Heterogeneous Lattice Research Articles

Synthesis of layered Co9S8-based composites for high-efficiency rotating evaporation of saturated brine

Harvesting freshwater via solar interfacial evaporation is a promising strategy with net-zero emissions. To achieve long-term stable freshwater acquisition, researchers have developed dynamic solar-driven water evaporators. However, these evaporators exhibit limited evaporation rates due to the insufficient photothermal conversion properties of the materials used. In this study, we prepared Co9S8/CoNiO2/Au composite materials through in-situ topological transformation, thereby improving the effect of the heterogeneous crystal lattice mismatch on electron transport. By embedding these materials into a spherical polyurethane sponge, we developed a new type of self-rotating evaporator with a solar full-spectrum absorbance of 95.84 %. The evaporator stably exhibited an evaporation rate of 3.10 kg m−2 h−1 within 240 h in saturated brine. The present work provides insights into the preparation of photothermal composites and the development of high-efficiency stable solar evaporators.

In-situ EBSD study of the active slip systems and substructure evolution in a medium-entropy alloy during tensile deformation

Electron backscatter diffraction (EBSD) coupled with in-situ tensile loading is powerful for investigating the microstructural evolution of alloys. Thermo-mechanically treated f.c.c. medium-entropy alloys (MEAs) typically have high densities of annealing twin boundaries (ATBs), which can not only strengthen but also toughen the MEA via interacting with dislocations. However, the evolution of ATBs and other substructures in plastically-deformed MEA has not yet been revealed. Plastic deformation involving dislocation evolution, active slip systems, lattice rotation, boundary transformation, and grain subdivision in a polycrystalline MEA Ni41.4Co23.3Cr23.3Al3Ti3V6 was studied using in-situ EBSD. The slip was accompanied by heterogeneous lattice rotation among grains and within grains, where inhomogeneous plasticity was accommodated by geometrically-necessary dislocations (GNDs). Both GND and low-angled boundaries (LABs) densities substantially increased with progressive strain, which was mainly concentrated in sites approaching ATBs or grain boundaries (GBs). Located stress, lattice rotation, or curvature caused a loss in the coherence of ATBs, which resulted in integrity loss with increasing strain and promoted a decrease in density by 60 %. Further, lattice rotation incompatibility due to constraints from neighboring grains leads to grain fragmentation into various misorientated volumes, which were separated by LABs or high-angle boundaries (HABs). The grain orientation angle increased with progressive strain and crystallographic 〈111〉 orientation gradually spread toward a tensile direction. Slip systems with maximum Schmid factor were activated first at ε ≥ 3.9 %, which is almost the same with experimental slip traces. Both single slip and double slip occurred during plasticity, where straight slip traces tend to curve due to lattice curvature. Slip transfers are not only controlled by geometric compatibility factor, which can occur between some neighboring grains with low geometric compatibility factor but high Schmid factor.

Variable offsets and processing of implicit forms toward the adaptive synthesis and analysis of heterogeneous conforming microstructure

AbstractThe synthesis of porous, lattice, or microstructure geometries has captured the attention of many researchers in recent years. Implicit forms, such as triply periodic minimal surfaces (TPMS) has captured a significant attention, recently, as tiles in lattices, partially because implicit forms have the potential for synthesizing with ease more complex topologies of tiles, compared to parametric forms. In this work, we show how variable offsets of implicit forms could be used in lattice design as well as lattice analysis, while graded wall and edge thicknesses could be fully controlled in the lattice and even vary within a single tile. As a result, (geometrically) heterogeneous lattices could be created and adapted to follow analysis results while maintaining continuity between adjacent tiles. We demonstrate this ability on several 3D models, including TPMS.

Programmable heterogeneous lamellar lattice architecture for dual mechanical protection

Shear bands frequently appear in lattice architectures subjected to compression, leading to an unstable stress-strain curve and global deformation. This deformation mechanism reduces their energy absorption and loading-bearing capacity and causes the architectures to prioritize mechanical protection of external components at the expense of the entire structure. Here, we leverage the design freedom offered by additive manufacturing and the geometrical relation of dual-phase nanolamellar crystals to fabricate heterogeneous lamellar lattice architectures consisting of body-centered cubic (BCC) and face-centered cubic (FCC) unit cells in alternating lamella. The lamellar lattice demonstrates more than 10 and 9 times higher specific energy absorption and energy absorption efficiency, respectively, compared to the BCC lattice. The drastic improvement arises as the nucleation of shear bands is inhibited by the discrete energy threshold for plastic buckling of adjacent heterogeneous lattice lamella during loading. Despite its lower density than the FCC lattice, the lamellar lattice exhibits significant enhancement in plateau stress and crushing force efficiency, attributed to the strengthening effect induced by simultaneous deformation of unit cells in the BCC lattice lamella and the resulting cushion shielding effect. The design improves the global mechanical properties, making lamellar lattices compare favorably against numerous materials proposed for mechanical protection. Additionally, it provides opportunities to program the local mechanical response, achieving programmable internal protection alongside overall external protection. This work provides a different route to design lattice architecture by combining internal and external dual mechanical protection, enabling a generation of multiple mechanical protectors in aerospace, automotive, and transportation fields.

Phase transitions in a heterogeneous lattice hydrodynamic model involving both communication distance and memory time duration differences

An in-depth analysis of vehicle heterogeneity characteristics in intelligent heterogeneous traffic flows, involving connected autonomous vehicles and human-driven vehicles, is essential to reveal the evolutionary mechanism of congestion and to understand its interaction among traffic factors. It has significant theoretical value in guiding the future field deployment and testing of large-scale connected autonomous vehicles through the systematic analysis of the complex dynamic characteristics of intelligent heterogeneous traffic flows from a traffic engineering perspective, as well as traffic management and control in intelligent heterogeneous traffic flow environments. In this study, the lattice hydrodynamics model is applied to construct a corresponding traffic flow model for the differences of communication capability and historical information memory capability for heterogeneous vehicles. The roles of these heterogeneous properties and their interactions are investigated. Through linear stability analysis and nonlinear analysis, we in this study explore the influence of key traffic factors involving the differences of communication capability and historical information memory capability contributing to ameliorating intelligent heterogeneous traffic dynamics, and numerical simulations are carried out to verify the accuracy and reliability of theoretical analysis. An interesting discovery is that longer memory duration gets better, but the optimizing impact of memory duration on the system being marginally decreasing.

Research on Phase Diagram of an Improved Dual-Lane Heterogeneous Lattice Hydrodynamic Model Considering Curved Road

The actual road traffic is a heterogeneous traffic flow composed of various types of vehicles. Ensuring safe operation of different types of vehicles while improving traffic stabilization has become a very important issue. Inspired by this, taking into account the discrepancy between the safety headway and the maximal velocity of different types of vehicles, an improved dual-lane heterogeneous lattice hydrodynamic model (DLHLHM) considering curved road is put forward in this research. The improved model’s stabilization condition is inferred by reductive perturbation method. The mKdV equation is also inferred to describe the evolutionary processes of traffic density wave. Numerical examples probed into the impact of lane-changing rate, angle of curved road and different maximum speeds and safety distances on traffic stabilization. The hysteresis loop for new model also is explored to study traffic flow stabilization. Numerical simulation results accord with theoretical analysis, which indicates the effectiveness and feasibility of the DLHLHM. This study provides a new perspective on the dynamic evolution of heterogeneous traffic flow.

The Composition of Graded Dental Zirconias

Zirconia dental ceramics have evolved from uniform blocks of 3 mol.% yttria (3Y) to strength- and color-graded blocks containing 3 mol.% and 5 mol.% components. Relatively little is known about the graded materials’ compositions and microstructures. Concerns have been raised about aging and degradation. This study investigated the microstructure, elemental composition, and phase content of different zones of strength- and color-graded zirconia blocks using scanning electron microscopy, x-ray fluorescence, and x-ray diffraction. Specimens were made from green-state blocks using CAD/CAM machining and sintering. Two strength- and color-graded zirconia materials had different grain sizes, elemental compositions, and phase contents between their top and bottom zones, these data being internally consistent as well as being broadly consistent with prior compositional physical property data. A color-graded zirconia material did not exhibit substantial differences between its top and bottom zones, consistent with expectations and previously published data. Modeling phase content for complex yttria-doped zirconia crystal systems with multiple heterogeneous crystal lattices from XRD data was inherently difficult, which may account for the ranges among previously published data; authors should describe detailed methodologies. Detailed compositional data at the scale of the microstructure is needed to relate composition to phase content, physical behavior, including crack evolution.

Superior Lightness-Strength and biocompatibility of bio-inspired heterogeneous glass sponge Ti6Al4V lattice structure fabricated via laser powder bed fusion

Ti6Al4V lattice structures (LSs) have great potentials in medical implants due to their excellent biocompatibility and high strength-to-weight ratio. This paper investigates the manufacturability and performance of unique Ti6Al4V heterogeneous glass sponge (GS) LSs fabricated via laser powder bed fusion (LPBF). Compared with the commonly used LSs, including Cross, body-centered cubic (BCC), Diamond and octet-truss (OCT), Ti6Al4V GS LSs exhibit the strongest compressive strength and energy absorption ability of 58 MPa and 23.84 J/cm3, respectively. Finite element (FE) models are established to evaluate the macroscopic deformation, microscopic stress and strain evolution in the solid struts of five different LSs. Local plastic stresses are found to generate near the nodes of Cross, BCC, Diamond and OCT LSs, thus forming plastic hinges, while the GS LSs can evenly transfer local plastic stresses to the grid-like rods of each layer, eventually showing a uniform stress distribution. Moreover, all the LSs are featured with satisfactory biocompatibility concerning cytotoxicity, cell proliferation, and cell attachment. The results indicate that the Ti6Al4V GS LSs can address the conflict between lightness and strength simultaneously, thus achieving excellent energy absorption performance, compressive properties and great biocompatibility, endowing it with tremendous application potential in the field of medical implants.

Optimization Research of Heterogeneous 2D-Parallel Lattice Boltzmann Method Based on Deep Computing Unit

Optimization Research of Heterogeneous 2D-Parallel Lattice Boltzmann Method Based on Deep Computing Unit

Easy manufacturing constraint based topology optimization of dual-scale and dual-constituent lattice metastructure with thermal dimensional stability

Thermal dimensional stability (TDS) is a crucial issue in the development of high-end industry equipment and precision instruments that work in fluctuating thermal environments. To endow meta-structures with high load-carrying capacity and TDS functionality simultaneously, this paper proposes a topology optimization framework to optimize the topologies of lattice meta-structures at macroscopic structural and microscopic material scales concurrently. An important feature of the current optimization model is the introduction of a material concentration distribution (MCD) constraint to reduce the number of dual-constituent interfaces (DIs), which enables the easy manufacturing of the optimized structures because an additional fabrication process is required for the connection of heterogeneous lattice members. Designs for two dual-scale TDS structures, potentially employed for satellite payload platforms and the supporting structure of space telescopes, are completed. Compared with mono-scale TDS structures, the dual-scale schemes exhibit superior structural performances due to the opening of the dual-scale design space. Numerical experiments are performed to validate the ultra-low structural thermal deformations of the optimized TDS structures with values of 0.0743 μm/℃ and 0.153 μm/℃. Furthermore, the imposition of the MCD constraint significantly reduces the number of DIs from 38 to 10 within a lattice cell, enabling the easy assembly of the demonstrative 3D printing dual-constituent samples.

Dislocation flow turbulence simultaneously enhances strength and ductility

Multi-principal element alloys (MPEAs) exhibit outstanding strength attributed to the complex dislocation dynamics as compared to conventional alloys. Here, we develop an atomic-lattice-distortion-dependent discrete dislocation dynamics framework consisted of random field theory and phenomenological dislocation model to investigate the fundamental deformation mechanism underlying massive dislocation motions in body-centered cubic MPEA. Amazingly, the turbulence of dislocation speed is identified in light of strong heterogeneous lattice strain field caused by short-range ordering. Importantly, the vortex from dislocation flow turbulence not only acts as an effective source to initiate dislocation multiplication but also induces the strong local pinning trap to block dislocation movement, thus breaking the strength-ductility trade-off.

Virtual-Trim: A parametric geometric modeling method for heterogeneous strut-based lattice structures

Abstract Geometric modeling has been integral to the design process with the introduction of Computer-Aided Design. With additive manufacturing (AM), design freedom has reached new heights, allowing for the production of complex lattice structures not feasible with traditional manufacturing methods. However, there remains a significant challenge in the geometric modeling of these lattice structures, especially for heterogeneous strut-based lattice structures. Current methods show limitations in accuracy or geometric control. This paper presents the Virtual-Trim, a novel method for the geometric modeling of heterogeneous strut-based lattice structures that is both efficient and robust. Virtual-Trim begins with user-defined wireframe models and geometric information to create STL (STereoLithography) models ready for AM, eliminating the need for labor-intensive Boolean operations. The fundamental principles and steps involved in Virtual-Trim are extensively described within. Additionally, various models using Virtual-Trim method are designed, and the performance of Virtual-Trim in terms of generation time and model size is analyzed. The successful printing of these models attests to the method’s excellent manufacturability.

Nonlinear Analysis of an Extended Heterogeneous Lattice Hydrodynamic Model Considering on/off-Ramps

To study the impact of on/off-ramps on traffic stability in heterogeneous traffic flow, a novel lattice hydrodynamic model was presented. The new model’s stability condition was determined using the linear stability analysis method. The theoretical results reveal that traffic flow stability is influenced by the proportion of vehicles with different maximum speeds and safe headway, as well as the presence of on-ramps and off-ramps to a certain degree. Through the approximate perturbation method, the mKdV equation and the kink–antikink solution of the traffic density at the jam area are obtained. In order to verify the effectiveness and feasibility of the new model, numerical simulations were conducted to demonstrate on/off ramp effect and different proportions of vehicles which possess bigger maximum velocity or safe space headway affect the traffic stability. The numerical results indicate that in heterogeneous traffic flow scenarios, increasing the ratio of vehicles which possess bigger maximum velocity or bigger safe space headway can lead to a deterioration of traffic stability. The effect of on-ramp could cause traffic instability, while the effect of off-ramp is beneficial for easing traffic congestion.

Reduced order modeling based inexact FETI‐DP solver for lattice structures

SummaryThis paper addresses the overwhelming computational resources needed with standard numerical approaches to simulate architected materials. Those multiscale heterogeneous lattice structures gain intensive interest in conjunction with the improvement of additive manufacturing as they offer, among many others, excellent stiffness‐to‐weight ratios. We develop here a dedicated HPC solver that benefits from the specific nature of the underlying problem in order to drastically reduce the computational costs (memory and time) for the full fine‐scale analysis of lattice structures. Our purpose is to take advantage of the natural domain decomposition into cells and, even more importantly, of the geometrical and mechanical similarities among cells. Our solver consists in a so‐called inexact FETI‐DP method where the local, cell‐wise operators and solutions are approximated with reduced order modeling techniques. Instead of considering independently every cell, we end up with only few principal local problems to solve and make use of the corresponding principal cell‐wise operators to approximate all the others. It results in a scalable algorithm that saves numerous local factorizations. Our solver is applied for the isogeometric analysis of lattices built by spline composition, which offers the opportunity to compute the reduced basis with macro‐scale data, thereby making our method also multiscale and matrix‐free. The solver is tested against various 2D and 3D analyses. It shows major gains compared to black‐box solvers; in particular, problems of several millions of degrees of freedom can be solved with a simple computer within few minutes.

Why the Synthesis Affects Performance of Layered Transition Metal Oxide Cathode Materials for Li-Ion Batteries.

The limited cyclability of high-specific-energy layered transition metal oxide (LiTMO2) cathode materials poses a significant challenge to the industrialization of batteries incorporating these materials. This limitation can be attributed to various factors, with the intrinsic behavior of the crystal structure during the cycle process being a key contributor. These factors include phase transition induced cracks, reduced Li active sites due to Li/Ni mixing, and slower Li+ migration. In addition, the presence of synthesis-induced heterogeneous phases and lattice defects cannot be disregarded as they also contribute to the degradation in performance. Therefore, gaining a profound understanding of the intricate relationship among material synthesis, structure, and performance is imperative for the development of LiTMO2. This paper highlights the pivotal role of structural play in LiTMO2 materials and provides a comprehensive overview of how various control factors influence the specific pathways of structural evolution during the synthesis process. In addition, it summarizes the scientific challenges associated with diverse modification approaches currently employed to address the cyclic failure of materials. The overarching goal is to provide readers with profound insights into the study of LiTMO2.

Andreev reflection in graphene nanoribbons induced by d-wave superconductors

Honeycomb and square lattices are combined as a tight-binding model to examine the Andreev reflection in graphene nanoribbons induced by a superconductor. The superconducting symmetry is assumed to be the d-wave. The zero-bias tunneling conductance peak, which is generally produced by the d-wave superconductor, is absent for the nanoribbons under conditions similar to those when a quantum wire is the normal conductor. For the anisotropic superconductivity, propagating modes appear in the superconductor even for biases below the top of the superconducting energy gap. Features appear in the conductance at the subgap population thresholds of these propagating modes as a finite-size effect of the lattice system. The surface Andreev bound states responsible for the zero-bias anomaly also cause transport resonances in the vicinity of the zero bias despite the aforementioned destruction of the anomaly. The conductance spectra revealing these excitation behaviors are fairly unchanged regardless of the presence of a hopping barrier at the interface with the superconductor. The insensitivity to the interface scattering highlights the fact that barrier-less situation cannot be realized for the model due to the heterogeneous lattice. Concerning specular Andreev reflection, the wavefunction parity gives rise to its blocking for single-mode zigzag-edged nanoribbons. The blocking is suppressed when the anisotropic superconductivity is asymmetric for the nanoribbons.

Chaotic jam and phase transitions in heterogeneous lattice model integrating the delay characteristics difference with passing effect under autonomous and human-driven vehicles environment

In heterogeneous traffic flow, the response delay of different types' vehicles varies. Accordingly, a heterogeneous lattice model is created for the mixed traffic flows including autonomous vehicles and human-driven vehicles accounting for the delay difference characteristics with the passing effect. The neutral stability condition is acquired from the linear stability analysis, which shows that the stability region of the system significantly decreases with the increase of the passing effect, the proportion of regular vehicles and the reaction time coefficient. The kink-antikink solution of the modified Korteweg-de Vries equation is inferred via nonlinear analysis. The jamming transitions occur between the kink jam and no jam regions with lower passing effect. When the passing effect increases to a critical value, a chaotic jam region appears between the kink jam and no jam regions. And the chaotic jam region further expands with higher passing effect. Moreover, simulation experiments indicate that traffic stability gets better with the delayed time falling down in heterogeneous traffic flow. Also, the impact factors of chaos phenomenon, including the passing effect, the delayed time and proportion of regular vehicles, are investigated in heterogeneous lattice model through Poincaré phase diagram and Lyapunov exponent.

Reusability and energy absorption behavior of 4D-printed heterogeneous lattice structures based on biomass shape memory polyester

Uniform triply periodic minimal surfaces (TPMS) have been extensively used due to the good mechanical properties and energy absorption. The hybrid of lattices could combine the advantages of substructures with desirable properties. Moreover, the reusability of TPMS after external loading and the repeated energy absorption capacity are relatively unexplored. Herein, novel heterogeneous TPMS lattices composed of Gyroid and Diamond were designed and manufactured using a biomass shape memory polymer. First, a smooth transition between the adjacent substructures were achieved via structural design. Then, the external force (compression load) and thermal stimulated shape recovery cycles tests were conducted. The results showed that the heterogeneous samples exhibited multiple yielding stages and continuous energy absorption due to the synergistic effect of substructures. The large-deformed TPMS structures were able to recovery to the original shape under thermal stimulation, possessing a high rate of shape fixation and shape recovery (nearly 100 %). After experiencing several cold programming-shape recovery cycles, the total energies of heterogeneous structures did not sharply decrease and no obvious damage was detected by micro-CT, demonstrating a favorable reusability and repeated energy absorption capacity. Therefore, the development of 4D-printed heterogeneous lattice structures have great potentials in smart protective equipment and lightweight smart components.

Mechanical performance of heterogeneous lattice structure

Heterogeneous lattice structure was constructed with rhombic dodecahedron and octet-truss lattice structures. The rhombic dodecahedron lattice was bending-dominated, while octet-truss lattice was stretching-dominated. The rhombic dodecahedron lattice fabricated by selective laser melting (SLM) was compressed by a universal testing machine, which was also investigated by finite element model. Afterwards, the validated numerical model was used to study the designed heterogeneous lattice. Calculations indicates that heterogeneous lattice structures outperform the rhombic dodecahedron lattice structure. The introduction of octet-truss unit cell enhances the mechanical behavior of the heterogeneous lattice structure in terms of Young’s modulus and stress magnitude, which depends on the pattern of octet-truss cells.

Corrigendum to “Heterogeneous lattice hydrodynamic model and jamming transition mixed with connected vehicles and human-driven vehicles” [Physica A 623 (2023) 128903

Corrigendum to “Heterogeneous lattice hydrodynamic model and jamming transition mixed with connected vehicles and human-driven vehicles” [Physica A 623 (2023) 128903