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Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (11)
- 8.4 Akustische und elektromagnetische Verfahren (11)
- 2 Prozess- und Anlagensicherheit (3)
- 2.1 Sicherheit von Energieträgern (3)
- 3 Gefahrgutumschließungen; Energiespeicher (3)
- 3.2 Gefahrguttanks und Unfallmechanik (3)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (3)
- 8.6 Faseroptische Sensorik (3)
- 9 Komponentensicherheit (3)
- 9.6 Additive Fertigung metallischer Komponenten (3)
Eingeladener Vortrag
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Schäden an Rohrleitungen können zu hohen Umweltbelastungen und wirtschaftlichen Schäden führen. Um die dauerhafte Verfügbarkeit der Infrastruktur zu gewährleisten, wird im Rahmen des Projekts AGIFAMOR an der Bundesanstalt für Materialforschung und -prüfung (BAM) erprobt, inwiefern das Verfahren der verteilten akustischen faseroptischen Sensorik (Distributed acoustic sensing – DAS) zur kontinuierlichen Überwachung von Rohrleitungen eingesetzt werden kann. Neben der DAS werden erprobte Verfahren der zerstörungsfreien Prüfung wie Schallemissionsanalyse (SEA) und Beschleunigungssensoren eingesetzt. An dieser Stelle soll detailliert auf die Hauptschadensursachen an Rohrleitungen, den Versuchsstand zur mechanischen Belastung von Rohren sowie die Möglichkeiten zu Untersuchungen im Realmaßstab eingegangen werden.
Guided waves cover comparably long distances and thus allow for online structural health monitoring of safety relevant components, e.g. lightweight composite overwrapped pressure vessels (COPV) as used for the transportation of pressurised gases. Reliable non-destructive assessment of COPVs’ condition is not available yet due to their complex composite structure comprising a thin metal liner and a fibre reinforced plastics (FRP) overwrap. The conventional overload hydrostatic pressure testing used for the metal vessels is not suitable for the composite vessels, because it may damage the FRP overwrap reducing the service life of the COPV. Therefore, ISO and CEN defined a maximum service life of composite pressure vessels as of 15 to 20 years. To extend the COPVs’ service life and to ensure a safer usage a structural health monitoring system based on guided ultrasonic waves is to be developed.
In this contribution first results of guided waves propagation in a flat composite plate consisting of an aluminium layer firmly bonded to a carbon fibre reinforced plastic laminate are presented. Based on experimental results material properties of FRP are reconstructed by means of the Scaled Boundary Finite Element Method (SBFEM).
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.
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.
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.
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.
Austenitic stainless steel welds as well as dissimilar metal welds with nickel alloy filler material, used in safety relevant parts of nuclear power plants, still challenge the ultrasonic inspection. The weld material forms large oriented grains which lead on the one hand to high sound scattering and on the other hand – to inhomogeneity and to the acoustic anisotropy of the weld structure. The ultrasonic wave fronts propagate not linearly, as in ferritic weld joints, but along the curves, which depend on the specific grain structure of the weld. Due the influence of these phenomena, it is difficult to analyze the inspection results and to classify the ultrasonic indications, which could be both from the weld geometry and from the material defects. A correct flaw sizing is not possible.
In an ongoing research project, different techniques to improve the reliability of ultrasonic testing at these kinds of welds are investigated. In a first step (in the previous research project) two ultrasonic inspection techniques were developed and validated on plane test specimens with artificial and realistic flaws. In the ongoing project, these techniques are applied to circumferential pipe welds with longitudinal and transverse flaws.
The technique developed at the Federal Institute for Materials Research and Testing (BAM) in Germany uses a combination of ray tracing and synthetic aperture focusing technique (SAFT). To investigate the unknown grain structure, the velocity distribution of weld-transmitting ultrasound waves is measured and used to model the weld by ray tracing.
The second technique, developed at the Fraunhofer Institute for Nondestructive Testing (IZFP) in Germany, uses Sampling Phased Array (Full Matrix Capture) combined with the reverse phase matching (RPM) and the gradient elastic constant descent algorithm (GECDM). This inspection method is able to estimate the elastic constants of the columnar grains in the weld and offers an improvement of the reliability of ultrasonic testing through the correction of the sound field distortion. The unknown inhomogeneity and anisotropy are investigated using a reference indication and the special optimization algorithm.
Both reconstruction techniques give quantitative inspection results and allow the defect sizing. They have been compared to conventional ultrasonic testing with techniques, which are state of the art for components in nuclear power plants. The improvement will be quantified by the comparison of the probability of detection (POD) of each technique.
Composite pressure vessels are important components in the storage of gases under high pressure. Among others, a common type of pressure vessel is made of a metal liner overwrapped with a fibre-reinforced plastic material. Conventional hydrostatic tests, used to assess the integrity of pressure vessels, may overstress the material and thus reduce the remaining lifetime of the tested component. Therefore, a truly non-destructive structural health monitoring (SHM) system would not only ensure a safer usage and extended lifetime, but also remove the necessity for periodic inspection and the testing of pressure vessels. The authors propose the use of guided ultrasonic waves, which have the potential to detect the main damage types, such as cracking in the metal liner, fibre breaks and composite matrix delamination. For the design of such an SHM system, multimodal ultrasonic wave propagation and defect-mode interaction must be fully understood. In this paper, simulation results obtained by means of finite element modelling (FEM) are presented. Based on the findings, suggestions are made regarding appropriate wave modes and their interaction with different flaw types, as well as the necessary excitation and suitable sensor configurations. Finally, a first approach for a reliable SHM system for composite pressure vessels is suggested.
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
Schäden an Rohrleitungen können zu hohen Umweltbelastungen und wirtschaftlichen Schäden führen. Um die dauerhafte Verfügbarkeit der Infrastruktur zu gewährleisten, wird im Rahmen des Projekts AGIFAMOR an der Bundesanstalt für Materialforschung und -prüfung (BAM) erprobt, inwiefern das Verfahren der verteilten akustischen faseroptischen Sensorik (Distributed acoustic sensing - DAS) zur kontinuierlichen Überwachung von Rohrleitungen verwendet werden kann. Neben der DAS werden erprobte Verfahren der zerstörungsfreien
Prüfung wie Schallemissionsanalyse (SEA) und Beschleunigungssensoren eingesetzt. An dieser Stelle soll detailliert auf die unterschiedlichen Messverfahren und deren spezifischen Einsatz im Rahmen des Projektes eingegangen werden.