Browsing by Keyword "Space"
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Item Performance of Gradient-Based Solutions versus Genetic Algorithms in the Correlation of Thermal Mathematical Models of Spacecrafts(2017-05-24) Anglada, Eva; Martinez-Jimenez, Laura; Garmendia, Iñaki; CIRMETALThe correlation of the thermal mathematical models (TMMs) of spacecrafts with the results of the thermal test is a demanding task in terms of time and effort. Theoretically, it can be automatized by means of optimization techniques, although this is a challenging task. Previous studies have shown the ability of genetic algorithms to perform this task in several cases, although some limitations have been detected. In addition, gradient-based methods, although also presenting some limitations, have provided good solutions in other technical fields. For this reason, the performance of genetic algorithms and gradient-based methods in the correlation of TMMs is discussed in this paper to compare the pros and cons of them. The case of study used in the comparison is a real space instrument flown on board the International Space Station.Item A study of parameter and post-processing effects on surface quality improvement of Binder Jet 3D-printed Invar36 alloy parts(2022-02) Lores, A.; Azurmendi, N.; Agote, I.; Espinosa, E.; García-Blanco, M. B.; EXTREMATBinder Jetting Additive Manufacturing technology, besides its high-productivity manufacturing potential, it also offers a high accuracy fabrication route for less common metal alloys or special purpose applications. In the present work, Binder Jet 3D-printed Invar36 alloy parts’ surface quality improvement is studied. Invar36 is a Fe–Ni alloy which presents near zero coefficient of thermal expansion below its curie temperature (279 °C) and it is widely used for high precision instrumentation in space environment. D90 < 22 µm grade Invar36 powder was used and printing process parameters were optimized following the Taguchi DoE methodology, to reduce sintered parts’ surface roughness. Additional sandblasting and electropolishing operations were performed and part surface roughness was reduced from 5 µm Ra to 1.5 µm Ra. Near surface closed porosity emerged and enlarged during the electropolishing process, leaving a non-homogeneous surface appearance. Consequently, a Hot Isostatic Pressing (HIP) thermal treatment was applied to reduce part overall and near-surface porosity, reaching a relative density of 99.8%. After the sandblasting and electropolishing of HIP-ed parts, surface roughness was further reduced to 1 µm Ra maintaining and homogeneous and clean surface. The results of the study showed that Binder Jet 3D-printed Invar36 parts with low surface roughness can be obtained, getting this process and material closer to future space optics developments.