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Im Teilprojekt B3 werden die grundlegenden Auswirkungen der Prozessführung beim Laserstrahlschmelzen von Kunststoffen auf die resultierenden Bauteileigenschaften analysiert. Dabei werden die komplexen Wechselwirkungen der Teilprozesse Pulverauftrag, Belichtung und Konsolidierung sowie die zugrundeliegende Temperaturführung wissenschaftlich untersucht. Das Ziel ist es, mithilfe neuer Prozessstrategien die Herstellung von Bauteilen mit reproduzierbaren und definierten Eigenschaften zu ermöglichen.

Das Lasersintern von Kunststoffen ermöglicht durch die schichtweise Fertigung eine nahezu unbegrenzte Geometriefreiheit. Ursprünglich fand das Verfahren insbesondere im Protoypenbau Anwendung. Im letzten Jahrzehnt konnte es sich im Bereich der schnellen und individualisierten industriellen Bauteilherstellung von Einzelteilen und Kleinserien etablieren. Allerdings stellt die Einstellung von reproduzierbaren Material- und Bauteileigenschaften, wie der Maßhaltigkeit, der Porosität oder der Mechanik immer noch eine Herausforderung dar. Dies ist auf die mannigfaltigen und in Wechselwirkung stehenden Material- und Prozesseinflüsse zurückzuführen, da diese die Temperaturhistorie bei der Bauteilentstehung direkt beeinflussen. Entsprechend des Stands der Forschung kommt dem Belichtungsvorgang die entscheidende Rolle zur Steuerung der Temperaturfelder und somit der Bauteileigenschaften zu. Aus diesem Grund werden im Rahmen dieser Dissertation belichtungsparameter-, schicht- und geometriespezifisch die Belichtungstemperaturen analysiert und in Bezug auf die resultierenden Bauteileigenschaften bei der Verarbeitung von Polyamid 12 charakterisiert. Es wird festgestellt, dass die bei der Belichtung gemessenen geometrieabhängigen Maximaltemperaturen schichtunabhängig und aufgrund der kurzen Wirkdauer nicht maßgeblich für die resultierenden Bauteileigenschaften sind. Als entscheidende thermische Größen können die Abklingzeit und die Durchwärmung des Pulverbetts oberhalb der Schmelze identifiziert werden. Die Größen beschreiben die thermischen Wechselwirkungen zwischen den aufeinanderfolgenden Schichten. Bei gleichbleibender Querschnittsfläche ist eine belichtungsparameterunabhängige Schichtabhängigkeit dieser Größen bis zur annähernden Schichtkonstanz bei zehn bis 15 Schichten nachweisbar. Diese Schichtkonstanz korreliert mit der Menge an Material, das basierend auf der Schmelztiefe aufgeschmolzen werden muss. Auf diesen Erkenntnissen aufbauend kann der Bedarf an schicht- und geometrieabhängigen oder geometrieinvarianten Belichtungsparametern abgeleitet werden, um die Reproduzierbarkeit von Bauteileigenschaften weiter zu erhöhen. Laser sintering of polymers allows for the fabrication of parts with almost unlimited geometrical freedom through layer-by-layer production. Originally, the process was used for prototype generation, but in the last decade, the process emerged towards the field of rapid manufacturing and individualized industrial component production of individualized parts or small series. However, the defined setting of reproducible material and component properties, such as dimensional accuracy, porosity or mechanics remains a challenge. This is due to the manifold and interacting material and process influences that affect the temperature history of the component during part generation. According to the state of the art, the exposure process plays a decisive role in controlling the temperature fields and thus the component properties. For this reason, the temperature fields during exposure are analyzed within the framework of this dissertation. Therefore, exposure parameters and cross-sectional areas are varied. The layer-dependent and geometry-specific temperature values are measured via thermal imaging and validated with respect to the resulting component properties during processing of polyamide 12. It is found that the geometry-dependent maximum temperatures are layer-independent and, due to the short effective time of material-beam interaction, are not decisive for the resulting component properties. The decay time and the heating of the powder bed above the melt can be identified as decisive thermal variables. These values can be interpreted as measure for the thermal interactions between the subsequently manufactured layers. Regarding constant cross-sectional areas, a layer dependency can be detected, that is valid for different exposure parameters. Constant values can be measured after ten to 15 layers, which is correlating to the amount of material that has to be melted with respect to the melting depth. Based on these findings, the need for layer- and geometry-dependent exposure parameters or geometry invariant processing parameters can be derived to further increase the reproducibility of component properties.

Model-Driven Software Product Line Engineering (MDPLE) is a discipline that bespeaks increased productivity when developing variability-intense software by combining the benefits of both disciplines, model-driven software engineering (MDSE) and software product line engineering (SPLE): SPLE grounds on the principles of organized reuse and explicit variability to build a (multi-variant) platform from which customized software products can be derived automatically. In contrast, MDSE raises the level of abstraction by employing models of different kinds throughout the development process and eventually represents the software system with executable models. Model transformations serve to create not only different model representations from a given model but also to derive executable source code automatically. While MDPLE should take advantage of the positive effects of each discipline when combining them, several problems, such as the following, threaten these effects: Annotative product lines build the multi-variant platform by superimposing single variants of the software. For deriving a customized product, developers map annotations onto elements of the platform and provide a configuration of the distinguishing features of the product line. These annotations are Boolean expressions over the common and distinguishing features of the product line. A filter mechanism will remove elements from the platform if their annotations are not satisfied by the configuration. Since multiple artifacts, such as models, build scripts, and source code, form the platform, still annotating each of these artifacts is a manual process which is tedious and prone to errors. Few approaches automate this task by manipulating the execution semantics of model transformations. This requires exclusive access and, in the worst case, to consider variability explicitly in the trans- formation which increases the level of cognitive complexity and may require to learn new syntax. Therefore, in this thesis we develop a solution which acknowledges the existing and mature technology of (single-variant) model transformations which automate the creation of new models or source code but are unaware of the variability present in form of annotations in multi-variant product line artifacts. In contrast to existing approaches, our contribution does not modify the execution semantics of existing model transformation languages but reuses them and their generated artifacts to propagate annotations generically (i.e., independent of the transformation language and of the transformed instances of metamodels) and automatically. Specifically, the thesis contributes the informal and formal concepts and implementation of 1) an a posteriori bytecode model analysis, 2) an a posteriori propagation of annotations based on transformation trace, as well as 3) a propagation during the execution based on a generic aspect. Furthermore, the thesis examines the strengths and weaknesses of employing a propagation DSL and model matching of instances of different metamodels to reconstruct trace information. The evaluation confirms a significant reduction in manual efforts to annotate the product line: We examine the trace-based propagation of annotations based on traces of different completeness-levels and the generic aspect in a controlled setting with small to medium academic product lines. The aspect-oriented approach assigns 95 − 100% of the annotations correctly. Furthermore, even if the trace completeness is insufficient and does not record all target elements, our approaches compute more than 90% of the annotations correctly whereas the propagation based on generation-complete traces determines all target annotations correctly. In summary, the thesis solves the problem of diminished productivity in MDPLE by providing the concepts, realization, and evaluation of automated techniques to propagate annotations in annotative product lines without the need to change established technologies.

The 25th session of the Conference of the Parties (COP-25) of the United Nations Framework Convention on Climate Change (UNFCCC) became the longest COP on record - but yielded few results. It appears that four years after the adoption of the Paris Agreement, enthusiasm has waned and political bargaining and bean-counting have taken over. Countries, for even the slightest chance to keep temperatures 'well below' 2 degrees Celsius, must do much more than they have previously committed to and accelerate the shift towards a zero-carbon economy. However, the conference largely failed to heed the rallying cry of the Chilean presidency. The flagship decisions (grouped under the banner "Chile-Madrid Time for Action") neither produced new commitments - enhancing ambition or finance for developing countries - nor new rules that would nudge countries closer to the climate action targets needed. The leftover pieces from last year's negotiations of the "Paris Rulebook" were also not resolved, in particular the unfinished decisions on Article 6 on market- and non-market mechanisms. The procrastination shows that the new architecture of the Paris Agreement, while addressing several of the shortcomings of the Kyoto Protocol, suffers from its own weaknesses. The meager results of Madrid give reason to pause and reflect on the conditions that may hold countries back from fully embracing the Paris Agreement, but also to consider the future and nature of carbon markets and what is making the issue so difficult to resolve.