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Topology Optimization of Metamaterial Microstructures for negative poisson’s ratio under Large Deformation Using a Gradient-Free Method

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Computer Modeling in Engineering & sciences 2024年第5期139卷 2001-2026页

作者： Weida Wu Yiqiang Wang Zhonghao Gao Pai Liu state Key Laboratory of structural Analysis for Industrial Equipment Dalian University of TechnologyDalian116024China

negative poisson’s ratio(NPR)metamaterials are attractive for their unique mechanical behaviors and potential applications in deformation control and energy absorption.However,when subjected to significant stretching,NPR metamaterials designed under small strain assumption may experience a rapid degradation in NPR performance.To address this issue,this study aims to design metamaterials maintaining a targeted NPR under large deformation by taking advantage of the geometry nonlinearity mechanism.A representative periodic unit cell is modeled considering geometry nonlinearity,and its topology is designed using a gradient-free method.The unit cell microstructural topologies are described with the material-field series-expansion(MFsE)method.The MFsE method assumes spatial correlation of the material distribution,which greatly reduces the number of required design variables.To conveniently design metamaterials with desired NPR under large deformation,we propose a two-stage gradient-free metamaterial topology optimization method,which fully takes advantage of the dimension reduction benefits of the MFsE method and the Kriging surrogate model technique.Initially,we use homogenization to find a preliminary NPR design under a small deformation assumption.In the second stage,we begin with this preliminary design and minimize deviations in NPR from a targeted value under large deformation.Using this strategy and solution technique,we successfully obtain a group of NPR metamaterials that can sustain different desired NPRs in the range of[−0.8,−0.1]under uniaxial stretching up to 20% strain.Furthermore,typical microstructure designs are fabricated and tested through experiments.The experimental results show good consistency with our numerical results,demonstrating the effectiveness of the present gradientfree NPR metamaterial design strategy.

关键词： Topology optimization microstructural design negative poisson’s ratio large deformation

negative poisson's ratio and peripheral strain of an NPR anchor cable

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Journal of Mountain science 2022年第8期19卷 2435-2448页

作者： TAO Zhi-gang XU Hao-tian REN shu-lin GUO Long-ji QIN Ke ZHU Yi-fei state Key Laboratory for Geomechanics&Deep Underground Engineering Beijing 100083China school of Mechanics and Civil Engineering China University of Mining&TechnologyBeijing 100083China

Materials with a negative poisson’s ratio effect perform significantly better than traditional materials for rock mass impact resistance,shear resistance,and energy absorption.Based on these advantages,a negative poisson’s ratio anchor cable(NPR anchor cable)with high elongation and constant resistance was developed and successfully applied in the field of mine disaster control.However,theoretical and experimental research on the negative poisson’s ratio effect and peripheral strain characteristics of NPR anchor cables is currently incomplete.This study used several theories and methods,such as static tensile,peripheral strain measurement,and static negative poisson’s ratio measurement,to investigate the radial deformation law of an NPR anchor cable and the negative poisson’s ratio characteristics.Experimental results elucidated constant resistance changes in an NPR anchor cable during operation,the motion of the constant resistance body in the constant resistance sleeve,and the deformation law of the constant resistance sleeve.negative poisson’s ratio characteristics of the NPR anchor cable and its superior energy absorption characteristics were verified and it provided a theoretical and experimental basis for energy absorption mechanisms of an NPR anchor cable.

关键词： NPR anchor cable static tensile test negative poisson’s ratio Energy absorption

3D-printed auxetic-structured intervertebral disc implant for potential treatment of lumbar herniated disc

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生物活性材料(英文) 2023年第2期20卷 528-538页

作者： Yulin Jiang Kun shi Luonan Zhou Miaomiao He Ce Zhu Jingcheng Wang Jianhua Li Yubao Li Limin Liu Dan sun Ganjun Feng Yong Yi Li Zhang Analytical and Testing Center Department of Orthopedic Surgery and Orthopedic Research InstituteSichuan UniversityChengdu610065China school of Materials science and Engineering Southwest University of Science and TechnologyMianyang621010China Advanced Composite Research Group(ACRG) School of Mechanical and Aerospace EngineeringQueen’s University BelfastBT95AHUK

In this study,a novel artificial intervertebral disc implant with modified“Bucklicrystal”structure was designed and 3D printed using thermoplastic polyurethane.The new implant has a unique auxetic structure with building blocks joined“face-to-face”.The accompanied negative poisson’s ratio enables its excellent energy absorption and stability under compression.The deformation and load distribution behavior of the implant under various loading conditions(bending,torsion,extension and flexion)has been thoroughly evaluated through finite element method.Results show that,compared to natural intervertebral disc and conventional 3D implant,our new implant exhibits more effective stress transfer and attenuation under practical loading conditions.The implant’s ability to contract laterally under compression can be potentially used to alleviate the symptoms of lumbar disc herniation.Finally,the biocompatibility of the implant was assessed in vitro and its ability to restore the physiological function of the disc segment was validated in vivo using an animal model.

关键词： negative poisson’s ratio Lumbar disc herniation Finite element simulation

Programmable soft bending actuators with auxetic metamaterials

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science China(Technological sciences) 2020年第12期63卷 2518-2526页

作者： PAN Qi CHEN shiTong CHEN FeiFei ZHU XiangYang Robotics Institute School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China state Key Laboratory of Mechanical system and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

soft robotics has been receiving increasing attention due to its flexibility and adaptability offered by embodied intelligence. A soft robot may undergo complex motions including stretching,contraction,bending,twisting,and their intricate combinations.Among these basic motions,bending plays a central role when a robot accomplishes tasks such as locomotion,grasping and manipulation. Although a rich repertoire of bending mechanisms has been reported,a systematic and rational design framework is still lack. In this paper,we provide a novel design strategy for soft bending actuators which allows integral modeling and design optimization. Nowadays,metamaterials are emerging as a new tool for soft robots,by encoding the desired complex motions directly within the material architectures,leading to conformable monolithic systems. We combine pneumatic actuators and flexible metamaterials to provide an alternative solution to soft bending actuators,with advantages of compact design,large bending motion,and convenient fabrication. A regular pneumatic chamber is embedded inside auxetic and non-auxetic metamaterials,and bending is generated when inflated. We carry out dimensionless analysis to identify the key design variables. To provide insight into design optimization,we develop a computation framework by modeling metamaterial structures with beam elements and the inner chamber with shell elements as an integral part,allowing efficient simulation of the coupled system. We systematically investigate how the bending angle varies with the key design variables and find the optimal design parameters.The experimental results are well in line with the simulation,and a remarkable bending motion of 0.43°/mm is achieved.

关键词： soft robotics bending actuator auxetic metamterials negative poisson’s ratio

Effect of Axial Deformation on Elastic Properties of Irregular Honeycomb structure

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Chinese Journal of Mechanical Engineering 2021年第4期34卷 276-287页

作者： Ning Wang Qingtian Deng school of science Chang’an UniversityXi’an 710064China

Irregular honeycomb structures occur abundantly in nature and in man-made products,and are an active area of research.In this paper,according to the optimization of regular honeycomb structures,two types of irregular honeycomb structures with both positive and negative poisson’s ratios are presented.The elastic properties of irregular honeycombs with varying structure angles were investigated through a combination of material mechanics and structural mechanics methods,in which the axial deformation of the rods was considered.The numerical results show that axial deformation has a significant influence on the elastic properties of irregular honeycomb structures.The elastic properties of the structure can be considered by the enclosed area of the unit structure,the shape of the unit structure,and the elastic properties of the original materials.The elastic properties considering the axial deformation of rods studied in this study can provide a reference for other scholars.

关键词： Axial deformation Elastic modulus Positive poisson’s ratio negative poisson’s ratio Irregular honeycombs

A novel wavy non-uniform ligament chiral stent with J-shaped stress-strain behavior to mimic the native trachea

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Bio-Design and Manufacturing 2021年第4期4卷 851-866页

作者： Jiapeng Liu Xinhua Yao Zhenwei Wang Jian Ye Congcong Luan Jianzhong Fu Yong He state Key Laboratory of Fluid Power and Mechatronic systems College of Mechanical EngineeringZhejiang UniversityHangzhou 310027China Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province College of Mechanical EngineeringZhejiang UniversityHangzhou 310027China Department of Pneumology Affiliated Hangzhou First People’s HospitalZhejiang University School of MedicineHangzhou 310006China

Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trachea,which leads to a variety of serious complications.In this study,inspired by the structure of the native trachea,a wavy non-uniform ligament chiral tracheal stent is proposed,in which J-shaped stress-strain behavior and negative poisson's ratio response are achieved by replacing the tangential ligament of tetrachiral and anti-tetrachiral hybrid structure with a wavy non-uniform ligament.Through the combination of theoretical analysis,finite element analysis and experimental tests,a wide range of desired J-shaped stress-strain curves are explored to mimic the native porcine trachea by tailoring the stent geometry.Besides,the negative poisson’s ratio and auxetic diameter curves versus axial strain of the stent are also studied in detail,thus contributing to the enhancement of cross-section ventilation and reducing the migration of the stent.This novel tracheal stent with a unique microstructure shows a potential to perfectly match the physiological activities of the native trachea and thereby reduce potential complications.

关键词： Tracheobronchial stenosis Tracheal stent Chiral auxetic structure Wavy non-uniform ligament J-shaped stress-strain behavior negative poisson’s ratio

Data-Driven structural Design Optimization for Petal-shaped Auxetics Using Isogeometric Analysis

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Computer Modeling in Engineering & sciences 2020年第2期122卷 433-458页

作者： Yingjun Wang Zhongyuan Liao shengyu shi Zhenpei Wang Leong Hien Poh National Engineering Research Center of Novel Equipment for Polymer Processing the Key Laboratory of Polymer Processing Engineering of the Ministry of Education(South China University of Technology)Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced ManufacturingSouth China University of TechnologyGuangzhou510641China. Institute of High Performance Computing(IHPC) Agency for ScienceTechnology and Research(A*STAR)1 Fusionopolis Way138632Singapore. Department of Civil and Environmental Engineering National University of Singapore 1 Engineering Drive 2E1A 07-03117576Singapore

Focusing on the structural optimization of auxetic materials using data-driven methods,a back-propagation neural network(BPNN)based design framework is developed for petal-shaped auxetics using isogeometric analysis.Adopting a NURBsbased parametric modelling scheme with a small number of design variables,the highly nonlinear relation between the input geometry variables and the effective material properties is obtained using BPNN-based fitting method,and demonstrated in this work to give high accuracy and efficiency.such BPNN-based fitting functions also enable an easy analytical sensitivity analysis,in contrast to the generally complex procedures of typical shape and size sensitivity approaches.

关键词： Data-driven BP neural network petal-shaped auxetics negative poisson’s ratio structural design isogeometric analysis.

Auxetics in Biomedical Applications: A Review

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Journal of Minerals and Materials Characterization and Engineering 2023年第2期11卷 27-35页

作者： sean Rose Dexter siu JD Zhu Reem Roufail Department of systems Design Engineering University of Waterloo Waterloo ON Canada

Materials exhibiting auxetic properties have a negative poisson’s ratio, which intrigued researchers to understand the behavior of auxetic structure. several researchers focused on the different auxetic cell designs, while others focused on the auxetic applications. With the advance of additive manufacturing methods, computer-aided design and finite element analysis in recent decades, auxetics have been explored. One of the interesting applications is in the field of biomedical devices or implants, especially for certain natural biomedical organs such as tissues, certain ligaments that have auxetic properties. This paper is an overview of auxetic design approaches and biomedical applications.

关键词： Auxetics negative poisson’s ratio Biomaterials Biomedical Engineering

Unit Cell Modelling of Auxetic structure

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Journal of Minerals and Materials Characterization and Engineering 2022年第4期10卷 360-369页

作者： sydney Pothier Reem Roufail Margaret Malton systems Design Engineering University of Waterloo Waterloo Canada

Auxetic material structures exhibit a negative poisson ratio. The structure expands in the axial and transverse directions under tensile loading and vice versa under compression loading. Many fabricated designs for auxetic materials exist such as re-entrant hexagonal, chiral, and arrowhead geometries. This paper studies the unit cell of the re-entrant hexagonal geometry to understand how changing the internal angle and fillet radius of the structure affects the poisson’s ratio. The material chosen for this study is acrylonitrile butadiene styrene (ABs) due to its availability and frequent use in additive manufacturing. The study was based on finite element analysis. It is observed that the direction of load applied to the unit cell affects the unit cell strain, poisson’s ratio, and maximum load capacity before failure responses. It is noticed that the re-entrant cell starts by showing a standard non-auxetic behavior until it reaches a specific axial strain value. A quadratic correlation is identified between axial and transverse strain. Designing an auxetic structure starts with understanding the behavior of a unit cell structure. The auxetic structure design is a complex process that requires a compromise between auxetic property to be achieved and load capacity via avoiding stress concentration zones.

关键词： Auxetic Material negative poisson’s ratio Re-Entrant Hexagon Finite Element Analysis Unit Cell Design