47 research outputs found
Smoothing the Rough Edges: Evaluating Automatically Generated Multi-Lattice Transitions
Additive manufacturing is advantageous for producing lightweight components
while addressing complex design requirements. This capability has been
bolstered by the introduction of unit lattice cells and the gradation of those
cells. In cases where loading varies throughout a part, it may be beneficial to
use multiple, distinct lattice cell types, resulting in multi-lattice
structures. In such structures, abrupt transitions between unit cell topologies
may cause stress concentrations, making the boundary between unit cell types a
primary failure point. Thus, these regions require careful design in order to
ensure the overall functionality of the part. Although computational design
approaches have been proposed, smooth transition regions are still difficult to
achieve, especially between lattices of drastically different topologies. This
work demonstrates and assesses a method for using variational autoencoders to
automate the creation of transitional lattice cells, examining the factors that
contribute to smooth transitions. Through computational experimentation, it was
found that the smoothness of transition regions was strongly predicted by how
closely the endpoints were in the latent space, whereas the number of
transition intervals was not a sole predictor.Comment: 23 Pages, 8 Figure
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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
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Multiple-Material Topology Optimization of Compliant Mechanisms Created via Polyjet 3D Printing
Compliant mechanisms are able to transfer motion, force, and energy using a monolithic
structure without discrete hinge elements. The geometric design freedoms and multi-material
capability offered by the PolyJet 3D printing process enables the fabrication of compliant
mechanisms with optimized topology. The inclusion of multiple materials in the topology
optimization process has the potential to eliminate the narrow, weak, hinge-like sections that are
often present in single-material compliant mechanisms. In this paper, the authors propose a
design and fabrication process for the realization of 3-phase, multiple-material compliant
mechanisms. The process is tested on a 2D compliant force inverter. Experimental and
theoretical performance of the resulting 3-phase inverter is compared against a standard 2-phase
design.Mechanical Engineerin
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Hybrid Geometry/Property Autoencoders for Multi-Lattice Transitions
Additive manufacturing has revolutionized structural optimization by enhancing component
strength and reducing material requirements. One approach used to achieve these improvements
is the application of multi-lattice structures. The performance of these structures heavily relies on
the detailed design of mesostructural elements. Many current approaches use data-driven design
to generate multi-lattice transition regions, making use of models that jointly address the geometry
and properties of the mesostructures. However, it remains unclear whether the integration of
mechanical properties into the data set for generating multi-lattice interpolations is beneficial
beyond geometry alone. To address this issue, this work implements and evaluates a hybrid
geometry/property machine learning model for generating multi-lattice transition regions. We
compare the results of this hybrid model to results obtained using a geometry-only model. Our
research determined that incorporating physical properties decreased the number of variables to
address in the latent space, and therefore improves the ability of generative models for developing
transition regions of multi-lattice structures.Mechanical Engineerin
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Dreaming of Data: Examining Data Augmentation for Machine Learning in Additive Manufacturing
The data generated during additive manufacturing (AM) practice can be used to train machine
learning (ML) tools to reduce defects, optimize mechanical properties, or increase efficiency. In
addition to the size of the repository, emerging research shows that other characteristics of the data
also impact suitability of the data for AM-ML application. What should be done in cases for which
the data in too small, too homogeneous, or otherwise insufficient? Data augmentation techniques
present a solution, offering automated methods for increasing the quality of data. However, many
of these techniques were developed for machine vision tasks, and hence their suitability for AM
data has not been verified. In this study, several data augmentation techniques are applied to
synthetic design repositories to characterize if and to what degree they enhance their performance
as ML training sets. We discuss the comparative advantage of these data augmentation techniques
across several canonical AM-ML tasks.Mechanical Engineerin
Ebola virus persistence in breast milk after no reported illness:A likely source of virus transmission from mother to child
Diverse BRCA1 and BRCA2 Reversion Mutations in Circulating Cell-Free DNA of Therapy-Resistant Breast or Ovarian Cancer
Purpose:; Resistance to platinum-based chemotherapy or PARP inhibition in germline; BRCA1; or; BRCA2; mutation carriers may occur through somatic reversion mutations or intragenic deletions that restore BRCA1 or BRCA2 function. We assessed whether; BRCA1/2; reversion mutations could be identified in circulating cell-free DNA (cfDNA) of patients with ovarian or breast cancer previously treated with platinum and/or PARP inhibitors.; Experimental Design:; cfDNA from 24 prospectively accrued patients with germline; BRCA1; or; BRCA2; mutations, including 19 patients with platinum-resistant/refractory ovarian cancer and five patients with platinum and/or PARP inhibitor pretreated metastatic breast cancer, was subjected to massively parallel sequencing targeting all exons of 141 genes and all exons and introns of; BRCA1; and; BRCA2; Functional studies were performed to assess the impact of the putative; BRCA1/2; reversion mutations on BRCA1/2 function.; Results:; Diverse and often polyclonal putative; BRCA1; or; BRCA2; reversion mutations were identified in cfDNA from four patients with ovarian cancer (21%) and from two patients with breast cancer (40%).; BRCA2; reversion mutations were detected in cfDNA prior to PARP inhibitor treatment in a patient with breast cancer who did not respond to treatment and were enriched in plasma samples after PARP inhibitor therapy. Foci formation and immunoprecipitation assays suggest that a subset of the putative reversion mutations restored BRCA1/2 function.; Conclusions:; Putative; BRCA1/2; reversion mutations can be detected by cfDNA sequencing analysis in patients with ovarian and breast cancer. Our findings warrant further investigation of cfDNA sequencing to identify putative; BRCA1/2; reversion mutations and to aid the selection of patients for PARP inhibition therapy.; Clin Cancer Res; 23(21); 6708-20. ©2017 AACR;
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Exploring the Manufacturability and Resistivity of Conductive Filament Used in Material Extrusion Additive Manufacturing
Additive manufacturing (AM) has the unique ability to build multifunctional parts with
embedded electronics without the need for post-print assembly. However, many existing forms of
multifunctional AM are not easily accessible to hobby-level users. Most hobby-level desktop 3D
printers are only used with non-conductive filaments. Recently however, conductive filaments
have become increasingly available for material extrusion desktop printers. Ideally, the use of these
filaments would allow circuitry to be printed simultaneously with the rest of the structure, enabling
complex, inexpensive, multifunctional structures. However, the resistivity of conductive filament
is significantly impacted by the geometry of the print and the printing parameters used in the build
process. In this study, two types of commercially-available conductive filament were tested under
a variety of parameters. It was found that print temperature, layer height, and orientation all
significantly affect the resistivity in various ways. The knowledge from this research will allow
users to design better multifunctional parts that have reduced resistivity.Mechanical Engineerin
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Influence of Embedding Process on Mechanical Properties of Material Extrusion Parts
The layer-by- layer deposition of material in Additive Manufacturing (AM) introduces the
capability for in-situ embedding of functional components into printed parts. The typical
embedding process involves, i) designing the cavity for the embedded component, ii) pausing the
print when the top layer of the cavity is reached, iii) manually inserting the component, and iv)
resuming the build process. However, the effect of different interfacial materials (due to the
presence or absence of a shape converter) and the pause time during the build process on a part’s
material properties is not well-understood. Therefore, the tensile strength of 3D-printed embedded
specimens with and without shape converters and with different intervals of pause time is tested
in this study. The results from this experimental analysis can be useful for the design guidelines
for AM with embedded components as they provide an initial understanding of mechanical
properties of these parts.Mechanical Engineerin
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Quantifying the Effect of Embedded Component Orientation on Flexural Properties in Additively Manufactured Structures
In-situ embedding with Additive Manufacturing (AM) enables a user to insert functional
components in a part by pausing the print, inserting the component into a specially designed cavity,
and then resuming the print. This introduces the capability to merge the reliable functionality of
external parts into AM structures, allowing multifunctional products to be manufactured in a single
build. Previous research has shown that process interruption introduces weaknesses at the paused
layer, and the presence of an embedding cavity further reduces the maximum tensile strength of
the part. The research presented in this paper expands this understanding by investigating the
impact of the process and design considerations for embedding on the strength of the material
extrusion parts. A cuboidal geometry is embedded with different orientations with a flush surface
at the paused layer, and tested for maximum bending strength. The findings help to further design
guidelines for embedding with material extrusion AM.Mechanical Engineerin