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

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

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

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

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

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 Pérez, 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 Pérez, 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

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