A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH,...A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH, a unit cell （UC） for thermal transport analysis was selected to calculate its effective thermal conductivity. Without introducing any empirical coefficient, we modified and extended the analytical model of parallel-series thermal-electric network to a wider porosity range （0.7 ~ 0.98） by considering the effects of two-dimensional local heat conduction in solid ligaments inside each UC. Good agreement was achieved between analytical predictions and numerical simulations based on the method of finite volume. The concept of ligament heat conduction efficiency （LTCE） was proposed to physically explain the mechanisms underlying the effects of ligament configuration on effective thermal conductivity （ETC）. Based upon the proposed theory, a construct strategy was developed for designing the ETC by altering the equivalent interaction angle with the direction of heat flow： relatively small average interaction angle for thermal conduction and relatively large one for thermal insulation.展开更多
Anal fistula is one of the three greatest anorectal diseases with a high prevalence. The traditional treatments（e.g., surgery） for fistula have limitations due to damage to the internal anal sphincter of patients. W...Anal fistula is one of the three greatest anorectal diseases with a high prevalence. The traditional treatments（e.g., surgery） for fistula have limitations due to damage to the internal anal sphincter of patients. With recent advances in biomaterials, treatments based on biomaterial filling （e.g., scleraprotein injection, fistula plug） have emerged as novel therapies for fistula. The anal fistula plug （e.g., based on small intestinal submucosa （SIS）） has attracted increasing attention because of short term healing rate and biocompatibility. However, challenges remain for this method such as plug falling as observed in clinics. To address this, this paper analyzes the case of SIS falling under physiological condition from mechanical point of view using ANSYS simulation. It then proposes three new geometrical structures for fistula plug and compares their mechanical behavior （e.g., axial stress, reaction of constraint） with that of clinically used structure （cone shape）. Based on the simulation, it optimizes the geometric parameters of fistula plug. The approach developed here can help to improve the design of fistula plug for better clinical treatments.展开更多
The oblique penetration performance of lightweight hybrid-cored sand- wich plates are investigated numerically. To compose the hybrid-core, ceramic prisms are inserted into pyramidal metal lattice trusses and fixed us...The oblique penetration performance of lightweight hybrid-cored sand- wich plates are investigated numerically. To compose the hybrid-core, ceramic prisms are inserted into pyramidal metal lattice trusses and fixed using epoxy resin. Three-dimensional finite element simulations are carried out for the hybrid- cored sandwich impacted at 15°, 30°, 45°, and 60°obliquity by a hemispherical projectile. The ballistic limit, the energy absorbed by the constituting elements, and the critical oblique angle are quantified. The physical mechanisms underly- ing the failure and the influence of fundamental system parameters are explored. The angle of obliquity is found to have significant influence on the ballistic trajec- tory and erosion of the projectile, thus it is important for the impact response and penetration resistance of the sandwich. For oblique angles equal to or larger than 45°, the projectile moves mainly horizontally and can not effectively penetrate across the sandwich.展开更多
The natural convective heat transfer performance of an aluminum hexagonal honeycomb acting as a novel heat sink for LED cooling is experi- mentally investigated. The concept of adding an adiabatic square chimney ex- t...The natural convective heat transfer performance of an aluminum hexagonal honeycomb acting as a novel heat sink for LED cooling is experi- mentally investigated. The concept of adding an adiabatic square chimney ex- tension for heat transfer enhancement is proposed, and the effects of chimney shape, height, and diameter are quantified. The average Nuav of a heated hon- eycomb with straight chimney is significantly higher than that without chimney, and the enhancement increases with increasing chimney height. At a given chim- ney height, honeycombs with divergent chimneys perform better than those with convergent ones. For a fixed divergent angle, the Nuav number increases mono- tonically with increasing chimney height. In contrast, with the convergent angle fixed, there exists an optimal chimney height to achieve maximum heat transfer.展开更多
An alternate yet general form of the classical effective thermal conductivity model （Maxwell model） for two-phase porous materials is presented, serving an explicit thermo-physicM basis. It is demonstrated that the ...An alternate yet general form of the classical effective thermal conductivity model （Maxwell model） for two-phase porous materials is presented, serving an explicit thermo-physicM basis. It is demonstrated that the reduced effective thermal conductivity of the porous media due to non-conducting pore inclusions is caused by the mechanism of thermal stretching, which is a combi- nation of reduced effective heat flow area and elongated heat transfer distance （thermal tortuosity）.展开更多
The concept of combining metallic honeycomb with folded thin metallic sheets （corrugation） to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is man...The concept of combining metallic honeycomb with folded thin metallic sheets （corrugation） to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is manufactured by filling the interstices of aluminum corrugations with precision-cut trapezoidal aluminum honeycomb blocks, bonded together using epoxy glue. The performance of such hybrid-cored sandwich panels subjected to out-of-plane compression, transverse shear, and three-point bending is investigated, both experimentally and numerically. The strength and energy absorption of the sandwich are dramatically enhanced, compared to those of a sandwich with either empty corrugation or honeycomb core. The enhancement is induced by the beneficial interaction effects of honeycomb blocks and folded panels on improved buckling resistance as well as altered crushing modes at large plastic deformation. The present approach provides an effective method to further improve the mechanical properties of conventional honeycomb-cored sandwich constructions with low relative densities.展开更多
Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remain...Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remains elusive. We experimentally studied the thermal and strain rate- dependent viscoelastic behavior of skin in uniaxial stretch and numerically investigated the effects of temperature and strain rate on pain sensation. The results indicate that the viscosity of skin tissue decreases with increasing temperature and reducing strain rate, which subsequently decreases the discharge frequency of skin nociceptor and thus relieves the pain sensation. The results would contribute to the understanding of pain relief mechanism and optimizing for mechanical treatment.展开更多
We develop an acoustomechanical theory for semicrystalline polymers and demonstrate that acoustic radiation force is capable of causing giant deformation in these materials. When a polymer layer is subjected to combin...We develop an acoustomechanical theory for semicrystalline polymers and demonstrate that acoustic radiation force is capable of causing giant deformation in these materials. When a polymer layer is subjected to combined tensile mechanical force in plane and acoustic force （sound pressure） through thickness, it becomes initially homogeneously thin but soon inhomogeneous when the two forces reach critical conditions. Critical conditions for such acoustomechanical instability are theoretically determined based on the J2-deformation theory. We demonstrate that pull-in instability can he acoustically triggered even if the in-plane mechanical force is fixed. Bifurcation in the critical condition for acoustomechanical instability occurs when the polymer exhibits sufficiently large hardening. The findings of this study enable reliability design of novel acoustic actuated devices.展开更多
Thermal transport in a highly porous metallic wire-woven bulk Kagome （WBK） is numerically and analytically modeled. Based on topology similarity and upon introducing an elongation parameter in thermal tortuosity, an...Thermal transport in a highly porous metallic wire-woven bulk Kagome （WBK） is numerically and analytically modeled. Based on topology similarity and upon introducing an elongation parameter in thermal tortuosity, an idealized Kagome with non-twisted struts is employed. Special focus is placed upon quanti- fying the effect of topological anisotropy of WBK upon its effective conductivity. It is demonstrated that the effective conductivity reduces linearly as the poros- ity increases, and the extent of the reduction is significantly dependent on the orientation of WBK. The governing physical mechanism of anisotropic thermal transport in WBK is found to be the anisotropic thermal tortuosity caused by the intrinsic anisotropic topology of WBK.展开更多
Indentation is a simple and nondestructive method to measure the mechanical properties of soft materials, such as hydrogels, elastomers and soft tissues. In this work, we have developed a micro-indentation system with...Indentation is a simple and nondestructive method to measure the mechanical properties of soft materials, such as hydrogels, elastomers and soft tissues. In this work, we have developed a micro-indentation system with high-precision to measure the mechanical properties of soft materials, where the shear modulus and Poisson＇s ratio of the materials can be obtained by analyzing the load relaxation curve. We have validated the accuracy and stability of the system by comparing the measured mechanical properties of a polyethylene glycol sample with that obtained from a commercial instrument. The mechanical properties of another typical polydimethylsiloxane sample submerged in heptane are measured by using conical and spherical indenters, respectively. The measured values of shear modulus and Poisson＇s ratio are within a reasonable range.展开更多
An insightful understanding of the formation mechanism of process-inherent defects anddeformation is increasingly important for the property evaluation and structural design of ceramicmatrix composites (CMCs). For thi...An insightful understanding of the formation mechanism of process-inherent defects anddeformation is increasingly important for the property evaluation and structural design of ceramicmatrix composites (CMCs). For this purpose, a coupled thermal–diffusive–mechanical modelingapproach was proposed by considering three important phenomena that occur during the pyrolysisprocess for manufacturing CMCs: variations of the physical and mechanical properties of theconstituents, generation and diffusive of pyrolysis gas, and multiple thermal deformations. Thesynergistic effects of these three phenomena on the stress, damage development, microstructuralmorphology, and process deformation of SiC matrix composites were investigated using finiteelement simulations. This new approach was validated by comparing the simulation and experimentalresults. Significant volume shrinkage of the matrix during the polymer-to-ceramic transformationresulted in large tensile stresses and subsequent highly fragmented microstructure in CMCs. Thepyrolysis-gas-induced expansion on the matrix under a damage state may yield a positive processdeformation of CMCs at the macroscale, overcoming the effects of the volume shrinkage of the bulkmatrix at the microscale. The modeling approach is expected to guide high-quality manufacturing ofCMCs and comprehensive studies of structure–processing–property relationships.展开更多
The expanded metal sheets were folded with 11% work-hardening. These were sub- sequently used with resistance welding to construct X-type lattice truss sandwich panels having a core relative density of 0.17. The sandw...The expanded metal sheets were folded with 11% work-hardening. These were sub- sequently used with resistance welding to construct X-type lattice truss sandwich panels having a core relative density of 0.17. The sandwich panels were tested in uniaxial compression and, for comparison, the method of finite elements was employed to simulate the measured compressive stress-strain curves. The peak compressive strength was 32% higher than that of pyramidal core sandwiches. The enhanced mechanical properties of the work-hardened X-Type lattice structures mainly originate from the contribution of straight struts with low degree of curvature and work hardening, rather than the two-dimensional staggered nodes.展开更多
Past decades have witnessed the explosive growth of interest in the field of bioinspired materials,of which the structures and properties can be well utilized for industrial and bioengineering applications.Among these...Past decades have witnessed the explosive growth of interest in the field of bioinspired materials,of which the structures and properties can be well utilized for industrial and bioengineering applications.Among these structures,the natural fibrous structures propose diverse strategies to adapt to their environment,offering inspirations for versatile applications,especially droplet manipulation.With various well-adapted soft structures and materials,these fibrous structures show good control over their interaction with liquids(e.g.,water),providing a database full of effective solutions to these droplet-related scientific and technical problems(e.g.,colloidal synthesis,single-cell gene sequencing,drug delivery and solution synthesis).In this review,the current achievements in water collection by multiple fibrous structures are highlighted;the structures,basic models,bio-inspired structures and their applications are presented;and the current challenges and future prospects for the development of bio-inspired fibrous structures are discussed.展开更多
基金supported by the National Natural Science Foundation of China(51506160,11472208,11472209)China Post-Doctoral Science Foundation Project(2015M580845)+1 种基金the Fundamental Research Funds for Xi’an Jiaotong University(xjj2015102)the Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering(NR2016K01)
文摘A comparative optimal design of fluid-saturated prismatic cellular metal honeycombs （PCMHs） having different cell shapes is presented for thermal management applications. Based on the periodic topology of each PCMH, a unit cell （UC） for thermal transport analysis was selected to calculate its effective thermal conductivity. Without introducing any empirical coefficient, we modified and extended the analytical model of parallel-series thermal-electric network to a wider porosity range （0.7 ~ 0.98） by considering the effects of two-dimensional local heat conduction in solid ligaments inside each UC. Good agreement was achieved between analytical predictions and numerical simulations based on the method of finite volume. The concept of ligament heat conduction efficiency （LTCE） was proposed to physically explain the mechanisms underlying the effects of ligament configuration on effective thermal conductivity （ETC）. Based upon the proposed theory, a construct strategy was developed for designing the ETC by altering the equivalent interaction angle with the direction of heat flow： relatively small average interaction angle for thermal conduction and relatively large one for thermal insulation.
基金supported by the Major International (Regional) Joint Research Program of China (11120101002)the National Natural Science Foundation of China(10825210 and 31050110125)the National 111 Project of China(B06024)
文摘Anal fistula is one of the three greatest anorectal diseases with a high prevalence. The traditional treatments（e.g., surgery） for fistula have limitations due to damage to the internal anal sphincter of patients. With recent advances in biomaterials, treatments based on biomaterial filling （e.g., scleraprotein injection, fistula plug） have emerged as novel therapies for fistula. The anal fistula plug （e.g., based on small intestinal submucosa （SIS）） has attracted increasing attention because of short term healing rate and biocompatibility. However, challenges remain for this method such as plug falling as observed in clinics. To address this, this paper analyzes the case of SIS falling under physiological condition from mechanical point of view using ANSYS simulation. It then proposes three new geometrical structures for fistula plug and compares their mechanical behavior （e.g., axial stress, reaction of constraint） with that of clinically used structure （cone shape）. Based on the simulation, it optimizes the geometric parameters of fistula plug. The approach developed here can help to improve the design of fistula plug for better clinical treatments.
基金supported by the National Basic Research Program of China(2011CB610305)
文摘The oblique penetration performance of lightweight hybrid-cored sand- wich plates are investigated numerically. To compose the hybrid-core, ceramic prisms are inserted into pyramidal metal lattice trusses and fixed using epoxy resin. Three-dimensional finite element simulations are carried out for the hybrid- cored sandwich impacted at 15°, 30°, 45°, and 60°obliquity by a hemispherical projectile. The ballistic limit, the energy absorbed by the constituting elements, and the critical oblique angle are quantified. The physical mechanisms underly- ing the failure and the influence of fundamental system parameters are explored. The angle of obliquity is found to have significant influence on the ballistic trajec- tory and erosion of the projectile, thus it is important for the impact response and penetration resistance of the sandwich. For oblique angles equal to or larger than 45°, the projectile moves mainly horizontally and can not effectively penetrate across the sandwich.
基金supported by the National 111 Project of China(B06024)the National Basic Research Program of China(2011CB610305)the National Natural Science Foundation of China(51206128)
文摘The natural convective heat transfer performance of an aluminum hexagonal honeycomb acting as a novel heat sink for LED cooling is experi- mentally investigated. The concept of adding an adiabatic square chimney ex- tension for heat transfer enhancement is proposed, and the effects of chimney shape, height, and diameter are quantified. The average Nuav of a heated hon- eycomb with straight chimney is significantly higher than that without chimney, and the enhancement increases with increasing chimney height. At a given chim- ney height, honeycombs with divergent chimneys perform better than those with convergent ones. For a fixed divergent angle, the Nuav number increases mono- tonically with increasing chimney height. In contrast, with the convergent angle fixed, there exists an optimal chimney height to achieve maximum heat transfer.
基金supported by the National 111 Project of China (B06024)the National Basic Research Program of China (2011CB610305)+1 种基金the Major International Joint Research Program of China (11120101002)the National Natural Science Foundation of China (51206128)
文摘An alternate yet general form of the classical effective thermal conductivity model （Maxwell model） for two-phase porous materials is presented, serving an explicit thermo-physicM basis. It is demonstrated that the reduced effective thermal conductivity of the porous media due to non-conducting pore inclusions is caused by the mechanism of thermal stretching, which is a combi- nation of reduced effective heat flow area and elongated heat transfer distance （thermal tortuosity）.
基金supported by the National Natural Science Foundation of China(11472208)the National 111 Project of China(B06024)
文摘The concept of combining metallic honeycomb with folded thin metallic sheets （corrugation） to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is manufactured by filling the interstices of aluminum corrugations with precision-cut trapezoidal aluminum honeycomb blocks, bonded together using epoxy glue. The performance of such hybrid-cored sandwich panels subjected to out-of-plane compression, transverse shear, and three-point bending is investigated, both experimentally and numerically. The strength and energy absorption of the sandwich are dramatically enhanced, compared to those of a sandwich with either empty corrugation or honeycomb core. The enhancement is induced by the beneficial interaction effects of honeycomb blocks and folded panels on improved buckling resistance as well as altered crushing modes at large plastic deformation. The present approach provides an effective method to further improve the mechanical properties of conventional honeycomb-cored sandwich constructions with low relative densities.
基金supported by the National Natural Science Foundation of China (11372243, 11372243, 1152219)the International Science and Technology Cooperation Program of China (2013DFG02930)
文摘Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remains elusive. We experimentally studied the thermal and strain rate- dependent viscoelastic behavior of skin in uniaxial stretch and numerically investigated the effects of temperature and strain rate on pain sensation. The results indicate that the viscosity of skin tissue decreases with increasing temperature and reducing strain rate, which subsequently decreases the discharge frequency of skin nociceptor and thus relieves the pain sensation. The results would contribute to the understanding of pain relief mechanism and optimizing for mechanical treatment.
基金supported by the National Natural Science Foundation of China(51528501 and 11321062)the Fundamental Research Funds for Central Universities(2014qngz12)supported by China Scholarship Council as a visiting scholar to Harvard University
文摘We develop an acoustomechanical theory for semicrystalline polymers and demonstrate that acoustic radiation force is capable of causing giant deformation in these materials. When a polymer layer is subjected to combined tensile mechanical force in plane and acoustic force （sound pressure） through thickness, it becomes initially homogeneously thin but soon inhomogeneous when the two forces reach critical conditions. Critical conditions for such acoustomechanical instability are theoretically determined based on the J2-deformation theory. We demonstrate that pull-in instability can he acoustically triggered even if the in-plane mechanical force is fixed. Bifurcation in the critical condition for acoustomechanical instability occurs when the polymer exhibits sufficiently large hardening. The findings of this study enable reliability design of novel acoustic actuated devices.
基金supported by the National 111 Project of China(B06024)the National Basic Research Program of China(2011CB610305)
文摘Thermal transport in a highly porous metallic wire-woven bulk Kagome （WBK） is numerically and analytically modeled. Based on topology similarity and upon introducing an elongation parameter in thermal tortuosity, an idealized Kagome with non-twisted struts is employed. Special focus is placed upon quanti- fying the effect of topological anisotropy of WBK upon its effective conductivity. It is demonstrated that the effective conductivity reduces linearly as the poros- ity increases, and the extent of the reduction is significantly dependent on the orientation of WBK. The governing physical mechanism of anisotropic thermal transport in WBK is found to be the anisotropic thermal tortuosity caused by the intrinsic anisotropic topology of WBK.
基金supported by the National "111 Project" Foundation of China(B06024)the National Natural Science Foundation of China(11372243)+3 种基金"Zhi Gu" Innovation Program of Southern Chinathe Major InternationalJoint Research Program of China(11120101002)International Science and Technology Cooperation Program of China(2013DFG02930)partially supported by the Fundamental Research Funds for the Central Universities(NCET-12-0437)
文摘Indentation is a simple and nondestructive method to measure the mechanical properties of soft materials, such as hydrogels, elastomers and soft tissues. In this work, we have developed a micro-indentation system with high-precision to measure the mechanical properties of soft materials, where the shear modulus and Poisson＇s ratio of the materials can be obtained by analyzing the load relaxation curve. We have validated the accuracy and stability of the system by comparing the measured mechanical properties of a polyethylene glycol sample with that obtained from a commercial instrument. The mechanical properties of another typical polydimethylsiloxane sample submerged in heptane are measured by using conical and spherical indenters, respectively. The measured values of shear modulus and Poisson＇s ratio are within a reasonable range.
基金The research is supported in part by the National Key R&D Program of China(No.2021YFF0501800)in part by the National Natural Science Foundation of China(Nos.12272174,12102179,and U22B6009)+1 种基金Natural Science Foundation of Jiangsu Province(No.BK20200409)the High Level Personnel Project of Jiangsu Province(No.JSSCBS20210618).
文摘An insightful understanding of the formation mechanism of process-inherent defects anddeformation is increasingly important for the property evaluation and structural design of ceramicmatrix composites (CMCs). For this purpose, a coupled thermal–diffusive–mechanical modelingapproach was proposed by considering three important phenomena that occur during the pyrolysisprocess for manufacturing CMCs: variations of the physical and mechanical properties of theconstituents, generation and diffusive of pyrolysis gas, and multiple thermal deformations. Thesynergistic effects of these three phenomena on the stress, damage development, microstructuralmorphology, and process deformation of SiC matrix composites were investigated using finiteelement simulations. This new approach was validated by comparing the simulation and experimentalresults. Significant volume shrinkage of the matrix during the polymer-to-ceramic transformationresulted in large tensile stresses and subsequent highly fragmented microstructure in CMCs. Thepyrolysis-gas-induced expansion on the matrix under a damage state may yield a positive processdeformation of CMCs at the macroscale, overcoming the effects of the volume shrinkage of the bulkmatrix at the microscale. The modeling approach is expected to guide high-quality manufacturing ofCMCs and comprehensive studies of structure–processing–property relationships.
基金supported by the National Basic Research Program of China(No. 2011CB610300)the National Science Foundation for Young Scientists of China(No. 11102152)+1 种基金the Fundamental Research Funds for Xi'an Jiaotong University(No. xjj2011007)the National 111 Project of China (No. B06024)
文摘The expanded metal sheets were folded with 11% work-hardening. These were sub- sequently used with resistance welding to construct X-type lattice truss sandwich panels having a core relative density of 0.17. The sandwich panels were tested in uniaxial compression and, for comparison, the method of finite elements was employed to simulate the measured compressive stress-strain curves. The peak compressive strength was 32% higher than that of pyramidal core sandwiches. The enhanced mechanical properties of the work-hardened X-Type lattice structures mainly originate from the contribution of straight struts with low degree of curvature and work hardening, rather than the two-dimensional staggered nodes.
基金This work was financially supported by the National Natural Science Foundation of China(11532009,11522219).
文摘Past decades have witnessed the explosive growth of interest in the field of bioinspired materials,of which the structures and properties can be well utilized for industrial and bioengineering applications.Among these structures,the natural fibrous structures propose diverse strategies to adapt to their environment,offering inspirations for versatile applications,especially droplet manipulation.With various well-adapted soft structures and materials,these fibrous structures show good control over their interaction with liquids(e.g.,water),providing a database full of effective solutions to these droplet-related scientific and technical problems(e.g.,colloidal synthesis,single-cell gene sequencing,drug delivery and solution synthesis).In this review,the current achievements in water collection by multiple fibrous structures are highlighted;the structures,basic models,bio-inspired structures and their applications are presented;and the current challenges and future prospects for the development of bio-inspired fibrous structures are discussed.
