Porous structures of natural materials and bionic design

This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as the epidermis of apples, with SEM (Scanning Electronic Microscope) showed that natural structures’ pores can be classified into uniform pores, gradient pores and multi pores from the viewpoint of the distribution variation of pore density, size and geometry. Furthermore, an optimal design of porous bearings was for the first time developed based on the gradient configuration of natural materials. The bionic design of porous structures is predicted to be widely developed and applied in the fields of materials and mechanical engineering in the future.

The Lightweight Design of Low RCS Pylon Based on Structural Bionics

A concept of Specific Structure Efficiency (SSE) was proposed that can be used in the lightweight effect evaluation ofstructures.The main procedures of bionic structure design were introduced systematically.The parameter relationship betweenhollow stem of plant and the minimum weight was deduced in detail.In order to improve SSE of pylons, the structural characteristicsof hollow stem were investigated and extracted.Bionic pylon was designed based on analogous biological structuralcharacteristics.Using finite element method based simulation, the displacements and stresses in the bionic pylon were comparedwith those of the conventional pylon.Results show that the SSE of bionic pylon is improved obviously.Static, dynamic andelectromagnetism tests were carried out on conventional and bionic pylons.The weight, stress, displacement and Radar CrossSection (RCS) of both pylons were measured.Experimental results illustrate that the SSE of bionic pylon is markedly improvedthat specific strength efficiency and specific stiffness efficiency of bionic pylon are increased by 52.9% and 43.6% respectively.The RCS of bionic pylon is reduced significantly.

Improving the design of reinforcing frames by simulating the arch and peltate venation structures

Based on the analyses on arch and peltate venation structures, the design of reinforcing frames was improved. First, distribution rules of the arch structure were summarized. According to the load condition and the structure of the frame, a mechanical model of arch structure was devel- oped, and two solutions for the model were analyzed and compared with each other. Through the a- nalysis, application rules of arch structure for improving the design were obtained. Then, distribu- tion rules of peltate venation structure were summarized. By using the same method, application rules of peltate venation structure for improving the design were also obtained. Finally, mechanical problem of the frame was described, and rib arrangement of the frame was redesigned. A parameter optimization for the widths of ribs in bionic arrangement was also carried out to accomplish the im- proving design. Comparison between bionic and conventional reinforcing frames shows that the weight is reduced by as much as 15.3%.

Crashworthiness Design and Multi-Objective Optimization for Bio-Inspired Hierarchical Thin-Walled Structures

Thin-walled structures have been used in many fields due to their superior mechanical properties.In this paper,two types of hierarchical multi-cell tubes,inspired by the self-similarity of Pinus sylvestris,are proposed to enhance structural energy absorption performance.The finite element models of the hierarchical structures are established to validate the crashworthiness performance under axial dynamic load.The theoreticalmodel of themean crushing force is also derived based on the simplified super folded element theory.The finite element results demonstrate that the energy absorption characteristics and deformation mode of the bionic hierarchical thin-walled tubes are further improved with the increase of hierarchical sub-structures.It can be also obtained that the energy absorption performance of corner self-similar tubes is better than edge self-similar tubes.Furthermore,multiobjective optimization of the hierarchical tubes is constructed by employing the response surface method and genetic algorithm,and the corresponding Pareto front diagram is obtained.This research provides a new idea for the crashworthiness design of thin-walled structures.

Lightweight Design and Verification of Gantry Machining Center Crossbeam Based on Structural Bionics

The lightweight and high efficiency of natural structures are the inexhaustible sources for engineering improvements. The goal of the study is to find innovative solutions for mechanical lightweight design through the application of structural bionic approaches. Giant waterlily leaf ribs and cactus stem are investigated for their optimal framework and superior performance. Their structural characteristics are extracted and used in the bio-inspired design of Lin MC6000 gantry machining center crossbeam. By mimicking analogous network structure, the bionic model is established, which has better load-carrying capacity than conventional distribution. Finite Element Method （FEM） is used for numerical simulation. Results show better specific stiffness of the bionic model, which is increased by 17.36%. Finally the scaled models are fabricated by precision casting for static and dynamic tests. The physical experiments are compared to numerical simulation. The results show that the maximum static deformation of the bionic model is reduced by about 16.22%, with 3.31% weight reduction. In addition, the first four natural frequencies are improved obviously. The structural bionic design is a valuable reference for updating conventional mechanical structures with better performance and less material consumption.

Study of Impact Resistance Based on Porcupine Quills Bionic Thin-walled Structure

Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,maximum impact force withstood,and impact force efficiency was evaluated using Ansys finite element simulation software to simulate the structure's impact.To examine the impact of ribs on the structural performance of the bionic porcupine quills,a control structure was developed.According to the results of the finite element simulation,the presence of ribs in the Bionic porcupine quills structure can transfer stress uniformly to the overall structure and share stress for some of the rupture-prone regions.Ribs reduce stress concentration in specific areas and increase the impact force efficiency of the structure.The SEA and IFE values of bionic porcupine quills were 30.01 kJ/kg and 84.22%,respectively.The structure is then optimized for parameter design in order to find the optimal structure by response surface in order to improve the structure's SEA and decrease its MIF.In order to evaluate the precision of the response surface,the optimal structure predicted is validated using finite element simulation.

The Principle of Square Hole Machining and It＇s Tooling Structure Design

In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.

Design of A Bionic Spudcan and Analysis of Penetration and Extraction Performances for Jack-up Platform

The mechanisms of soil structure interaction have drawn much attention in the past years in the installation and operation of jack-up platform. A bionic spudcan produced by biomimetic of egg and snail shell is proposed, and the performance of the penetration and extraction are analyzed by numerical method. The geometric contour of egg and snail shell is measured, and its mathematical model is established respectively. According to the structure of existing spudcan of jack-up platform, three kinds of typical biomimetic spudcan are designed. Furthermore, numerical analysis models of biomimetic spudcan are established respectively to study the soil structure interaction mechanism in the process of penetration and extraction, and contrastive analysis of resistance characteristics are carried out. To conclude, the results show that the biomimetic spudcan facilitates the platform installation, and it is also beneficial to the improvement of the bearing capacity of spudcan.

Compression Behavior and Failure Mechanisms of Bionic Porous NiTi Structures Built via Selective Laser Melting

Inspired by the crystal microstructure of metals and the bamboo,the bionic porous NiTi structures with the porosities in the range of 75.8%–84.9%were built via selective laser melting(SLM).The compression behavior and the failure mechanisms of the porous NiTi structures were evaluated.It demonstrated an increase in the elastic modulus and ultimate strength when the porosity was decreased,from 3.06 to 7.66 GPa and from 34.1 to 147.6 MPa,respectively.The relationship between the elastic modulus and the porosity obtained by the finite element analysis exhibited similar tendency with the experiment,and agreed well with the Gibson-Ashby model’s prediction.Based on the theoretical model above and the observation of the deformation processing,the plastic deformation behavior and failure mechanisms of the SLMed porous NiTi structures were analyzed.

Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo

High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.

Structural bionic design for high-speed machine tool working table based on distribution rules of leaf veins

High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes the surface-to-volume ratio.It can be seen as a plate structure stiffened by veins.Compared with a high-speed machine tool working table,leaf veins play a role of supporting part which is similar to that of stiffening ribs,and they can provide some new design ideas for lightweight design of the table.In this paper,distribution rules of leaf veins were investigated,and a structural bionic design for the table was achieved based on regulation of leaf veins.First,statistical analysis on geometric structure of leaf veins was carried out,and four distribution rules were obtained.Then,relevant mechanical models were developed and analyzed in finite element software.Based on the results from mechanical analysis on those relevant models,the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved.Both simulation and experimental verifications were carried out,and results showed that the average displacement of the working table was reduced by about 33.9%.

3D fully-enclosed triboelectric nanogenerator with bionic fish-like structure for harvesting hydrokinetic energy

The hydrokinetic energy of river current,as one of the essential and widespread renewable energies,is difficult to be harvested in low flow velocity and shallow water areas.In this work,a three-dimensional(3D)fully-enclosed triboelectric nanogenerator(FETENG)with bionic fish-like structure for harvesting hydrokinetic energy is reported,which is comprised of the triboelectric powergeneration unit,bionic fish-like structure and connection unit.Through the bionic structure,the FE-TENG realizes zero head power generation in shallow water with low flow velocity.What’s more,the effect of external excitations and bionic structures on the electrical performance are systematically studied in this work.The FE-TENG can generate peak power density of 7 and 0.36 W/m^(3)respectively under the simulated swing state with frequency of 1.25 Hz and simulated river current with flow velocity of 0.81 m/s.In practical applications,due to the 3D fully-enclosed design,the FE-TENG immersed in water for 35 days demonstrates excellent immersion durability with undiminished electrical performance.Therefore,the work proposes an efficient method realizing zero head power generation,and provides a good candidate for long-term service in the river current.

Shock-Resistant and Energy-Absorbing Properties of Bionic NiTi Lattice Structure Manufactured by SLM

Each specific structure of organisms is the best choice under specific circumstances.The excellent characteristic structures of these organisms have great application potential in the design and multi-functional optimization of energy-absorbing structures such as vehicle collisions,satellite landings,and military equipment.In this paper,using the principle of structural bionics,using the advantages of the honeycomb structure and the light weight and high strength of beetle elytra,four bionic lattice structures are studied:CH,ZPRH,SCH and IBE.Using NiTi shape memory alloy,a unique material as the base material,samples are prepared using selective laser melting(SLM)technology.By comparing the test results of the quasi-static compression test with the results of the numerical simulation,it is found that compared with the other three bionic lattice structures,the SCH structure has the best energy absorption effect in the effective stroke in the test,and the specific energy absorption can reach 6.32 J/g.ZPRH,SCH,and IBE structures not only have good and stable deformation behavior,but also have excellent impact resistance and shape memory properties.The design of these structures provides a reference for the design of anti-shock cushioning structures with self-recovery functions in the future.

Systematic Method of Applying Structural Characteristics of Natural Organisms to Mechanical Structures

Structural bionic design lacks mature and scientific theories, and the excellent structural characteristics of natural organisms sometimes cannot be transferred into engineering structures effectively. Aiming at overcoming the existing problems, this paper summarizes three related theories: similarity theory, fuzzy evaluation theory and optimization theory. Based on the related theories, a method of structural bionic design is introduced, which includes four steps: selecting the most useful structural characteristic of natural organism; analyzing the structural characteristic finally chosen for engineering problem; completing the structural bionic design for engineering structure; and verifying the structural bionic design. Similarity theory and fuzzy evaluation theory are employed to achieve Step 1. In Step 2 and Step 3, optimization theory is employed to analyze the parameters of structures. Together with the thoughts of simplification and grouping, optimization theory can reveal the relationship between organism structure and engineering structure, providing a way to structural bionic design. A general evaluation criterion is proposed in Step 4, which is feasible to evaluate the performance of different structures. Finally, based on the method, a structural bionic design of thin-walled cylindrical shell is introduced.

Development of Bionic UAVs Cluster Technology

With the wider use of UAV in various fields,the raising task complexity and the increasing environmental uncertainties,the higher requirements for UAV technology are put forward.The bionic UAV cluster system has the potential advantages of good stealth performance,strong environmental adaptability,wide expansion of task and high operational efficiency.It has excellent prospects in future information warfare,electronic warfare and conventional combat field.By reviewing the development of bionic UAV cluster technology,this paper summarizes and analyzes the latest research progresses of the key technologies such as aerodynamic mechanism and aerodynamic configuration design,driving mechanism design,autonomous flight control,adaptive networking and cluster control of bionic aircrafts.

A Novel Worm-like In-Pipe Robot with the Rigid and Soft Structure

Soft in-pipe robot has good adaptability in tubular circumstances,while its rigidity is insufficient,which affects the traction performance.This paper proposes a novel worm-like in-pipe robot with a rigid and soft structure,which not only has strong traction ability but also flexible mobility in the shaped pipes.Imitating the structure features of the earthworm,the bionic in-pipe robot structure is designed including two soft anchor parts and one rigid telescopic part.The soft-supporting mechanism is the key factor for the in-pipe robot excellent performance,whose mathematical model is established and the mechanical characteristics are analyzed,which is used to optimize the structural parameters.The prototype is developed and the motion control strategy is planned.Various performances of the in-pipe robot are tested,such as the traction ability,moving velocity and adaptability.For comparative analysis,different operating scenarios are built including the horizontal pipe,the inclined pipe,the vertical pipe and other unstructured pipes.The experiment results show that the in-pipe robot is suitable for many kinds of pipe applications,the average traction is about 6.8N,the moving velocity is in the range of 9.5 to 12.7 mm/s.

A Review:From Aquatic Lives Locomotion to Bio-inspired Robot Mechanical Designations

With the development of camera technology,high-speed cameras have greatly contributed to capturing the movement and posture of animals,which has dramatically promoted experimental biology research.At the same time,with the concept of bionics gradually gaining popularity among researchers,the design of robots is absorbing more and more biological features,where the interest in the bio-inspired robot is hewed out.Compared with the traditional robot,the bio-inspired robot imitates the motion pattern to achieve similar propulsion features,which may be more effective and reasonable.In this paper,the motion patterns of aquatic animals are divided into four categories according to their propulsion mechanisms:drag-based,lift-based,jet-based,and interface-based.And bio-inspired robots imitating aquatic prototypes are introduced and reviewed.Finally,the prospect of aquatic bio-inspired robots is discussed.

Study of the Ballistic Impact Behavior of Protective Multi-Layer Composite Armor

The abalone shell,a composite material whose cross-section is composed of inorganic and organic layers,has high strength and toughness.Inspired by the abalone shell,several multi-layer composite plates with different layer sequences and thicknesses are studied as bullet-proof material in this paper.To investigate the ballistic performance of this multi-layer structure,the complete characterization model and related material parameters of large deformation,failure and fracture ofAl_(2)O_(3)ceramics andCarbon Fiber Reinforced Polymer(CFRP)are studied.Then,3D finite element models of the proposed composite plates with different layer sequences and thicknesses impacted by a 12.7 mm armor-piercing incendiary(API)are built using Abaqus to predict failure.The simulation results show that the CFRP/Al2O3 ceramic/Ultrahigh Molecular Weight Polyethylene(UHMWPE)/CFRP(1 mm/4 mm/4 mm/1 mm)composite is the optimized stack of layers.The simulation results under specified layer sequence and thickness have a reasonable correlation with the experimental results and reflect the failure and fracture of the multi-layer composite protective armor.

Pomelo Peel-Inspired 3D-Printed Porous Structure for Efficient Absorption of Compressive Strain Energy

The porous structure in pomelo peel is believed to be responsible for the protection of its fruit from damage during the free falling from a tree.The quantitative understanding of the relationship between the deformation behavior and the porous structure could pave the way for the design of porous structures for efficient energy absorption.Here,a universal feature of pore distribution in pomelo peels along the radial direction is extracted from three varieties of pomelos,which shows strong correlation to the deformation behavior of the peels under compression.Guided by the porous design found in pomelo peels,porous polyether-ether-ketone(PEEK)cube is additively manufactured and possesses the highest ability to absorb energy during compression as compared to the non-pomelo-inspired geometries,which is further confirmed by the finite element simulation.The nature-optimized porous structure revealed here could guide the design of lightweight and high-energy-dissipating materials/devices.

Study on Functional Mechanical Performance of Honeycomb Array Structures Inspired by Gideon Beetle

To obtain bio-inspired structures with superior biological function,four bio-inspired structures named regular arrangement honeycomb structure(RAHS),staggered arrangement honeycomb structure(SAHS),floral arrangement honeycomb structure(FLAHS)and functional arrangement honeycomb structure(FUAHS)are designed by observing the microstructure of the Gideon beetle,based on the optimal size bio-inspired cells by response surface method(RSM)and particle swarm optimization(PSO)algorithm.According to Euler theory and buckling failure theory,compression deformation properties of bio-inspired structures are explained.Experiments and simulations further verify the accuracy of theoretical analysis results.The results show that energy absorption of FLAHS is,respectively,increased by 26.95%,22.85%,and 121.45%,compared with RAHS,SAHS,and FUAHS.Elastic modulus of FLAHS is 110.37%,110.37%,and 230.56% of RAHS,SAHS,and FUAHS,respectively.FLAHS perfectly inherits crashworthiness and energy absorption properties of the Gideon beetle,and FLAHS has the most stable force.Similarly,RAHS,SAHS,and FUAHS,respectively,inherit mechanical properties of the Gideon beetle top horn,the Gideon beetle middle horn,and the abdomen of the beetle.This method,designing bio-inspired structures with biological functions,can be introduced into the engineering field requiring the special function.