13,672 research outputs found
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Multi-Material Ultrasonic Consolidation
Ultrasonic consolidation (UC) is a recently developed direct metal solid freeform
fabrication process. While the process has been well-demonstrated for part fabrication in Al alloy
3003 H18, including with intricate cooling channels, some of the potential strengths of the
process have not been fully exploited. One of them is its flexibility with build materials and the
other is its suitability for fabrication of multi-material and functionally graded material parts with
enhanced functional or mechanical properties. Capitalizing on these capabilities is critical for
broadening the application range and commercial utilization of the process. In the current work,
UC was used to investigate ultrasonic bonding of a broad range of engineering materials, which
included stainless steels, Ni-base alloys, brass, Al alloys, and Al alloy composites. UC multimaterial part fabrication was examined using Al alloy 3003 as the bulk part material and the
above mentioned materials as performance enhancement materials. Studies were focused on
microstructural aspects to evaluate interface characteristics between dissimilar material layers.
The results showed that most of these materials can be successfully bonded to Al alloy 3003 and
vice versa using the ultrasonic consolidation process. Bond formation and interface
characteristics between various material combinations are discussed based on oxide layer
characteristics, material properties, and others.Mechanical Engineerin
Multi-material additive manufacturing of electronics components: A bibliometric analysis
The study presents a bibliometric analysis of studies conducted on multi-materials printing of electronic com-ponents via additive manufacturing technologies. Using the R package and the associated biblioshiny, the study analyzed publications from Web of Science and Scopus. The study analyzed 405 research articles after removing 104 duplicates. The study applied performance analysis, keyword analysis, and network analysis. The perfor-mance analysis showed that the publications on multi-materials additive manufacturing are multi-disciplinary. Whilst the publications span almost three decades, most contributions started after 2015. The United States of America is the country with the highest production. The keyword analysis showed a changed focus before and after 2015. The trending topics show that the most recent trend is in the 'aerospace industry'. Finally, the thematic analysis shows that the emerging themes in the area are interfaces, moisture, diffusion, microstructure, mechanical properties, and powder metallurgy. These emerging themes are discussed as they are conceived as the future directions of multi-materials printing of electronic components and devices. The current trend of research focuses on understanding and improving the interfacial bonding between the various multi-material interfaces. Overcoming the weak interfacial bonding issues would improve the mechanical properties of multi-materials electronic components
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Virtual Simulation for Multi-material LM Process
In an ONR funded MURI program, to improve quality of multi-material parts,
we've been developing an advanced computer simulation for the multi-material layered
manufacturing (LM) process. The CAD models and their .stLfiles are created using. the
commercially available software such as I-DEAS and ProE. Using this information, one
tool path file per material is generated. Our file preparation algorithm, systematically,
layer by layer, integrates all tool path files into one multi-material tool path file. The
results of the multi-material tool path are graphically visualized using the simulation
algorithm (written in c++ & SGI OpenGL). From a virtual simulation, we can check the
LM process, and make the best selection of tool path parameters afterwards. After several
trials from design to simulation, if the simulation result is acceptable, the real
manufacturing can be started. And the part's quality should be better than a part
manufactured without running simulation in advance. This paper will represent .•. new
studies on using real toadshapes to get more realistic simulation results. Many parts have
been successfully simulated using our method.Mechanical Engineerin
SPH-based simulation of multi-material asteroid collisions
We give a brief introduction to smoothed particle hydrodynamics methods for
continuum mechanics. Specifically, we present our 3D SPH code to simulate and
analyze collisions of asteroids consisting of two types of material: basaltic
rock and ice. We consider effects like brittle failure, fragmentation, and
merging in different impact scenarios. After validating our code against
previously published results we present first collision results based on
measured values for the Weibull flaw distribution parameters of basalt.Comment: Accepted and to be published in Astronomical Note
Total variation regularization of multi-material topology optimization
This work is concerned with the determination of the diffusion coefficient
from distributed data of the state. This problem is related to homogenization
theory on the one hand and to regularization theory on the other hand. An
approach is proposed which involves total variation regularization combined
with a suitably chosen cost functional that promotes the diffusion coefficient
assuming prespecified values at each point of the domain. The main difficulty
lies in the delicate functional-analytic structure of the resulting
nondifferentiable optimization problem with pointwise constraints for functions
of bounded variation, which makes the derivation of useful pointwise optimality
conditions challenging. To cope with this difficulty, a novel reparametrization
technique is introduced. Numerical examples using a regularized semismooth
Newton method illustrate the structure of the obtained diffusion coefficient.
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Multi-Material Stereolithography: Spatially-Controlled Bioactive Poly(Ethylene Glycol) Scaffolds for Tissue Engineering
Challenges remain in tissue engineering to control the spatial and temporal mechanical and
biochemical architectures of scaffolds. Unique capabilities of stereolithography (SL) for
fabricating multi-material spatially-controlled bioactive scaffolds were explored in this work. To
accomplish multi-material builds with implantable materials, a new mini-vat setup was designed,
constructed and placed on top of the existing build platform to allow for accurate and selfaligning X-Y registration during fabrication. Precise quantities of photocrosslinkable solution
were added to and removed from the mini-vat using micro-pipettes. The mini-vat setup allowed
the part to be easily removed and rinsed and different photocrosslinkable solutions could be
easily removed and added to the vat to aid in multi-material fabrication. Two photocrosslinkable
hydrogel biopolymers, poly(ethylene glycol dimethacrylate) (PEG-dma, molecular wt 1,000) and
poly(ethylene glycol)-diacrylate (PEG-da, molecular wt 3,400), were used as the primary
scaffold materials, and controlled concentrations of fluorescently labeled dextran or bioactive
PEG were prescribed and fabricated in different regions of the scaffold using SL. The
equilibrium swelling behavior of the two biopolymers after SL fabrication was determined and
used to design constructs with the specified dimensions at the swollen state. Two methods were
used to measure the spatial gradients enabled by this process with multi-material spatial control
successfully demonstrated down to 500-µm. First, the presence of the fluorescent component in
specific regions of the scaffold was analyzed with fluorescent microscopy. Second, human
dermal fibroblast cells were seeded on top of the fabricated scaffolds with selective bioactivity,
and phase contrast microscopy images were used to show specific localization of cells in the
regions patterned with bioactive PEG. The use of multi-material SL and the relative ease of
conjugating different bioactive ligands or growth factors to PEG allows for the fabrication of
tailored three-dimensional constructs with specified spatially-controlled bioactivity.Mechanical Engineerin
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