With the continuous advancement in topology optimization and additive manufacturing(AM)technology,the capability to fabricate functionally graded materials and intricate cellular structures with spatially varying micr...With the continuous advancement in topology optimization and additive manufacturing(AM)technology,the capability to fabricate functionally graded materials and intricate cellular structures with spatially varying microstructures has grown significantly.However,a critical challenge is encountered in the design of these structures–the absence of robust interface connections between adjacent microstructures,potentially resulting in diminished efficiency or macroscopic failure.A Hybrid Level Set Method(HLSM)is proposed,specifically designed to enhance connectivity among non-uniform microstructures,contributing to the design of functionally graded cellular structures.The HLSM introduces a pioneering algorithm for effectively blending heterogeneous microstructure interfaces.Initially,an interpolation algorithm is presented to construct transition microstructures seamlessly connected on both sides.Subsequently,the algorithm enables the morphing of non-uniform unit cells to seamlessly adapt to interconnected adjacent microstructures.The method,seamlessly integrated into a multi-scale topology optimization framework using the level set method,exhibits its efficacy through numerical examples,showcasing its prowess in optimizing 2D and 3D functionally graded materials(FGM)and multi-scale topology optimization.In essence,the pressing issue of interface connections in complex structure design is not only addressed but also a robust methodology is introduced,substantiated by numerical evidence,advancing optimization capabilities in the realm of functionally graded materials and cellular structures.展开更多
Cellular thin-shell structures are widely applied in ultralightweight designs due to their high bearing capacity and strength-to-weight ratio.In this paper,a full-scale isogeometric topology optimization(ITO)method ba...Cellular thin-shell structures are widely applied in ultralightweight designs due to their high bearing capacity and strength-to-weight ratio.In this paper,a full-scale isogeometric topology optimization(ITO)method based on Kirchhoff-Love shells for designing cellular tshin-shell structures with excellent damage tolerance ability is proposed.This method utilizes high-order continuous nonuniform rational B-splines(NURBS)as basis functions for Kirchhoff-Love shell elements.The geometric and analysis models of thin shells are unified by isogeometric analysis(IGA)to avoid geometric approximation error and improve computational accuracy.The topological configurations of thin-shell structures are described by constructing the effective density field on the controlmesh.Local volume constraints are imposed in the proximity of each control point to obtain bone-like cellular structures.To facilitate numerical implementation,the p-norm function is used to aggregate local volume constraints into an equivalent global constraint.Several numerical examples are provided to demonstrate the effectiveness of the proposed method.After simulation and comparative analysis,the results indicate that the cellular thin-shell structures optimized by the proposed method exhibit great load-carrying behavior and high damage robustness.展开更多
Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully...Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.展开更多
Cellular structures are regarded as excellent candidates for lightweight-design,load-bearing,and energy-absorbing applications.In this paper,a novel S-based TPMS hollow isotropic cellular structure is proposed with bo...Cellular structures are regarded as excellent candidates for lightweight-design,load-bearing,and energy-absorbing applications.In this paper,a novel S-based TPMS hollow isotropic cellular structure is proposed with both superior load-bearing and energy-absorbing performances.The hollow cellular structure is designed with Boolean operation based on the Fischer-Koch(S)implicit triply periodic minimal surfaces(TPMS)with different level parameters.The anisotropy and effective elasticity properties of cellular structures are evaluated with the numerical homogenization method.The finite element method is further conducted to analyze the static mechanical performance of hollow cellular structure considering the size effect.The compression experiments are finally carried out to reveal the compression properties and energy-absorption characteristics.Numerical results of the Zener ratio proved that the S-based hollow cellular structure tends to be isotropic,even better than the sheet-based Gyroid TPMS.Compared with the solid counterpart,the S-based hollow cellular structure has a higher elastic modulus,better load-bearing and energy absorption characteristics.展开更多
Functional graded cellular structure(FGCS)usually shows superiormechanical behaviorwith lowdensity and high stiffness.With the development of additivemanufacturing,functional graded cellular structure gains its popula...Functional graded cellular structure(FGCS)usually shows superiormechanical behaviorwith lowdensity and high stiffness.With the development of additivemanufacturing,functional graded cellular structure gains its popularity in industries.In this paper,a novel approach for designing functionally graded cellular structure is proposed based on a subdomain parameterized level set method(PLSM)under local volume constraints(LVC).In this method,a subdomain level set function is defined,parameterized and updated on each subdomain independently making the proposed approach much faster and more cost-effective.Additionally,the microstructures on arbitrary two adjacent subdomains can be connected perfectly without any additional constraint.Furthermore,the local volume constraint for each subdomain is applied by virtue of the augmented Lagrange multiplier method.Finally,several numerical examples are given to verify the correctness and effectiveness of the proposed approach in designing the functionally graded cellular structure.From the optimized results,it is also found that the number of local volume constraints has little influence on the convergence speed of the developed approach.展开更多
The microstructural modification for cellular structures can achieve the improvement of dynamic me-chanical properties of a selective laser melted FeCoNiCrMo_(0.2)high-entropy alloy(SLM-FeCoNiCrMo_(0.2)HEA)and can exp...The microstructural modification for cellular structures can achieve the improvement of dynamic me-chanical properties of a selective laser melted FeCoNiCrMo_(0.2)high-entropy alloy(SLM-FeCoNiCrMo_(0.2)HEA)and can expand its promising applications in the field of high-velocity deformation.In this work,FeCoNiCrMo_(0.2)HEAs with cellular structures in different sizes were produced by selective laser melt-ing(SLM)with different process parameters.The dynamic mechanical properties and microstructure of the SLM-FeCoNiCrMo_(0.2)HEA were studied.The dynamic mechanical properties of the SLM-FeCoNiCrMo_(0.2)HEA increased with decrease of average size of cellular structures,and the values of them were sensitive to strain rates.The energy absorption,compressive strength and yield strength of the SLM-FeCoNiCrMo_(0.2)HEAs reached 315.6 MJ/m^(3),2.2 GPa and 775.6 MPa,respectively at a strain rate of 2,420 s^(−1),under the process parameters of laser power and scanning speed of 330 W and 800 mm/s,respectively,where the corresponding average size of cellular structures in the HEAs was 483.6 nm.The value of strain-hardening rate of the SLM-FeCoNiCrMo_(0.2)HEA was about 5.1 GPa at a strain level of 0.1,which was much higher than that of the powder-metallurgy FeCoNiCrMo_(0.2)HEA.The cellular structure was formed inside the molten pool with segregation of Mo on the boundary.Deformation localization appeared in the cellular structures,forming several deformation bands after high strain-rate deformation.The elemental segre-gation strengthening and dislocation strengthening are considered to be the main strengthening mecha-nisms in SLM-FeCoNiCrMo_(0.2)HEA.展开更多
The properties of functionally graded(FG) cellular structures vary spatially, and the varying properties can meet the requirements of different working environments. In this study, we fabricated FG cellular structures...The properties of functionally graded(FG) cellular structures vary spatially, and the varying properties can meet the requirements of different working environments. In this study, we fabricated FG cellular structures with shape memory effect by 4D printing and evaluated the compressive performance and shape memory behavior of these structures with temperature through experimental analysis and finite element simulations. The results show that the maximum energy absorption gradually decreases but the compressive modulus gradually increases with increasing gradient parameters. Moreover, the finite element simulations also show that the compressive deformation mode of the structure shifts from uniform to non-uniform deformation with increasing gradient parameters. The compressive modulus and compressive strength of 4D printed FG structures decrease with increasing temperature due to the influence of the shape memory polymer, and they exhibit outstanding shape recovery capability under high-temperature stimulus. The proposed 4D printed FG structures with such responsiveness to stimulus shed light on the design of intelligent energy-absorbing devices that meet specific functional requirements.展开更多
The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natu...The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natural organisms,have exhibited exceptional structural utilization in terms of energy absorption compared with traditional structures.In recent years,various innovative cellular structures have been proposed to meet different engineering needs,resulting in significant performance improvements.This paper provides a comprehensive overview of novel cellular structures for energy absorption applications.In particular,it outlines the application forms and design concepts of cellular structures under typical loading conditions in vehicle collisions,including axial loading,oblique loading,bending loading,and blast loading.Cellular structures have evolved to meet the demands of complex loading conditions and diverse research methods,focusing on achieving high-performance characteristics across multiple load cases.Moreover,this review discusses manufacturing techniques and strate-gies for enhancing the manufacturing performance of cellular structures.Finally,current key challenges and future research directions for cellular structures are discussed.The aim of this study is to provide valuable guidelines for researchers and engineers in the development of next-generation lightweight cellular structures.展开更多
Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the the...Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process.It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side.When polyethylene terephthalate(PET)films were applied,the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate(PC)and thermoplastic polyurethane(TPU)films.And the effects of film types on the cellular structure,forming defects and mechanical properties of IMD/MIM parts were also studied experimentally.The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts.Under certain film thickness,the offset distance of core layer was the largest with PET film used,while the offset distance was the smallest with TPU film used.And similar results were found for the warpage of the parts.However,an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.展开更多
Shaped Mg alloy foams with closed-cell structure are highly interested for a great potential to be utilized in the fields where weight reduction is urgently required.A powder metallurgical method,namely gas release re...Shaped Mg alloy foams with closed-cell structure are highly interested for a great potential to be utilized in the fields where weight reduction is urgently required.A powder metallurgical method,namely gas release reaction powder metallurgy route to fabricate Mg-X(X=Al,Zn or Cu)alloy foams,was summarized.The principles on shaped Mg-X foams fabrication via the route were proposed.In addition,the effects of alloying elements,sintering treatment and foaming temperatures on fabrication of shaped Mg-X alloy foams were investigated experimentally.The results show that the key to ensure a successful foaming of Mg-X alloy foams is to add alloying metals alloyed with Mg to form lower melting(<600℃)intermetallic compounds by the initial sintering treatment.The foaming mechanism of Mg-X alloy foams also has been clarified,that is,the low-melting-point Mg-based intermetallic compounds melt first,and then reactions between the melt and CaCO_(3),a foaming agent,release CO gas to make the precursor foamed and finally shaped Mg-X alloy foam with a promising cellular structure is prepared.This route has been verified by successful fabrication on shaped Mg-Al,Mg-Zn and Mg-Cu foams with cellular structure.展开更多
The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone ti...The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone tissue in-growth.However,there is a gap in the knowledge in regard to the relationship between the pore characteristics and the electrochemical performance of open-cellular structured titanium alloys.In this study,we elucidate the influence of pore characteristics on the electrochemical performance of open-cellular structured Ti-6Al-4V alloys produced by electron beam melting(EBM).Intriguingly,the passive film formed on cellular structured Ti-6Al-4V alloy with a larger pore size was more stable and protective,and the corrosion performance was superior compared to the samples with a smaller pore size in phosphate buffered saline(PBS),mainly because of relatively smaller exposed surface area and unlimited flow of electrolyte.However,in acidic PBS containing fluoride ions,the pore characteristics did not play an important role in the corrosion resistance.It was considered that the protective film breaks down such that the corrosion performance of cellular structured alloys was comparable to each other in this harsh environment.展开更多
An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard frag...An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard fragment has the fourth degree of axial symmetry.The classification of the polar structures are described and a method of various quadra-structure synthesis is developed.A possibility to provide high strength of the structure due to preservation of faces reinforcement pattern is presented.Arrangement of the plane core on a bi-curvature surface is also introduced.Besides,provision of isotropy of the core in two or three directions are described.Finally,examples of cellular folded cores manufactured from basalt reinforced plastic are demonstrated.展开更多
This paper aims to instantly predict within any accuracy the stress distribution of cellular structures under parametric design,including the shapes or distributions of the cell geometries,or the magnitudes of externa...This paper aims to instantly predict within any accuracy the stress distribution of cellular structures under parametric design,including the shapes or distributions of the cell geometries,or the magnitudes of external loadings.A classical model reduction technique has to balance the simulation accuracy and interaction speed,and has difficulty achieving this goal.We achieve this by computing offline a design-to-stress mapping that ultimately expresses the stress distribution as an explicit function in terms of its design parameters.The mapping is determined as a solution to an extended finite element analysis problem in a high-dimension space,including both the spatial coordinates and the design parameters.The well-known curse of dimensionality intrinsic to the high-dimension problem is(partly)resolved through a spatial separation using two main techniques.First,the target mapping takes a reduced form as a sum of the products of separated one-variable functions,extending the proper generalized decomposition technique.Second,the simulation problem in a varied computation domain is reformulated as that in a fixed-domain,taking an integration function as the sum of the products of separated one-variable functions,in combination with high-order singular value decomposition.Extensive 2D and 3D examples are shown to demonstrate the approach’s performance.展开更多
To adapt the practical demand,designing and constructing the multifunctional microwave absorbers(MAs)is the key future direction of research and development.However,effective integrating the multiple functions into a ...To adapt the practical demand,designing and constructing the multifunctional microwave absorbers(MAs)is the key future direction of research and development.However,effective integrating the multiple functions into a single material remains a huge challenge.Herein,cellular carbon foams(CCFs)with different porous structures were elaborately designed and fabricated in high efficiency through a facile continuous freeze-drying and carbonization processes using a sustainable biomass chitosan as the precursor.The obtained results revealed that the thermal treated temperature and g-C_(3)N_(4) amount played a great impact on the carbonization degrees,pore sizes,and morphologies of CCFs,which led to their tunable electromagnetic(EM)parameters,improved conduction loss,and polarization loss abilities.Owing to the special cellular structure,the designed CCFs samples simultaneously displayed the strong absorption capabilities,broad absorption bandwidths,and thin matching thicknesses.Meanwhile,the as-prepared CCFs exhibited the strong hydrophobicity and good thermal insulation,endowing its attractive functions of self-cleaning and thermal insulation.Therefore,our findings not only presented a facile approach to produce different porous structures of CCFs,but also provided an effective strategy to develop multifunctional high-performance MAs on basis of three-dimensional CCFs.展开更多
In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as c...In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as cross-linking agent and TEMPO as cross-linking inhibitor,azodicarbonamide (AC) was used as foaming agent and citric acid as foaming promoter.The density,expansion ratio,cellular structure and mechanical property of these two kinds of controllable materials were studied.Experimental results show that,properties of these two kinds of materials appear similar trend:cellular size and expansion ratio are enlarged with the amount of cross-linking inhibitor or foaming promoter increasing,while density and mechanical strength appear decreasing trend.Through comparing those two material systems’ properties,cross-linking polyethelene foaming system with citric acid as foaming promoter has better properties.展开更多
In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ...In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ZrO_(2)contents and investigated the influence of the ZrO_(2)content on the magnetic properties and resistive anisotropism.The results showed that not only was the resistivity of the magnet improved,but,in addition,the coercivity of the magnet was significantly increased.The microstructure was studied with TEM,which showed that ZrO_(2)doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures.The increased grain boundaries and Sm_(2)O_(3)phases were favorable to the improvement of resistivity.The decrease of the lamellar phases caused a narrowing of the resistive anisotropism.The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However,an excessive amount caused an increase of the Zr_6(Fe Co)_(23)phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity.展开更多
Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different struc...Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.展开更多
We have investigated the low cycle fatigue(LCF)properties and the extent of strengthening in a dense additively manufactured stainless steel containing different volume fractions of cell structures but having all othe...We have investigated the low cycle fatigue(LCF)properties and the extent of strengthening in a dense additively manufactured stainless steel containing different volume fractions of cell structures but having all other microstructure characteristics the same.The samples were produced by laser powder bed fusion(L-PBF),and the concentration of cell structures was varied systematically by varying the annealing treatments.Load-controlled fatigue experiments performed on samples with a high fraction of cell structures reveal an up to 23 times increase in fatigue life compared to an essentially cell-free sample of the same grain configuration.Multiscale electron microscopy characterizations reveal that the cell structures serve as the soft barriers to the dislocation propagation and the partials are the main carrier for cyclic loading.The cell structures,stabilized by the segregated atoms and misorientation between the adjacent cells,are retained during the entire plastic deformation,hence,can continuously interact with dislocations,promote the formation of nanotwins,and provide massive 3D network obstacles to the dislocation motion.The compositional micro-segregation caused by the cellular solidification features serves as another nonnegligible strengthening mechanism to dislocation motion.Specifically,the cell structures with a high density of dislocation debris also appear to act as dislocation nucleation sites,very much like coherent twin boundaries.This work indicates the potential of additive manufacturing to design energy absorbent alloys with high performance by tailoring the microstructure through the printing process.展开更多
Additive manufacturing is believed to open up a new era in precise microfabrication,and the dynamic microstructure evolution during the process as well as the experiment-simulation correlated study is conducted on a p...Additive manufacturing is believed to open up a new era in precise microfabrication,and the dynamic microstructure evolution during the process as well as the experiment-simulation correlated study is conducted on a prototype multi-principal-element alloys FeCrNi fabricated using selective laser melting(SLM).Experimental results reveal that columnar crystals grow across the cladding layers and the dense cellular structures develop in the filled crystal.At the micron scale,all constituent elements are evenly distributed,while at the near-atomic scale,Cr element is obviously segregated.Simulation results at the atomic scale illustrate that i)the solid-liquid interface during the grain growth changes from horizontal to arc due to the radial temperature gradient;ii)the precipitates,microscale voids,and stacking faults also form dynamically as a result of the thermal gradient,leading to the residual stress in the SLMed structure.In addition,we established a microstructure-based physical model based on atomic simulation,which indicates that strong interface strengthening exists in the tensile deformation.The present work provides an atomic-scale understanding of the microstructural evolution in the SLM process through the combination of experiment and simulation.展开更多
New ambient sound absorption material,lightweight isocyanate-based polyimide foam(IBPIF),was fabricated by operable combination between different distinctive acoustic IBPIF.Cellular structure of IBPIF was facilely and...New ambient sound absorption material,lightweight isocyanate-based polyimide foam(IBPIF),was fabricated by operable combination between different distinctive acoustic IBPIF.Cellular structure of IBPIF was facilely and obviously adjusted by increased slurry temperature corresponding to change in distinctive acoustic properties.Moreover,density of all IBPIF kept at only 12-17 kg/m3.With increasing slurry temperature from 0℃to 40℃,cell size and window opening rate gradually increased from 553μm to 791μm and from 6.85%to 58.46%,respectively.In this study,IBPIF generated by slurries at 0℃(marked as PIF-2)and 40℃(marked as PIF-6)showed best and distinctive acoustic behavior in 315-800 Hz and 800-6300 Hz regions,respectively.After acoustic behavior study of combined IBPIF prepared by stitching combination between two distinctive acoustic IBPIFs,results showed that only when PIF-6 sheet used as sound receiving surface even though with thickness of only 10 mm could the combined IBPIF possess the best acoustic level in 800-6300 Hz region as PIF-6.Furtherly,acoustic behavior in 315-800 Hz region could be significantly enhanced by increasing thickness of PIF-2 and could reach or close to the best acoustic level.展开更多
基金the National Key Research and Development Program of China(Grant Number 2021YFB1714600)the National Natural Science Foundation of China(Grant Number 52075195)the Fundamental Research Funds for the Central Universities,China through Program No.2172019kfyXJJS078.
文摘With the continuous advancement in topology optimization and additive manufacturing(AM)technology,the capability to fabricate functionally graded materials and intricate cellular structures with spatially varying microstructures has grown significantly.However,a critical challenge is encountered in the design of these structures–the absence of robust interface connections between adjacent microstructures,potentially resulting in diminished efficiency or macroscopic failure.A Hybrid Level Set Method(HLSM)is proposed,specifically designed to enhance connectivity among non-uniform microstructures,contributing to the design of functionally graded cellular structures.The HLSM introduces a pioneering algorithm for effectively blending heterogeneous microstructure interfaces.Initially,an interpolation algorithm is presented to construct transition microstructures seamlessly connected on both sides.Subsequently,the algorithm enables the morphing of non-uniform unit cells to seamlessly adapt to interconnected adjacent microstructures.The method,seamlessly integrated into a multi-scale topology optimization framework using the level set method,exhibits its efficacy through numerical examples,showcasing its prowess in optimizing 2D and 3D functionally graded materials(FGM)and multi-scale topology optimization.In essence,the pressing issue of interface connections in complex structure design is not only addressed but also a robust methodology is introduced,substantiated by numerical evidence,advancing optimization capabilities in the realm of functionally graded materials and cellular structures.
基金supported by the National Key R&D Program of China(Grant Number 2020YFB1708300)China National Postdoctoral Program for Innovative Talents(Grant Number BX20220124)+1 种基金China Postdoctoral Science Foundation(Grant Number 2022M710055)the New Cornerstone Science Foundation through the XPLORER PRIZE,the Knowledge Innovation Program of Wuhan-Shuguang,the Young Top-Notch Talent Cultivation Program of Hubei Province and the Taihu Lake Innovation Fund for Future Technology(Grant Number HUST:2023-B-7).
文摘Cellular thin-shell structures are widely applied in ultralightweight designs due to their high bearing capacity and strength-to-weight ratio.In this paper,a full-scale isogeometric topology optimization(ITO)method based on Kirchhoff-Love shells for designing cellular tshin-shell structures with excellent damage tolerance ability is proposed.This method utilizes high-order continuous nonuniform rational B-splines(NURBS)as basis functions for Kirchhoff-Love shell elements.The geometric and analysis models of thin shells are unified by isogeometric analysis(IGA)to avoid geometric approximation error and improve computational accuracy.The topological configurations of thin-shell structures are described by constructing the effective density field on the controlmesh.Local volume constraints are imposed in the proximity of each control point to obtain bone-like cellular structures.To facilitate numerical implementation,the p-norm function is used to aggregate local volume constraints into an equivalent global constraint.Several numerical examples are provided to demonstrate the effectiveness of the proposed method.After simulation and comparative analysis,the results indicate that the cellular thin-shell structures optimized by the proposed method exhibit great load-carrying behavior and high damage robustness.
基金Funded by the National Innovation Platform Open Fund(No.2017YJ163)
文摘Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.
基金This research was funded by the National Natural Science Foundation of China(NSFC,Project No.51775308)National Natural Science Foundation of Hubei(No.2021CFB236)+1 种基金Youth Talent Project of Hubei Provincial Department of Education(No.Q20201205)Hubei Key Laboratory of Hydroelectric Machinery Design&Maintenance Open Foundation(No.2020KJX04).The authors would like to thank for these financial supports.
文摘Cellular structures are regarded as excellent candidates for lightweight-design,load-bearing,and energy-absorbing applications.In this paper,a novel S-based TPMS hollow isotropic cellular structure is proposed with both superior load-bearing and energy-absorbing performances.The hollow cellular structure is designed with Boolean operation based on the Fischer-Koch(S)implicit triply periodic minimal surfaces(TPMS)with different level parameters.The anisotropy and effective elasticity properties of cellular structures are evaluated with the numerical homogenization method.The finite element method is further conducted to analyze the static mechanical performance of hollow cellular structure considering the size effect.The compression experiments are finally carried out to reveal the compression properties and energy-absorption characteristics.Numerical results of the Zener ratio proved that the S-based hollow cellular structure tends to be isotropic,even better than the sheet-based Gyroid TPMS.Compared with the solid counterpart,the S-based hollow cellular structure has a higher elastic modulus,better load-bearing and energy absorption characteristics.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.12072242,11772237)the Natural Science Foundation of Hubei Province(Grant No.2020CFB816)the open funds of the State Key Laboratory of Structural Analysis for Industrial Equipment(Dalian University of Technology)through contract/Grant No.GZ19110.
文摘Functional graded cellular structure(FGCS)usually shows superiormechanical behaviorwith lowdensity and high stiffness.With the development of additivemanufacturing,functional graded cellular structure gains its popularity in industries.In this paper,a novel approach for designing functionally graded cellular structure is proposed based on a subdomain parameterized level set method(PLSM)under local volume constraints(LVC).In this method,a subdomain level set function is defined,parameterized and updated on each subdomain independently making the proposed approach much faster and more cost-effective.Additionally,the microstructures on arbitrary two adjacent subdomains can be connected perfectly without any additional constraint.Furthermore,the local volume constraint for each subdomain is applied by virtue of the augmented Lagrange multiplier method.Finally,several numerical examples are given to verify the correctness and effectiveness of the proposed approach in designing the functionally graded cellular structure.From the optimized results,it is also found that the number of local volume constraints has little influence on the convergence speed of the developed approach.
基金The present work was financially supported by the National Natural Science of China(No.52020105013)by the State Key Laboratory of Powder Metallurgy(No.62102172).
文摘The microstructural modification for cellular structures can achieve the improvement of dynamic me-chanical properties of a selective laser melted FeCoNiCrMo_(0.2)high-entropy alloy(SLM-FeCoNiCrMo_(0.2)HEA)and can expand its promising applications in the field of high-velocity deformation.In this work,FeCoNiCrMo_(0.2)HEAs with cellular structures in different sizes were produced by selective laser melt-ing(SLM)with different process parameters.The dynamic mechanical properties and microstructure of the SLM-FeCoNiCrMo_(0.2)HEA were studied.The dynamic mechanical properties of the SLM-FeCoNiCrMo_(0.2)HEA increased with decrease of average size of cellular structures,and the values of them were sensitive to strain rates.The energy absorption,compressive strength and yield strength of the SLM-FeCoNiCrMo_(0.2)HEAs reached 315.6 MJ/m^(3),2.2 GPa and 775.6 MPa,respectively at a strain rate of 2,420 s^(−1),under the process parameters of laser power and scanning speed of 330 W and 800 mm/s,respectively,where the corresponding average size of cellular structures in the HEAs was 483.6 nm.The value of strain-hardening rate of the SLM-FeCoNiCrMo_(0.2)HEA was about 5.1 GPa at a strain level of 0.1,which was much higher than that of the powder-metallurgy FeCoNiCrMo_(0.2)HEA.The cellular structure was formed inside the molten pool with segregation of Mo on the boundary.Deformation localization appeared in the cellular structures,forming several deformation bands after high strain-rate deformation.The elemental segre-gation strengthening and dislocation strengthening are considered to be the main strengthening mecha-nisms in SLM-FeCoNiCrMo_(0.2)HEA.
基金supported by the National Natural Science Foundation of China (Grant Nos.12072094 and 12172106)。
文摘The properties of functionally graded(FG) cellular structures vary spatially, and the varying properties can meet the requirements of different working environments. In this study, we fabricated FG cellular structures with shape memory effect by 4D printing and evaluated the compressive performance and shape memory behavior of these structures with temperature through experimental analysis and finite element simulations. The results show that the maximum energy absorption gradually decreases but the compressive modulus gradually increases with increasing gradient parameters. Moreover, the finite element simulations also show that the compressive deformation mode of the structure shifts from uniform to non-uniform deformation with increasing gradient parameters. The compressive modulus and compressive strength of 4D printed FG structures decrease with increasing temperature due to the influence of the shape memory polymer, and they exhibit outstanding shape recovery capability under high-temperature stimulus. The proposed 4D printed FG structures with such responsiveness to stimulus shed light on the design of intelligent energy-absorbing devices that meet specific functional requirements.
基金supported by National Key Research and Development Program of China(2022YFB2503502)National Natural Science Foundation of China(51975244).
文摘The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natural organisms,have exhibited exceptional structural utilization in terms of energy absorption compared with traditional structures.In recent years,various innovative cellular structures have been proposed to meet different engineering needs,resulting in significant performance improvements.This paper provides a comprehensive overview of novel cellular structures for energy absorption applications.In particular,it outlines the application forms and design concepts of cellular structures under typical loading conditions in vehicle collisions,including axial loading,oblique loading,bending loading,and blast loading.Cellular structures have evolved to meet the demands of complex loading conditions and diverse research methods,focusing on achieving high-performance characteristics across multiple load cases.Moreover,this review discusses manufacturing techniques and strate-gies for enhancing the manufacturing performance of cellular structures.Finally,current key challenges and future research directions for cellular structures are discussed.The aim of this study is to provide valuable guidelines for researchers and engineers in the development of next-generation lightweight cellular structures.
基金financially supported by the National Natural Science Foundation of China(Nos.51801141 and 51605356)the 111 Project(No.B17034)+1 种基金the Innovative Research Team Development Program of Ministry of Education of China(No.IRT17R83)the Fundamental Research Funds for the Central Universities(No.WUT:2017IVB035)。
文摘Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process.It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side.When polyethylene terephthalate(PET)films were applied,the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate(PC)and thermoplastic polyurethane(TPU)films.And the effects of film types on the cellular structure,forming defects and mechanical properties of IMD/MIM parts were also studied experimentally.The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts.Under certain film thickness,the offset distance of core layer was the largest with PET film used,while the offset distance was the smallest with TPU film used.And similar results were found for the warpage of the parts.However,an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.
基金supported by National Natural Science Foundation of China(No.51971017)Science Funds for Creative Research Groups of China(51921001)+2 种基金Program for Changjiang Scholars and Innovative Research Team in University of China(IRT_14R05)Projects of SKLAMM-USTB(2018Z-19)the financial support from the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-18-004C1).
文摘Shaped Mg alloy foams with closed-cell structure are highly interested for a great potential to be utilized in the fields where weight reduction is urgently required.A powder metallurgical method,namely gas release reaction powder metallurgy route to fabricate Mg-X(X=Al,Zn or Cu)alloy foams,was summarized.The principles on shaped Mg-X foams fabrication via the route were proposed.In addition,the effects of alloying elements,sintering treatment and foaming temperatures on fabrication of shaped Mg-X alloy foams were investigated experimentally.The results show that the key to ensure a successful foaming of Mg-X alloy foams is to add alloying metals alloyed with Mg to form lower melting(<600℃)intermetallic compounds by the initial sintering treatment.The foaming mechanism of Mg-X alloy foams also has been clarified,that is,the low-melting-point Mg-based intermetallic compounds melt first,and then reactions between the melt and CaCO_(3),a foaming agent,release CO gas to make the precursor foamed and finally shaped Mg-X alloy foam with a promising cellular structure is prepared.This route has been verified by successful fabrication on shaped Mg-Al,Mg-Zn and Mg-Cu foams with cellular structure.
基金partial support from the National Key Research and Development Program of China(Nos.2017YFC1104902,2016YFC1100502 and 2018YFC1105503)the National Natural Science Foundation of China(Nos.51871220 and 51631007)+3 种基金the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC031-02)the Natural Science Foundation of Liaoning Province of China(No.2019-MS-327 and 2020-KF-14-01)the State Key Laboratory of Light Alloy Casting Technology for Highend Equipment(No.LACT-007)the Shenyang Talents Program(No.RC200230)。
文摘The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone tissue in-growth.However,there is a gap in the knowledge in regard to the relationship between the pore characteristics and the electrochemical performance of open-cellular structured titanium alloys.In this study,we elucidate the influence of pore characteristics on the electrochemical performance of open-cellular structured Ti-6Al-4V alloys produced by electron beam melting(EBM).Intriguingly,the passive film formed on cellular structured Ti-6Al-4V alloy with a larger pore size was more stable and protective,and the corrosion performance was superior compared to the samples with a smaller pore size in phosphate buffered saline(PBS),mainly because of relatively smaller exposed surface area and unlimited flow of electrolyte.However,in acidic PBS containing fluoride ions,the pore characteristics did not play an important role in the corrosion resistance.It was considered that the protective film breaks down such that the corrosion performance of cellular structured alloys was comparable to each other in this harsh environment.
基金supported by the Ministry of Education and Science of Russian Federation (No.RFMEFI57414X0078)
文摘An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard fragment has the fourth degree of axial symmetry.The classification of the polar structures are described and a method of various quadra-structure synthesis is developed.A possibility to provide high strength of the structure due to preservation of faces reinforcement pattern is presented.Arrangement of the plane core on a bi-curvature surface is also introduced.Besides,provision of isotropy of the core in two or three directions are described.Finally,examples of cellular folded cores manufactured from basalt reinforced plastic are demonstrated.
基金The work described in this paper is partially supported by the National Key Research and Development Program of China(No.2018YFB1700603)the NSF of China(No.61872320).
文摘This paper aims to instantly predict within any accuracy the stress distribution of cellular structures under parametric design,including the shapes or distributions of the cell geometries,or the magnitudes of external loadings.A classical model reduction technique has to balance the simulation accuracy and interaction speed,and has difficulty achieving this goal.We achieve this by computing offline a design-to-stress mapping that ultimately expresses the stress distribution as an explicit function in terms of its design parameters.The mapping is determined as a solution to an extended finite element analysis problem in a high-dimension space,including both the spatial coordinates and the design parameters.The well-known curse of dimensionality intrinsic to the high-dimension problem is(partly)resolved through a spatial separation using two main techniques.First,the target mapping takes a reduced form as a sum of the products of separated one-variable functions,extending the proper generalized decomposition technique.Second,the simulation problem in a varied computation domain is reformulated as that in a fixed-domain,taking an integration function as the sum of the products of separated one-variable functions,in combination with high-order singular value decomposition.Extensive 2D and 3D examples are shown to demonstrate the approach’s performance.
基金supported by the Platform of Science and Technology and Talent Team Plan of Guizhou province(No.GCC[2023]007)the Doctorial Start-up Fund of Guizhou University(No.2011-05)+3 种基金the Fok Ying Tung Education Foundation(No.171095)the Talent Project of Guizhou Provincial Education Department(No.2022-094)the Guizhou Provincial Science and Technology Projects(No.ZK 2022-General 044)the National Natural Science Foundation of China(No.11964006).
文摘To adapt the practical demand,designing and constructing the multifunctional microwave absorbers(MAs)is the key future direction of research and development.However,effective integrating the multiple functions into a single material remains a huge challenge.Herein,cellular carbon foams(CCFs)with different porous structures were elaborately designed and fabricated in high efficiency through a facile continuous freeze-drying and carbonization processes using a sustainable biomass chitosan as the precursor.The obtained results revealed that the thermal treated temperature and g-C_(3)N_(4) amount played a great impact on the carbonization degrees,pore sizes,and morphologies of CCFs,which led to their tunable electromagnetic(EM)parameters,improved conduction loss,and polarization loss abilities.Owing to the special cellular structure,the designed CCFs samples simultaneously displayed the strong absorption capabilities,broad absorption bandwidths,and thin matching thicknesses.Meanwhile,the as-prepared CCFs exhibited the strong hydrophobicity and good thermal insulation,endowing its attractive functions of self-cleaning and thermal insulation.Therefore,our findings not only presented a facile approach to produce different porous structures of CCFs,but also provided an effective strategy to develop multifunctional high-performance MAs on basis of three-dimensional CCFs.
基金Funded by National Natural Science Foundation of China (No.21975108)Fundamental Research Funds for the Central Universities of China (No.JUSRP121033)。
文摘In order to prepare the polyethylene materials with controlling properties,we developed two kinds of controllable cross-linking polyethylene foaming system.2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane was used as cross-linking agent and TEMPO as cross-linking inhibitor,azodicarbonamide (AC) was used as foaming agent and citric acid as foaming promoter.The density,expansion ratio,cellular structure and mechanical property of these two kinds of controllable materials were studied.Experimental results show that,properties of these two kinds of materials appear similar trend:cellular size and expansion ratio are enlarged with the amount of cross-linking inhibitor or foaming promoter increasing,while density and mechanical strength appear decreasing trend.Through comparing those two material systems’ properties,cross-linking polyethelene foaming system with citric acid as foaming promoter has better properties.
基金the National Natural Science Foundation of China(Grant No.51877094)Ningbo Science and Technology Project(Grant No.2014B11009)。
文摘In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ZrO_(2)contents and investigated the influence of the ZrO_(2)content on the magnetic properties and resistive anisotropism.The results showed that not only was the resistivity of the magnet improved,but,in addition,the coercivity of the magnet was significantly increased.The microstructure was studied with TEM,which showed that ZrO_(2)doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures.The increased grain boundaries and Sm_(2)O_(3)phases were favorable to the improvement of resistivity.The decrease of the lamellar phases caused a narrowing of the resistive anisotropism.The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However,an excessive amount caused an increase of the Zr_6(Fe Co)_(23)phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity.
基金supported by the National Natural Science Foundation of China(Grant No.51772028).
文摘Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.
基金financially supported by the Swedish Governmental Agency for Innovation Systems(Vinnova grant No.2016–05175)the Center for Additive Manufacturingmetal(CAM2)+2 种基金financially supported in part by a research grant from Science Foundation Ireland(SFI)under Grant No.16/RC/3872cofounded under the European Regional Development Fund and by the I-Form industry partnersfinancial support(Grant No.X210141TL210)。
文摘We have investigated the low cycle fatigue(LCF)properties and the extent of strengthening in a dense additively manufactured stainless steel containing different volume fractions of cell structures but having all other microstructure characteristics the same.The samples were produced by laser powder bed fusion(L-PBF),and the concentration of cell structures was varied systematically by varying the annealing treatments.Load-controlled fatigue experiments performed on samples with a high fraction of cell structures reveal an up to 23 times increase in fatigue life compared to an essentially cell-free sample of the same grain configuration.Multiscale electron microscopy characterizations reveal that the cell structures serve as the soft barriers to the dislocation propagation and the partials are the main carrier for cyclic loading.The cell structures,stabilized by the segregated atoms and misorientation between the adjacent cells,are retained during the entire plastic deformation,hence,can continuously interact with dislocations,promote the formation of nanotwins,and provide massive 3D network obstacles to the dislocation motion.The compositional micro-segregation caused by the cellular solidification features serves as another nonnegligible strengthening mechanism to dislocation motion.Specifically,the cell structures with a high density of dislocation debris also appear to act as dislocation nucleation sites,very much like coherent twin boundaries.This work indicates the potential of additive manufacturing to design energy absorbent alloys with high performance by tailoring the microstructure through the printing process.
基金supported by the National Natural Science Foundation of China(Nos.52020105013,51871092,and 11902113)the Natural Science Foundation of Hunan Province(Nos.2019JJ50068 and 2021JJ40032)+1 种基金the Changsha Municipal Natu-ral Science Foundation(No.kq2014126)support from the National Science Foundation(Nos.DMR-1611180 and 1809640).
文摘Additive manufacturing is believed to open up a new era in precise microfabrication,and the dynamic microstructure evolution during the process as well as the experiment-simulation correlated study is conducted on a prototype multi-principal-element alloys FeCrNi fabricated using selective laser melting(SLM).Experimental results reveal that columnar crystals grow across the cladding layers and the dense cellular structures develop in the filled crystal.At the micron scale,all constituent elements are evenly distributed,while at the near-atomic scale,Cr element is obviously segregated.Simulation results at the atomic scale illustrate that i)the solid-liquid interface during the grain growth changes from horizontal to arc due to the radial temperature gradient;ii)the precipitates,microscale voids,and stacking faults also form dynamically as a result of the thermal gradient,leading to the residual stress in the SLMed structure.In addition,we established a microstructure-based physical model based on atomic simulation,which indicates that strong interface strengthening exists in the tensile deformation.The present work provides an atomic-scale understanding of the microstructural evolution in the SLM process through the combination of experiment and simulation.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.3072020CF1019)Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z19137)Natural Science Foundation of Heilongjiang Province(No.LH2019E038)。
文摘New ambient sound absorption material,lightweight isocyanate-based polyimide foam(IBPIF),was fabricated by operable combination between different distinctive acoustic IBPIF.Cellular structure of IBPIF was facilely and obviously adjusted by increased slurry temperature corresponding to change in distinctive acoustic properties.Moreover,density of all IBPIF kept at only 12-17 kg/m3.With increasing slurry temperature from 0℃to 40℃,cell size and window opening rate gradually increased from 553μm to 791μm and from 6.85%to 58.46%,respectively.In this study,IBPIF generated by slurries at 0℃(marked as PIF-2)and 40℃(marked as PIF-6)showed best and distinctive acoustic behavior in 315-800 Hz and 800-6300 Hz regions,respectively.After acoustic behavior study of combined IBPIF prepared by stitching combination between two distinctive acoustic IBPIFs,results showed that only when PIF-6 sheet used as sound receiving surface even though with thickness of only 10 mm could the combined IBPIF possess the best acoustic level in 800-6300 Hz region as PIF-6.Furtherly,acoustic behavior in 315-800 Hz region could be significantly enhanced by increasing thickness of PIF-2 and could reach or close to the best acoustic level.
