cranfield university mahadi abd murad an integrated structural ...

More documents

Recommendations

Info

from the problems described earlier for embedded or attached sensors. In his study, he has found that the electrical resistance method is only particularly effective for detecting small and subtle defects in composite materials and in joints. Based on the above literature, SHM can be summarised as the acquisition of information to enable the diagnosis and prognosis of structural integrity and the ultimate objective is to continuously monitor and assess the status of the integrity of a structure or its components with a high level of confidence and reliability. Each of the techniques has its own advantages and disadvantages. Therefore, selection of the right sensors to be used for the right application will ensure the success of the SHM. Having described the full definitions and concepts of SHM, FEA and experiments that have been used as an integrated approach to the diagnosis and prognosis of the composite based pipeline repair will be discussed in the following sections. 2.7 Introduction to Finite Element Analysis (FEA) FEA (also known as the method) has been successfully used for many years in the analysis of complex structures (Walz et al., 1968) and historically, it was first developed in the 1940s by Alexander Hrennikoff and Richard Courant. During this period it was called the finite-element method. In 1965 the first finite-element software was created by NASA and it was called NASTRAN. At present, there are many types of structural analysis software on the market. Some of these brands include: ALGOR, ANSYS, ABAQUS and MARC (Knoxville, 2009). The Finite Element is a numerical technique for finding approximate solutions for partial differential equations (PDEs) as well as for integral equations. The solution approach is based either on eliminating the differential equation completely (steady state problems), or rendering the PDE into an approximating system of ordinary differential equations, which are then numerically integrated using standard techniques such as Euler's method, Runge-Kutta, etc. (Gilbert and Fix, 1973). The major sources of error resulting from the use of finite element methods are round-off error and 42
discretization error. Round-off error is the error associated with the accuracy with which numbers are manipulated in a computer and discretization error is the error that is associated with using discrete variables to represent a problem where the state variables are continuous (Walz et al., 1968). In order to overcome this problem, a study of the convergence of the numerical results as the number of elements increase, has to be carried out. The most effective method, as suggested by the University of Alberta, (2002) is to conduct a convergence test, beginning with a mesh discretization and then recording the solution. The problem with a finer mesh (i.e. more elements) should be repeated and the result compared with the previous test. If the results are similar, then the first mesh is probably good enough for that particular loading, geometry and constraint. An example of a good convergence study was carried out by Longest and Vinchurkar (2007). They established the effects of mesh generation techniques and grid convergence on velocity fields and particle deposition patterns in bifurcating respiratory models, which included structured hexahedral, unstructured tetrahedral, flow adaptive tetrahedral and hybrid grids. From their observations based on a Grid Convergence Index, generating structured meshes based on hexahedral elements requires significant time and effort; however, these meshes are associated with high quality solutions. Beden et al. (2008) point out that an FEA technique that has been used for modelling and simulation is able to produce more accurate fatigue life predictions for pipe elbows. They demonstrate how Tet10 ABAQUS element mesh predicts higher maximum principle stresses than the Tet4 mesh of the same size, but with a greater number of elements, nodes and degree of freedom. However, they have not compared with other element types such as hexahedral which would produce better results. DeVries et al. (2009) demonstrate their developed IA-FEMesh as a user friendly toolkit for generating FE models in orthopaedic (biomedical) research. IA-FEMesh enables geometrically accurate hexahedral meshes to take less time than traditional methods such as PATRAN which have proved to be time-consuming and laborious. Their study of IA-FEMesh is capable of generating anatomically accurate hexahedral meshes of the human phalanx in less time than the traditionally used commercial mesh generator. 43
Page 1:
CRANFIELD UNIVERSITY MAHADI ABD MUR
Page 4 and 5:
ABSTRACT One of the most common pro
Page 7 and 8:
TABLE OF CONTENTS ABSTRACT ........
Page 9 and 10:
3.7.1 Introduction ................
Page 11: 5.6 Summary and Conclusions .......
Page 14 and 15: Figure 3.1: Schematic diagram of th
Page 16 and 17: Figure 5.4: The average temperature
Page 18 and 19: NOMENCLATURES ACFM Alternating Curr
Page 21 and 22: 1 INTRODUCTION One of the most comm
Page 23 and 24: 1.1 Objectives Knowing this backgro
Page 25 and 26: The methodology of this integrated
Page 27 and 28: Chapter 6 contains the summary and
Page 29 and 30: period of the major part of the exi
Page 31 and 32: Figure 2.2: Reported interest in de
Page 33 and 34: 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: egistered by the piezoelectric sens
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 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 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 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 183 and 184:
Mircostrain 300 250 200 150 100 50
Page 185 and 186:
Mircostrain 600 500 400 300 200 100
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
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,
Page 239 and 240:
General Technical Specifications: T
Page 241 and 242:
Photos of the Design and Build of t
Page 243 and 244:
Composite Installation Process usin
Page 245 and 246:
APPENDIX 3 - STRAIN GAUGE INSTALLAT
Page 247 and 248:
Figure 7: Mylar tape was stuck onto
Page 249 and 250:
Figure 19: Repeating the above proc
Page 251:
2) Electrical Insulation Test Resul
show all

cranfield university mahadi abd murad an integrated structural ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?