Motion-Induced Eddy Current Techniques for Non-Destructive Testing and Evaluation

✍ Scribed by Hartmut Brauer, Marek Ziolkowski, Konstantin Weise, Matthias Carlstedt, Robert P. Uhlig, Mladen Zec

• Publisher: Institution of Engineering and Technology
• Year: 2019
• Tongue: English
• Leaves: 360
• Series: Control, Robotics and Sensors
• Category: Library

✦ Synopsis

Non-destructive testing (NDT) analysis techniques are used in science, technology and medicine to evaluate the properties of a material, component or system, without causing damage or altering the article being inspected. It is a highly valuable technique that can save money and time in product evaluation, troubleshooting, and research. Well known and widely used in industrial applications since the 60s, the NDT market is developing and growing fast. This book focuses on electromagnetic NDT methods and more specifically on the motion induced eddy current testing and evaluation (MIECTE) techniques used for conductive materials via electromagnetic methods, focusing on the Lorentz force eddy current testing (LET) method which was introduced recently. The authors present the modelling and simulation of LET systems as well as the optimal design of the measurement setups. They also show the wide variety of applications of the LET method including defect identification and sigmometry to estimate electrical conductivity of the tested material.

✦ Table of Contents

Cover
Contents
Author Biographies
Preface
1 Introduction
What is Nondestructive Testing (NDT)?
What is Nondestructive Evaluation (NDE)?
Brief history of NDT
Methods and techniques
Applications
Summary
1.1 Electromagnetic testing
1.1.1 Brief historical review
1.1.2 Electromagnetic NDT methods
1.1.2.1 Eddy current testing
1.1.2.2 Pulsed eddy current testing
1.1.2.3 Remote field eddy current testing
1.1.2.4 Magnetic particle testing
1.1.2.5 Liquid or dye penetrant testing
1.1.2.6 Magnetic flux leakage
1.1.3 Capabilities of electromagnetic techniques
1.1.3.1 Thickness measurement
1.1.3.2 Defect detection
1.1.4 Present state of eddy current inspection
1.1.4.1 Perspectives of NDT
1.1.4.2 Perspectives of ECT
1.1.4.3 Summary
1.1.4.4 Electromagnetic UGWT
1.1.4.5 Metal magnetic memory testing
1.2 Eddy current testing
1.2.1 Eddy current and ECT
1.2.1.1 Eddy currents
1.2.1.2 Eddy current testing
1.2.2 ECT principles
1.2.2.1 Current-induced ECT
1.2.2.1.1 Equipment and measurements
1.2.2.1.2 Limitations of ECT
1.2.2.2 Motion-induced ECT
1.2.2.3 Other ECT techniques
1.2.2.3.1 Pulsed eddy current technique
1.2.2.3.2 Remote field eddy current testing
1.2.2.3.3 Low frequency electromagnetic testing
1.2.2.3.4 Alternating current field measurement
1.2.2.3.5 Eddy current array (ECA) testing
1.2.3 Applications
1.3 Motion-induced ECT
1.3.1 Introduction
1.3.2 Lorentz force eddy current testing
1.3.3 Theory
1.3.4 Experiments
1.3.5 Comparison of ECT and LET
2 Forward simulation methods
2.1 Moving coordinate systems—transformations
2.2 Semianalytical methods used in LET systems
2.2.1 Calculation of forces in 2D LET systems
2.2.2 Lorentz forces acting on 3D permanent magnets above moving conducting plate without defects
2.2.3 Calculation of forces in 3D LET systems
2.2.4 Oscillatory motion of permanent magnets above a conducting plate
2.2.4.1 Introduction and motivation
2.2.4.2 Mathematical formulation of the problem
2.2.4.2.1 The governing equations and its solutions
2.2.4.2.2 Fourier transform of the source current
2.2.4.2.3 Force calculation
2.2.4.3 Comparison to numerical simulations
2.2.4.3.1 The 2D numerical model
2.2.4.3.2 The 2D analytical model
2.2.4.3.3 Comparison of analytical and numerical results
2.2.4.4 Results and discussion
2.2.4.4.1 Constant rectilinear motion
2.2.4.4.2 Harmonic motion
2.2.4.4.3 Constant rectilinear motion superimposed by harmonic oscillations
2.2.4.4.4 Conclusions
2.2.5 The simplest approach to calculate DRS
2.2.6 A hole in a thin, large, conductive sheet
2.2.7 An extended area approach in the calculation of DRS
2.3 Surface charge simulation method
2.4 Numerical simulations with FEM
2.4.1 Introduction and motivation
2.4.2 Computation of eddy current distributions including moving parts
2.4.3 Numerical modeling of conductivity anomalies
2.4.3.1 Benchmark problem definition
2.4.3.2 Logical expression approaches
2.4.3.2.1 Moving magnet approach
2.4.3.2.2 Moving defect approach
2.4.3.3 Quasi-static approach
2.4.3.4 Weak reaction approaches
2.4.3.4.1 Extended weak reaction approach
2.4.3.4.2 Direct weak reaction approach
2.4.3.5 Summary and overview
2.4.4 Comparison of numerical approaches
3 Sensors for MIECT
3.1 Force measurement systems
3.1.1 Principles of force transducers
3.1.1.1 Elastic deformation with resistance measurement
3.1.1.2 Elastic deformation with displacement measurement
3.1.1.3 Inverse magnetostrictive effect
3.1.1.4 Piezoelectric effect
3.1.1.5 Electromagnetic force compensation
3.1.2 Differential Lorentz force eddy current testing sensor
3.1.3 Characteristics and calibration of force measurement systems
3.2 Optimization of PM systems
3.2.1 Introduction and motivation
3.2.2 Methods
3.2.2.1 Problem definition
3.2.2.2 Magnet system and design variables
3.2.2.3 Scaling parameters
3.2.2.4 System parameters
3.2.2.5 Objective function
3.2.2.6 Definition of constraints
3.2.2.7 Optimization strategies
3.2.2.7.1 Volume and force constraint optimization
3.2.2.7.2 Volume adaptive force constraint optimization
3.2.2.8 SQP algorithm
3.2.2.9 Objective and constraint function evaluation
3.2.2.9.1 Step 1: Primary magnetic flux density (2D)
3.2.2.9.2 Step 2: Induced eddy currents in the conductor free of defects (3D)
3.2.2.9.3 Step 3: Induced eddy currents in the conductor with defect (3D)
3.2.3 Optimization results and discussion
3.2.4 Prototypes of optimized LET magnet systems
3.2.5 Defect depth study
3.2.6 Conclusions
4 Experiments and LET measurements
4.1 Measurement procedure
4.1.1 Measurement principle
4.1.2 Measurement method
4.1.3 Experimental setup
4.1.3.1 Linear drive
4.1.3.2 2D-positioning stage
4.1.3.3 Sensor system
4.1.3.3.1 3-Axes force sensor
4.1.3.3.2 3-Axes acceleration sensor
4.1.3.3.3 1-Axis DiLET sensor
4.1.3.3.4 Incremental position encoder
4.1.3.4 DAQ and measurement control system
4.2 Validation procedure
4.2.1 DSP and basic statistics
4.2.1.1 Concepts of signal ensembles
4.2.1.1.1 Ideal signal ensemble
4.2.1.1.2 Artificial signal ensemble
4.2.1.2 Basics of signal alignment
4.2.1.2.1 Signal alignment based on external trigger signals
4.2.1.2.2 Correlation of time-continuous signals
4.2.1.2.3 Correlation of time-discrete signals
4.2.2 Autocorrelation on typical force signals
4.2.3 Program flowchart for DSP
4.2.3.1 Loading data
4.2.3.2 Static offset correction and tailoring
4.2.3.3 Filtering data
4.2.3.4 Aligning data
4.2.3.4.1 Arbitrary ensemble member as reference signal
4.2.3.4.2 QSA simulation as reference signal
4.2.3.5 Statistic evaluation of the signal ensemble
4.2.4 Experimental study
4.2.4.1 Design of experiment
4.2.4.2 Result of the force measurement F(t)
4.2.4.3 Result of the force DRS ΔF(t)
4.2.4.4 Result of the DiLET voltage measurement Vz(t)
4.2.4.5 Concluding remarks
4.2.5 Uncertainty analysis
4.2.5.1 Introduction and motivation
4.2.5.2 The Generalized Polynomial Chaos Method
4.2.5.2.1 β-distribution
4.2.5.2.2 Orthogonality
4.2.5.2.3 Normalization
4.2.5.2.4 Set of basis functions
4.2.5.2.5 Regression approach to determine the gPC coefficients
4.2.5.2.6 Postprocessing
4.2.5.3 Problem definition in LET
4.2.5.4 Uncertainty quantification of model parameters
4.2.5.4.1 Experimental LET setup
4.2.5.5 Results and discussion
4.2.5.6 Conclusions
5 Lorentz force evaluation
5.1 Identification of conductivity anomalies
5.2 Inverse solution techniques
5.2.1 Theory
5.2.2 Classification of inverse problems
5.2.3 Regularization
5.3 Lorentz force evaluation
5.4 Summary
6 Applications
6.1 Sigmometry
6.1.1 Introduction and motivation
6.1.2 Basic principle
6.1.3 Semianalytical and numerical calibration
6.1.4 Experimental validation
6.1.4.1 Methodology characterization
6.1.4.2 Conductivity measurement
6.1.5 Findings
6.2 Defectocscopy of multilayered structures
6.2.1 LET measurements of alucobond specimen
6.2.2 Forward simulations
6.2.3 Defect identification
6.2.3.1 Inverse solution strategy
6.2.4 Results and discussion
6.3 Inspection of composites
6.3.1 Composite material
6.3.2 Glass laminate aluminum reinforced epoxy (GLARE)
6.3.2.1 Magnetic field measurement
6.3.2.2 Force measurements
6.3.2.3 Defect localization
6.3.3 Carbon fiber reinforced polymer (CFRP)
6.3.3.1 Introduction to FRP
6.3.3.2 CFRP test specimens
6.3.3.3 Conductivity measurement
6.3.3.4 Measurements with CFRP samples
6.3.3.5 Numerical modeling of CFRP
6.3.3.6 LET experiments with CFRP
6.3.3.7 Summary
6.4 Defectoscopy of friction stir welding
6.4.1 Friction stir welding (FSW)
6.4.1.1 Imperfections/defects caused by FSW
6.4.1.2 Typical weld seam defects
6.4.2 FSW experiments
6.4.3 NDT of friction stir welds
6.4.4 MIECT measurements of friction stir welds
6.4.5 Potential applications of MIECT
6.4.5.1 Nondestructive defect detection of FSW
6.4.5.2 Material science
6.4.5.3 Process control and monitoring
6.5 Application to ferromagnetic materials
References
Index
Back Cover