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An Evaluation of Non-Stochastic Lattice Structures Fabricated Via Electron Beam Melting
Metal foam structures have many applications and can be used as structural supports, heat
exchangers, shock absorbers, and implant materials. Stochastic metal foams having different cell
sizes and densities have been commercially available for a number of years. This paper addresses
a different type of foams which are known as non-stochastic foams, or lattice structures. These
foams have a well defined repeating unit cell structure rather than the random cell structure in
commercially available stochastic foams. The paper reports on preliminary research on the
fabrication of non-stochastic Ti-6Al-4V alloy foams using the Electron Beam Melting process.
Behavior of the structures in compression, bending, and low cycle repeating load tests are
discussed, and recommendations about cell geometry and processing conditions are made.Mechanical Engineerin
Systematic Improvements in Transmon Qubit Coherence Enabled by Niobium Surface Encapsulation
We present a novel transmon qubit fabrication technique that yields
systematic improvements in T coherence times. We fabricate devices using an
encapsulation strategy that involves passivating the surface of niobium and
thereby preventing the formation of its lossy surface oxide. By maintaining the
same superconducting metal and only varying the surface structure, this
comparative investigation examining different capping materials and film
substrates across different qubit foundries definitively demonstrates the
detrimental impact that niobium oxides have on the coherence times of
superconducting qubits, compared to native oxides of tantalum, aluminum or
titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T
coherence times 2 to 5 times longer than baseline niobium qubit devices with
native niobium oxides. When capping niobium with tantalum, we obtain median
qubit lifetimes above 200 microseconds. Our comparative structural and chemical
analysis suggests that amorphous niobium suboxides may induce higher losses.
These results are in line with high-accuracy measurements of the niobium oxide
loss tangent obtained with ultra-high Q superconducting radiofrequency (SRF)
cavities. This new surface encapsulation strategy enables further reduction of
dielectric losses via passivation with ambient-stable materials, while
preserving fabrication and scalable manufacturability thanks to the
compatibility with silicon processes
Formation of New Bone with Preferentially Oriented Biological Apatite Crystals Using a Novel Cylindrical Implant Containing Anisotropic Open Pores Fabricated by the Electron Beam Melting (EBM) Method
Quasi-static analysis of mechanical properties of Ti6Al4V lattice structures manufactured using selective laser melting
© 2017, Springer-Verlag London Ltd. Selective laser melting (SLM) is a transformative manufacturing process due to its ability to manufacture complex metal parts directly from various bulk powders. With the capability of reducing powder consumption and decreasing fabrication times, lattice structures, which are used as infilling materials within hollow parts, offer an effective solution for decreasing the high costs that currently impede the wider application of SLM in various industries. The assessment of mechanical properties of SLM-built lattice structures, however, remain challenging due to their complicated geometries, while pursuing experimental studies proves to be time-consuming due to the requirement of numerous part fabrication and physical testing. To address these research challenges, this study proposes an analytical modelling approach conducting quasi-static analysis on Ti6Al4V (Ti64) lattice structures. In order to investigate the structures’ mechanical properties, dynamic balance equation of the structures under compression loads were first established, and the stress distribution of the structures was calculated explicitly using central difference method. The modelling approach was validated by conducting uniaxial compression tests on samples fabricated using SLM. The experiments showed that the equivalent elastic modulus (E*) and the ultimate stress (UTS) values of the Ti64 structures predicted by the analytical method were in good agreement with the experimental results. The paper also discusses the design principles of SLM-built lattice structures (mainly the selection of proper topologies and relative densities) and examines the necessity and flexibility of the proposed analytical approach compared with conventional theoretical methods and their experimental studies in the context of SLM process