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Die transiente nichtlineare 3D-Wärmeleitungsgleichung wurde zur numerischen Lösung mittels der Finite-Elemente-Methode im Ort und mittels explizitem Eulerschema in der Zeit diskretisiert. Der resultierende Algorithmus wurde in ein Computerprogramm überführt wobei besonderer Wert auf paralleles Rechnen gelegt wurde. Das Programm wurde auf die numerische Berechnung eines schweißtypischen transienten Temperaturfelds angewandt. Die Rechenzeit und Skalierbarkeit des Computerprogramms bezüglich der Anzahl verwendeter CPU Kerne wurde untersucht und mit dem kommerziellen FEM Programm Abaqus 6.14 verglichen. Die Anwendung der expliziten Zeitintegration resultiert in verbesserter Skalierbarkeit bezüglich der Anzahl verwendeter CPU Kerne und Rechenzeitersparnis gegenüber der in Abaqus implementierten impliziten Zeitintegrationsmethode.
More than 80 representatives of SMEs, industrial companies and research institutes met on September 12 at the workshop "Challenges in Additive Manufacturing: Innovative Materials and Quality Control" at BAM in Adlershof to discuss the latest developments in materials and quality control in additive manufacturing.
In special lectures, researchers, users and equipment manufacturers reported on the latest and future developments in additive manufacturing. Furthermore, funding opportunities for projects between SMEs and research institutions on a national and European level were presented.
This study examines the relationship between the magnetic mesostructure with the microstructure of low carbon steel tungsten inert gas welds. Optical microscopy revealed variation in the microstructure of the parent material, in the heat affected and fusion zones, correlating with distinctive changes in the local magnetic stray fields measured with high spatial resolution giant magneto resistance sensors. In the vicinity of the heat affected zone high residual stresses were found using neutron diffraction.
Notably, the gradients of von Mises stress and triaxial magnetic stray field modulus follow the same tendency transverse to the weld. In contrast, micro-X-ray fluorescence characterization indicated that local changes in element composition had no independent effect on magnetic stray fields.
In order to generate a material data base for computational welding mechanics, temperature and strain-rate dependent stress-strain experiments were performed by using a Gleeble®3500 testing system. The object of the investigation was HSLA transformable steel S960QL and related solid phases as bainite, martensite and austenite. For the production of these solid phases, the base material was heat treated according to an average weld temperature cycle which was extracted within the heat affected zone of a thermal numerical weld simulation of a GMA weld. The hot tensile tests were carried out via cost-saving flat specimen geometries. Two experimental series with different strain-rates were conducted, where the longitudinal strain-rate was controlled by specification of the transversal strain-rate applying Poisson’s-ratio. Subsequently, the resulting stress-strain curves were approximated in accordance with the Ramberg-Osgood-materials law. Consequently, it is shown that the temperature and strain-rate dependent stress-strain behavior of metals can be successfully characterized by means of a Gleeble®-system.
However, this requires a control of the longitudinal strain-rate by specification of the transversal strain-rate. The related experimental procedure and the method of evaluation are explained in detail. With regard to all tested solid phases, a significant strain-rate dependency can only be observed upwards from temperatures of 400 °C. Based on experimental results, Ramberg-Osgood-parameters will be presented to describe the stress-strain behavior of steel S960QL and related solid phases for temperatures between 25 °C and 1200 °C. Furthermore, the use of costsaving flat specimen-geometry appears reasonable.
An approach to develop an arc sensor for gap width estimation during automated NG-GMAW with a weaving electrode motion is introduced by combining arc sensor readings with optical measurements of the groove shape to allow precise analyses of the process. The two test specimen welded for this study were designed to feature a variable groove geometry in order to maximize efficiency of the conducted experimental efforts, resulting in 1696 individual weaving cycle records with associated arc sensor measurements, process parameters and groove shape information. Gap width was varied from 18 mm to 25 mm and wire feed rates in the range of 9 m/min to 13 m/min were used in the course of this study. Artificial neural networks were applied as a modelling tool to derive an arc sensor for estimation of gap width suitable for online process control that can adapt to changes in process parameters as well as changes in the weaving motion of the electrode. Wire feed rate, weaving current, sidewall dwell currents and angles were defined as inputs to calculate the gap width. The evaluation of the proposed arc sensor model shows very good estimation capabilities for parameters sufficiently covered during the experiments.
Zur Effizienzsteigerung beim Einsatz von Lichtbogenverfahren für Fügeaufgaben im Dickblechbereich werden häufig angepasste Verfahren mit möglichst geringer Nahtquerschnittsfläche angewendet, beispielsweise das MSG-Engspaltschweißen für I-Nähte. Die Herausforderung für die Automatisierung des Verfahrens besteht neben der komplexen Prozessführung auch in der oftmals schlechten Zugänglichkeit der Prozesszone für optische Sensorik, weswegen verstärkt auf prozessorientierte Sensorik zurückgegriffen wird. Zur Steigerung des Prozessverständnisses und Entwicklung neuer Regelungskonzepte wurde ein Versuchsaufbau umgesetzt, der sowohl optische Messsysteme als auch prozessorientierte Sensorik in einer gemeinsamen Steuerungsumgebung vereint. Die umfassende prozessbegleitende Sensorik ermöglicht die sukzessive Erweiterung des Prozesswissens, welches direkt zur Umsetzung neuer Steuer- und Regelalgorithmen basierend auf Regressionsmodellen genutzt werden kann. Der gemeinsame Einsatz optischer und prozessorientierter Sensorik wurde zur Auslegung eines Lichtbogensensors zur Höhenführung genutzt. Die Versuchsdurchführung mit dem Ziel der Ableitung nichtlinearer Regressionsmodelle erfolgt automatisiert mit Hilfe eines optischen Sensors. Der Vorteil dieses Verfahrens liegt dabei neben der schnellen Umsetzbarkeit in der direkten Korrelation der Messwerte zu realen physikalischen Systemgrößen und der schnellen Adaption auf unterschiedliche Schweißparameter und -prozesse.
An approach to develop an arc sensor for gap-width estimation during automated NG-GMAW with a weaving electrode motion is introduced by combining arc sensor readings with optical measurement of the groove shape to allow precise analyses of the process. The two test specimen welded for this study were designed to feature a variable groove geometry in order to maximize efficiency of the conducted experimental efforts, resulting in 1696 individual weaving cycle records with associated arc sensor measurements, process parameters and groove shape information. Gap width was varied from 18 to 25 mm and wire feed rates in the range of 9 to 13 m/min were used in the course of this study. Artificial neural networks were used as a modelling tool to derive an arc sensor for estimation of gap width suitable for online process control that can adapt to changes in process parameters as well as changes in the weaving motion of the electrode. Wire feed rate, weaving current, sidewall dwell currents and angles were used as inputs to calculate the gap width. Evaluation the proposed arc sensor model show very good estimation capabilities for parameters sufficiently covered during experiments.
Automatisierungs- und Regelkonzepte für das MSG-Engspaltschweißen - Pendel- und Füllgradregelung
(2018)
Das MSG-Engspaltschweißen eignet sich auf Grund der I-Nahtvorbereitung besonders für das wirtschaftliche Fügen bei hohen Blechdicken über 100 mm und bietet darüber hinaus zusätzliche technologische Vorteile. Für die automatisierte Anwendung des Verfahrens unter Produktionsbedingungen muss dabei die Prozesssicherheit auch für mitunter große Variationen der Spaltbreite entlang der Schweißnaht gesichert bleiben. In erster Linie betrifft dies bei mechanischer Auslenkung der Drahtelektrode die Adaption der Pendelbewegung auf die jeweilige Spaltbreite um eine ausreichende Flankenanbindung zu garantieren. Für die Online-Regelung der Pendelbewegung mittels Lichtbogensensorik wurde eine Methode implementiert die die notwendigen Pendelwinkel an jeder Nahtflanke unabhängig ermittelt und darüber hinaus Fehlstellungen des Brenners sowie Veränderungen des Kontaktrohrabstandes und der Prozessparameter eigenständig kompensiert. Eine Füllgradregelung auf Grundlage optischer Erfassung und Auswertung der Schweißnahtgeometrie wurde zusätzlich eingesetzt um bei veränderlichen Nahtquerschnittsflächen einen vorgegebenen, gleichbleibenden Lagenaufbau zu erzielen.
The development within the offshore wind energy sector towards more powerful turbines combined with increasing water depth for new wind parks is challenging both, the designer as well as the manufacturer of support structures. Besides XL-monopiles the jacket support structure is a reasonable alternative due to the high rigidity combined with low material consumption. However, the effort for manufacturing of the hollow section joints reduces the economic potential of jacket structures significantly. Therefore, a changeover from an individual towards a serial production based on automated manufactured tubular joints combined with standardized pipes must be achieved. Hence, this paper addresses the welding process chain of automated manufactured tubular joints including digitization of the relevant manufacturing parameters such as laser scanning of the weld seam geometry. Additionally, a methodology for the computation of the notch radius as well as the weld seam angle is presented based on the scanned profiles of three analysis points of an automated manufactured tubular X-joint. Subsequently, these parameters are considered within the notch stress approach based fatigue design and their impact is quantified by a comparison with the structural stress approach using equivalent stress concentration factors.
The digitalization of industrial processes is the most discussed topic in society these days. New business models have been developed to benefit from the opportunities offered by a digitally connected world. However, the focus in on the smart factory consisting of autonomous acting cyber physical systems (CPS). The efficient implementation of such CPS within an industrial environment requires the digitalization of the corresponding production processes. The digital twin of the process under investigation enables to develop sophisticated monitoring and control strategies which are necessary to fulfil the requirements of individual product design.
The need for a digitalization of the welding process is a logical consequence especially with regards to its industrial importance. The theoretical investigations and derived mathematical models of the welding process are well known since many decades. Anyhow, there is still a lack of industrial applicability of such models for an efficient and safe design of welded components. With respect to structural welding simulation that targets the heat effects of welding in terms of global quantities like temperature, solid phase distribution and residual stresses as well as distortions, the limited predictability of these quantities for arbitrary process parameters hinders its usability.
This presentation aims to give an overview of the current state of the art in structural welding simulation to predict the evolution of welding induced temperatures, stresses and distortions. Emphasis is given to industrial applicability of such models by reduction of the calculation times for large real-world structures and improved prediction of optimal process parameters. Furthermore, the role of such models within a weld data management system is demonstrated. The accumulation and relational storage of simulation and measuring data improves the overall process knowledge. This enables virtual cause and effect analyses of new process parameters as basis for a control system design.