Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different purposes.Among them,lattice structures are increasingly used in applications r...Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different purposes.Among them,lattice structures are increasingly used in applications requiring a compromise among lightness and suited mechanical properties,like improved energy absorption capacity and specific stiffness-to-weight and strength-to-weight ratios.A dedicated modeling strategy to assess the energy absorption capacity of lattice structures under uni-axial compression loading is presented in this work.The numerical model is developed in a non-linear framework accounting for the strain rate effect on the mechanical responses of the lattice structure.Four geometries,i.e.,cubic body centered cell,octet cell,rhombic-dodecahedron and truncated cuboctahedron 2+,are investigated.Specifically,the influence of the relative density of the representative volume element of each geometry,the strain-rate dependency of the bulk material and of the presence of the manufacturing process-induced geometrical imperfections on the energy absorption capacity of the lattice structure is investigated.The main outcome of this study points out the importance of correctly integrating geometrical imperfections into the modeling strategy when shock absorption applications are aimed for.展开更多
The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,...The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,however,which feature unique characteristics,pose greater challenges in the LPBF process than solid structures and exhibit more significant distortion.The underlying mechanisms and influencing factors of this distortion remain unclear,presenting a significant research gap.This study investigates the generation mechanism of residual stress in Ti-6Al-4V lattice structures during LPBF and examines how process and geometric parameters influence residual distortion.Lattice-type cantilever structures with various arm thicknesses and strut diameters were fabricated using different laser powers and scan patterns.The residual distortion after removal from the building substrate was measured using a non-contact coordinate-measuring machine.The results suggest that increasing the arm thickness,reducing the strut diameter,and employing a scanning pattern with interlayer rotation effectively reduce residual distortion.Among these factors,the scanning pattern had the most distinct impact,differing significantly from those affecting solid structures.P2(45°)scanning pattern resulted in the greatest residual distortion,approximately twice that of the least distorted pattern.Meanwhile,the laser power exerted a minor influence on the distortion of the lattice structures.These findings provide insights and guidance for fabricating lattice structures using the LPBF process,broadening its applications in aerospace,automotive,and other weight-sensitive industries.展开更多
Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understa...Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understanding the compression behavior and failure mechanism of such structures under loading remains a challenge.In this study,considering the correlation between the strut angle and bearing capacity,body-centered tetragonal(BCT)lattice structures with varying angles are designed based on a body-centered cubic(BCC)structure.BCT Al_(2)O_(3) ceramic lattice structures with varying angles are fabricated by vat photopolymerization.The mechanical properties,deformation process,and failure mechanism of the Al_(2)O_(3) ceramic lattice structures are characterized through a combination of ex-and in-situ X-ray computed tomography(X-CT)compression testing and analyzed using a finite element method(FEM)at macro-and micro-levels.The results demonstrate that as the angle increases,the stress concentration gradually expands from the node to the strut,resulting in an increased loadbearing capacity.Additionally,the failure mode of the Al_(2)O_(3) ceramic lattice structures is identified as diagonal slip shear failure.These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.展开更多
Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanica...Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g-1 at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.展开更多
Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation a...Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.展开更多
Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption(SEA)capacity.In this paper,square-cell latt...Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption(SEA)capacity.In this paper,square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption(EA)performance.Finite element(FE)simulations of in-plane compression are carried out,and the theoretical models from the energy balance principle are developed for calculating the EA of these lattice structures.Satisfactory agreement is achieved between the FE simulation results and the theoretical results.It indicates that the 30◦oriented lattice has the largest EA capacity.Furthermore,inspired by the polycrystal microstructure of metals,novel structures of bi-crystal lattices and quad-crystal lattices are developed through combining multiple singly oriented lattices together.The results of FE simulations of compression indicate that the EA performances of symmetric lattice bi-crystals and quad-crystals are better than those of the identical lattice polycrystal counterparts.This work confirms the feasibility of designing superior energy absorbers with architected meso-structures from the inspiration of metallurgical concepts and microstructures.展开更多
Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal l...Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal lattice structures with triply periodic minimal surfaces is proposed.Four types of lattice structures including uniform,helicoidal,FG,and combined FG and helicoidal are fabricated by the additive manufacturing technology.The deformation behaviors,mechanical properties,energy absorption,and acoustic properties of lattice samples are thoroughly investigated.The load-bearing capability of helicoidal lattice samples is gradually improved in the plateau stage,leading to the plateau stress and total energy absorption improved by over 26.9%and 21.2%compared to the uniform sample,respectively.This phenomenon was attributed to the helicoidal design reduces the gap in unit cells and enhances fracture resistance.For acoustic properties,the design of helicoidal reduces the resonance frequency and improves the peak of absorption coefficient,while the FG design mainly influences the peak of absorption coefficient.Across broad range of frequency from 1000 to 6300 Hz,the maximum value of absorption coefficient is improved by18.6%-30%,and the number of points higher than 0.6 increased by 55.2%-61.7%by combining the FG and helicoidal designs.This study provides a novel strategy to simultaneously improve energy absorption and sound absorption properties by controlling the internal architecture of lattice structures.展开更多
As a new type of lightweight structure,metallic lattice structure has higher stiffness and strength to weight ratio.To freely obtain 316L lattice structures with designed cell structure and adjustable porosity,additiv...As a new type of lightweight structure,metallic lattice structure has higher stiffness and strength to weight ratio.To freely obtain 316L lattice structures with designed cell structure and adjustable porosity,additive manufacturing combined with investment casting was conducted to fabricate the 316L lattice structures with Kelvin cell.The compression simulation of 316L lattice structures with different porosities was carried out by using the finite element method.The numerical simulation results were verified by compression experiment,and the simulated results were consistent with the compression tests.The compressive mechanical properties of 316L lattice structures are directly related to porosity and independent of strut diameters.The 316L lattice structures with Kelvin cell have a smooth stress-strain curve and obvious plastic platform,and the hump stress-strain curves are avoided.展开更多
This study establishes amultiscale andmulti-material topology optimization model for thermoelastic lattice structures(TLSs)consideringmechanical and thermal loading based on the ExtendedMultiscale Finite ElementMethod...This study establishes amultiscale andmulti-material topology optimization model for thermoelastic lattice structures(TLSs)consideringmechanical and thermal loading based on the ExtendedMultiscale Finite ElementMethod(EMsFEM).The corresponding multi-material and multiscale mathematical formulation have been established with minimizing strain energy and structural mass as the objective function and constraint,respectively.The Solid Isotropic Material with Penalization(SIMP)interpolation scheme has been adopted to realize micro-scale multi-material selection of truss microstructure.The modified volume preserving Heaviside function(VPHF)is utilized to obtain a clear 0/1 material of truss microstructure.Compared with the classic topology optimization of single-material TLSs,multi-material topology optimization can get a better structural design of the TLS.The effects of temperatures,size factor,and mass fraction on optimization results have been presented and discussed in the numerical examples.展开更多
In order to solve the problem of substantial computational resources of lattice structure during optimization, a local relative density mapping(LRDM) method is proposed. The proposed method uses solid isotropic micros...In order to solve the problem of substantial computational resources of lattice structure during optimization, a local relative density mapping(LRDM) method is proposed. The proposed method uses solid isotropic microstructures with penalization to optimize a model at the macroscopic scale. The local relative density information is obtained from the topology optimization result. The contour lines of an optimized model are extracted using a density contour approach, and the triangular mesh is generated using a mesh generator. A local mapping relationship between the elements’ relative density and the struts’ relative cross?sectional area is established to automatically determine the diameter of each individual strut in the lattice structures. The proposed LRDM method can be applied to local finite element meshes and local density elements, but it is also suitable for global ones. In addition, some cases are con?sidered in order to test the e ectiveness of the LRDM method. The results show that the solution time of the LRDM is lower than the RDM method by approximately 50%. The proposed method provides instructions for the design of more complex lattice structures.展开更多
Lattice structures with excellent physical properties have attracted great research interest.In this paper,a novel volume parametric modeling method based on the skeleton model is proposed for the construction of thre...Lattice structures with excellent physical properties have attracted great research interest.In this paper,a novel volume parametric modeling method based on the skeleton model is proposed for the construction of threedimensional lattice structures.The skeleton model is divided into three types of nodes.And the corresponding algorithms are utilized to construct diverse types of volume parametric nodes.The unit-cell is assembled with distinct nodes according to the geometric features.The final lattice structure is created by the periodic arrangement of unit-cells.Several different types of volume parametric lattice structures are constructed to prove the stability and applicability of the proposed method.The quality is assessed in terms of the value of the Jacobian matrix.Moreover,the volume parametric lattice structures are tested with the isogeometric analysis to verify the feasibility of integration of modeling and simulation.展开更多
The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma ...The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma lattice structures induced by the nanosecond pulsed laser in the cavity may be similar to the Wigner crystal structure. It is interesting that the beautiful diffraction pattern could be observed in the plasma lattice structure. The radiation lifetime could be shortened to the nanosecond range throughout the entire spectral range and the relaxation time could be lengthened for higher emission efficiency in the Purcell cavity, which results in the fact that the plasmonic emission is stronger and its threshold is lower.展开更多
Star-shaped lattice structures with a negative Poisson’s ratio(NPR)effect exhibit excellent energy absorption capacity,making them highly promising for applications in aerospace,vehicles,and civil protection.While pr...Star-shaped lattice structures with a negative Poisson’s ratio(NPR)effect exhibit excellent energy absorption capacity,making them highly promising for applications in aerospace,vehicles,and civil protection.While previous research has primarily focused on single-walled cells,there is limited investigation into negative Poisson’s ratio structures with nested multi-walled cells.This study designed three star-shaped cell structures and three lattice configurations,analyzing the Poisson’s ratio,stress–strain relationship,and energy absorption capacity through tensile experiments and finite element simulations.Among the single structures,the star-shaped configuration r3 demonstrated the best elastic modulus,NPR effect,and energy absorption effect.In contrast,the uniform lattice structure R3 exhibited the highest tensile strength and energy absorption capacity.Additionally,the stress intensity and energy absorption of gradient structures increased with the number of layers.This study aims to provide a theoretical reference for the application of NPR materials in safety protection across civil and vehicle engineering,as well as other fields.展开更多
Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have ga...Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have garnered increasing research interest.However,most metallic lattice structures generally exhibit anisotropic characteristics,which limits their application ranges.Additionally,a limited number of studies have successfully developed precise mechanical models,which have undergone experimental validation,for the purpose of describing the mechanical response exhibited by additively manufactured metallic lattice structures.In this study,Kelvin lattice structures with varying porosities were systematically designed and fabricated using laser powder bed fusion(LPBF)technology.By integrating finite element simulations with experimental characterization,an enhanced mechanical model was developed through a modification of the Gibson-Ashby model,providing an accurate quantitative description of the relationship between porosity and mechanical properties.The results show that the revised mechanical model can accurately describe the relationship between the geometric parameters and properties of metallic lattice structures.Specifically,the designed Kelvin lattice structures exhibit a smooth stress-strain curve with an obvious yield platform,demonstrating isotropic mechanical properties in all the three spatial directions.This enhances their suitability for complex loading conditions.Meanwhile,the microstructure and manufacturing accuracy of the Kelvin lattice structures were observed and analyzed by micro computed tomography.The results show that the fabricated metallic lattice structures achieved precise dimensional control and optimal densification.This study presents the complete process involved in modeling the Kelvin structure,including its conceptualization,manufacturing,implementation,and ultimately,disposal.展开更多
A novel melting infiltration by ultrasonic vibration was investigated and applied to fabricate Ti6Al4V(TC4)lattice structure-reinforced Mg-10Gd-2Y-1Zn-xZr(refer to VW92 hereafter,x=0,0.5 wt%)alloy matrix composites.Th...A novel melting infiltration by ultrasonic vibration was investigated and applied to fabricate Ti6Al4V(TC4)lattice structure-reinforced Mg-10Gd-2Y-1Zn-xZr(refer to VW92 hereafter,x=0,0.5 wt%)alloy matrix composites.The edge-to-edge matching model indicates that the well-matching and possible orientation relationships(ORs)between theα-Mg andα-Ti,[10-10]_(α-Mg)//[11-23]_(α-Ti) in(0002)_(α-Mg)//(10-10)_(α-Ti) possesses the smallest misfit of 0.4%(f_(r)),and thus theα-Mg grains can nucleate on the TC4 lattice structure.Interfacial reaction occurred in the TC4/VW92+0.5 wt%Zr composites,and the reaction product was confirmed to be Al_(2)Zr_(3),AlZr_(2) andα-Ti(Zr)particles formed by continuous solution of Zr-Ti.Among the interfacial products,the AlZr_(2) phase is a brittle phase with high-volume fraction,which is not conducive to the load transfer.But generally speaking,theα-Ti(Zr)and theα-Mg tend to form a coherent interface,which is beneficial for improving the interfacial bonding strength of composites.展开更多
In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compli...In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compliance of cubic lattice structures.Capitalizing on the periodic spatial distribution,we employ a unit cell methodology to deduce the homogenized stress-strain relationship for the lattice structures,subsequently obtaining the associated equivalent compliance.The equivalent compliance can be conveniently reduced to instances without hypergravity influence.Furthermore,numerical simulations are executed to validate the derivations and to illustrate that hypergravity indeed affects the mechanical properties of lattice structures.We introduce a non-dimensional hypergravity factor,which quantifies the impact of hypergravity magnitude relative to the Young’s modulus of the base material.Our findings reveal that the hypergravity factor influences perpendicular compliance quadratically and parallel compliance linearly.Simultaneously,the perpendicular shear compliance remains unaffected,whereas the parallel shear compliance experiences an inverse effect.Additionally,the lattice structure transforms into a gradient material oriented in the hypergravity direction,consequently generating a scale effect.展开更多
Improving the shape memory effect and superelasticity of Cu-based shape memory alloys(SMAs)has always been a research hotspot in many countries.This work systematically investigates the effects of Gyroid triply period...Improving the shape memory effect and superelasticity of Cu-based shape memory alloys(SMAs)has always been a research hotspot in many countries.This work systematically investigates the effects of Gyroid triply periodic minimal surface(TPMS)lattice structures with different unit sizes and volume fractions on the manufacturing viability,compressive mechanical response,superelasticity and heating recovery properties of CuAlMn SMAs.The results show that the increased specific surface area of the lattice structure leads to increased powder adhesion,making the manufacturability proportional to the unit size and volume fraction.The compressive response of the CuAlMn SMAs Gyroid TPMS lattice structure is negatively correlated with the unit size and positively correlated with the volume fraction.The superelastic recovery of all CuAlMn SMAs with Gyroid TPMS lattice structures is within 5%when the cyclic cumulative strain is set to be 10%.The lattice structure shows the maximum superelasticity when the unit size is 3.00 mm and the volume fraction is 12%,and after heating recovery,the total recovery strain increases as the volume fraction increases.This study introduces a new strategy to enhance the superelastic properties and expand the applications of CuAlMn SMAs in soft robotics,medical equipment,aerospace and other fields.展开更多
Traditional structural forms are difficult to meet the lightweight requirements of subsequent spacecraft for load-bearing structures.In the aerospace industry,filling structure with lattices is a popular approach to r...Traditional structural forms are difficult to meet the lightweight requirements of subsequent spacecraft for load-bearing structures.In the aerospace industry,filling structure with lattices is a popular approach to reduce the weight of a spacecraft.However,this design strategy has deficiencies in the spatial distribution of lattice cells as well as its affection on the mechanical properties.In this study,a two-step topology optimization technique is proposed to solve the spatial distribution problem of nanosatellite.Firstly,an entire nanosatellite box composed of panels which filled with uniform lattices is sent to the vibration test to obtain the frequency data.Then,a finite element(FE)model of the nanosatellite structure which contains the same uniform lattices is built and validated with the obtained frequency data above.For the subsequent calculation of topology optimization.An equivalent model of the verified FE model is established by replacing the lattice cells in the sandwich layer with equivalent fictional elements.Subsequently,a topology optimization problem under the mass constraints is formulated for maximize the nature frequency,and a new light weighted nanosatellite which filled with non-uniform lattices is established by applying the density mapping method and the previous topology configuration result.By separating the design problem of nanosatellite into two steps,the proposed optimization design method achieves the maximum frequency design under the weight constraint.Furthermore,the frequency is also guaranteed to be around the nature frequency.The results reveal that the mass of the new structure with non-uniform lattices is reduced by 50.32%and the frequency is increased by 1.19%.An important technical importance and application value of this proposed technique is that it improves the performance and design efficiency of the load-bearing structures of a nanosatellite,and this method has significant technical significance and application value.展开更多
In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to eluc...In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.展开更多
New techniques have been developed to make materials with a periodic three-dimensional lattice structure. The high stiffness per unit weight and multifunction of such lattice structures make them attractive for use in...New techniques have been developed to make materials with a periodic three-dimensional lattice structure. The high stiffness per unit weight and multifunction of such lattice structures make them attractive for use in aeronautic and astronautic structures. In this paper, epoxy-soaked continuous carbon fibres were first introduced to make lattice composite structures, which maximize the specific load carrying capacity. A micromechanical analysis of several designs, each corresponding to a different manufacturing route, was carried out, in order to find the optimized lattice structure with maximum specific stiffness. An intertwining method was chosen and developed as the best route to make lattice composite materials reinforced by carbon fibers. A sandwich-weaved sample with a three-dimensional intertwined lattice structure core was found to be best. The manufacturing of such a composite lattice material was outlined, In addition to a high shear strength of the core and the integral manufacturing method, the lattice sandwich structure is expected to possess better mechanical capability.展开更多
文摘Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different purposes.Among them,lattice structures are increasingly used in applications requiring a compromise among lightness and suited mechanical properties,like improved energy absorption capacity and specific stiffness-to-weight and strength-to-weight ratios.A dedicated modeling strategy to assess the energy absorption capacity of lattice structures under uni-axial compression loading is presented in this work.The numerical model is developed in a non-linear framework accounting for the strain rate effect on the mechanical responses of the lattice structure.Four geometries,i.e.,cubic body centered cell,octet cell,rhombic-dodecahedron and truncated cuboctahedron 2+,are investigated.Specifically,the influence of the relative density of the representative volume element of each geometry,the strain-rate dependency of the bulk material and of the presence of the manufacturing process-induced geometrical imperfections on the energy absorption capacity of the lattice structure is investigated.The main outcome of this study points out the importance of correctly integrating geometrical imperfections into the modeling strategy when shock absorption applications are aimed for.
基金supported by National Key Research and Development Program of China(Grant No.2021YFB1715400)National Natural Science Foundation of China(Grant No.52105261)High-level Special Funds at the Southern University of Science and Technology(Grant No.G03034K003).
文摘The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,however,which feature unique characteristics,pose greater challenges in the LPBF process than solid structures and exhibit more significant distortion.The underlying mechanisms and influencing factors of this distortion remain unclear,presenting a significant research gap.This study investigates the generation mechanism of residual stress in Ti-6Al-4V lattice structures during LPBF and examines how process and geometric parameters influence residual distortion.Lattice-type cantilever structures with various arm thicknesses and strut diameters were fabricated using different laser powers and scan patterns.The residual distortion after removal from the building substrate was measured using a non-contact coordinate-measuring machine.The results suggest that increasing the arm thickness,reducing the strut diameter,and employing a scanning pattern with interlayer rotation effectively reduce residual distortion.Among these factors,the scanning pattern had the most distinct impact,differing significantly from those affecting solid structures.P2(45°)scanning pattern resulted in the greatest residual distortion,approximately twice that of the least distorted pattern.Meanwhile,the laser power exerted a minor influence on the distortion of the lattice structures.These findings provide insights and guidance for fabricating lattice structures using the LPBF process,broadening its applications in aerospace,automotive,and other weight-sensitive industries.
基金supported by National Natural Science Foundation of China(Grant Nos.52275310,52402084)the China Postdoctoral Science Foundation(Grant No.2024M751646).
文摘Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understanding the compression behavior and failure mechanism of such structures under loading remains a challenge.In this study,considering the correlation between the strut angle and bearing capacity,body-centered tetragonal(BCT)lattice structures with varying angles are designed based on a body-centered cubic(BCC)structure.BCT Al_(2)O_(3) ceramic lattice structures with varying angles are fabricated by vat photopolymerization.The mechanical properties,deformation process,and failure mechanism of the Al_(2)O_(3) ceramic lattice structures are characterized through a combination of ex-and in-situ X-ray computed tomography(X-CT)compression testing and analyzed using a finite element method(FEM)at macro-and micro-levels.The results demonstrate that as the angle increases,the stress concentration gradually expands from the node to the strut,resulting in an increased loadbearing capacity.Additionally,the failure mode of the Al_(2)O_(3) ceramic lattice structures is identified as diagonal slip shear failure.These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.
基金supported by the financial support from the National Natural Science Foundation of China(Nos.51735005 and U1930207)the Basic Strengthening Program(No.2019-JCJQ-JJ-331)+1 种基金National Natural Science Founda-tion of China for Creative Research Groups(No.51921003)the 15th Batch of‘Six Talents Peaks’Innovative Talents Team Program(No.TD-GDZB-001).
文摘Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g-1 at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.
基金supported by the National Natural Science Foundation of China (Grant No. 52175333)Tribology Science Fund of the State Key Laboratory of Tribology,Tsinghua University (Grant No. SKLT2021B05)+1 种基金Foshan Science and Technology Innovation Team Project (Grant No. 2018IT100142)National Science and Technology Major Project of China (Grant No. J2019-VII-0002-0142)
文摘Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.
基金Project supported by the National Natural Science Foundation of China(No.11772231)。
文摘Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption(SEA)capacity.In this paper,square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption(EA)performance.Finite element(FE)simulations of in-plane compression are carried out,and the theoretical models from the energy balance principle are developed for calculating the EA of these lattice structures.Satisfactory agreement is achieved between the FE simulation results and the theoretical results.It indicates that the 30◦oriented lattice has the largest EA capacity.Furthermore,inspired by the polycrystal microstructure of metals,novel structures of bi-crystal lattices and quad-crystal lattices are developed through combining multiple singly oriented lattices together.The results of FE simulations of compression indicate that the EA performances of symmetric lattice bi-crystals and quad-crystals are better than those of the identical lattice polycrystal counterparts.This work confirms the feasibility of designing superior energy absorbers with architected meso-structures from the inspiration of metallurgical concepts and microstructures.
基金supported by the NUS R&G Postdoc Fellowship Program (No.A-0000065-76-00)the China Scholarship Council (No.202006050088)。
文摘Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal lattice structures with triply periodic minimal surfaces is proposed.Four types of lattice structures including uniform,helicoidal,FG,and combined FG and helicoidal are fabricated by the additive manufacturing technology.The deformation behaviors,mechanical properties,energy absorption,and acoustic properties of lattice samples are thoroughly investigated.The load-bearing capability of helicoidal lattice samples is gradually improved in the plateau stage,leading to the plateau stress and total energy absorption improved by over 26.9%and 21.2%compared to the uniform sample,respectively.This phenomenon was attributed to the helicoidal design reduces the gap in unit cells and enhances fracture resistance.For acoustic properties,the design of helicoidal reduces the resonance frequency and improves the peak of absorption coefficient,while the FG design mainly influences the peak of absorption coefficient.Across broad range of frequency from 1000 to 6300 Hz,the maximum value of absorption coefficient is improved by18.6%-30%,and the number of points higher than 0.6 increased by 55.2%-61.7%by combining the FG and helicoidal designs.This study provides a novel strategy to simultaneously improve energy absorption and sound absorption properties by controlling the internal architecture of lattice structures.
基金supported by the Technology Development Fund of the China Academy of Machinery Science and Technology(No.170221ZY01).
文摘As a new type of lightweight structure,metallic lattice structure has higher stiffness and strength to weight ratio.To freely obtain 316L lattice structures with designed cell structure and adjustable porosity,additive manufacturing combined with investment casting was conducted to fabricate the 316L lattice structures with Kelvin cell.The compression simulation of 316L lattice structures with different porosities was carried out by using the finite element method.The numerical simulation results were verified by compression experiment,and the simulated results were consistent with the compression tests.The compressive mechanical properties of 316L lattice structures are directly related to porosity and independent of strut diameters.The 316L lattice structures with Kelvin cell have a smooth stress-strain curve and obvious plastic platform,and the hump stress-strain curves are avoided.
基金the National Natural Science Foundation of China(Nos.U1906233,11732004,Jun Yan,No.12002278,Zunyi Duan)the Key R&D Program of Shandong Province(2019JZZY010801,Jun Yan)the Fundamental Research Funds for the Central Universities(DUT20ZD213,DUT20LAB308,DUT21ZD209,Jun Yan,G2020KY05308,Zunyi Duan).
文摘This study establishes amultiscale andmulti-material topology optimization model for thermoelastic lattice structures(TLSs)consideringmechanical and thermal loading based on the ExtendedMultiscale Finite ElementMethod(EMsFEM).The corresponding multi-material and multiscale mathematical formulation have been established with minimizing strain energy and structural mass as the objective function and constraint,respectively.The Solid Isotropic Material with Penalization(SIMP)interpolation scheme has been adopted to realize micro-scale multi-material selection of truss microstructure.The modified volume preserving Heaviside function(VPHF)is utilized to obtain a clear 0/1 material of truss microstructure.Compared with the classic topology optimization of single-material TLSs,multi-material topology optimization can get a better structural design of the TLS.The effects of temperatures,size factor,and mass fraction on optimization results have been presented and discussed in the numerical examples.
基金National Hi-tech Research and Development Program of China(863 Program,Grant No.2015BAF04B00)China Aerospace Science and Technology Corporation Program of China(CASIC Program,Grant No.461717)
文摘In order to solve the problem of substantial computational resources of lattice structure during optimization, a local relative density mapping(LRDM) method is proposed. The proposed method uses solid isotropic microstructures with penalization to optimize a model at the macroscopic scale. The local relative density information is obtained from the topology optimization result. The contour lines of an optimized model are extracted using a density contour approach, and the triangular mesh is generated using a mesh generator. A local mapping relationship between the elements’ relative density and the struts’ relative cross?sectional area is established to automatically determine the diameter of each individual strut in the lattice structures. The proposed LRDM method can be applied to local finite element meshes and local density elements, but it is also suitable for global ones. In addition, some cases are con?sidered in order to test the e ectiveness of the LRDM method. The results show that the solution time of the LRDM is lower than the RDM method by approximately 50%. The proposed method provides instructions for the design of more complex lattice structures.
基金supported by the National Nature Science Foundation of China under Grant No.52075340.
文摘Lattice structures with excellent physical properties have attracted great research interest.In this paper,a novel volume parametric modeling method based on the skeleton model is proposed for the construction of threedimensional lattice structures.The skeleton model is divided into three types of nodes.And the corresponding algorithms are utilized to construct diverse types of volume parametric nodes.The unit-cell is assembled with distinct nodes according to the geometric features.The final lattice structure is created by the periodic arrangement of unit-cells.Several different types of volume parametric lattice structures are constructed to prove the stability and applicability of the proposed method.The quality is assessed in terms of the value of the Jacobian matrix.Moreover,the volume parametric lattice structures are tested with the isogeometric analysis to verify the feasibility of integration of modeling and simulation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11264007 and 61465003)
文摘The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma lattice structures induced by the nanosecond pulsed laser in the cavity may be similar to the Wigner crystal structure. It is interesting that the beautiful diffraction pattern could be observed in the plasma lattice structure. The radiation lifetime could be shortened to the nanosecond range throughout the entire spectral range and the relaxation time could be lengthened for higher emission efficiency in the Purcell cavity, which results in the fact that the plasmonic emission is stronger and its threshold is lower.
基金support of the National Natural Science Foundation of China(12202038)the Fundamental Research Funds for the Central Universities(FRF-TP-22-028A1).
文摘Star-shaped lattice structures with a negative Poisson’s ratio(NPR)effect exhibit excellent energy absorption capacity,making them highly promising for applications in aerospace,vehicles,and civil protection.While previous research has primarily focused on single-walled cells,there is limited investigation into negative Poisson’s ratio structures with nested multi-walled cells.This study designed three star-shaped cell structures and three lattice configurations,analyzing the Poisson’s ratio,stress–strain relationship,and energy absorption capacity through tensile experiments and finite element simulations.Among the single structures,the star-shaped configuration r3 demonstrated the best elastic modulus,NPR effect,and energy absorption effect.In contrast,the uniform lattice structure R3 exhibited the highest tensile strength and energy absorption capacity.Additionally,the stress intensity and energy absorption of gradient structures increased with the number of layers.This study aims to provide a theoretical reference for the application of NPR materials in safety protection across civil and vehicle engineering,as well as other fields.
基金financially supported by the Liaoning Province Applied Fundamental Research Program (No.2023JH2/101700039)Liaoning Province Natural Science Foundation (No.2023-MSLH-328).
文摘Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have garnered increasing research interest.However,most metallic lattice structures generally exhibit anisotropic characteristics,which limits their application ranges.Additionally,a limited number of studies have successfully developed precise mechanical models,which have undergone experimental validation,for the purpose of describing the mechanical response exhibited by additively manufactured metallic lattice structures.In this study,Kelvin lattice structures with varying porosities were systematically designed and fabricated using laser powder bed fusion(LPBF)technology.By integrating finite element simulations with experimental characterization,an enhanced mechanical model was developed through a modification of the Gibson-Ashby model,providing an accurate quantitative description of the relationship between porosity and mechanical properties.The results show that the revised mechanical model can accurately describe the relationship between the geometric parameters and properties of metallic lattice structures.Specifically,the designed Kelvin lattice structures exhibit a smooth stress-strain curve with an obvious yield platform,demonstrating isotropic mechanical properties in all the three spatial directions.This enhances their suitability for complex loading conditions.Meanwhile,the microstructure and manufacturing accuracy of the Kelvin lattice structures were observed and analyzed by micro computed tomography.The results show that the fabricated metallic lattice structures achieved precise dimensional control and optimal densification.This study presents the complete process involved in modeling the Kelvin structure,including its conceptualization,manufacturing,implementation,and ultimately,disposal.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030006)the National Natural Science Foundation of China (52225101)+2 种基金the Scientific Research Foundation of Chongqing University of Technology (2020ZDZ006)the Science and Technology Research Program of the Chongqing Municipal Education Commission (KJZD-K202201108)the University Innovation Research Group of Chongqing (CXQT20023).
文摘A novel melting infiltration by ultrasonic vibration was investigated and applied to fabricate Ti6Al4V(TC4)lattice structure-reinforced Mg-10Gd-2Y-1Zn-xZr(refer to VW92 hereafter,x=0,0.5 wt%)alloy matrix composites.The edge-to-edge matching model indicates that the well-matching and possible orientation relationships(ORs)between theα-Mg andα-Ti,[10-10]_(α-Mg)//[11-23]_(α-Ti) in(0002)_(α-Mg)//(10-10)_(α-Ti) possesses the smallest misfit of 0.4%(f_(r)),and thus theα-Mg grains can nucleate on the TC4 lattice structure.Interfacial reaction occurred in the TC4/VW92+0.5 wt%Zr composites,and the reaction product was confirmed to be Al_(2)Zr_(3),AlZr_(2) andα-Ti(Zr)particles formed by continuous solution of Zr-Ti.Among the interfacial products,the AlZr_(2) phase is a brittle phase with high-volume fraction,which is not conducive to the load transfer.But generally speaking,theα-Ti(Zr)and theα-Mg tend to form a coherent interface,which is beneficial for improving the interfacial bonding strength of composites.
基金supported by the National Natural Science Foundation of China(Grant Nos.11925206,51988101,and 12272340)Zhejiang Provincial Natural Science Foundation of China(Grant No.LD21A020002).
文摘In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compliance of cubic lattice structures.Capitalizing on the periodic spatial distribution,we employ a unit cell methodology to deduce the homogenized stress-strain relationship for the lattice structures,subsequently obtaining the associated equivalent compliance.The equivalent compliance can be conveniently reduced to instances without hypergravity influence.Furthermore,numerical simulations are executed to validate the derivations and to illustrate that hypergravity indeed affects the mechanical properties of lattice structures.We introduce a non-dimensional hypergravity factor,which quantifies the impact of hypergravity magnitude relative to the Young’s modulus of the base material.Our findings reveal that the hypergravity factor influences perpendicular compliance quadratically and parallel compliance linearly.Simultaneously,the perpendicular shear compliance remains unaffected,whereas the parallel shear compliance experiences an inverse effect.Additionally,the lattice structure transforms into a gradient material oriented in the hypergravity direction,consequently generating a scale effect.
基金supported by the National Natural Science Foundation of China(No.51974028)the Fundamental Research Funds for the Central Universities(No.2021JCCXJD01)the Key R&D and transformation projects in Qinghai Province(No.2023-HZ-801).
文摘Improving the shape memory effect and superelasticity of Cu-based shape memory alloys(SMAs)has always been a research hotspot in many countries.This work systematically investigates the effects of Gyroid triply periodic minimal surface(TPMS)lattice structures with different unit sizes and volume fractions on the manufacturing viability,compressive mechanical response,superelasticity and heating recovery properties of CuAlMn SMAs.The results show that the increased specific surface area of the lattice structure leads to increased powder adhesion,making the manufacturability proportional to the unit size and volume fraction.The compressive response of the CuAlMn SMAs Gyroid TPMS lattice structure is negatively correlated with the unit size and positively correlated with the volume fraction.The superelastic recovery of all CuAlMn SMAs with Gyroid TPMS lattice structures is within 5%when the cyclic cumulative strain is set to be 10%.The lattice structure shows the maximum superelasticity when the unit size is 3.00 mm and the volume fraction is 12%,and after heating recovery,the total recovery strain increases as the volume fraction increases.This study introduces a new strategy to enhance the superelastic properties and expand the applications of CuAlMn SMAs in soft robotics,medical equipment,aerospace and other fields.
文摘Traditional structural forms are difficult to meet the lightweight requirements of subsequent spacecraft for load-bearing structures.In the aerospace industry,filling structure with lattices is a popular approach to reduce the weight of a spacecraft.However,this design strategy has deficiencies in the spatial distribution of lattice cells as well as its affection on the mechanical properties.In this study,a two-step topology optimization technique is proposed to solve the spatial distribution problem of nanosatellite.Firstly,an entire nanosatellite box composed of panels which filled with uniform lattices is sent to the vibration test to obtain the frequency data.Then,a finite element(FE)model of the nanosatellite structure which contains the same uniform lattices is built and validated with the obtained frequency data above.For the subsequent calculation of topology optimization.An equivalent model of the verified FE model is established by replacing the lattice cells in the sandwich layer with equivalent fictional elements.Subsequently,a topology optimization problem under the mass constraints is formulated for maximize the nature frequency,and a new light weighted nanosatellite which filled with non-uniform lattices is established by applying the density mapping method and the previous topology configuration result.By separating the design problem of nanosatellite into two steps,the proposed optimization design method achieves the maximum frequency design under the weight constraint.Furthermore,the frequency is also guaranteed to be around the nature frequency.The results reveal that the mass of the new structure with non-uniform lattices is reduced by 50.32%and the frequency is increased by 1.19%.An important technical importance and application value of this proposed technique is that it improves the performance and design efficiency of the load-bearing structures of a nanosatellite,and this method has significant technical significance and application value.
基金supported by the Defense Industrial Technology Development Program(Grant No.JCKY2018604B004)the National Natural Science Foundation of China(Grant No.11972007)。
文摘In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.
文摘New techniques have been developed to make materials with a periodic three-dimensional lattice structure. The high stiffness per unit weight and multifunction of such lattice structures make them attractive for use in aeronautic and astronautic structures. In this paper, epoxy-soaked continuous carbon fibres were first introduced to make lattice composite structures, which maximize the specific load carrying capacity. A micromechanical analysis of several designs, each corresponding to a different manufacturing route, was carried out, in order to find the optimized lattice structure with maximum specific stiffness. An intertwining method was chosen and developed as the best route to make lattice composite materials reinforced by carbon fibers. A sandwich-weaved sample with a three-dimensional intertwined lattice structure core was found to be best. The manufacturing of such a composite lattice material was outlined, In addition to a high shear strength of the core and the integral manufacturing method, the lattice sandwich structure is expected to possess better mechanical capability.
