Acoustic Emission (eBook)

Preface 6
Contents 8
Abbreviations 12
Nomenclature 14
1 The Generation of Elastic Acoustic Emission Waves Due to the Fracture of Solids 16
1.1 Some Fracture Mechanics Criteria Under Quasi-Static Loading of Materials 16
1.1.1 Energy Criteria 19
1.1.2 Force Criteria 22
1.1.3 Deformation Criteria 26
1.2 Micro-Cracking of Solids 28
1.3 Physical Grounds of AE Generation 29
1.4 Basic Parameters of the AE Signals 32
1.4.1 Cumulative Count [60] 33
1.4.2 AE Count Rate [60] 33
1.4.3 Amplitude Distribution of AES 34
1.4.4 Spectral and Energy Distribution of AES 34
1.4.5 Identification of AES by the Waveform Type 35
1.5 Basic Analytical Dependences Between the Fracture Parameters and the AE Signals 35
References 38
2 Propagation of Elastic Waves in Solids 44
2.1 Types of Elastic Waves 44
2.1.1 Some General Ideas on Elastic Strain 44
2.1.2 A Wave Equation for a Solid 46
2.1.3 Main Ideas of the Wave Process 47
2.1.4 Spatial Elastic Waves 50
2.1.5 Rayleigh Surface Wave 53
2.1.6 Head (Creeping) Wave 55
2.1.7 Waves at an Interface of Two Media 56
2.1.8 Waves in Layers and Plates 57
2.1.9 Waves in Bars 61
2.1.10 Other Types of Waves 62
2.2 Some Basic Acoustic Properties of Media 65
2.2.1 Impedance and Wave Resistance of a Medium 65
2.2.2 Decay of Elastic Waves 66
2.2.3 Diffraction of Elastic Waves 71
2.2.4 Refraction of Elastic Waves 76
2.3 AE Sources 76
References 84
3 Analysis of Acoustic Emission Caused by Internal Cracks 89
3.1 Nucleation and Sub-critical CRACK Growth 90
3.1.1 Nucleation of a Mode I Penny-Shaped Crack 90
3.1.2 Nucleation of a Mode III Penny-Shaped Crack 97
3.2 Modelling the Sub-critical Crack Growth at Local Areas of Its Contour as a Source of Acoustic Emission Signals 102
3.3 The Effect of Body Boundaries on AE Signals Caused by the Growth of an Internal Defect 105
3.4 The Waveguide Effect on the Change of the Parameters of AE Signals 109
3.5 The Assessment of Surface Displacements Caused by an Internal AE Source 112
References 117
4 Some Methodological Foundations for Selecting and Processing AE Signals 120
4.1 Some General Methodical Guidelines on the Use of the AE Method in the Mechanical Testing of Materials with Cracks 120
4.2 Technical Aspects of Preparation for AE Tests 124
4.3 Selection of Informative Parameters of AE Signals 126
4.4 Simulation of AE Sources 127
4.5 Simulation of AE Events at the AET Output 133
4.6 Spectrum of the AE Signals During Macro-crack Growth 137
4.7 Directional Diagram of AE Radiation During Macro-crack Growth 143
4.8 Estimation of AE Signals Caused by Propagation of Internal Crack-like Defects 147
4.9 Methods of the AET Mounting at IO 152
4.10 Selection of Useful AES During AE Tests 154
4.10.1 Selection of a Working Frequency Band of AE Facilities 155
4.10.2 Filtration of AES by Instrumental Facilities 161
4.10.3 Application of the “Dead Time” Mode 161
4.10.4 The Kaiser Effect Application 163
4.10.5 A Method of Spatial Selection of AES 164
4.10.6 Other Methodical Approaches 166
References 167
5 Evaluation of Mechanical Characteristics and Static Crack Growth Resistance of Materials with the Use of Aes 173
5.1 Identification of the AES Generated During Plastic Zone Growth 173
5.2 A Method for Evaluating a Macro-Crack Start 177
5.3 AE Estimation of the Stages of Sub-Critical Crack Propagation 183
5.3.1 Types of Specimens and Modes of AE Signals Selection 183
5.3.2 Interpretation of Investigation Results 186
5.4 Estimation of a Macro-Crack Length Increment and SIF Increase Under Static Loading 190
5.4.1 Some Theoretical Bases for AE Estimation of Macro-Crack Propagation Parameters 190
5.4.2 Test Results 192
5.5 AE Estimation of Strength Characteristics of Structural Materials 197
5.5.1 Investigation of Concrete Hardening by AE Signals [31] 197
5.5.2 AE Estimation of AES Amplitudes at a Fracture of Concrete in the Bridge Structure 206
5.5.3 AE Estimation of Mechanical Characteristics of Steels 213
5.5.4 AES Generation Under Reinforced Concrete Beam Bending 219
References 223
6 Some Aspects of Applying the Acoustic Emission Method 230
6.1 Specific Features of Long-Term AE Testing of Industrial Objects 231
6.1.1 Selection of a Frequency Band and AET Placing 231
6.1.2 Calibration of an AE Testing System 233
6.1.3 Analysis and Presentation of AE Test Results 233
6.1.4 Stability of AE Parameters 234
6.1.5 Classification of AE Sources by Their Activity 239
6.2 Using the AE Methods for Testing the Offshore Platforms 244
6.3 Using the AE for Testing the Nuclear Reactors 247
6.4 Application of AE Method for Estimation of Strength of Pressure Vessels and Pipelines 251
6.5 AE Inspection of Welded Joints 254
6.5.1 Verification of Selection of Materials, the Type of Specimens, and an Investigation Method [21] 256
6.5.2 Results of the AE Research of the Welded Joints and Their Interpretation 258
6.6 Selective On-Line AE Hydraulic Testing of an Oil Storage Reservoir 266
6.6.1 Some Methodological Features of AE Testing of a Reservoir 267
6.6.2 Criteria for Classifying AE Sources 270
6.6.3 Results of the AE Testing and Their Interpretation 273
6.7 AE Testing and Diagnostics of Building Structures 275
6.8 The AE Inspection of Bridges in Ukraine 278
6.9 Prospects for Further AE Application 287
References 289