7,748 research outputs found
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Manufacturing Metallic Parts with Designed Mesostructure via Three-Dimensional Printing of Metal Oxide Powder
Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer
high strength accompanied by a relatively low mass. In this paper, the authors investigate the use of ThreeDimensional Printing (3DP) to manufacture metallic cellular materials by selectively printing binder into a
bed of metal oxide ceramic powder. The resulting green part undergoes a thermal chemical post-process in
order to convert it to metal. As a result of their investigation, the authors are able to create cellular
materials made of maraging steel that feature wall sizes as small as 400 µm and angled trusses and channels
that are 1 mm in diameter.Mechanical Engineerin
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Examining Variability in the Mechanical Properties of Parts Manufactured via PolyJet Direct 3D Printing
In Objet’s PolyJet process, part layers are created by selectively inkjetting photopolymers
onto a build substrate and then cured with ultraviolet lamps. With an eye towards using PolyJet
as a manufacturing process to fabricate end-use products, the authors examine the sensitivity of
part material properties to variation in process parameters. Specifically, a design of experiments
is conducted using a full-factorial design to analyze the effects of three parameters on the
specimens’ tensile strength and tensile modulus: the in-build plane part orientation (X-Y), the
out-of-build plane part orientation (Z), and the distance between specimens. Results show that
part spacing has the largest effect on the tensile strength, but the three parameters produced no
statistically significant effects on the tensile modulus. Orienting specimens in XZ orientation
with minimal part spacing resulted in the highest tensile strength and modulus. Whereas,
orienting specimens in the YZ orientation at the farthest part spacing led to the lowest
mechanical properties.Mechanical Engineerin
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Fatigue Characterization of 3D Printed Elastomer Material
The Objet PolyJet 3D Printing process provides the ability to print graded materials featuring
both stiff and elastomeric polymers. This capability allows for a variety of new design
possibilities for additive manufacturing such as living hinges, shock absorbing casings, and
integrated gaskets. Such design features typically rely upon the ability of traditional elastomers
to experience large and repeated strains without permanent deformation or damage. However,
voids and other flaws inherent to many Additive Manufacturing (AM) processes can have a
significant negative impact on the fatigue life of elastomeric AM materials. In this paper, the
authors seek to fill a gap in the literature by characterizing the fatigue life of a direct 3D printed
elastomer, and the multi-material interface. Based on the results, the authors offer advice for
improving fatigue life of printed elastomeric components.Mechanical Engineerin
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Effect of Bimodal Powder Mixture on Powder Packing Density and Sintered Density in Binder Jetting of Metals
The Binder Jetting Additive Manufacturing process provides an economical and scalable
means of fabricating complex metal parts from a wide variety of materials. However, the
performance metrics of the resulting sintered parts (e.g., thermal, electrical, and mechanical
properties) are typically lower than traditionally manufactured counterparts due to challenges in
achieving full theoretical density. This can be attributed to an imposed constraint on particle size
and its deleterious effects on powder bed packing density and green part density. To address this
issue, the authors explore the use of bimodal powder mixtures to improve the sintered density and
material properties within the context of copper parts fabricated by Binder Jetting. The
effectiveness of using bimodal powder mixtures in an effort to improve sintered density is studied
in terms of particle size distribution and powder packing density.Mechanical Engineerin
Galaxy Morphology - Halo Gas Connections
We studied a sample of 38 intermediate redshift MgII absorption-selected
galaxies using (1) Keck/HIRES and VLT/UVES quasar spectra to measure the halo
gas kinematics from MgII absorption profiles and (2) HST/WFPC-2 images to study
the absorbing galaxy morphologies. We have searched for correlations between
quantified gas absorption properties, and host galaxy impact parameters,
inclinations, position angles, and quantified morphological parameters. We
report a 3.2-sigma correlation between asymmetric perturbations in the host
galaxy morphology and the MgII absorption equivalent width. We suggest that
this correlation may indicate a connection between past merging and/or
interaction events in MgII absorption-selected galaxies and the velocity
dispersion and quantity of gas surrounding these galaxies.Comment: 6 pages; 3 figures; contributed talk for IAU 199: Probing Galaxies
through Quasar Absorption Line
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Exploring Variability in Material Properties of Multi-Material Jetting Parts
With Additive Manufacturing (AM) capabilities rapidly expanding in industrial applications,
there exists a need to quantify materials' mechanical properties to ensure reliable performance
that is robust to variations in environment and build orientation. While prior research has
examined process-parameter and environmental effects for AM processes such as extrusion, vat
photopolymerization, and powder bed fusion, existing similar research on the material jetting
process is limited. Focusing on polypropylene-like (VeroWhitePlus) and elastomer-like
(TangoBlackPlus) materials, the authors first characterize the anisotropic properties of six
different gradients produced from mixing the two materials in preset quantities. Three build
orientations were used to fabricate parts and analyze tensile stress, modulus of elasticity, and
elongation at break for each material. The authors also present results from an investigation of
how aging of parts in different lighting conditions affects material properties. The results from
these experiments provide an enhanced understanding of the material behaviors relating to
material jetting process parameters and can inform material selection when manufacturing loadbearing parts.Mechanical Engineerin
A new species of Crinoniscus PĂ©rez, 1900 (Crustacea: Isopoda: Crinoniscidae) parasitising the pedunculate barnacle Heteralepas newmani Buhl-Mortensen & Mifsud (Cirripedia: Heteralepadidae) with notes on its ecology and a review of the genus
The new species Crinoniscus stroembergi n. sp. belonging to the parasitic isopod family Crinoniscidae Bonnier, 1900, is described from a pedunculate barnacle host collected in the Mediterranean Sea. This is the first species of Crinoniscus PĂ©rez, 1900 described from a host in the genus Heteralepas Pilsbry. The male cryptoniscus larva is distinguished from congeneric species by having a dorsoventrally flattened body with the posterolateral margins of the cephalon scarcely extending beyond the anterior margin of pereomere 1 (in contrast to C. cephalatus Hosie, 2008 with extended margins); articles 1 and 2 of the antennule being subequal in width and the anterodistal angle of antennule article being low and rounded; propodus of pereopods 6 and 7 having a sinuous dorsal margin that is distally narrowing and the posterior margin of the pleotelson being short and rounded. The mature females of species in Crinoniscus are of two basic forms: those with ventrolateral lobes on the pereomeres (C. alepadis (Gruvel, 1901) n. comb., and C. politosummus Hosie, 2008) and those lacking such lobes (C. cephalatus and C. stroembergi n. sp.). The mature females of C. stroembergi n. sp. can be distinguished from other species of Crininiscus based on their lacking lobes on the anterior end. The material examined includes the male and three female developmental stages of the parasite in the host, Heteralepas newmani Buhl-Mortensen & Mifsud. The mouthparts of the immature female are described and the feeding biology and effects on the host are discussed along with a review of feeding modes in species of the Cryptoniscoidea. Leponiscus alepadis is transferred to Crinoniscus; the latter genus now contains five species. A modified diagnosis of Crinoniscus is provided.publishedVersio
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Additive Manufacturing (AM) and Nanotechnology: Promises and Challenges
The narrow choice of materials used in Additive Manufacturing (AM) remains a key
limitation to more advanced systems. Nanomaterials offer the potential to advance AM materials
through modification of their fundamental material properties. In this paper, the authors provide
a review of available published literature in which nanostructures are incorporated into AM
printing media as an attempt to improve the properties of the final printed part. Specifically, we
review the research in which metal, ceramic, and carbon nanomaterials have been incorporated
into AM technologies such as stereolithography, laser sintering, fused filament fabrication, and
three-dimensional printing. The purpose of this article is to summarize the research done to date,
to highlight successes in the field, and to identify opportunities that the union of AM and
nanotechnology could bring to science and technology.Mechanical Engineerin
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