TY - JOUR A1 - Lozano, Daniel A1 - Bulling, Jannis A1 - Gravenkamp, Hauke A1 - Birk, Carolin T1 - Domain decoupling implementation for efficient ultrasonic wave simulations using scaled boundary finite elements and the mortar method N2 - We introduce a novel approach that combines the scaled boundary finite element method (SBFEM) with a mortar coupling to enhance the computational modelling of elastic wave propagation and interaction with local features in the ultrasonic range. The key objective is to achieve decoupling between different regions of interest, enabling independent meshes for the zones where waves either propagate or interact with localised discontinuities in the elastic media. This decoupling allows us to exploit the benefits offered by various SBFEM formulations. Thus, we can select the most suitable solution for each specific region. An important concept we emphasise is the differentiation between the near field and far field regions. The near field encompasses zones where the precise representation of small features compared to the wavelength is crucial. At the same time, the far field comprises homogeneous regions where the waves propagate without interactions, eventually radiating towards infinity if the domain is unbounded. By separating these two zones, we can improve the computational performance by employing finer discretisation only where necessary. Furthermore, this decoupling enables the reuse of far field models in parametric analyses, making it highly valuable for scenarios focused particularly on local elastic wave interactions. This approach offers considerable potential in such cases. The modelling technique is validated, and its potential is demonstrated through practical applications. KW - Computer Science Applications KW - General Physics and Astronomy KW - Mechanical Engineering KW - Mechanics of Materials KW - Computational Mechanics PY - 2023 DO - https://doi.org/10.1016/j.cma.2023.116465 SN - 0045-7825 VL - 417 IS - Part A SP - 1 EP - 21 PB - Elsevier BV AN - OPUS4-58478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bulling, Jannis A1 - Jurgelucks, B. A1 - Prager, Jens A1 - Walther, A. T1 - Defect Characterization in Plate Models Facilitated by Algorithmic Differentiation N2 - In non-destructive testing and structural health monitoring with ultrasonic waves, the quantification of damage in components is one of the main tasks. In many shell-like structures, such as plates, pipes, or laminate components, ultrasonic waves propagate as guided waves. Although guided waves enable the testing of large areas, their multimodal and dispersive properties make it challenging to analyze signals. So, there is a need for more advanced algorithms to handle these properties, especially when reconstructing damage position and geometry. The reconstruction can be formulated as an inverse problem where the measured signals are fitted with a simulative forward model. Due to the small wavelength of ultrasonic waves, classic forward models based on, e.g., the Finite Element Method are computationally intensive. In contrast, the authors use the semi-analytical Scaled Boundary Finite Element Method (SBFEM) to reduce the computational effort. The SBFEM approximates arbitrary long, undamaged parts of the structure with only a few degrees of freedom. This contribution summarizes a general inverse procedure based on algorithmic differentiation in combination with the SBFEM. Results are presented for damaged 2D cross-sectional models of waveguides. These results include an analysis of the robustness of the proposed algorithms against noise. T2 - DAGA 22 CY - Stuttgart, Germany DA - 21.03.2022 KW - Structural health monitoring KW - Inverse Methods KW - SBFEM KW - Algorithmic Differentiation KW - Non-destructive testing PY - 2022 VL - 2022 SP - 871 EP - 874 AN - OPUS4-56547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bulling, Jannis A1 - Jurgelucks, B. A1 - Prager, Jens A1 - Walther, A. T1 - Defect reconstruction in a two-dimensional semi-analytical waveguide model via derivative-based optimization N2 - This paper considers an indirect measurement approach to reconstruct a defect in a two-dimensional waveguide model for a non-destructive ultrasonic inspection via derivative-based optimization. The propagation of the mechanical waves is simulated by the scaled boundary finite element method that builds on a semi-analytical approach. The simulated data are then fitted to given data associated with the reflected waves from a defect which is to be reconstructed. For this purpose, we apply an iteratively regularized Gauss-Newton method in combination with algorithmic differentiation to provide the required derivative information accurately and efficiently. We present numerical results for three kinds of defects, namely, a crack, delamination, and corrosion. The objective function and the properties of the reconstruction method are investigated. The examples show that the parameterization of the defect can be reconstructed efficiently as well as robustly in the presence of noise. KW - Mechanical waves KW - Corrosion KW - Finite-element analysis KW - Ultrasonic testing KW - Nondestructive testing techniques KW - Symbolic computation KW - Materials analysis KW - MATLAB KW - Newton Raphson method PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565485 DO - https://doi.org/10.1121/10.0013574 VL - 152 IS - 2 SP - 1217 EP - 1229 PB - AIP Publ. CY - Melville, NY AN - OPUS4-56548 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lozano, Daniel A1 - Bulling, Jannis A1 - Prager, Jens T1 - Quadtree decomposition as a meshing strategy for guided waves simulations using the scaled boundary finite element method N2 - Structural health monitoring techniques associate strongly with damage detection and characterization. Ultrasonic guided waves (UGW), for such scope, arise as one of the most promising methods for many reasons i.e. UGW are able to travel long distances and they have high sensitivity to damage. In this context, the necessity to model realistic wave-defect interaction occurs to be critical. Realistic damage scenarios can be modeled through the usage of image-based quadtree meshes. Images, such as the outcome from X-ray scans, C-scans, etc., can be converted into meshes for further integration in a computational domain. Quadtree meshes are created by converting the intensity of the pixels to quadrilateral cells. Homogeneous regions inside one image result in one quad, whereas fine features such as discontinuities can be described with smaller quads. This contribution proposes an efficient methodology to model wave defect interaction, using as a framework the scaled boundary finite element method (SBFEM) and quadtree meshes. Problems as non-conforming regions in the mesh due to the space tree decomposition can be easily avoided using SBFEM’s polygonal elements. Moreover, the semi-analytical nature of the SBFEM allows the modeling of arbitrarily long prismatic/undamaged regions of the waveguides without an increase in the computational burden. T2 - DAGA 2022 CY - Stuttgart, Germany DA - 21.03.2022 KW - Wave defect interaction KW - Scaled Boundary Finite Element Method KW - Quadtree meshes KW - Image-based models KW - Transient analysis PY - 2022 SP - 887 EP - 890 CY - Stuttgart AN - OPUS4-57153 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bulling, Jannis A1 - Jurgelucks, B. A1 - Prager, Jens A1 - Walther, A. T1 - Schadensrekonstruktion mittels geführter Wellen in Stahlplatten N2 - Ein Hauptziel der zerstörungsfreien Prüfung und der Strukturüberwachung (engl. Structural Health Monitoring - SHM) mit Ultraschallwellen ist die Charakterisierung von Schäden in Bauteilen. In vielen schalenförmigen Bauteilen, wie zum Beispiel Rohrleitungen, Laminaten und Platten, breitet sich der Ultraschall in Form geführter Wellen aus. Zwar erlauben geführte Wellen eine großflächige Prüfung durch das langsame Abklingen der Wellen. Jedoch breiten sich die Wellen in verschiedenen dispersiven Moden aus, was die Analyse der vom Schaden erzeugten Reflexionen erschwert. Eine Möglichkeit, die Messsignale zu interpretieren, um Schäden zu charakterisieren, ist der direkte Vergleich mit einem Simulationsmodell. Die Rekonstruktion des Schadens stellt ein inverses Problem dar. Das inverse Problem kann als Optimierungsproblem formuliert werden. Für die Optimierung werden mehrere Vorwärtsrechnungen gebraucht, um das Schadensmodell an die Messdaten anzupassen. Aufgrund der kurzen Wellenlängen von Ultraschallwellen sind klassische Methoden für die Vorwärtsrechnung, wie z.B. die Finite Elemente Methode (FEM), rechenintensiv. Eine Möglichkeit den Rechenaufwand zu reduzieren, bietet die Approximation der Wellenausbreitung mittels der semi-analytischen Scaled Boundary Finite Element Method (SBFEM). Frühere Untersuchungen haben gezeigt, dass die benötigten Freiheitsgrade im Vergleich zur FEM wesentlich geringer sind [1]. Im Beitrag wird eine Optimierung basierend auf einem Gradientenverfahren in Kombination mit der SBFEM vorgestellt und an verschiedenen Schadenstypen in 2D-Querschnittsmodellen von Stahlplatten getestet. Der Gradient des Vorwärtsmodells wird durch Algorithmisches Differenzieren berechnet, wodurch eine genaue und schnelle Optimierung ermöglicht wird. Es werden Untersuchungen zum inversen Problem und das Finden einer geeigneten Zielfunktion präsentiert. Es wird verdeutlicht, dass der entwickelte Algorithmus robust gegenüber von Rauscheinflüssen ist. In diesen Untersuchungen werden zunächst „Messdaten“ aus unabhängigen Simulationen verwendet [2]. Erste Schritte für die experimentelle Validierung und Erweiterung auf 3D Modelle werden anschließend vorgestellt. T2 - Doktorandenworkshop in Kloster Lehnin CY - Kloster Lehnin, Germany DA - 19.10.22 KW - SBFEM KW - Zerstörungsfreie Prüfung KW - Structural Health Monitoring KW - Ultraschallwellen PY - 2022 AN - OPUS4-56551 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bulling, Jannis A1 - John, V. A1 - Knobloch, P. T1 - Isogeometric analysis for flows around a cylinder N2 - This note studies the accuracy of Isogeometric Analysis (IGA) applied in the simulation of incompressible flows around a cylinder in two and three dimensions. Quantities of interest, like the drag coefficient, the lift coefficient, and the difference of the pressure between the front and the back of the cylinder are monitored. Results computed with standard finite element methods are used for comparison. KW - Isogeometric Analysis (IGA) KW - Drag coefficient Lift KW - Flow around a cylinder KW - Coefficient PY - 2017 DO - https://doi.org/10.1016/j.aml.2016.07.023 SN - 0893-9659 VL - 2017/63 SP - 65 EP - 70 PB - Elsevier Ltd. AN - OPUS4-38608 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wasmer, Paul A1 - Krome, Fabian A1 - Bulling, Jannis A1 - Prager, Jens T1 - A fluid model for the simulation of fluid‐structure interaction in the Scaled Boundary Finite Element Method for prismatic structures N2 - The Scaled Boundary Finite Element Method is known as an efficient method for the simulation of ultrasonic wave propagation. As to investigate acoustic wave behavior in case of fluid‐structure interaction, a fluid model is implemented in the SBFEM for prismatic structures. To omit coupling terms a displacement‐based formulation is used. Spurious modes, which occur in the solution, are suppressed using a penalty parameter. To verify this formulation dispersion curves obtained with Comsol Multiphysics are compared to results of SBFEM. The results of both methods are in very good agreement T2 - GAMM 2018 CY - Munich, Germany DA - 19.03.2018 KW - Scaled Boundary Finite Element Method KW - Penalty Parameter KW - Fluid-Structure Interaction KW - Guided Waves PY - 2018 DO - https://doi.org/10.1002/pamm.201800139 VL - 18 IS - 1 SP - e201800139 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-47063 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bulling, Jannis T1 - Ein Überblick über die Scaled Boundary Finite Element Method für akustische Wellenausbreitung in Festköpern N2 - In diesen Vortrag sind Ergebnissen der letzten Jahre zu der SBFEM an der BAM zu finden. Dabei wurde besonders auf die Stärken der Methode eingegangen. T2 - Doktorandenseminar – Ultraschallmesstechnik CY - Gohrisch, Germany DA - 28.10.2018 KW - SBFEM KW - Kontaktbedingungen PY - 2018 AN - OPUS4-46452 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wasmer, Paul A1 - Krome, Fabian A1 - Bulling, Jannis A1 - Prager, Jens T1 - Entwicklung eines Ultraschallsensors zur Flüssigkeitsanalyse in Rohrleitungen N2 - Zur Messung von Konzentrationen in Flüssigkeiten können akustische Sensoren genutzt werden. Ziel der vorliegend Arbeit ist es einen Sensor zu entwerfen der sehr hohe Messgenauigkeiten erzielen kann. Der Sensor besteht aus einem rechteckigen Rohr, welches auf einem Halbraum angebracht ist. Die Konzentrationsbestimmung erfolgt anhand des Resonanzverhaltens der Struktur, wodurch eine hohe Messgenauigkeit erreicht werden kann. Um den Sensors zu verwirklichen, muss eine Optimierung der Geometrie mit vielen Iterationsschritten durchlaufen werden. Da keine analytische Beschreibung des akustischen Verhaltens vorliegt, wird eine effiziente Simulationsmethode benötigt. Die Scaled Boundary Finite Element Method (SBFEM) für prismatische Strukturen erscheint für die Simulation geeignet, da Teile der Geometrie ohne neue Vernetzung geändert werden können. Für die Berechnung des Sensors wird ein Modell der akustischen Fluid-Struktur Interaktion benötigt, das bisher nicht vorhanden ist. Die Präsentation behandelt die Implementierung des Fluidmodells in die SBFEM und deren Validierung. Für die Validierung werden die Ergebnisse mit analytischen Beispielen ohne Fluid-Struktur Kopplung und mit Comsol-Ergebnissen der Dispersionskurven mit Wasser gefüllter Rohre verglichen. Schließlich wird das neuartige Verfahren für die Modellierung der Sensorgeometrie angewendet. An einer einfachen Geometrie wird das Sensorprinzip zur Bestimmung der Salzkonzentration demonstriert. T2 - DAGA 2018 - 44. Jahrestagung für Akustik CY - Munich, Germany DA - 19.03.2018 KW - Scaled Boundary Finite Element Method KW - Penalty Parameter KW - Sensorentwicklung PY - 2018 SN - 978-3-939296-13-3 VL - 2018 SP - 1023 EP - 1026 AN - OPUS4-45262 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lugovtsova, Yevgeniya A1 - Bulling, Jannis A1 - Krome, Fabian A1 - Prager, Jens T1 - Effiziente Modellierung von geführten Wellen mit der Scaled Boundary Finite Elemente Methode und deren Anwendung für Composite-Druckbehälter N2 - Die Scaled Boundary Finite Elemente Methode (SBFEM) ist eine semi-analytische Methode, die speziell für Modellierung von geführten Wellen weiterentwickelt und optimiert wurde. Da nur den Rand der Rechendomäne diskretisiert wird, hat die SBFEM einen geringen Rechenaufwand. In diesem Beitrag wird die SBFEM benutzt, um die Ausbreitung geführter Wellen in einer Metall-Faserverbund-Werkstoffstruktur zu analysieren. Mittels der SBFEM ist es möglich, verschiede Fehlertypen, z.B. Ermüdungsrisse, Poren, Delaminationen, Korrosion, in das numerische Modell zu integrieren und damit Defekt-Mode-Wechselwirkung zu analysieren. Die Ergebnisse wurden für die Entwicklung einer Methode zur Zustandsüberwachung von Composite-Druckbehältern verwendet. T2 - DGZfP-Jahrestagung 2018 CY - Leipzig, Germany DA - 07.05.2018 KW - Wasserstoffspeicher KW - Automobilindustrie KW - Kohlenstofffaserverstärkter Kunststoff KW - Hybrid Materialien PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-449797 SP - 1 EP - 4 AN - OPUS4-44979 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lugovtsova, Yevgeniya A1 - Bulling, Jannis A1 - Prager, Jens A1 - Boller, C. T1 - Efficient modelling of guided ultrasonic waves using the Scaled Boundary FEM towards SHM of composite pressure vessels N2 - The Scaled Boundary Finite Element Method (SBFEM) is a semi-analytical method that shows promising results in modelling of guided ultrasonic waves. Efficiency and low computational cost of the method are achieved by a discretisation of the boundary of a computational domain only, whereas for the domain itself the analytical solution is used. By means of the SBFEM different types of defects, e.g. cracks, pores, delamination, corrosion, integrated into a structure consisting of anisotropic and isotropic materials can be modelled. In this contribution, the SBFEM is used to analyse the propagation of guided waves in a structure consisting of an isotropic metal bonded to anisotropic carbon fibre reinforced material. The method allows appropriate wave types (modes) to be identified and to analyse their interaction with different defects. Results obtained are used to develop a structural health monitoring system for composite pressure vessels used in automotive and aerospace industries. T2 - 9th European Workshop on Structural Health Monitoring (EWSHM) CY - Manchester, UK DA - 10.07.2018 KW - Structural Health Monitoring KW - Pressure tanks KW - Hydrogen storage KW - Finite Element Modelling KW - Composites PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-454859 SP - 1 EP - 7 AN - OPUS4-45485 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lozano, Daniel A1 - Bulling, Jannis T1 - The SBFEM to simulate the scattering of ultrasonic guided waves interacting with defects in 3D plate structures N2 - In the field of guided waves for non-destructive testing, the interaction of these waves with damages or other discontinuities in a structure is critical. When a guided wave mode travels and hits a defect, it scatters in all directions, converting to other modes and reflecting the existing one. These interactions are captured in scattered far field complex amplitudes and characterise the elastodynamic behaviour of a defect completely. Simulating these interactions is challenging, and analytical solutions only exist for simple geometries. Still, using general tools like the finite element method results in large, usually costly models. We employ a method based on a numerical implementation of the Kirchhoff–Helmholtz integral that allows the computation of the scattering matrices using a model containing only the damaged region. However, classical techniques to resolve the far field and low-order elements are commonly used, leading to large models yet more efficient than using other strategies.We propose using the SBFEM as an alternative to enhance the computation of the far field scattering. The damaged region is discretised using high-order polyhedral elements, while the far field is constructed using a modified version of the SBFEM. Examples compared to the literature demonstrate the validity of the approach. T2 - DAGA 2024 - 50. Jahrestagung für Akustik CY - Hannover, Germany DA - 18.03.2024 KW - Simulations KW - Guided waves KW - SBFEM PY - 2024 SP - 636 EP - 639 CY - Hannover AN - OPUS4-62713 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bulling, Jannis T1 - On the efficient simulation of ultrasonic waves on polygonal meshes N2 - At many stages of technology development in ultrasonic Non-Destructive Testing (NDT) and Structural Health Monitoring (SHM), simulation tools are essential. Many modern approaches to ultrasonic testing, such as Model Assisted Probability of Detection, inverse problems with iterative optimization, or the generation of data for AI training, benefit from highly effcient simulation tools in terms of simulation time. In this talk, we investigate explicit time stepping with the Scaled Boundary Finite Element Method (SBFEM) for approximating the linear elastic wave equation on 2D polygonal meshes, enhanced with a mass lumping technique for faster simulation times. We present the proposed changes to the formulation to successfully use mass lumping. Examples are used to demonstrate that there is no loss of quality due to the approximated mass matrix. Furthermore, mass lumping reduces the simulation time and makes the simulation more effcient. In addition, the proposed simulation method has the advantages of SBFEM meshing techniques. These advantages include fast meshing using an image-based quadtree algorithm or polygonal meshing by transforming triangular meshes based on a CAD model. The latter meshing method can include special crack tip elements that effciently handle the crack tip singularity. T2 - DAS | DAGA 2025 CY - Copenhagen, Denmark DA - 17.03.2025 KW - Non-Destructive Testing (NDT) KW - Scaled Boundary Finite Element Method (SBFEM) KW - Structural Health Monitoring (SHM) PY - 2025 AN - OPUS4-63016 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -