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This paper presents the numerical modeling of the Lamb
wave propagation in plate like structures with the
Elastodynamic Finite Integration Technique (EFIT) and its
validation with the measured results. In general, Lamb
waves offer an attractive method to detect the defects inside
long plate like structures efficiently. However, such a nondestructive
testing (NDT) requires profound understanding
of the Lamb wave propagation in the plates, generation of
the symmetric and anti-symmetric modes of different orders
and their interaction with the defects of the materials.
Modern simulation tools based on numerical methods can be
used to model this complex NDT situation. EFIT is an
effective tool to model such problems in an efficient way.
With the help of the simulation results obtained from the
EFIT tool the propagation of different symmetric and antisymmetric
Lamb wave modes is analyzed and thus a proper
technique is developed to excite different modes and to
separate them from each other precisely. A validation of the
numerical results with the measured results is also presented.
This paper presents the numerical modeling of the Lamb wave propagation in thin plates with the elastodynamic finite integration technique (EFIT) and its validation with the measured results. In general, Lamb waves offer an attractive method to detect the defects inside long plate like structures efficiently. However, such a nondestructive testing (NDT) requires profound understanding of the Lamb wave propagation in the plates, generation of the symmetric and anti-symmetric modes of different orders and their interaction with the defects of the materials. Modern simulation tools based on numerical methods such as the finite integration technique (FIT), the finite element method (FEM) and the boundary element method (BEM) can be used to model this NDT situation. The elastodynamic finite integration technique (EFIT) is an effective tool to model Lamb wave propagation in plates over long distances in an efficient way. With the help of the simulation results obtained from the EFIT tool the propagation of different symmetric and anti-symmetric modes is analyzed and thus a proper technique is developed to excite different modes and to separate them from each other precisely. A validation of the numerical results with the analytical results is also presented.
In this contribution a 3D ray tracing model for ultrasonic
field evaluation in inhomogeneous anisotropic materials
such as austenitic welds is presented. The inhomogenity of
austenitic weld material is represented as several
homogeneous layers. The general problem of energy
reflection and transmission at the boundaries of the layers
are solved resulting 3D amplitude and energy reflection and
transmission coefficients. The directivity factor for the ray in
general arbitrary oriented austenitic weld material (including
lay back orientation) is determined based on Lambs
reciprocity theorem. The transducer excited ultrasonic fields
are accurately evaluated by employing ray directivity factor,
transmission coefficients, divergence of the ray bundle and
density of rays. Finally, the comparison between theoretical
and experimental results will be described.
Ultrasonic investigation of inhomogeneous anisotropic materials such as austenitic welds is complicated because its columnar grain structure leads to curved energy paths, beam splitting and asymmetrical beam profiles. A ray tracing model has potential advantage in analyzing the ultrasonic sound field propagation and there with optimizing the inspection parameters. In this contribution we present a 2D ray tracing model to predict energy ray paths, ray amplitudes and travel times for the three wave modes quasi longitudinal, quasi shear vertical, and shear horizontal waves in austenitic weld materials. Inhomogenity in the austenitic weld material is represented by discretizing the inhomogeneous region into several homogeneous layers. At each interface between the layers the reflection and transmission problem is computed and yields energy direction, amplitude and energy coefficients. The ray amplitudes are computed accurately by taking into account directivity, divergence and density of rays, phase relations as well as transmission coefficients. Ultrasonic sound fields obtained from the ray tracing model are compared quantitatively with the 2D Elastodynamic Finite Integration Technique (EFIT). The excellent agreement between both models confirms the validity of the presented ray tracing results. Experiments are conducted on austenitic weld samples with longitudinal beam transducer as transmitting probe and amplitudes at the rear surface are scanned by means of electrodynamical probes. Finally, the ray tracing model results are also validated through the experiments.
Der Einsatz geführter Wellen für die
zerstörungsfreie Prüfung mit Ultraschall eröffnet neue Möglichkeiten,
räumlich ausgedehnte Bauteile mit begrenzter Zugänglichkeit
auf ihre Integrität zu prüfen und gewinnt daher
zunehmend an Bedeutung. Dieser Artikel behandelt die
physikalischen Grundlagen der Schallausbreitung. Deren Verständnis
bildet die Grundlage für die Entwicklung geeigneter
Prüfsysteme. An Beispielen werden verschiedene Möglichkeiten
zur Simulation der Schallausbereitung vorgestellt. Aktuelle
Lösungsansätze zur Prüfung von plattenförmigen Strukturen
und von Rohrleitungen werden beschrieben, wobei besonders
auf die Sensortechnik und die speziellen Anforderungen
an die Prüfhardware eingegangen wird. -----------------------------------------------------------------------------------------------------------------------------------
Guided waves are widely used for non-destructive
testing using ultrasound. Recently, the method has become increasingly
important for integrity tests of spatially extended
components with limited accessibility. This article discusses the
basic physics of the sound propagation of guided waves. Their
understanding forms the basis for the successful development
of adapted inspection systems. Examples for simulating the
wave propagation using different methods are presented. Current
approaches for the inspection of plate-like structures and
pipelines are described with focus on sensor technology and the
specific requirement on the test hardware.
Ultrasound propagation in inhomogeneous anisotropic materials is difficult to examine because of the directional dependency of elastic properties. Simulation tools play an important role in developing advanced reliable ultrasonic testing techniques for the inspection of anisotropic materials particularly austenitic cladded materials and dissimilar welds. A 2-D Ray tracing method is developed for evaluating ray path, amplitude and travel time for three wave modes namely quasi longitudinal wave (qP), quasi shear vertical wave (qSV) and shear horizontal waves (SH) in anisotropic materials such as austenitic cladded materials. The inhomogenity in the anisotropic material is represented by discretizing the anisotropic region into several homogeneous layers. The ray paths are traced during its propagation through the various interfaces between those layers. At each interface the problem of reflection and refraction is solved. The ray amplitudes are computed by taking into account the directivity and phase relations. Ray divergence variation and ray transmission coefficients at each refraction boundary are considered. The Ray tracing results for ultrasonic field profiles in austenitic cladded materials are validated quantitatively by 2-D Elastodynamic Finite Integration Technique (EFIT) results and by the experiments.
In diesem Beitrag wird die numerische Modellierung und deren messtechnische Validierung der elastischen Wellenausbreitung in austenitischen Schweißnähten vorgestellt. Die Ultraschallprüfung von austenitischen Schweißverbindungen war und ist immer noch eine der schwierigsten Aufgaben der ZfP. Für eine optimierte Prüfkonfiguration ist es notwendig, verschiedene Prüfparameter wie Einschallwinkel, Prüfkopfposition und -Orientierung richtig einzustellen. Um die beste Anordnung zu ermitteln, wurde die Schallausbreitung in den austenitischen Schweißnähten mit verschiedenen Verfahren wie elastische finite Integrationstechnik (EFIT) und Raytracing simuliert. Mit Hilfe der Simulationsergebnisse wurde die verwendete Gruppenstrahlerprüftechnik optimiert. Es wurden zahlreiche Untersuchungen an anisotropen Testkörpern in V-Durchschallung und an bezüglich der Schweißnaht transversal orientierten Rissen durchgefühlt. Die Ergebnisse der auf Raytracing bzw. EFIT basierenden Simulationstools wurden untereinander und auch mit den Messergebnissen verglichen.