Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformab...Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformable wings inspired by the wing structures of birds.Shape Memory Alloy(SMA)is applied as a smart material to the deformable wing.Compared with other drive methods,SMA actuators have the advantages of high drive capacity and a simple structure for driving wing deformation.According to the shape memory effect,SMA actuators are classified as single-range and dual-range actuators.The wing structure designed for each SMA drive is unique.By comparing and analyzing the structures of airfoils,airfoils with similar drive forms and deformation structures are put together for review and discussion.The deformable wings are categorized into out-of-face deformation,in-face deformation,airfoil curvature deformation,and combined deformation with multiple degrees of freedom based on the structure and location of the wing that produces the deformation.An overview of the deformed wing is introduced by telling the bionic theory of seagulls.The principles of deformation of the wing,the mechanics of the SMA actuator mechanism,and the aerodynamic characteristics of the deformable wing are presented.The structure and working principle of SMA actuators for each type of deformable wing are explained in detail.Methods and approaches to study the deformability of deformable wings are analyzed and summarized.This work provides comprehensive insights and perspectives for future studies of SMA-driven deformable airfoils.展开更多
Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stre...Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa. The water contact angles of the as-anodized bionic samples were measured using a contact angle meter （JC2000A） with the 3μL water drop at room temperature. The measurement of the wetting property showed that the water contact angle of the unmodi- fied as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time. The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure. The structure is composed of the micro-scaled alumina columns and pores. The height of columns and the depth of pores depend on the ano- dizing time. The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol （ODT）, showing a change in the wettability from hydrophobicity to su- per-hydrophobicity. This improvement in the wetting property chemical modification. is attributed to the decrease in the surface energy caused by the展开更多
The wet grip of tire has always been the focus because it is related to the personal safety of passengers directly.Many methods were employed to improve the wet grip of tire.Researchers paid more attention on bionics ...The wet grip of tire has always been the focus because it is related to the personal safety of passengers directly.Many methods were employed to improve the wet grip of tire.Researchers paid more attention on bionics method recent years.In nature,tree frogs have high adhesion ability in wet environment,which is mainly due to their footpads having fine polygon grooves(mainly hexagon grooves).To improve the performance of wet grip of tire,from the perspective of bionics,inspired by the footpad of tree frog,the bionic hexagon tread pattern was designed.The friction test was carried out to compare with the common tread patterns such as serrated,striped and square patterns.The results showed that the bionic hexagon tread pattern generally had high friction coefficient and directional stability of friction.The main reason was that the hexagon tread block was less affected by the friction-induced torque and the groove of bionic hexagon tread pattern had better drainage characteristic.The bionic hexagon tread pattern provides new idea and method for the design of tires with high wet grip.展开更多
Using the method of structural finite element topology optimization and analysis of the hindwings of Trypoxylus dichotomus,this work identified the main loading force transmission path and designed the initial structu...Using the method of structural finite element topology optimization and analysis of the hindwings of Trypoxylus dichotomus,this work identified the main loading force transmission path and designed the initial structure of a bionic flexible wing.A structural design scheme of the vibration damping unit was proposed,and the structural mechanics and modal vibration characteristics were simulated and analyzed.3D printing technology was used to manufacture the designed bionic wing skeleton,which was combined with two kinds of wing membrane materials.The Flapping Wing Micro-aerial Vehicle(FWMAV)transmission mechanism vibration characteristics were observed and analyzed by a high-speed digital camera.A triaxial force transducer was used to record the force vibration of the flexible bionic wing flapping in a wind tunnel.A wavelet processing method was used to process and analyze the force signal.The results showed that the force amplitude was more stable,the waveform roughness was the lowest,and the peak shaving phenomenon at the z-axis was the least obvious for the bionic flexible wing model that combined the topology-optimized bionic wing skeleton with a polyamide elastic membrane.This was determined to be the most suitable design scheme for the wings of FWMAVs.展开更多
The appendages of mantis shrimp often bear bending loads from different directions during the in the process of preying on prey with its grazing limb.Hence,it has excellent bending resistance and isotropy to confront ...The appendages of mantis shrimp often bear bending loads from different directions during the in the process of preying on prey with its grazing limb.Hence,it has excellent bending resistance and isotropy to confront complex and changeable external load.The outstanding performance owes to the helical Bouligand structure with a certain interlayer corner,which is also widely found in other natural materials.Hence,the bio-inspired materials with basalt fiber are fabricated with outstanding bending resistance,isotropy and toughness.The research shows laminates with 18°interlayer corners exhibit relatively excellent bending resistance and isotropy,and the laminate with 11.25°interlayer corner has best toughness.Compared with traditional composites,average bending strength along different loading direction of bio-inspired materials increased by 28%,and anisotropy decreased by 86%.Besides,the maximum toughness of laminates can increase to 1.7 times of the original.Following the introduction of interlayer corners,the bio-inspired composite tends to be isotropic.To explore the reason for the change of the isotropic performance caused by diverse interlayer corners,the Finite Element Analysis based on classical laminate theory and Tsai–Wu and Tsai–Hill failure criterion.Besides,further experiments and observations are conducted to explore possible reasons.In conclusion,following the introduction of interlayer corners,the bio-inspired composites tend to be isotropic.This bio-inspired composites are expected to be applied to various complex modern engineering fields,such as vehicle,rail transit and aerospace.展开更多
A variety of prosthetic ankles have been successfully developed to reproduce the locomotor ability for lower limb amputees in daily lives. However, they have not been shown to sufficiently improve the natural gait mec...A variety of prosthetic ankles have been successfully developed to reproduce the locomotor ability for lower limb amputees in daily lives. However, they have not been shown to sufficiently improve the natural gait mechanics commonly observed in comparison to the able-bodied, perhaps due to over-simplified designs of functional musculoskeletal structures in prostheses. In this study, a flexible bionic ankle prosthesis with joints covered by soft material inclusions is developed on the basis of the human musculoskeletal system. First, the healthy side ankle–foot bones of a below-knee amputee were reconstructed by CT imaging. Three types of polyurethane rubber material configurations were then designed to mimic the soft tissues around the human ankle, providing stability and flexibility. Finite element simulations were conducted to determine the proper design of the rubber materials, evaluate the ankle stiffness under different external conditions, and calculate the rotation axes of the ankle during walking. The results showed that the bionic ankle had variable stiffness properties and could adapt to various road surfaces. It also had rotation axes similar to that of the human ankle, thus restoring the function of the talocrural and subtalar joints. The inclination and deviation angles of the talocrural axis, 86.2° and 75.1°, respectively, as well as the angles of the subtalar axis, 40.1° and 29.9°, were consistent with the literature. Finally, dynamic characteristics were investigated by gait measurements on the same subject, and the flexible bionic ankle prosthesis demonstrated natural gait mechanics during walking in terms of ankle angles and moments.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025053)National Natural Science Foundation of China(No.52305302)+1 种基金the Natural Science Foundation of Jilin Province(No.20220101216JC)the asterisk indicates the corresponding authors.
文摘Birds have developed near-perfect structures and functionality over millions of years of natural evolution.To improve the efficiency of fixed-wing vehicles in different environments,researchers have developed deformable wings inspired by the wing structures of birds.Shape Memory Alloy(SMA)is applied as a smart material to the deformable wing.Compared with other drive methods,SMA actuators have the advantages of high drive capacity and a simple structure for driving wing deformation.According to the shape memory effect,SMA actuators are classified as single-range and dual-range actuators.The wing structure designed for each SMA drive is unique.By comparing and analyzing the structures of airfoils,airfoils with similar drive forms and deformation structures are put together for review and discussion.The deformable wings are categorized into out-of-face deformation,in-face deformation,airfoil curvature deformation,and combined deformation with multiple degrees of freedom based on the structure and location of the wing that produces the deformation.An overview of the deformed wing is introduced by telling the bionic theory of seagulls.The principles of deformation of the wing,the mechanics of the SMA actuator mechanism,and the aerodynamic characteristics of the deformable wing are presented.The structure and working principle of SMA actuators for each type of deformable wing are explained in detail.Methods and approaches to study the deformability of deformable wings are analyzed and summarized.This work provides comprehensive insights and perspectives for future studies of SMA-driven deformable airfoils.
基金The authors are grateful to the National Nature Science Foundation of China （Grant No. 50635030） and the development project on industrialization of bionic non-adhesive cooker （Grant No. 2006D90304010） for the support of this work.
文摘Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa. The water contact angles of the as-anodized bionic samples were measured using a contact angle meter （JC2000A） with the 3μL water drop at room temperature. The measurement of the wetting property showed that the water contact angle of the unmodi- fied as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time. The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure. The structure is composed of the micro-scaled alumina columns and pores. The height of columns and the depth of pores depend on the ano- dizing time. The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol （ODT）, showing a change in the wettability from hydrophobicity to su- per-hydrophobicity. This improvement in the wetting property chemical modification. is attributed to the decrease in the surface energy caused by the
基金supported by the National Key R&D Plan(2016YFD0701102)the Graduate Innovation Fund of Jilin University(101832020CX166)+3 种基金the Science-Technology Development Plan Project of Jilin Province(20200403038SF,20200501013GX,20200403006SF)the"13th Five-Year Plan"Scientific Research Foundation of the Education Department of Jilin Province(JJKH20201000KJ,JJKH20211120KJ)the Talent Development Foundation of Jilin Province(2020015)the Fundamental Research Foundation for the Central Universities.
文摘The wet grip of tire has always been the focus because it is related to the personal safety of passengers directly.Many methods were employed to improve the wet grip of tire.Researchers paid more attention on bionics method recent years.In nature,tree frogs have high adhesion ability in wet environment,which is mainly due to their footpads having fine polygon grooves(mainly hexagon grooves).To improve the performance of wet grip of tire,from the perspective of bionics,inspired by the footpad of tree frog,the bionic hexagon tread pattern was designed.The friction test was carried out to compare with the common tread patterns such as serrated,striped and square patterns.The results showed that the bionic hexagon tread pattern generally had high friction coefficient and directional stability of friction.The main reason was that the hexagon tread block was less affected by the friction-induced torque and the groove of bionic hexagon tread pattern had better drainage characteristic.The bionic hexagon tread pattern provides new idea and method for the design of tires with high wet grip.
基金supported by the National Natural Science Foundation of China(grant number 31970454)the Aviation Science Foundation of China(2020Z0740R4001)+1 种基金the Graduate Innovation Fund of Jilin University(2022189)Undergraduate Innovation and Entrepreneurship Training Program Project of Jilin University(S202210183259).
文摘Using the method of structural finite element topology optimization and analysis of the hindwings of Trypoxylus dichotomus,this work identified the main loading force transmission path and designed the initial structure of a bionic flexible wing.A structural design scheme of the vibration damping unit was proposed,and the structural mechanics and modal vibration characteristics were simulated and analyzed.3D printing technology was used to manufacture the designed bionic wing skeleton,which was combined with two kinds of wing membrane materials.The Flapping Wing Micro-aerial Vehicle(FWMAV)transmission mechanism vibration characteristics were observed and analyzed by a high-speed digital camera.A triaxial force transducer was used to record the force vibration of the flexible bionic wing flapping in a wind tunnel.A wavelet processing method was used to process and analyze the force signal.The results showed that the force amplitude was more stable,the waveform roughness was the lowest,and the peak shaving phenomenon at the z-axis was the least obvious for the bionic flexible wing model that combined the topology-optimized bionic wing skeleton with a polyamide elastic membrane.This was determined to be the most suitable design scheme for the wings of FWMAVs.
基金This work was supported by the National Key Research and Development Program of China(No.2018YFA0703300)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.52021003)+5 种基金National Natural Science Foundation of China(No.51835006,51875244,U19A20103)Program for JLU Science and Technology Innovative Research Team(No.2020TD-03)the Natural Science Foundation of Jilin Province(No.20200201232JC)Graduate innovation research program of Jilin University(101832020CX161)Interdisciplinary Integration and Innovation Project of JLU(No.JLUXKJC2021ZZ03)supported by“Fundamental Research Funds for the Central Universities”.
文摘The appendages of mantis shrimp often bear bending loads from different directions during the in the process of preying on prey with its grazing limb.Hence,it has excellent bending resistance and isotropy to confront complex and changeable external load.The outstanding performance owes to the helical Bouligand structure with a certain interlayer corner,which is also widely found in other natural materials.Hence,the bio-inspired materials with basalt fiber are fabricated with outstanding bending resistance,isotropy and toughness.The research shows laminates with 18°interlayer corners exhibit relatively excellent bending resistance and isotropy,and the laminate with 11.25°interlayer corner has best toughness.Compared with traditional composites,average bending strength along different loading direction of bio-inspired materials increased by 28%,and anisotropy decreased by 86%.Besides,the maximum toughness of laminates can increase to 1.7 times of the original.Following the introduction of interlayer corners,the bio-inspired composite tends to be isotropic.To explore the reason for the change of the isotropic performance caused by diverse interlayer corners,the Finite Element Analysis based on classical laminate theory and Tsai–Wu and Tsai–Hill failure criterion.Besides,further experiments and observations are conducted to explore possible reasons.In conclusion,following the introduction of interlayer corners,the bio-inspired composites tend to be isotropic.This bio-inspired composites are expected to be applied to various complex modern engineering fields,such as vehicle,rail transit and aerospace.
基金supported by the National Key Research and Development Program of China(No.2018YFC2001300)the National Natural Science Foundation of China(No.52005209,91948302,No.91848204,No.52021003)the Natural Science Foundation of Jilin Province(No.20210101053JC,No.20220508130RC).
文摘A variety of prosthetic ankles have been successfully developed to reproduce the locomotor ability for lower limb amputees in daily lives. However, they have not been shown to sufficiently improve the natural gait mechanics commonly observed in comparison to the able-bodied, perhaps due to over-simplified designs of functional musculoskeletal structures in prostheses. In this study, a flexible bionic ankle prosthesis with joints covered by soft material inclusions is developed on the basis of the human musculoskeletal system. First, the healthy side ankle–foot bones of a below-knee amputee were reconstructed by CT imaging. Three types of polyurethane rubber material configurations were then designed to mimic the soft tissues around the human ankle, providing stability and flexibility. Finite element simulations were conducted to determine the proper design of the rubber materials, evaluate the ankle stiffness under different external conditions, and calculate the rotation axes of the ankle during walking. The results showed that the bionic ankle had variable stiffness properties and could adapt to various road surfaces. It also had rotation axes similar to that of the human ankle, thus restoring the function of the talocrural and subtalar joints. The inclination and deviation angles of the talocrural axis, 86.2° and 75.1°, respectively, as well as the angles of the subtalar axis, 40.1° and 29.9°, were consistent with the literature. Finally, dynamic characteristics were investigated by gait measurements on the same subject, and the flexible bionic ankle prosthesis demonstrated natural gait mechanics during walking in terms of ankle angles and moments.
