should be between 20 and 28 bar and
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welded weld neck flange at both end
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Figure 4.7: Sensor and heating elem
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Figure 4.9: A summary of data acqui
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One of the objectives of doing this
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Figure 4.14: A schematic diagram of
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Table 4.1: Strain gauge readings at
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microstrain 3.00E-04 2.50E-04 2.00E
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However, the axial load transfer is
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Mircostrain 500 450 400 350 300 250
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Since the defect is not a flat notc
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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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