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PublicationMachinability study in orthogonal cutting of additively manufactured Inconel 718 with specifically induced porosity( 2024-02-01)In comparison to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight design concepts and high material efficiency. In aerospace and turbomachinery, this technology is increasingly coming into focus, especially the laser-based powder bed fusion of metals (PBF-LB/M) process. PBF-LB/M is already used for some aerospace components, which are often exposed to high thermal and mechanical loads. Dependent on the component geometry, support structures are required for AM, which then usually have to be removed by machining. One suitable support structure is the use of material with specifically induced porosity. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in PBF-LB/M. However, the machinability of porous, additively manufactured material has hardly been researched so far. One preliminary investigation of milling porous, additively manufactured Inconel 718, though, showed significantly poorer machinability of the porous material compared to the dense material. To further examine this phenomenon, this paper presents the results of fundamental machinability studies with porous, additively manufactured Inconel 718 in orthogonal cutting. The investigations with tungsten carbide cutting tools on a special fundamental test rig include the analysis of the cutting force, the chip geometry, the chip temperature and the surface quality. The research results provide explanations for the poorer machinability of the porous material and derived approaches for improving the machinability in future studies.
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PublicationAnalysis of Waterjet Treatment for Herbicide-free Vegetation Management on Railway Tracks( 2022)Vegetation management is essential for the functionality and operational safety of railway tracks. Because the approval of the herbicide glyphosate on railway tracks will expire by the end of 2022 in Europe, there is an urgent need for alternative vegetation management strategies. An eco-compatible alternative could be the use of pressurized water, possibly supplemented with abrasives, to substitute current herbicides. This study examines two different approaches of waterjet methods to remove plants from railway tracks, either by cutting or defibering the aerial parts of plants. Here, a range of plant species and infrastructure components (e.g., cable insulation) were processed at varying process parameters. Furthermore, the benefit of using garnet abrasive for enhanced plant damage was examined. The experiments revealed that, with an appropriate parameterization of the waterjet process, plants could be effectively damaged without affecting the surrounding infrastructure.
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PublicationMachinability analysis for milling of additively manufactured Inconel 718 with specifically induced porosity( 2022)Compared to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight construction concepts and high material efficiency. This technology is increasingly coming into focus in aerospace and turbomachinery engineering, especially the Laser Powder Bed Fusion (LPBF) process. LPBF is already being used for some aerospace components that are often subject to high thermal and mechanical loads. Depending on the component geometry, support structures are required for additive manufacturing, which then have to be removed, usually by machining. Among others, the use of material with specifically induced porosity is suitable as a support structure. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in the LPBF process. However, the machinability of porous, additively manufactured material has hardly been researched to date. This paper therefore presents the results of machinability investigations with porous, additively manufactured Inconel 718. The investigations included the analysis of active cutting force, cutting tool wear, surface finish and chip geometry in the milling process with tungsten carbide cutting tools. It was found that with the porous material, the dominant type of wear is early starting chipping of the cutting tool edges. The active force decreases with increasing porosity. Partial smearing of the pores was observed on the milled surfaces. The chips of the porous material show a disrupted surface. In future investigations, the aim is to improve the wear behaviour when milling porous Inconel 718.
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PublicationNumerical and experimental determinations of contact heat transfer coefficients in nonisothermal glass molding( 2020)
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PublicationApproaches and Methodologies for Process Development of Thin Glass FormingThe steadily growing thin glass market is driven by a vast amount of applications among which automobile interiors and consumer electronics are, such as 3D glass covers for displays, center consoles, speakers, etc. or as part of optics within head up-displays. Today, glass manufacturers are suffering from challenges brought about by the increases of shape complexity, accuracy and product variants while simultaneously reducing costs. The direct manufacturing method via grinding and polishing is no longer suitable because of its limited machinability for thin glasses in respect to fracture and its cost insufficiency due to the length of the process chain. Instead, replication-based technologies or thin glass forming become promising manufacturing methods to overcome the aforementioned technical and economic challenges. For instance, thermal slumping is only able to satisfy the most basic requirements and is in particular limited regarding the deformation degree and shape complexity of thin glass products. Technologies such as vacuum-assisted slumping or deep drawing are currently in development at the Fraunhofer Institute for Production Technology IPT and promise additional cost benefits. This paper introduces all potential process variants for thin glass forming. The suitability of different methods for process development, specifically process modeling based on either experimental-, simulation- or machine learning approaches (white box and black box models), will be addressed and discussed. Furthermore, process efficiency is examined on both an economic and technical level, where molding time, suitable geometries and accuracy are the focus. The methodologies presented in this paper aim at developing a guideline for glass manufacturers on determining the optimal strategy for the process development of thin glass production.
