Metal Lattice Research Articles

Flexible Impact-Resistant Composites with Bioinspired Three-Dimensional Solid–Liquid Lattice Designs

The ubiquitous solid-liquid systems in nature usually present an interesting mechanical property, the rate-dependent stiffness, which could be exploited for impact protection in flexible systems. Herein, a typical natural system, the durian peel, has been systematically characterized and studied, showing a solid-liquid dual-phase cellular structure. A bioinspired design of flexible impact-resistant composites is then proposed by combining 3D lattices and shear thickening fluids. The resulting dual-phase composites offer, simultaneously, low moduli (e.g., 71.9 kPa, lower than those of many reported soft composites) under quasi-static conditions and excellent energy absorption (e.g., 425.4 kJ/m3, which is close to those of metallic and glass-based lattices) upon dynamic impact. Numerical simulations based on finite element analyses were carried out to understand the enhanced buffering of the developed composites, unveiling a lattice-guided fluid-structure interaction mechanism. Such biomimetic lattice-based flexible impact-resistant composites hold promising potential for the development of next-generation flexible protection systems that can be used in wearable electronics and robotic systems.

Ink Tuning for Direct Ink Writing of Planar Metallic Lattices

316L and Cu‐based inks are developed to 3D‐printed tetrachiral auxetic structures. The main objectives of the work are to study the effects of powders composition and powder:binder volume ratio on rheological properties and printability of the inks. Following these results, customized Gcode is developed using FullControl Gcode Designer open‐source software to 3D print intricate tetrachiral auxetic structures. The results reported in this work show how powder composition (316L versus Cu) has less effect on the inks’ rheological behavior than powder size distribution and powders:binder volume ratio. In terms of rheological parameters, the zero‐shear rate viscosity mainly affects the capability of the printed ink to retain its shape after printing, while the yield stress affects the printability. The printed and sintered auxetic structures achieve the intended lattice‐geometry design.

3D printed lattice metal structures for enhanced heat transfer in latent heat storage systems

The low thermal conductivity of Phase Change Materials (PCMs), e.g., paraffin waxes, is one of the main drawbacks of latent heat storage, especially when fast charging and discharging cycles are required. The introduction of highly conductive fillers in the PCM matrix may be an effective solution; however, it is difficult to grant their stable and homogeneous dispersion, which therefore limits the resulting enhancement of the overall thermal conductivity. Metal 3D printing or additive manufacturing, instead, allows to manufacture complex geometries with precise patterns, therefore allowing the design of optimal paths for heat conduction within the PCM. In this work, a device-scale latent heat storage system operating at medium temperatures (∼90 ℃) was manufactured and characterized. Its innovative design relies on a 3D Cartesian metal lattice, fabricated via laser powder bed fusion, to achieve higher specific power densities. Numerical and experimental tests demonstrated remarkable specific power (approximately 714 ± 17 W kg−1 and 1310 ± 48 W kg−1 during heat charge and discharge, respectively). Moreover, the device performance remained stable over multiple charging and discharging cycles. Finally, simulation results were used to infer general design guidelines to further enhance the device performance. This work aims at promoting the use of metal additive manufacturing to design efficient and responsive thermal energy storage units for medium-sized applications, such as in the automotive sector (e.g. speed up of the engine warm up or as an auxiliary for other enhanced thermal management strategies).

Optimization Strategy for Molecular Dynamics Simulations of Nanometric Cutting of Aluminium Alloy Using Molecular Modelling

Atoms constituting a metal define its molecular crystal structure (atomic system) and interact in molecular dynamics simulations of nanometric cutting of the metal. The removal of the material (metal) at nanoscale and generation of high quality surface with a nanometric finish is largely influenced by the mechanical and physical properties of the metal as it associates with the metal lattice (atomistic) structure. Improved studies of the molecular modelling (behaviour of molecules) as it creates mathematical models of molecular properties and behaviour of atomistic systems are required for condition prediction of a nanometric surface finish. In this study, atomic system of rapidly solidified aluminium (RSA) alloy, grade RSA 431, with the use of its alloying elemental compositions by weight percentage is designed and constructed with cell geometry and atom positions that are written into a data file using AtomsK program. In addition, atomic concentration influencing the structural properties of the alloying elements were calculated. Obtained microstructure depicts the spread of the elemental compositions and the data file is suitable for a code performing simulations on classical particles like the large-scale atomic/molecular massively parallel simulator (LAMMPS) software. Understanding the computer simulations (molecular dynamics) for analyzing the physical movements of atoms and molecules, and the peculiar characteristic properties of the composing alloying elements of the RSA 431 determine how much influence each of them (elements) has on the nanometric cutting surface. Hence, the nanometric surface finish of the RSA 431.

Degradation of the internal well equipment steel under continuous service in the corrosive and aggressive environments

Purpose is to analyze steel degradation of the internal well equipment during its continuous service while contacting directly the corrosive environments. Methods. A range of research concerning the damaged metal tubes of the internal equipment for oil and gas wells, in particular regarding continuous service tubing, comprised both standard and specific studies involving different variations of X-ray spectral analysis with the use of scanning electron microscope JSM-35CF (JEOL Company, Japan) and SEM-515 with microanalyzer Link by Philips Company. The studied samples have been made of tubing in the period of the unauthorized and emergency well shutdowns; life of the wells is 0 up to 15 years. To analyze both structure and chemical composition of metal inclusive of such gases as oxygen and hydrogen, chippings were produced mechanically from various parts of tube walls. Findings. X-ray structural studies have made it possible to obtain data confirming cementite decay (Fe3С) in the tube metal during continuous operation of the internal well equipment. X-ray structural analysis methods have helped identify the parameters of crystal lattice of a matrix; and a level of elastic distortions of the lattice (i.e. microstresses of the distortions) has been evaluated as well as carbon distribution within ferrite and cementite. The abovementioned offered the possibility to describe both reason and mechanism of the reduced resistance to corrosion in the context of internal well equipment. Originality. New regularities under cementite decay in tube metal have been identified in addition to changes in the parameters of a crystal a lattice; microstresses of the lattice distortions; and carbon distribution within ferrite and cementite. The aforesaid helps explain in a new way both reason and mechanism of the reduced resistance to corrosion in the context of internal well structures operating continuously in aggressive environments. The basic sources and mechanisms of tube steel degradation, resulting from the metal hydrogenation and oxidation, have been defined which becomes the foundation to develop scientifically the substantiated measures mitigating the negative impact on the condition of the internal well facilities operating continuously in the chemically aggressive environments. Practical implications. Degrading hydrogen effect on the crystal lattice of metal has been proved. The effect creates conditions under which tube structures of oil and gas wells experience their failure.

Mechanical performances of novel cosine function cell-based metallic lattice structures under quasi-static compressive loading

This study proposes a novel lattice structure named cosine function cell-based (CFCB) lattice, in which cell rods are designed in the shape of cosine function curve. Several quasi-static compression tests are conducted to explore their compression behaviors, and their advantages are explored by comparing with traditional body-centered cubic (BCC) lattice structure. Further, influences of several key parameters on mechanical performances are experimentally investigated for CFCB lattice structures. The experimental results indicate that CFCB lattice structures have distinct superiority in compressive stiffness and strength, and their energy absorption characteristics are more than twice as high as those of BCC lattice structure. Further, it is also found that their cell rod diameter and cosine function period length have larger influences on mechanical performances. Subsequently, association relationship between deformation modes and key parameters is numerically explored for CFCB lattice structures, and a distribution map is plotted for their deformation modes. The numerical results indicate that cell rod diameter is positively associated with their energy absorption characteristics, and negatively correlated with their densification strain. Besides, it is also found that the performance indicators exhibit a reducing trend firstly but increase with further raising period length on the whole. With increasing relative density, their energy absorption characteristics and plateau stress show a general upward trend, while a general downward trend is observed in their densification strain. Finally, based on collapse mechanisms of the typical unit cell, theoretical models are deduced to predict equivalent elastic modulus, Poisson’s ratio and plateau stress for the proposed CFCB lattice structures.

Enhancing Mechanical Properties of 3D Printing Metallic Lattice Structure Inspired by Bambusa Emeiensis.

Metallic additive manufacturing process parameters, such as inclination angle and minimum radius, impose constraints on the printable lattice cell configurations in complex components. As a result, their mechanical properties are usually lower than their design values. Meanwhile, due to unavoidable process constraints (e.g., additional support structure), engineering structures filled with various lattice cells usually fail to be printed or cannot achieve the designed mechanical performances. Optimizing the cell configuration and printing process are effective ways to solve these problems, but this is becoming more and more difficult and costly with the increasing demand for properties. Therefore, it is very important to redesign the existing printable lattice structures to improve their mechanical properties. In this paper, inspired by the macro- and meso-structures of bamboo, a bionic lattice structure was partitioned, and the cell rod had a radius gradient, similar to the macro-scale bamboo joint and meso-scale bamboo tube, respectively. Experimental and simulated results showed that this design can significantly enhance the mechanical properties without adding mass and changing the printable cell configuration. Finally, the compression and shear properties of the Bambusa-lattice structure were analyzed. Compared with the original scheme, the bamboo lattice structure design can improve the strength by 1.51 times (β=1.5). This proposed strategy offers an effective pathway to manipulate the mechanical properties of lattice structures simultaneously, which is useful for practical applications.

Microstructure and geometry effects on the compressive behavior of LPBF-manufactured inconel 718 honeycomb structures

This work discusses the combined effect of the microstructure and geometry on the deformation modes and energy-absorbing characteristics of laser powder bed fusion (LPBF)-manufactured Inconel 718 (IN718) hexagonal honeycomb structures tested under quasi-static compression. Three different geometries of the hexagonal cells, varying only in the cell wall thickness (0.4, 0.6 and 0.8 mm) were manufactured using LPBF. Electron backscatter diffraction (EBSD) imaging of the three studied geometries revealed three distinct zones of grain morphologies and textures across the 0.6 and 0.8 mm cell walls and only two zones and higher overall <001> texture across the 0.4 mm cell walls. Miniature tensile tests were performed on 0.4 and 0.8 mm thick tensile samples to evaluate the thickness and orientation effects on the parent material behavior. Each hexagonal geometry was loaded in three different directions resulting in nine study sets. Exhibiting monotonically increasing plateau stress and specific energy absorbed (SEA) in addition to the high SEA/plateau stress ratios, LPBF-manufactured IN718 hexagonal honeycomb structures were demonstrated to be a viable candidate for additively-manufactured (AMed) metallic lattice structures in energy absorption applications. The reduction in the cell wall thickness influenced the instability failure mechanism for the in-plane load direction X1 but no pronounced effect was observed for the in-plane direction X2. As a result of the coupled change of the material properties with the variation in the cell wall thickness, a non-normalized anisotropic form of the Gibson-Ashby model for stochastic foams was proposed to characterize the honeycomb-structure mechanical properties. The findings of this paper more generally provide useful insights into optimizing the design of metallic AMed lattice structures.

An Innovative Method to Analyse the Geometrical Accuracy of Ti6Al4V Octet-Truss Lattice Structures.

Metal lattice structures manufactured utilising additive techniques are attracting increasing attention thanks to the high structural efficiency they can offer. Although many studies exist on the characterisation of massive parts in Ti6Al4V processed by Electron Beam Melting (EBM), several investigations are necessary to characterise the Ti6Al4V lattice structures made by the EBM process. The objective of this paper is to develop a measurement method to assess the dimensional accuracy of Ti6Al4V octet truss lattice structures manufactured by EBM technology. Beam specimens with a 2 mm diameter and different growth orientations with respect to the build direction were analysed. The geometry differences between the designed and the manufactured beam specimens were highlighted. Two effects were identified: (i) The EBM-manufactured beams are generally thinner than the designed ones, and (ii) the shape of the section was found to be almost circular for the beam specimens oriented at 45° and 90°; on the contrary, the section of the horizontal beam (0°) cannot be considered circular.

Optical Characterization of Plasmonic Indium Lattices Fabricated via Electrochemical Deposition.

The optical properties of periodic metallic nanoparticle lattices have found many exciting applications. Indium is an emerging plasmonic material that offers to extend the plasmonic applications given by gold and silver from the visible to the ultraviolet spectral range, with applications in imaging, sensing, and lasing. Due to the high vapor pressure/low melting temperature of indium, nanofabrication of ordered metallic nanoparticles is nontrivial. In this work, we show the potential of selective area electrochemical deposition to generate large-area lattices of In pillars for plasmonic applications. We study the optical response of the In lattices by means of angle-dependent extinction measurements demonstrating strong plasmonic surface lattice resonances and a good agreement with numerical simulations. The results open avenues toward high-quality lattices of plasmonic indium nanoparticles and can be extended to other promising plasmonic materials that can be electrochemically grown.

Massive and fast fabrication of pentamode devices through a multiphase honeycomb-corrugation configuration

Pentamode material (PM) is a special fluid-like acoustic metamaterial with intrinsic broadband merits. The unit cells of PM acoustic devices were based on single-material in previous reports, whose features make the available fabrication techniques very limited and the corresponding fabrication is not economic. In this investigation, a novel PM configuration composed of multi-materials is proposed to facilitate the designing and fabrication of PM devices. The novel multiphase PM configuration contains three parts: honeycomb-corrugation latticed microstructures, mass adjusting weights and interconnecting phases. The mass adjusting weights are bond to metallic latticed structure via interconnecting materials, while metallic lattices are fabricated by stamping forming technique. Simulated Annealing algorithm integrated with numerical homogenization method is developed for optimization of PM designing. A water impedance matching multiphase PM device based on this novel configuration was designed and verified in this study, and it was revealed from both numerical simulation and experiments that the designed multiphase PM device mimicked the acoustic properties of water below 25 kHz. The results indicate that the multiphase PM configuration exhibits superior performance on many aspects such as withstanding much higher hydrostatic pressure, cutting down manufacturing cost by 90% and reducing construction period by 98% compared with conventional techniques.

On the solubility of gases in liquid casting alloys

It has been shown that hydrogen and oxygen atoms cannot be present in the open pores of crystal lattices of base metals of casting alloys. The solubility of gases in liquid casting alloys is a nanostructured process. Hydrogen and oxygen atoms in melts are adsorbed by basic metal elemental nanocrystals. Nitrogen dissolves in liquid iron, nickel and chromium not in atomic form, but in the composition of elementary nanocrystals and nitride molecules. After deoxidation of molten casting alloys, the main gas dissolved in them is hydrogen.

Direct Imprinting of Large-Area Metallic Photonic Lattices for Infrared Polarization Filters with Broadband Tunability.

Metallic photonic lattices are promising in their application to plasmonic optical devices; however, scalable fabrication strategies are limited by sample size, response wavelength (mostly in the visible range), cost, and duration. This paper proposes a direct imprinting strategy to fabricate large-area metallic photonic lattices, which present a strong plasmonic response and broadband angle-resolved tuning properties in the infrared region. This simple fabrication strategy combines solution-synthesized Au nanoparticle colloid and imprinting technology, which does not require the use of photoresist or lithography. Thus, the feature size and response wavelength can exceed the limitations of the beam size and wave band, thereby offering the advantages of a low cost and high throughput.

Methane storage in metal-organic framework HKUST-1 with enhanced heat management using 3D printed metal lattices

The adsorbed natural gas (ANG) concept uses a high-capacity adsorbent packed in the fuel tank allowing high-density fuel storage at a reduced pressure (30–60 bar). One major problem of ANG is during a fast tank filling: generation of heat of adsorption is not released fast, increasing the temperature of the adsorbent and reducing its storage capacity. In this work, we have evaluated the temperature evolution of a storage tank packed with HKUST-1 and subjected to a fast filling of methane under different external heat transfer conditions. When the tank is operated in adiabatic regime, the sudden temperature excursion damaged the HKUST-1 adsorbent with a reduction of 10% of its surface area. To enhance heat transfer and protect the integrity of the adsorbent, the MOF was packed inside 3D printed metal lattices with different lengths. The experiments showed a significant enhancement of the heat transfer which can be particularly beneficial for larger storage tanks.

Deformation Behaviors Investigation of CoCr Alloy Lattice Structures under Compression Test

ith the development of the additive manufacturing method, the production of lattice structures with complex geometries attracts increasing attention. These lattice structures can be designed with the desired properties, and they are encountered in many areas such as automotive, aerospace and aviation, and manufacturing industries, as they offer the freedom to control their physical, mechanical and geometric properties. The high strength characteristic of lattice structures that can be designed at any scale makes these structures useful for producing different designs. Since the mechanical responses of the lattice structures depend on the lattice design parameters, such as the large number of independent struts forming the lattice, cell size and cell geometry, the mechanical behaviour of these structures should be examined. In this study, a porous lattice structure with four different cell models, namely Dode Medium, Diamond, Rhombic Dodecahedron, and Dode Thin, was produced by Selective Laser Melting (SLM) method. In order to reveal the mechanical properties and deformation responses of the porous lattice structures, they were analyzed under compression test and by the finite element method, and experimental and numerical procedures were compared. The effect of the compression test on the lattice properties and how the deformation is distributed throughout the lattice structure were investigated. The finite Element Analysis and Digital Image Processing (DIP) method was used to determine how the lattices deform. The results obtained will be useful for designing new metallic lattice structures with more excellent deformation resistance in future studies.

A novel strategy to improve the compressive characteristic and flexural stiffness of the metallic lattices by introducing the CFRP composite surfaces

A novel strategy to improve the compressive characteristic and flexural stiffness of the metallic lattices by introducing the CFRP composite surfaces

Low-Temperature Plasma Nitriding of Martensitic and Austenitic Steels to Increase Tribocorrosion Resistance*

Abstract Tribocorrosion is the simultaneous occurrence of wear and corrosion in a tribosystem and their interaction. In many applications, such as media-lubricated rolling bearings and (cutting-)tools in the food industry or medicine, tribocorrosion occurs and leads to a high material loss and damage to materials. The tribocorrosion resistance of mechanically and chemically stressed steel surfaces can be significantly increased by low-temperature plasma nitriding at T &lt; 400 °C. In this process, nitrogen is forcibly dissolved in the surface area (up to approx. 20 μm) in high contents of 15 wt.-% without precipitation. This results in an extreme expansion and distortion of the metal lattice (“expanded martensite”, “expanded austenite”), which leads to an increase in hardness of up to 1000 HV with the same or even increased pitting corrosion resistance. Due to the formation of expanded martensite/austenite, the tribocorrosion resistance of the martensitic steels X40Cr14 and X54CrMnN13-2 and that of an austenitic CrMn steel can be significantly improved compared to the initial state, which is expressed in a 40–70 % lower material loss under tribocorrosive attack. It was found that the tribocorrosion resistance depends on the process parameters of the surface treatment and on the chemical composition of the steels and their crystal lattice.

Deformation behavior of metallic lattice structures with symmetrical gradients of porosity manufactured by metal additive manufacturing

Additive manufacturing of complex metallic parts is a topic of broad interest among researchers as it is imperative for critical applications like aerospace parts and biomedical implants. In this work, Functionally Gradient Lattice (FGL) structures confined within top and bottom solid skins are designed and additively manufactured (AM) by Selective Laser Melting (SLM) using Ti–6Al–4V powder. The SLM fabricated samples show the presence of a martensitic microstructure with the strut dimensions correlating with the CAD struct dimensions with slight variations in the micron regime. The struts were attached with non-melted Ti6Al4V powder particles, characteristic of the SLM process. The manufacturability and compressive performance of the struts were assessed, and the deformation behavior was studied using Digital Image Correlation (DIC) technique. The usability of the FGL structures is elucidated by comparing their uniaxial compression test results with uniform BCC structures of the same relative density (RD). The gradient structures were found to function better in both energy absorption characteristics and strength.

Optimized corrosion resistance in pure copper via surface mechanical attrition treatment and subsequent annealing

Surface mechanical attrition treatment (SMAT) was used on the surface refinement of pure copper mainly to study the electrochemical corrosion behavior of pure copper in a 3.5 wt% NaCl solution, under grain refinement and short-time annealing conditions. Fine crystalline copper showed higher corrosion resistance than coarse crystalline copper, and the samples with grain refinement exhibited increased corrosion resistance under annealing conditions. This improvement may be attributable to the enhanced passivation of the surface passivation film after grain refinement. In addition, the residual stress after annealing reduces the activation energy of atoms leaving the metal lattice and entering the solution, reducing the dissolution rate of the anode. Consequently, the corrosion resistance of fine crystalline copper is improved. Grain refinement and short-time annealing help design corrosion-resistant pure copper.

Synthesis of superconducting hcp- ZrH3 under high hydrogen pressure

Zirconium trihydride and, for comparison, trideuteride with hexagonal close-packed (hcp) metal lattices were synthesized at a hydrogen/deuterium pressure of 9 GPa and a temperature of 873 K using toroid-type high-pressure chambers. After a rapid cooling (quenching) to 100 K and lowering the pressure to atmospheric, the quenched sample was removed from the chamber and studied by hot extraction analysis, powder x-ray diffraction, and ac magnetic susceptometry. The hot extraction showed that thermal decomposition of both hcp-${\mathrm{ZrH}}_{3}$ and hcp-${\mathrm{ZrD}}_{3}$ in vacuum begins after heating at a rate of 10 K/min to \ensuremath{\sim}200 K and almost ceases at 270 K, leaving tetragonal $\ensuremath{\varepsilon}\text{\ensuremath{-}}{\mathrm{ZrH}}_{2}/\ensuremath{\varepsilon}\text{\ensuremath{-}}{\mathrm{ZrD}}_{2}$ as a result. The x-ray diffraction study at 85 K gave lattice parameters $a=3.443(2)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=5.964(4)\phantom{\rule{0.16em}{0ex}}\AA{}$ for hcp-${\mathrm{ZrH}}_{3}$ and somewhat smaller values of $a=3.430(5)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=5.947(5)\phantom{\rule{0.16em}{0ex}}\AA{}$ for hcp-${\mathrm{ZrD}}_{3}$. The measurements of magnetic susceptibility revealed superconductivity with an onset at 11.6(1) K for hcp-${\mathrm{ZrH}}_{3}$ and 9.5(2) K for hcp-${\mathrm{ZrD}}_{3}$.