Conventional ultrasonic methods based on ultrasonic characteristics in the linear elastic region are mainly sensitive to mature defects but are much less responsive to micro-damage or incipient material degradation. Recently, nonlinear ultrasonic characteristics beyond the linear ultrasonic amplitude range have been studied as a method for overcoming this limitation, and hence, many researchers are engaged in theoretical, experimental, and various application studies. However, the nonlinear ultrasonic characteristics are quite exacting compared to the linear phenomena so that they require vast experience and high proficiency in order to obtain proper experimental data. Actually, many researchers, especially beginners including graduate students, have difficulty in reliably measuring nonlinear ultrasonic characteristics. This book provides key technological know-how from experts with years of experience in this field, which willhelp researchers and engineers to obtain a clear understanding and high quality data in the nonlinear ultrasonic experiments and applications.

Autorentext
**Kyung-Young Jhang**** **received his PhD from Tokyo Institute of Technology, Japan in 1991. He is currently a Professor and the Chair of Mechanical Engineering at Hanyang University. His research focuses on the area of linear & nonlinear ultrasonics for NDT&E, laser ultrasonics and laser-material intraction, ultrasonic and optical measurements and signal & image processing. He was Vice-president of Korean Society for NDT and Editor-in-Chief of Journal of the Korean Society for NDT (2012-2017).

Klappentext

Conventional ultrasonic methods based on ultrasonic characteristics in the linear elastic region are mainly sensitive to mature defects but are much less responsive to micro-damage or incipient material degradation. Recently, nonlinear ultrasonic characteristics beyond the linear ultrasonic amplitude range have been studied as a method for overcoming this limitation, and hence, many researchers are engaged in theoretical, experimental, and various application studies. However, the nonlinear ultrasonic characteristics are quite exacting compared to the linear phenomena so that they require vast experience and high proficiency in order to obtain proper experimental data. Actually, many researchers, especially beginners including graduate students, have difficulty in reliably measuring nonlinear ultrasonic characteristics. This book provides key technological know-how from experts with years of experience in this field, which will help researchers and engineers to obtain a clear understanding and high quality data in the nonlinear ultrasonic experiments and applications.

Inhalt

Preface

Chapter 1. Overviews: Nonlinear Ultrasonic Characteristics and Measurands

Chapter 2**.** Elastic Nonlinearity induced Nonlinear Ultrasonic Characteristics

2.1 Higher Harmonics (HH) Generation

2.2 Nonlinear Ultrasonic Parameters

2.2.1 Absolute Nonlinear Ultrasonic Parameter

2.2.2 Relative Nonlinear Ultrasonic Parameter

2.3 Measurement of Nonlinear Ultrasonic Parameter

2.3.1 Capacitive Detection and Laser-interferometric Detection

2.3.2 Piezo-electric Detection

2.3.3 Control of Propagation Distance and Control of Incident Wave Power

2.3.4 Phase Inversion Technique

2.4 Factors Affecting to Measurement Reliability

2.4.1 Measurement System: Transducer, Input Power, Contact Pressure, Electronic Equipment

2.4.2 Digital Signal Processings: Bandwidth of Incident Wave, Time Resolution, Amplitude Resolution

2.5 Applications to Assessment of Material Damage 2.5.1 Fatigue Damage

2.5.2 Plastic Deformation

2.5.3 Thermal Aging References

Chapter 3. Nonlinear Acoustic Wave Interactions with Contact Interfaces: Methodologies and Applications ********

3.1. Nonlinear Reflection Approach to Interface Nonlinearity

3.1.1 Nonlinear acoustic reflection at an ideally bonded interface

3.2.1 Application of Reflection Concept to Nonlinear Interface Wave Propagation

3.3.1 Second Harmonic Generation of Interface Acoustic Waves

3.2. Acoustic Nonlinearity of a Non-Bonded Interface

3.2.1 Phenomenology of Contact Acoustic Nonlinearity (CAN) 3.2.2 Higher Harmonics (HH) Generation at Contact Interfaces 3.2.3 Nonlinear Acoustic Reflection by Fractured Defects

3.2.4 Acoustic Rectification and Nonlinear Polarization Effects via CAN

3.3. Non-Classical Nonlinear Effects in Resonant Contact Inclusions 3.3.1 Concept of Local Defect Resonance 3.3.2 Sub- and Super-harmonic Resonances 3.3.3 Nonlinear Parametric Instability Effects 3.4. Applications for Nonlinear Imaging of Defects

3.4.1 Nonlinear Scanning Laser Vibrometry

3.4.2 Nonlinear Air-Coupled Emission (NACE)

3.4.3 Case Studies of Nonlinear Imaging of Defects

References

Chapter 4**. Nonlinear** U****ltrasonic P****hased A****rray for M****easurement of C****losed-Crack D****epth **** 4.1. Introduction

4.2. Harmonics

4.2.1. Principles

4.2.2. Experimental conditions

4.2.3. Imaging results

4.3. Parallel and sequential transmission

4.3.1. Principles

4.3.2. Experimental conditions

4.3.3. Imaging results

4.4. Full-, odd- and even-elements transmission

4.4.1. Principles 4.4.2. Experimental conditions 4.4.3. Imaging results

4.5. Utilization of thermal stress

4.5.1. Principles