User's manual for RAVFAC - A radiation view factor digital computer program

Contour integrals and finite difference in Radiation View Digital Computer Progra

Radiation view factor program

Computer program, RAVFAC, calculates diffuse radiation view factors, using contour integrals. Technique is combined with finite difference /double summation/ technique to compose total program package

Modification to the shading routine in the HREC orbital drag coefficient computer program Final report

Shading and pre-shading techniques for modified orbital drag coefficient computer progra

Pbf-lb process-induced regular cavities for lightweight alsi10mg structures

In powder bed fusion with laser beam (PBF-LB), two process-induced defects by pore formation are known: local spherical pores by the keyhole effect and geometrically undefined pores caused by lack of fusion. Both pore types are heterogeneously distributed and can be used for lightweight or damping design applications. The achievable porosity is limited to around 13%. This article presents a novel process-controlled method enabling the targeted and reproducible manufacturing of solid parts with regularly distributed cavities, currently up to 60% porosity in AlSi10Mg, using the balling effect. This eliminates the need for time-consuming digital pre-processing work

Influence of initial powder layer thickness and focus deviation on the properties of hybrid manufactured parts by Laser Powder Bed Fusion

In hybrid-additive manufacturing using powder bed fusion with laser beam (PBF-LB) conventionally manufactured base-bodies are overprinted with an individual geometry. In this paper, the influence of deviations of the initial layer thickness, and the focal plane on the component properties are investigated. For separate consideration of the individual effects, purely additive (AlSi10Mg) and hybrid-additive (AlSi10Mg on EN AW6082) test specimens were manufactured. The layer thickness was varied from 0 to 200 µm, and the focal plane between 0 and -8 mm. The influence on the microstructure due to the altered induced energy input is analyzed. These findings are correlated with respect to the tensile strength and material hardness. The highest strength is achieved with an initial layer thickness of 50 µm. A hardness decrease of 8 % due to hot stress cracks in the interface is avoided by targeted shifting of the focal plane

Development of an ultrasonically excited recoating process in laser powder bed fusion to process non-spreadable 316L powder

Part quality in laser powder bed fusion is influenced by the uniformity and density of the powder layer. As a result, requirements for the powder regarding spreadability and flowability are restrictive. Many researchers reported recoating defects for cohesive and agglomerating powders. However, the processing of such powders is highly desirable since e.g. surface roughness can be reduced. Therefore, we propose a novel ultrasonically excited recoater system to process such powder. In order to qualify the new recoater system, five different geometries with various amplitudes and recoating velocities were evaluated and compared to a conventional system. The defect rate, determined with a camera and AI-based analysis, the deposited mass and segregation along the recoated distance and the powder layer density of the resulting powder bed were analyzed. A process window and optimal geometry could be identified. It was possible to reduce segregation to a minimum, while maintaining a smooth, dense layer

N sensor in practical use Experiences and results from the on farm research project

Im Projekt On Farm Research der Landwirtschaftskammer Schleswig-Holstein und der Gutsverwaltung Helmstorf werden in großflächigen Versuchen langjährig Verfahren des teilflächenspezifischen Acker- und Pflanzenbaus erprobt und verglichen. Dabei hat sich gezeigt, dass die teilflächenspezifische Bewirtschaftung ein erhebliches Maß an technischen, personellen und monetären Voraussetzungen erfordert.Nicht in jedem Fall konnten im bisherigen Projektverlauf wirtschaftliche Vorteile teilflächenspezifischer Bewirtschaftungsstrategien nachgewiesen werden. Das traf auch für die teilflächenspezifische Stickstoffdüngung mittels N-Sensor zu. Der alleinige Online-Ansatz – Bewertung des Stickstoffbedarfes der Pflanzen über den N-Sensor – war nur anteilig erfolgreich. Zukünftig wird eine Verbesserung des Verfahrens der teilflächenspezifischen Stickstoffdüngung über die Kombination von N-Sensor und Ertragspotenzialkarte angestrebt. Auch die Einmaldüngung wird in Zukunft nicht mehr konstant, sondern teilflächenspezifisch am Ertragspotenzial der Teilfläche orientiert, ausgebracht (Map-Overlay-Prinzip).Die inferenzstatistische Bewertung der Ergebnisse zum Vergleich teilflächenspezifischer Bewirtschaftungsverfahren steht im Projekt noch aus. Dies ist bei dem multi­variaten Ansatz „teilflächenspezifisches Produktionsverfahren“ und dem sich daraus ableitenden Erfordernis, die Effekte solcher Einflussgrößen wie zum Beispiel Bodenunterschiede, differenzierte Saatmengen und teilflächen­spezifische Grunddüngung im „System“ zu quantifizieren, nicht einfach.Der vorliegende Beitrag soll auch auf die Probleme solcher komplexer Lösungsansätze, wie sie in der Praxis bei teilflächenspezifischer Bewirtschaftung stattfinden, aufmerksam machen. Hier geht es nicht mehr um den „Erfolg“ monokausaler Ansätze, sondern um den Versuch der Bewertung komplexer Produktionssysteme, die in ihren Einzelbestandteilen auf erfolgreichen Erkenntnissen und „Bestvarianten“ aus Exaktversuchen beruhen. DOI: 10.5073/JfK.2014.02.03, https://doi.org/10.5073/JfK.2014.02.03The Landwirtschaftskammer Schleswig Holstein and the Helmstorf estate are testing precision farming technologies in the framework of the “on farm research project”. Precision farming requires a significant level of technical, human and monetary resources.The economic benefits of precision farming could not be shown in every case within the project; this was also true for site-specific nitrogen fertilization using the N-sensor. Using only the online approach with the N-Sensor was partially successful. Improvements are expected while using the combination of N-sensor and yield potential maps. In future constant fertilization will no longer be applied but based on site-specific yield potential in an offline approach.The statistical evaluation of the results for site specific management against conventional practice is still ongoing. The complex multivariate “site-specific production” approach requires quantifying the effects of additional factors like soil variability, different seed rates and site-specific fertilization.This paper will focus on the problems of complex solutions as they occur in site-specific management. DOI: 10.5073/JfK.2014.02.03, https://doi.org/10.5073/JfK.2014.02.0

Influence of TiC-Nanoparticles on the material properties of AlSi10Mg manufactured by Laser Powder Bed Fusion

Additive manufacturing enables the production of complex lightweight components. However, the poor use of atomized metal powders poses a challenge in terms of ensuring flowability and new high-strength aluminum alloys are still lacking. Some investigations show that the mechanical properties of AlSi10Mg can be improved by adding TiC nanoparticles. This study aims to determine if the influence of small amounts of TiC additions, which are normally used to improve the flowability of fine powders, is also sufficient to improve the mechanical properties. It was found that the addition of 0.46 wt% TiC-Nanoparticles with a size of 50 nm led to a homogeneous grain size distribution and an increase of 16 % in yield strength, but a 32 % decrease in elongation compared to pure AlSi10Mg. Further, a strong median grain size reduction from 5.08 to 2.74 µm could be observed by adding 0.96 wt% of TiC-Nanoparticles.Mechanical Engineerin