1,720,988 research outputs found
Manufacturability of non-assembly joints fabricated in AlSi10Mg by selective laser melting
No full textSelective Laser Melting is a promising Additive Manufacturing technology that makes possible the fabrication of
complex metallic components up to the production of mechanisms in one technological operation without the
need for a subsequent assembly. In order to permit the one-step fabrication of the joints, a lot of issues must be
considered to preserve their functionalities. In this work some of these aspects are investigated in order to
provide a manufacturability map of non-assembly joints taking into account the clearance, the joint shape and
the building orientation.
The results show multiple behaviors mainly affected by the dropping effect which is dependent upon the local
stratification angle: a little inclination of the joint improves its functionality and widens the manufacturability
window that permit to fabricate a working joint. The clearance and joint shape have combined effects on the
torque necessary to move the joint
La soddisfazione abitativa tra caratteristiche individuali e regionali: il caso italiano
No full textIn medio stat virtus? Housing quality and subjective wellbeing in urban areas in Italy [In medio stat virtus? Qualità abitativa e benessere individuale nelle aree urbane italiane]
No full textThis paper explores the concepts of housing quality and subjective wellbeing on a repre-sentative sample of Italian population. The analysis consists in the construction of several indices which combine objective, i.e. characteristics of the dwelling and its surroundings, and subjective variables, i.e. perceived subjective wellbeing. Through a cluster analysis, we identify specific groups and looked at their spatial distribution at different degrees of urban-ization
Study of selective laser melting process parameters to improve the obtainable roughness of AlSi10Mg parts
No full textSelective Laser Melting of AlSi10Mg parts has a lot of applications in different fields such as aerospace and automotive for its abilities to fabricate components characterized by complex shapes, good mechanical properties and low porosity. One of the main drawbacks for its application is the obtainable surface roughness widely not suitable for functional requirements. Typically, the improvement is handled by secondary operations thus markedly increasing the production time and costs. In this paper the possibility to improve the surface roughness by tuning Selective Laser Melting process parameters is investigated. A design of experiments is carried out considering not only the common laser process parameters but also the changing of the contour, upskin and downskin strategy definitions. This way the attained results show a marked decreasing of the roughness for vertical and horizontal surfaces
Effect of laser remelting on surface roughness and microstructure of AlSi10Mg selective laser melting manufactured parts
No full textSelective laser melting (SLM) allows to obtain components by a careful selection of process parameters. This technology is becoming more and more attractive because it is capable of producing dense and complex metallic parts. Considering that one of the main drawbacks of this technology is the high surface roughness, this research aims at reducing it by means of skin laser remelting performed during the fabrication process. Since the remelting strategy affects only the external skin, the building time is slightly affected by this additional operation and the infill part properties remain unchanged. In this work, the effect of process parameters on the surface morphology and alloy microstructure has been analyzed. The obtained results highlighted that the remelting process allows to improve the surface morphology but it affects the subsurface defect formation. The obtainable surface roughness for different surface slopes was modelled as a function of the process parameters
Powder bed monitoring via digital image analysis in additive manufacturing
Full text linkDue to the nature of Selective Laser Melting process, the built parts suffer from high chances of defects formation. Powders quality have a significant impact on the final attributes of SLM-manufactured items. From a processing standpoint, it is
critical to ensure proper powder distribution and compaction in each layer of the powder bed, which is impacted by particle size distribution, packing density, flowability, and sphericity of the powder particles. Layer-by-layer study of the process can provide better understanding of the effect of powder bed on the final part quality. Image-based processing technique could be used to examine the quality of parts fabricated by Selective Laser Melting through layerwise monitoring and to evaluate the results achieved by other techniques. In this paper, a not supervised methodology based on Digital Image Processing through the build-inmachine camera is proposed. Since the limitation of the optical system in terms of resolution, positioning, lighting, field-of-view, many efforts were paid to the calibration and to the data processing. Its capability to individuate possible defects on SLM parts was evaluated by a Computer Tomography results verification
Casa e lavoro. Tipologie di smart workers durante il primo lockdown a Milano
No full textL’articolo presenta i risultati di un’analisi dei profili degli smart workers a partire da un’indagine campionaria condotta su un campione di residenti del comune di Milano che nel corso della recente pandemia hanno lavorato da casa. La clu-ster analysis qui proposta raggruppa tre tipologie di smart workers sulla base della percezione di adeguatezza abitativa per il lavoro agile, dei diversi livelli di dotazione tecnologica, della qualità dell’alloggio, delle caratteristiche socio-economiche dei rispondenti: nuclei tradizionali, proprietari, con dotazione tecnologica media e adeguatezza degli spazi casalinghi; nuclei misti, in affitto, con dotazione tecnologica medio-bassa e adeguatezza dell’alloggio media; single, giovani adulti, con alta dotazione tecnologica e percezione positiva dell’adeguatezza degli spazi
Mold replication in injection molding of high density polyethylene
No full textIn order to deepen the mechanisms at the basis of mold surface replication onto the molded plastic surface, a novel experimental approach is proposed. Up to 20 different mold surface textures were made by machining with repetitive patterns of peaks and valleys. Mold replication tests were performed by over-molding of high density polyethylene (HDPE) on steel inserts. The surface morphology of inserts and injection molded parts was acquired by surface analyzer, and all the main roughness parameters were extracted and compared as well as the geometrical profiles. Surface morphology was also measured on molded samples after thermal relaxation at 100°C. As expected, a strong correlation was found between the roughness of mold insert and molded part over the full experimented range. Profiles on the molded surface have the same repetitive pattern of the corresponding insert surface but with lower peaks, higher valleys, and a horizontal shrinkage. Comparing molded HDPE surface profiles before and after thermal relaxation, it was observed a similar change to the one highlighted between mold insert and molded part. This occurrence suggests that the final surface appearance of the molded part is also a function of the relaxation mechanism during or immediately after injection molding
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