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Item type:Publication, Access status: without files , The legacy of STAHY: milestones, achievements, challenges, and open problems in statistical hydrology(AHS Press, 2024-09-25); ; ; ; Chebana, FatehStatistical tools are crucial for a variety of hydrological applications, whether to model processes and enhance understanding and knowledge or to design infrastructure systems. Given the rapid evolution of statistical methods and the need for a solid theoretical foundation for their correct application, a multidisciplinary community STAtistics in HYdrology Working Group (STAHY-WG) aggregated under the International Association of Hydrological Sciences (IAHS) umbrella to contribute to this research field. Now, more than 15 years since its inception, this paper summarizes the main achievements of this productive community collaboration in four (of many) branches of statistical hydrology: extreme value analysis, multivariate analysis, time series analysis, and regionalization. The aim is to provide an overview of recent developments, offer practical suggestions (e.g. software packages), and outline future challenges to support scientists and practitioners in their endeavours within the realm of statistical hydrology studies.Publicationtype: Journal Article7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimization of large-scale aeroengine parts produced by additive manufacturing(American Institute of Aeronautics and Astronautics (AIAA), 2024-01); ; ; ; Additive Manufacturing (AM) presents a ground-breaking opportunity to produce lightweight parts with enhanced functionality and design flexibility. It revolutionizes assembly by enabling integrated designs that significantly reduce component counts, minimizing assembly efforts and potential faults. Consequently, AM stands out as an appealing choice for manufacturing aerospace engine parts. Among AM techniques for metal parts, Laser Powder Bed Fusion (LPBF), also known as Direct Metal Laser Melting (DMLM), currently dominates the industry due to its capability to achieve high part quality and density using advanced machinery. However, limitations in part size stem from the build envelopes of these machines. Hence, this study explores the feasibility of printing large-scale engine parts, covering the design process, additive manufacturing, and aerothermal testing. A turbine center frame, nearly one meter in diameter, serves as a demonstrator case. Employing a multi-objective Design for Additive Manufacturing (DfAM) approach, the frame's structure underwent optimization through generative design, aiming to minimize mass, maximize stiffness, and meet strength requirements. Furthermore, the manifold section of the frame was optimized to reduce system pressure loss within the designated design space. Inconel 718 using LPBF was selected, with initial segments confirming manufacturability. The manufacturing process was fine-tuned for productivity and part properties, establishing design guidelines accordingly. Subsequently, the optimized manifold design underwent successful aerothermal testing on a specific test rig under various flow conditions. The redesigned frame showcased a 34% weight reduction and a 91% decrease in pressure loss while consolidating over 100 parts into one assembly. For the production, two alternatives are discussed. On the one hand, the final design was printed using the GE Additive ATLAS, the largest available LPBF system, validating the AM feasibility for large-scale parts under controlled laboratory conditions. On the other hand, a modified design is proposed that allows for the printing of segments on a regular-sized AM machine and a subsequent welding.Publicationtype: Conference Paper31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design guidelines for laser powder bed fusion in Inconel 718(Laser Inst. of America, 2022-02-01); ; ; ; Additive manufacturing (AM) has been leveraged across various industries to potentially open design spaces allowing the design of parts to reduce the weight, cost, and integrated design. Over the past decade, AM has sped up fast enough to penetrate various industry offering potential solutions for multiple materials, such as metals, alloys, plastics, polymers, etc. However, challenges lie to best utilize the opened design spaces as current generation engineers are trained to design parts for the conventional manufacturing process. With this lack of design guidelines for the AM process, users are limiting themselves to best utilize the offering made by advanced manufacturing. For aerospace parts, the design freedom of additive manufacturing is attractive mainly for two purposes: for weight reduction through lighter, integrated design concepts as well as for functional optimization of parts aiming at an increase of performance, e.g., by optimizing flow paths. For both purposes, it is vital to understand the material-specific and manufacturing process design limits. In AM, combination of each material and manufacturing process defines the design space by influencing minimum thickness, angle, roughness, etc. This paper outlines a design guideline for the laser powder bed fusion (also DMLM, direct metal laser melting) AM process with Inconel 718 material. Inconel 718 is a superalloy with superior mechanical properties and corrosion resistance at elevated temperatures up to 700 °C and is, therefore, used in several applications including aerospace engine parts. Due to its weldability, the alloy has also been extensively investigated in laser powder bed fusion and other additive manufacturing processes. A comprehensive study is provided both analytically and experimentally suggesting how parts can be designed having critical design features, manufacturing direction/orientation to meet design requirements, design accuracy, and quality. Design features presented include walls, overhangs, bore holes, and teardrop shapes, with their minimal feature sizes and effects on accuracy and roughness of the build parts. For the light-weight design of parts, different concepts such as lattices and stiffener structures are discussed. For gas or liquid carrying flow channels, the geometrical form and size are highlighted. Based on an approach by Kranz et al., design guidelines for Inconel 718 are derived from the experiments and provided in the form of a catalog for easy application.Publicationtype: Journal ArticleScopus© Citations 14 111 438