Metallurgical analysis of multiple launch railgun materials

Railgun materials play an important role in electromagnetic launch,and its performance has great effect on the shot-efficiency and lifetime of the launcher.In this paper,the effect of shots number on the performance of multiple launch railgun material under high current conditions is studied by metallurgical analysis.The metallographys of kinds of rails'surface at various locations are observed,and the details of damage zones at different positions are analyzed.The results indicate that molten aluminum from the armature deposits on the rail surface to form a thin film.The deposited film becomes thicker and multi-layered with the increase of shots number.When the velocity is greater than 2 km /s,the gouge phenomenon always appears.The gouge volume of material is measured by 3D laser image and the qualitative observations of the damage are obtained.The evidences show that gouge phenomenon mainly causes by the kinetic energy of the armature and it is related to the shear strength of rail materials closely.By the addition of nano-sized ceramic powders,the shear strength of rail materials increases,the volume of gouge decreases during multiple launches.

Multi-Material Topology Optimization for Spatial-Varying Porous Structures

This paper aims to propose a topology optimization method on generating porous structures comprising multiple materials.The mathematical optimization formulation is established under the constraints of individual volume fraction of constituent phase or total mass,as well as the local volume fraction of all phases.The original optimization problem with numerous constraints is converted into a box-constrained optimization problem by incorporating all constraints to the augmented Lagrangian function,avoiding the parameter dependence in the conventional aggregation process.Furthermore,the local volume percentage can be precisely satisfied.The effects including the globalmass bound,the influence radius and local volume percentage on final designs are exploited through numerical examples.The numerical results also reveal that porous structures keep a balance between the bulk design and periodic design in terms of the resulting compliance.All results,including those for irregular structures andmultiple volume fraction constraints,demonstrate that the proposedmethod can provide an efficient solution for multiple material infill structures.

Additive manufacturing and foundry innovation

Additive manufacturing is expected to transform and upgrade the traditional foundry industry to realize the integrated manufacturing and rapid and low-cost development of high-performance components with complex shapes.The additive manufacturing technology commonly applied in casting mold preparation(fusible molds,sand molds/cores and ceramic cores)mainly includes selective laser sintering(SLS)and binder injection three-dimensional printing(3DP).In this work,the research status of SLS/3DP-casting processes on material preparation,equipment development,process optimization,simulation and application cases in aerospace,automotive and other fields were elaborated.Finally,the developing trends of the additive manufacturing technology in the future of foundry field are introduced,including multi-material sand molds(metal core included),ceramic core-shell integration and die-casting dies with conformal cooling runners.

Color-tunable circularly polarized electroluminescence from a helical chiral multiple resonance emitter with B–N bonds

Chiral B,N-doped polycyclic aromatic hydrocarbons with circularly polarized luminescence(CPL) and small full-width at halfmaxima(FWHM) are promising multiple resonance(MR) emitters for CP organic light-emitting diodes(CP-OLEDs).This work presents a pair of chiral MR enantiomers,P/M-o[B-N]_(2)N_(2),featuring B–N bonds incorporated within a[7]-helicene skeleton.These enantiomers exhibit narrow 0-0 and 0-1 electronic transition bands,whose relative intensity can be fine-tuned by increasing doping concentrations,resulting in redshifts of the emission peak from 542 to 592 nm.The enantiomers show mirrorsymmetric CPL spectra with an asymmetry factor(|g_(PL)|) of 1.0×10^(-3).The hyperfluorescent CP-OLEDs with double-sensitized emitting layers display a FWHM of 33 nm,an external quantum efficiency of 25.1%,and a|g_(EL)|factor of 7.7×10^(-4).Notably,the CP-OLEDs realize color-tunable CP electroluminescence peak from 553 to 613 nm by regulating the vibrational coupling.This work provides a novel concept for the design of helical CP-MR materials and CP-OLEDs,highlighting their potential for future applications in advanced optoelectronic devices.

基于引入ResUNet生成对抗式网络以柔度最小为目标的高效多材料拓扑优化设计

拓扑优化由于其严格的数学理论,成为连续结构设计中决定材料分布的重要方法.然而,随着材料类型在设计域内的增加,传统拓扑优化方法的计算效率大大降低.本文提出了一种基于深度学习的拓扑优化方法,用于提高多材料结构拓扑优化设计的计算效率.首先,利用固体各向同性材料惩罚(SIMP)方法对大量多材料结构进行优化设计,构建了多材料拓扑优化数据集.其次,ResUNet被引入生成对抗式网络形成ResUNet-GAN,构建了设计参数和优化构型之间的高维映射.最后,利用预训练的ResUNet-GAN实现多材料拓扑优化设计.数值模拟验证了ResUNet-GAN成功地应用于双材料的悬臂梁、三材料悬臂梁、三材料简支梁结构的拓扑优化设计.研究表明,基于深度学习拓扑优化方法的计算效率优于传统方法,为高效拓扑优化设计的发展奠定了理论基础.

Multimaterial additive manufacturing manipulator for fabricating magnetoelectric pressure sensors

The simultaneous placement of different types of materials including polymers,ceramics,and metals,in their desired positions could be adopted to manufacture end-use devices/apparatuses with diverse functionalities and significantly reduce the fabrication cost and time.However,existing additive manufacturing(AM)approaches can only treat one material species at a time due to their intrinsic working mechanisms.Here we develop an AM manipulator for manufacturing a wide variety of material species,including polymers,ceramics,and metals,through a multifilament transport strategy assisted by laser power.The six-jaw manipulator contains three pairs of filament delivering/cutting systems for transporting diverse materials and a beam of tunable laser as the thermal source.The whole apparatus is integrated into a robotic manipulator to create a multifreedom manufacturing platform.With this innovation,products with multiple material species and desired complex geometries can be fabricated on demand.Furthermore,we synthesize a multimaterial(polymer/ceramic/metal)printed magnetoelectric pressure sensor that can convert applied mechanical forces to electricity and maintain efficiency even after undergoing 10000 cycles of pressure/recovery.With this multimaterial filament transport and laser manufacturing strategy,our AM manipulator exhibits promising application in the advanced manufacturing of embedded electronics,sensors,soft robotics,and customizable medical devices.

A desktop customised 3D printer with dual extruders to produce electronic circuitry

3D printing has opened new horizons for the manufacturing industry in general, and 3D printers have become the tools for technological advancements. There is a huge divide between the pricing of industrial and desktop 3D printers with the former being on the expensive side capable of producing excellent quality products and latter being on the low-cost side with moderate quality results. However, there is a larger room for improvements and enhancements for the desktop systems as compared to the industrial ones. In this paper, a desktop 3D printer called Prusa Mendel i2 has been modified and integrated with an additional extruder so that the system can work with dual extruders and produce bespoke electronic circuits. The communication between the two extruders has been established by making use of the In-Chip Serial Program- ming port on the Arduino Uno controlling the printer. The biggest challenge is to control the flow of electric paint （to be dispensed by the new extruder） and CFD （Computa- tional Fluid Dynamics） analysis has been carried out to ascertain the optimal conditions for proper dispensing. The final product is a customised electronic circuit with the base of plastic （from the 3D printer＇s extruder） and electronic paint （from the additional extruder） properly dispensed to create a live circuit on a plastic platform. This low-cost enhancement to a desktop 3D printer can provide a new prospect to produce multiple material parts where the additional extruder can be filled with any material that can be properly dispensed from its nozzle.

Active La-Nb-O compounds for fast lithium-ion energy storage

Searching for novel complex materials with enhanced lithium-ion battery performances is one of the most challenging efforts.Many kinds of transition metal oxides and polyanionic frameworks were developed with various structures,which can improve the energy density of lithium-ion batteries.In this work,we explored 4d and 4f transition metal La-Nb-O compounds as cathode materials for lithium-ion energy storage.Orthorhombic pyrochlore LaNb_(5)O_(14),orthorhombic perovskite LaNb_(3)O_(9),and monoclinic LaNbO_(4) compounds with different metal cation coordination polyhedra were synthesized using solid-state reaction.The orthorhombic pyrochlore LaNb_(5)O_(14) compound showed the highest capacity among these La-Nb-O compounds owing to its quasi‐2D network for Li‐ion incorporation.According to the electronegativity theory and ionic size,La^(3+)cations can form LaO12 polyhedra and hexahedral LaO_(8) units in different La-Nb-O compounds,which can stabilize octahedral NbO_(6) and/or pentahedral NbO_(7) and their assembled structures,resulting in easy lithium-ion diffusion.This work may provide some structure clues for the design of electrode materials for fast lithium storage.

An all-optical matrix multiplication scheme with non-linear material based switching system

Optics is a potential candidate in information, data, and image processing. In all-optical data and information processing, optics has been used as information carrying signal because of its inherent advantages of parallelism. Several optical methods are proposed in support of the above processing. In many algebraic, arithmetic, and image processing schemes fundamental logic and memory operations are conducted exploring all-optical devices. In this communication we report an all-optical matrix multiplication operation with non-linear material based switching circuit.