Preface	6
	Contents	8
	Structural Health Monitoring – Its Association and Use	9
	1 A Motivation for Structural Health Monitoring	9
	2 Loads and Overloads	19
	3 Fatigue, Fracture and Damage Tolerance	26
	3.1 Fatigue	26
	3.2 Fracture and Damage Tolerance	30
	3.3 SHM, Loads Monitoring and Damage Tolerance	43
	4 Non-Destructive Evaluation – Some Basic Principles	44
	4.1 Historic Background	44
	4.2 Magnetism	45
	4.3 Electromagnetic Ultrasound (EMUS)	54
	4.4 Eddy Current	55
	4.5 Ultrasonics	58
	4.6 Other Conventional NDT Techniques and Emerging Technologies	58
	5 Non-Destructive Evaluation in Composite Materials	62
	6 Approaches to Structural Health Monitoring	67
	7 Emerging SHM Applications and Concluding Remarks	80
	Bibliography	84
	Further Reading	87
	Structural Health Monitoring of Aircraft Structures	88
	1 Introduction	88
	2 Structural Health Monitoring Architectures	90
	2.1 Sensors Network Architecture	91
	2.2 Phased Arrays Architecture	94
	3 Piezoelectric Networks	97
	3.1 Damage Detection: Metallic Plates	100
	3.2 Development of a PCB Board for System Automation	107
	3.3 Damage Detection: Composite Plates	109
	3.4 Initial Acoustic Emission Experiments	115
	4 Phased Arrays	119
	4.1 Dispersion Curves	122
	4.2 Tuned Lamb Waves: Mode, Frequency and Transducer Selection	123
	4.3 Number of Elements in the Array	125
	4.4 Phased Array Actuation System	126
	4.5 Damage Detection Algorithms	129
	4.6 Damage Detection: Metallic Plates	134
	5 SHM using Fiber Optic Sensors	137
	5.1 Fiber Bragg Grating Sensors	141
	5.2 Etched Fiber Sensors	141
	5.3 Sensor Characterization	142
	5.4 Flow Monitoring	144
	5.5 Flow Monitoring of Panel Specimen	144
	5.6 Flow Monitoring of 3D Semicircle Specimen	146
	5.7 Strain Sensitivity Characterization	148
	5.8 Strain Sensitivity of Panel Specimen	150
	5.9 Strain Sensitivity of Semicircular Specimen	151
	6 Concluding Remarks	152
	Bibliography	153
	Vibration-Based Damage Diagnosis and Monitoring of External Loads	156
	1 Introduction	156
	2 Modeling and Diagnosis of Damaged Systems	158
	2.1 General Non-Linear Dynamical Model	158
	2.2 Feature Extraction	159
	2.3 Residual Vector and Damage Indicator	160
	2.4 Model-Based Diagnostics vs. Data-Based Damage Detection	161
	3 Diagnosis of Linear Systems	164
	3.1 Equation of Motion and State Space Representation	164
	3.2 Damage Identification in the Modal Domain	165
	3.3 Electro-Mechanical Impedance Method (EMIM)	167
	3.4 Time Domain Methods	168
	4 Data-based Damage Detection under Changing Environmental and Operational Conditions (EOC)	173
	4.1 Overview of Methods	173
	4.2 Environmental and operational conditions for wind energy plants	174
	4.3 Compensation of environmental effects on damage detection approach using fuzzy classification	175
	4.4 Example: Wind turbine	178
	5 Reconstruction of External Loads	180
	5.1 Problem overview and previous work	180
	5.2 Design of Simultaneous state and input estimator	192
	5.3 Application Examples	200
	6 Conclusions	205
	Bibliography	207
	Statistical Time Series Methods for Vibration Based Structural Health Monitoring	216
	1 Introduction	216
	2 The General Workframe	219
	2.1 The Structural States and the Data Sets	219
	2.2 The Baseline and Inspection Phases	220
	2.3 Classes of Statistical Time Series SHM Methods	222
	3 Statistical Time Series Models of the Structural Dynamics	223
	3.1 Non-Parametric Models	224
	3.2 Parametric Models	225
	3.3 Identification of Time Series Models	229
	4 Selected Non-Parametric Time Series SHM Methods	231
	4.1 PSD Based Method	232
	4.2 FRF Magnitude Based Method	233
	5 Selected Parametric Time Series SHM Methods	235
	5.1 Model Parameter Based Methods	236
	5.2 Model Residual Based Methods	238
	5.3 Functional Model (FM) Based SHM Methods	245
	6 Application of the Methods to a Laboratory Truss Structure	248
	6.1 The Laboratory Truss Structure and Problem Definition	248
	6.2 Baseline Phase: Structural Identification	250
	6.3 Inspection Phase: SHM via Selected Non-Parametric Methods	252
	6.4 Inspection Phase: SHM via Selected Parametric Methods	254
	6.5 Discussion	258
	7 Concluding Remarks and Future Research	261
	Bibliography	263
	A Appendix: Central limit theorem and statistical distributions associated with the normal	270
	A.1 The Central Limit Theorem (CLT)	270
	A.2 The x² distribution	270
	A.3 The Student’s t distribution	271
	A.4 The Fisher’s F distribution	271
	Fiber Optics Sensors	272
	1 Introduction	272
	2 Classification of Fiber Optic Sensors	274
	2.1 Intensity-based sensors	275
	2.2 Phase modulated optical fiber sensors, or Interferometers.	277
	2.3 Wavelength based sensors, or Bragg gratings.	278
	3 Fiber Bragg Gratings as Strain and Temperature Sensors	281
	3.1 Response of the FBG to uniaxial uniform strain fields.	282
	3.2 Sensitivity of the FBG to temperature.	282
	3.3 Response of the FBG to non-uniform uniaxial strain field.	283
	3.4 Response of the FBG to transverse stresses.	285
	3.5 Commercial FBG interrogation systems.	292
	4 Structures With Embedded Fiber Bragg Gratings	292
	4.1 Orientation of the optical fiber optic respective to the reinforcement fibers.	294
	4.2 Ingress/egress from the laminate.	295
	5 Examples of Applications in Aeronautics and Civil Structures	295
	5.1 Stiffened panels with embedded fiber Bragg gratings.	296
	5.2 Concrete beam repair	299
	6 Distributing Sensing	301
	7 Applications of Distributed Sensing	307
	8 Final Comments	317
	Bibliography	319
	Damage localisation using elastic waves propagation method. Experimental techniques.	324
	1 Structural Health Monitoring based on elastic waves propagation	324
	2 Elastic waves	326
	3 Elastic wave generation and sensing	334
	3.1 Elastic waves generation techniques	334
	3.2 Elastic waves sensing techniques	338
	4 Wave generation and sensing equipment	345
	5 Transducer network configurations	347
	6 Energy summing algorithm	351
	6.1 Basis for numerical algorithm	351
	6.2 Results	355
	6.3 Summary	361
	7 Beam forming algorithm	363
	7.1 Basis for numerical algorithm	363
	7.2 Results	367
	7.3 Summary	372
	Bibliography	374
	Application for Wind Turbine Blades	379
	1 A look at the Wind Energy Industry	379
	2 Condition Monitoring of Wind Turbine Blades	385
	3 Damage in Polymer Composite Materials	396
	4 Structural Testing of Wind Turbine Blades	412
	5 Future work	424
	Bibliography	432