Table Of ContentFoundations of Engineering Mechanics
Zinoviy Nazarchuk
Valentyn Skalskyi
Oleh Serhiyenko
Acoustic
Emission
Methodology and Application
Foundations of Engineering Mechanics
Series editors
V.I. Babitsky, Loughborough, Leicestershire, UK
Jens Wittenburg, Karlsruhe, Germany
More information about this series at http://www.springer.com/series/3582
Zinoviy Nazarchuk Valentyn Skalskyi
(cid:129)
Oleh Serhiyenko
Acoustic Emission
Methodology and Application
123
ZinoviyNazarchuk OlehSerhiyenko
Karpenko Physico-Mechanical Institute Karpenko Physico-Mechanical Institute
Lviv Lviv
Ukraine Ukraine
Valentyn Skalskyi
Karpenko Physico-Mechanical Institute
Lviv
Ukraine
ISSN 1612-1384 ISSN 1860-6237 (electronic)
Foundationsof Engineering Mechanics
ISBN978-3-319-49348-0 ISBN978-3-319-49350-3 (eBook)
DOI 10.1007/978-3-319-49350-3
LibraryofCongressControlNumber:2016958504
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Preface
A great amount of the industrial equipment in Ukraine long ago exhausted the
lifespan for which it was designed. Its replacement today is either economically
unprofitable or, for various other reasons, impossible. This causes us to use such
objects of durable operation in close-to-critical conditions. To extend the safe
operating life of the equipment, it is necessary to use new, modern methods and
facilities of strength and durability diagnostics. Besides, in some fields of pro-
duction, new materials and technologies are introduced, experience of their oper-
ation under conditions of intensive loading and the aggressive effect on the
environment is insufficient and therefore these objects need to be monitored.
An analysis of the causes of failure of structural materials, which are widely
applied in engineering, the power-generating industry, pipeline transport, aircraft
construction, chemical and oil industry, etc., has showed that in most cases failure
occurs due to the initiation and propagation of crack-like defects. Therefore,
investigationoftheseprocessesbecomesanextraordinarilyimportanttask.Itisalso
conditioned by the fact that on the one hand, it is necessary to study the mecha-
nismsofdefectinitiation,andpropagation,andtodeveloponthisbasistheeffective
methods of improvement of the durability, reliability, and other service character-
istics ofmaterials—andontheother toinvestigatethephenomenathat accompany
deformationandfractureofmaterialsandeventuallyprovidebasesofnewphysical
methods of non-destructive testing.
The initiation and development of defects cause a number of accompanying
physicalphenomena.Themostinterestingarethoserelatedtothetransferofenergy
or matter; they are what allows us to effectively detect the defects and determine
their parameters at certain (sometimes considerably large) distances from their
locations. The radiation of heat, electrons, electromagnetic and elastic waves are
among them.
A phenomenon of elastic wave radiation during the deformation or fracture of
materials, phase transformations and precipitation of second-phase particles, mag-
netic or surface transformations in materials is called “acoustic emission.”
Experienceoverthelastfew decades testifiestothegreatpotentialpossibilities for
the acoustic emission method. It is especially appropriate in situations where it is
v
vi Preface
impossibletovisuallycheckthecracks’initiation andpropagationbecauseoftheir
tunneling in material, or when there is no access to the inspected object. The
remotenessoftheexamination,highsensitivity,andpossibilitytodetectthedistant
defects,whichexceedtheirsizesbymanyordersofmagnitude—independentofthe
shapes and sizes of the inspected object—the realtime recording of fracture
developmentandsoon,aretheadvantagesthatplacetheacousticemissionmethod
in the lead among all the known prospective methods of non-destructive testing.
The successful application of the acoustic emission method for the observation
of the state of materials and products is possible only if scientifically grounded
methods and proper facilities for their realization are available. Today, despite a
great number of publications and undoubted progress in the development of
equipment, there are certain difficulties in correctly selecting and applying the
methodological bases of this method.
Inthismonograph,thephysicalaspectsoftheproblemareanalyzedindetail;the
methodologicalbasesofthepracticaluseofacousticemissiondevices,knownboth
inUkraine and outside it, aredescribed; theresults oftheoretical andexperimental
researchofpeculiaritiesofevaluationofthecrackgrowthresistanceofmaterialsare
discussed; and the selection of the useful AE signals, etc., are presented. The
methods’ efficiency is shown in the conditions of diagnostics of multi-purpose
industrial objects. The results of experimental research have been obtained by the
authors with the help of the new methods and facilities, and some of them are
thankstothesupportoftheScienceandTechnologyCenterinUkraine(grantsNos.
1689, 1628 and 3905).
Theauthorshavemadeanattempttosynthesizeandclassifynotonlytheirown,
but also other information culled from the literature, in order to create clear
approaches to the practical use of acoustic emission. They hope that the results
presentedinthismonographwillbeofgreatinteresttothespecialistswhodealwith
theproblemofnon-destructivetestingandthetechnicaldiagnosticsofproductsand
structures operating in various fields of human activity.
Acknowledgements The authors are grateful to Orest Ya. Tsurkovskyi for
translating and assisting in the preparation of this book.
Lviv, Ukraine Zinoviy Nazarchuk
Valentyn Skalskyi
Oleh Serhiyenko
Contents
1 The Generation of Elastic Acoustic Emission Waves Due to the
Fracture of Solids ... .... ..... .... .... .... .... .... ..... .... 1
1.1 Some Fracture Mechanics Criteria Under Quasi-Static Loading
of Materials ... .... ..... .... .... .... .... .... ..... .... 1
1.1.1 Energy Criteria ... .... .... .... .... .... ..... .... 4
1.1.2 Force Criteria .... .... .... .... .... .... ..... .... 7
1.1.3 Deformation Criteria ... .... .... .... .... ..... .... 11
1.2 Micro-Cracking of Solids.. .... .... .... .... .... ..... .... 13
1.3 Physical Grounds of AE Generation.. .... .... .... ..... .... 14
1.4 Basic Parameters of the AE Signals.. .... .... .... ..... .... 17
1.4.1 Cumulative Count [60] . .... .... .... .... ..... .... 18
1.4.2 AE Count Rate [60] ... .... .... .... .... ..... .... 18
1.4.3 Amplitude Distribution of AES... .... .... ..... .... 19
1.4.4 Spectral and Energy Distribution of AES ... ..... .... 19
1.4.5 Identification of AES by the Waveform Type..... .... 20
1.5 BasicAnalyticalDependencesBetweentheFractureParameters
and the AE Signals.. ..... .... .... .... .... .... ..... .... 20
References.. .... .... .... ..... .... .... .... .... .... ..... .... 23
2 Propagation of Elastic Waves in Solids... .... .... .... ..... .... 29
2.1 Types of Elastic Waves ... .... .... .... .... .... ..... .... 29
2.1.1 Some General Ideas on Elastic Strain .. .... ..... .... 29
2.1.2 A Wave Equation for a Solid .... .... .... ..... .... 31
2.1.3 Main Ideas of the Wave Process.. .... .... ..... .... 32
2.1.4 Spatial Elastic Waves .. .... .... .... .... ..... .... 35
2.1.5 Rayleigh Surface Wave. .... .... .... .... ..... .... 38
2.1.6 Head (Creeping) Wave . .... .... .... .... ..... .... 40
2.1.7 Waves at an Interface of Two Media .. .... ..... .... 41
2.1.8 Waves in Layers and Plates.. .... .... .... ..... .... 42
vii
viii Contents
2.1.9 Waves in Bars.... .... .... .... .... .... ..... .... 46
2.1.10 Other Types of Waves.. .... .... .... .... ..... .... 47
2.2 Some Basic Acoustic Properties of Media . .... .... ..... .... 50
2.2.1 Impedance and Wave Resistance of a Medium.... .... 50
2.2.2 Decay of Elastic Waves. .... .... .... .... ..... .... 51
2.2.3 Diffraction of Elastic Waves . .... .... .... ..... .... 56
2.2.4 Refraction of Elastic Waves . .... .... .... ..... .... 61
2.3 AE Sources.... .... ..... .... .... .... .... .... ..... .... 61
References.. .... .... .... ..... .... .... .... .... .... ..... .... 69
3 Analysis of Acoustic Emission Caused by Internal Cracks .... .... 75
3.1 Nucleation and Sub-critical CRACK Growth... .... ..... .... 76
3.1.1 Nucleation of a Mode I Penny-Shaped Crack ..... .... 76
3.1.2 Nucleation of a Mode III Penny-Shaped Crack.... .... 83
3.2 Modelling the Sub-critical Crack Growth at Local Areas
of Its Contour as a Source of Acoustic Emission Signals... .... 88
3.3 The Effect of Body Boundaries on AE Signals Caused
by the Growth of an Internal Defect.. .... .... .... ..... .... 91
3.4 The Waveguide Effect on the Change of the Parameters
of AE Signals.. .... ..... .... .... .... .... .... ..... .... 95
3.5 The Assessment of Surface Displacements Caused
by an Internal AE Source.. .... .... .... .... .... ..... .... 98
References.. .... .... .... ..... .... .... .... .... .... ..... .... 103
4 Some Methodological Foundations for Selecting and Processing
AE Signals. .... .... .... ..... .... .... .... .... .... ..... .... 107
4.1 Some General Methodical Guidelines on the Use of the AE
Method in the Mechanical Testing of Materials with Cracks .... 107
4.2 Technical Aspects of Preparation for AE Tests.. .... ..... .... 111
4.3 Selection of Informative Parameters of AE Signals .. ..... .... 113
4.4 Simulation of AE Sources . .... .... .... .... .... ..... .... 114
4.5 Simulation of AE Events at the AET Output ... .... ..... .... 120
4.6 Spectrum of the AE Signals During Macro-crack Growth .. .... 124
4.7 Directional Diagram of AE Radiation During Macro-crack
Growth... .... .... ..... .... .... .... .... .... ..... .... 130
4.8 Estimation of AE Signals Caused by Propagation of Internal
Crack-like Defects .. ..... .... .... .... .... .... ..... .... 134
4.9 Methods of the AET Mounting at IO. .... .... .... ..... .... 139
4.10 Selection of Useful AES During AE Tests. .... .... ..... .... 141
4.10.1 Selection of a Working Frequency Band
of AE Facilities... .... .... .... .... .... ..... .... 142
4.10.2 Filtration of AES by Instrumental Facilities . ..... .... 148
4.10.3 Application of the “Dead Time” Mode. .... ..... .... 148
4.10.4 The Kaiser Effect Application.... .... .... ..... .... 150
Contents ix
4.10.5 A Method of Spatial Selection of AES . .... ..... .... 151
4.10.6 Other Methodical Approaches.... .... .... ..... .... 153
References.. .... .... .... ..... .... .... .... .... .... ..... .... 154
5 Evaluation of Mechanical Characteristics and Static Crack
Growth Resistance of Materials with the Use of Aes .... ..... .... 161
5.1 Identification of the AES Generated During Plastic Zone
Growth... .... .... ..... .... .... .... .... .... ..... .... 161
5.2 A Method for Evaluating a Macro-Crack Start.. .... ..... .... 165
5.3 AE Estimation of the Stages of Sub-Critical Crack
Propagation.... .... ..... .... .... .... .... .... ..... .... 171
5.3.1 Types of Specimens and Modes of AE Signals
Selection ... ..... .... .... .... .... .... ..... .... 171
5.3.2 Interpretation of Investigation Results.. .... ..... .... 174
5.4 Estimation of a Macro-Crack Length Increment and SIF
Increase Under Static Loading .. .... .... .... .... ..... .... 178
5.4.1 Some Theoretical Bases for AE Estimation
of Macro-Crack Propagation Parameters .... ..... .... 178
5.4.2 Test Results. ..... .... .... .... .... .... ..... .... 180
5.5 AE Estimation of Strength Characteristics of Structural
Materials.. .... .... ..... .... .... .... .... .... ..... .... 185
5.5.1 Investigation of Concrete Hardening by AE Signals
[31]... .... ..... .... .... .... .... .... ..... .... 185
5.5.2 AE Estimation of AES Amplitudes at a Fracture
of Concrete in the Bridge Structure.... .... ..... .... 194
5.5.3 AE Estimation of Mechanical Characteristics
of Steels ... ..... .... .... .... .... .... ..... .... 201
5.5.4 AES Generation Under Reinforced Concrete Beam
Bending.... ..... .... .... .... .... .... ..... .... 207
References.. .... .... .... ..... .... .... .... .... .... ..... .... 211
6 Some Aspects of Applying the Acoustic Emission Method..... .... 219
6.1 Specific Features of Long-Term AE Testing of Industrial
Objects... .... .... ..... .... .... .... .... .... ..... .... 220
6.1.1 Selection of a Frequency Band and AET Placing .. .... 220
6.1.2 Calibration of an AE Testing System .. .... ..... .... 222
6.1.3 Analysis and Presentation of AE Test Results..... .... 222
6.1.4 Stability of AE Parameters .. .... .... .... ..... .... 223
6.1.5 Classification of AE Sources by Their Activity.... .... 228
6.2 Using the AE Methods for Testing the Offshore Platforms.. .... 233
6.3 Using the AE for Testing the Nuclear Reactors . .... ..... .... 236
6.4 Application of AE Method for Estimation of Strength
of Pressure Vessels and Pipelines.... .... .... .... ..... .... 240
