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The integration of finite element method (FEM) into the least-squares adjustment presented in is further extended for a joint evaluation of an elastostatic model and displacement field measurement. For linear solids which obey the Hooke's law, the material parameters determination from measurements is being examined.
Integration der Finite-Elemente-Methode in die Ausgleichsrechnung zur Parameteridentifikation
(2014)
Integration der Finite-Elemente-Methode in die Ausgleichsrechnung zur Parameteridentifikation
(2014)
Die Strukturüberwachung von Ingenieurbauwerken beruht heutzutage auf einer Auswertung räumlich und zeitlich verteilter hybrider Messungen, die z. B. mittels Tachymeter, Neigungssensoren, faseroptischen Sensoren (FOS), Dehnmessstreifen (DMS), GPS etc. erfasst werden. Für eine gemeinsame Auswertung müssen neue Methoden adaptiert werden, da diese, wie Lienhart (2012) aufzeigt, nur unter Verwendung eines mechanischen ‘Bauwerkmodells erfolgen kann.
In vielen Ingenieurwissenschaften, wie z. B. dem Bauingenieurwesen, findet die Modellierung physikalisch-mechanischer Eigenschaften von Strukturen mithilfe der Finite-Elemente-Methode (FEM) statt. Die Verifizierung eines derartigen Modells erfolgt vorwiegend lediglich durch stellenweise Messung von z. B. Durchbiegungen und einer anschließenden Gegenüberstellung mit den berechneten Modellwerten. Dies ist meist der Tatsache geschuldet, dass für die FE-Modellierung in der Regel kommerzielle Programme verwendet werden, und somit auf viele Teilprozesse des Auswertealgorithmus nicht zugegriffen werden kann. Aus diesem Grund erfolgt in vielen akademischen Fragestellungen die FE-’Modellierung mit Open-Source-Software, wie z. B. FEniCS (2013) oder OpenSees (2013), wodurch auch eine kombinierte Auswertung von Messungen und Modell nach der Methode 'der kleinsten Quadrate ermöglicht wird.
In diesem Beitrag wird eine messungs- und modellbasierte Strukturanalyse (MeMoS) durch (die Integration der Finite-Elemente-Methode in die Ausgleichungsrechnung am Beispiel eines Vier-Punkt-Biegeversuchs vorgestellt. In numerischen Untersuchungen wird gezeigt, wie diese integrierte Analyse für eine Parameteridentifikation angewendet werden kann. Für diese Untersuchungen wird ein Finite-Elemente-Modell mit bekannten Randbedingungen und Materialeigenschaften aufgestellt. Die Durchbiegungen, die als Beobachtungen in die Ausgleichung eingehen, werden mithilfe von Simulationsrechnungen erzeugt; der zu fidentifizierende Parameter ist der Elastizitätsmodul eines Balkens.
Es wird untersucht, mit welcher Genauigkeit Durchbiegungsmessungen durchgeführt werden müssen und an welcher Stelle des Bauwerks diese Messungen erfolgen sollen, um den Elastizitätsmodul möglichst genau zu bestimmen. Des Weiteren wird der Einfluss der Anzahl der Messstellen auf den zu identifizierenden Parameter untersucht.
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.
Der Grad der Finite-Elemente-Diskretisierung wird vom Verhältnis der Details zur Objektgröße bestimmt. Die Diskretisierung eines großen Objektes mit vielen kleinen Details führt zu einer hohen Anzahl an Elementen bzw. Knotenpunkten. Die Berechnung solcher Körper erfordern nicht nur sehr hohe Rechenzeit, sondern was die Berechnung unmöglich macht, ist der sehr hohe Speicherbedarf. Mit Hilfe eines Ersatzkörpers wird dieses Problem umgangen.
Many engineering structures are made of composite materials or metal foam. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle.
Many engineering structures are made of composite materials or metal foam. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear
equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle.
Many engineering structures are made of composite materials or metal foam. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle.
Many engineering structures are made of composite materials or metal foam. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle.
Leaking methane (CH4) from infrastructures, such as pipelines and landfills, is critical for the environment but can also pose a safety risk. To enable a fast detection and localization of these kind of leaks, we developed a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance over traditional methods. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing its performance under realistic conditions.
To examine the capability to detect and localise damage using the Measurement- and Model-based Structural Analysis (MeMoS), a small-scale truss bridge (1520 mm × 720 mm × 720 mm) made of aluminium profiles is built as a test specimen for this purpose. The truss frame of the test bridge is made of aluminium profiles with a sophisticated design of the cross-sectional area. In comparison, with solid profiles, only a fraction of the material is needed to produce the profiles, while their bending resistance decreases slightly. The profiles are built into a truss frame by connecting them by means of fastening sets made of steel. The bridge model is mounted on four steel bearings which each of them consist of a cylinder arranged between two plates. Fixed bearings are made by holding onto one end of the bridge. The bridge is subjected by an external load by placing a heavy object beneath it. At the same time, measurements can be conducted below the bridge. Therefore, the bridge specimen is elevated by attaching it on a pedestal with four columns. Damages can be induced by loosening the
fastening pieces.
To examine the capability to detect and localise damage using the Measurement- and Model-based Structural Analysis (MeMoS), a small-scale truss bridge (1520 mm × 720 mm × 720 mm) made of aluminium profiles is built as a test specimen for this purpose. The truss frame of the test bridge is made of aluminium profiles with a sophisticated design of the cross-sectional area. In comparison, with solid profiles, only a fraction of the material is needed to produce the profiles, while their bending resistance decreases slightly. The profiles are built into a truss frame by connecting them by means of fastening sets made of steel. The bridge model is mounted on four steel bearings which each of them consist of a cylinder arranged between two plates. Fixed bearings are made by holding onto one end of the bridge. The bridge is subjected by an external load by placing a heavy object beneath it. At the same time, measurements can be conducted below the bridge. Therefore, the bridge specimen is elevated by attaching it on a pedestal with four columns. Damages can be induced by loosening the fastening pieces.
By means of a small-scale truss bridge, the ability of the Measurement- and Model-based Structural Analysis to detect and localize damage was examined. Although there was no noteworthy difficulty in detecting damage, it turned out that damage localization responds sensitively to systematic influences, i.e. non-modelled properties of the mechanical model. Therefore, another experiment is being conducted to re-examine the Measurement- and Model-based Structural Analysis. For this purpose, the bending test is carried out as it has been already theoretically respectively numerically discussed. In this attempt, the systematic influences such as residual stress are kept as low as possible.
By means of a small-scale truss bridge, the ability of the Measurement- and Model-based Structural Analysis to detect and localize damage was examined. Although there was no noteworthy difficulty in detecting damage, it turned out that damage localization responds sensitively to systematic influences, i.e. non-modelled properties of the mechanical model. Therefore, another experiment is being conducted to re-examine the Measurement- and Model-based Structural Analysis. For this purpose, the bending test is carried out as it has been already theoretically respectively numerically discussed. In this attempt, the systematic influences such as residual stress are kept as low as possible.
Der Fokus des Arbeitsfelds ist die messtechnisch fundierte Anwendung der 3D-Verfahrenskombination zur Lösung vielfältiger Messaufgaben mit optimaler Datenqualität für interne und externe Kunden.
Das setzt insbesondere eine jeweils problembezogene Messmethodik voraus. Dazu setzen wir kameragestützte 3D-Koordinatenmessverfahren ein, die auf dem fotogrammetrischen Prinzip der Bildtriangulation beruhen. Darunter fallen folgende miteinander flexibel kombinierbare Verfahrensmodifikationen: Mehrbildfotogrammetrie, Messadapter für Geometriemerkmale, Streifenprojektionsverfahren, statische bis hochdynamische Stereofotogrammetrie auf Punktebasis oder aufgabenangepasster Oberflächenmuster und mechanisch-optische Taster.