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Bionic lightweight design of limb leg units for hydraulic quadruped robots by additive manufacturing and topology optimization

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Bio-Design and Manufacturing 2024年第1期7卷 1-13页

作者： Huaizhi Zong Junhui Zhang Lei Jiang Kun Zhang Jun Shen Zhenyu Lu Ke Wang Yanli Wang Bing Xu The State Key laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310058China Unmanned Vehicle research and Development Center China North Vehicle Research InstituteBeijing 100072China School of Mechatronic Engineering Nanchang UniversityNanchang 330031China Auclean high-Tech Ltd. Wuxi 214108China

Galloping cheetahs,climbing mountain goats,and load hauling horses all show desirable locomotion capability,which motivates the development of quadruped *** various quadruped robots,hydraulically driven quadruped robots show great potential in unstructured environments due to their discrete landing positions and large *** the most critical movement unit of a quadruped robot,the limb leg unit(LLU)directly affects movement speed and reliability,and requires a compact and lightweight *** by the dexterous skeleton–muscle systems of cheetahs and humans,this paper proposes a highly integrated bionic actuator system for a better dynamic performance of an *** propose that a cylinder barrel with multiple element interfaces and internal smooth channels is realized using metal additive manufacturing,and hybrid lattice structures are introduced into the lightweight design of the piston *** addition,additive manufacturing and topology optimization are incorporated to reduce the redundant material of the structural parts of the *** mechanical properties of the actuator system are verified by numerical simulation and experiments,and the power density of the actuators is far greater than that of cheetah *** mass of the optimized LLU is reduced by 24.5%,and the optimized LLU shows better response time performance when given a step signal,and presents a good trajectory tracking ability with the increase in motion frequency.

关键词： Additive manufacturing Bionic lightweight design Limb leg unit Quadruped robot Trajectory tracking

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high-Order Two-Scale Asymptotic Paradigm for the Elastodynamic Homogenization of Periodic Composites

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Acta Mechanica Solida Sinica 2024年第1期37卷 124-138页

作者： Wei-Zhi Luo Mu He Liang Xia Qi-Chang He State Key laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Laboratoire Modélisation et simulation Multi-Echelle MSME UMR 8208 CNRSUniversite Gustave Eiffel77454 Marne-la-ValléeFrance

The classical two-scale asymptotic paradigm provides macroscopic and microscopic analyses for the elastodynamic homogenization of periodic composites based on the spatial or/and temporal variable,which offers an approximate framework for the asymptotic homogenization analysis of the motion ***,in this framework,the growing complexity of the homogenization formulation gradually becomes an obstacle as the asymptotic order *** such a context,a compact,fast,and accurate asymptotic paradigm is *** work reviews the high-order spatial two-scale asymptotic paradigm with the effective displacement field representation and optimizes the implementation by symmetrizing the tensor to be ***,the modified implementation gets rid of the excessive memory consumption required for computing the high-order tensor,which is demonstrated by representative one-and two-dimensional *** numerical results show that(1)the contrast of the material parameters between media in composites directly affects the convergence rate of the asymptotic results for the homogenization of periodic composites,(2)the convergence error of the asymptotic results mainly comes from the truncation error of the modified asymptotic homogenized motion equation,and(3)the excessive norm of the normalized wavenumber vector in the two-dimensional inclusion case may lead to a non-convergence of the asymptotic results.

关键词： Composites Homogenization Asymptotic analysis Dynamics Dispersion

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Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

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Defence Technology（防务技术） 2024年第5期35卷 108-122页

作者： Jianqiang Deng Tao Liu Liming Chen Xin Pan Jingzhe Wang Shaowei Zhu Weiguo Li College of Aerospace Engineering Chongqing UniversityChongqing 400030China State Key laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China Chongqing Key laboratory of Heterogeneous material Mechanics Chongqing UniversityChongqing 400030China State Key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels(FSP)under high-velocity impact using the explicit non-linear finite element *** on the geometric topology of the FSP system,three FSP configurations with the same areal density are derived,namely multi-layer,gradient core and asymmetric face sheet,and three key structural parameters are identified:core thickness(t_(c)),face sheet thickness(t_(f))and overlap face/core number(n_(o)).The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity(BLV),deformation modes,energy dissipation mechanism,and specific penetration energy(SPE).The results show that the FSP system exhibits a significant configuration dependence,whose ballistic performance ranking is:asymmetric face sheet>gradient core>*** mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP *** BLV and SPE increase with tf,while the raising tcor noleads to an increase in BLV but a decrease in ***,a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis,based on which the ballistic optimization procedure is also conducted and a design chart is *** study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

关键词： Sandwich panel numerical simulation Ballistic resistance Specific penetration energy Energy analysis

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AViscosity-Splitting Method for the Navier-Stokes/ Darcy Problem

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Advances in Applied Mathematics and Mechanics 2020年第1期12卷 251-277页

作者： Yunxia Wang Xuefeng Han Zhiyong Si School of materials Science and Engineering Henan Polytechnic UniversityJiaozuoHenan 454003China henan joint international research laboratory for high performance metallic material and their numerical simulation Henan Polytechnic UniversityJiaozuoHenan 454003China School of Mathematics and Information Science Henan Polytechnic UniversityJiaozuoHenan 454003China School of Mathematics and Computational Science Xiangtan UniversityXiangtanHunan 411105China

In this report,we give a viscosity splitting method for the Navier-Stokes/Darcy *** this method,the Navier-Stokes/Darcy equation is solved in three *** the first step,an explicit/implicit formulation is used to solve the nonlinear *** introduce an artificial diffusion term qDu in our scheme whose purpose is to enlarge the time stepping and enhance numerical stability,especially for small viscosity parameter n,by choosing suitable parameter *** the second step,we solve the Stokes equation for velocity and *** the third step,we solve the Darcy equation for the piezometric head in the porous media *** use the numerical solutions at last time level to give the interface condition to decouple the Navier-Stokes equation and the Darcy’s *** stability analysis,under some condition △t≤k0,k0>0,is *** error estimates prove our method has an optimal convergence ***,some numerical results are presented to show the performance of our algorithm.

关键词： Navier-Stokes/Darcy equations fractional step method viscosity-splitting method,stability analysis optimal error analysis

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On the thermodynamics of plasticity during quasi-isentropic compression of metallic glass

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Matter and Radiation at Extremes 2024年第2期9卷 74-89页

作者： Kaiguo Chen Bo Chen Yinan Cui Yuying Yu Jidong Yu Huayun Geng Dongdong Kang Jianhua Wu Yao Shen Jiayu Dai College of Science National University of Defense TechnologyChangsha 410073People’s Republic of China Hunan Key laboratory of Extreme Matter and Applications National University of Defense TechnologyChangsha 410073People’s Republic of China Applied Mechanics laboratory Department of Engineering MechanicsSchool of AerospaceTsinghua UniversityBeijing 100084People’s Republic of China Institute of Fluid Physics China Academy of Engineering PhysicsMianyangPeople’s Republic of China Department of material Science and Technology Shanghai Jiao Tong UniversityShanghaiPeople’s Republic of China

Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physicalproperties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change aresuccessfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relativelyinsensitive to the strain rate ˙γ when ˙γ ranges from 7.5 × 10^(8) to 2 × 10^(9)/s, which are values reachable in QIC experiments, with a magnitudeof the order of 10^(−2)kB/atom per GPa. However, when ˙γ is extremely high (>2 × 10^(9)/s), a notable increase in entropy production rate with˙γ is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated thatentropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase inconfigurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamentalrelation between microstructure evolution and plastic dissipation.

关键词： entropy metallic regime

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Ultra-efficient and parameter-free computation of submicron thermal transport with phonon Boltzmann transport equation

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Fundamental research 2024年第4期4卷 907-915页

作者： Yue Hu Yongxing Shen Hua Bao University of Michigan-Shanghai Jiao Tong University joint Institute Shanghai Jiao Tong UniversityShanghai 200240China

Understanding thermal transport at the submicron scale is crucial for engineering applications,especially in the thermal management of electronics and tailoring the thermal conductivity of thermoelectric *** the submicron scale,the macroscopic heat diffusion equation is no longer valid and the phonon Boltzmann transport equation(BTE)becomes the governing equation for thermal ***,previous thermal simulations based on the phonon BTE have two main limitations:relying on empirical parameters and prohibitive computational ***,the phonon BTE is commonly used for qualitatively studying the non-Fourier thermal transport phenomena of toy *** this work,we demonstrate an ultra-efficient and parameter-free computational method of the phonon BTE to achieve quantitatively accurate thermal simulation for realistic materials and *** properly integrating the phonon properties from first-principles calculations,our method does not rely on empirical material properties *** can be generally applicable for different materials and the predicted results can match well with experimental ***,by developing a suitable ensemble of advanced numerical algorithms,our method exhibits superior numerical *** full-scale(from ballistic to diffusive)thermal simulation of a 3-dimensional fin field-effect transistor with 13 million degrees of freedom,which is prohibitive for existing phonon BTE solvers even on supercomputers,can now be completed within two hours on a single personal *** method makes it possible to achieve the predictive design of realistic nanostructures for the desired thermal *** also enables accurately resolving the temperature profiles at the transistor level,which helps in better understanding the self-heating effect of electronics.

关键词： Submicron thermal transport Boltzmann transport equation Deterministic numerical method Phonon transport Transistors Nanostructured materials

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Gamma ray multiplicity of a^(240)Pu solid sphere simulated by JMCT

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Nuclear Science and Techniques 2022年第5期33卷 8-15页

作者： Huan-Huan Ding Fan Gao Chang-Bing Lu Rui Li Chen-Guang Li Zhao-Hong Mo Dun-Fu Shi Ming Su De-Shan Zhao Mao-Bing Shuai Zhong-Hua Xiong Bin-Yuan Xia Yun Bai Institute of materials China Academy of Engineering PhysicsMianyang 621908China The 93147th Unit of PLA Mianyang 621000China CAEP Software Center for high performance numerical simulation Beijing 100088China Institute of Applied Physics and Computational Mathematics Beijing 100088China

Determining the mass of plutonium metal is an important research objective in the field of nuclear material accounting and *** on the 3D neutron and photon transport code JMCT(jointed Monte Carlo Transport),the gamma ray multiplicity of ^(240)Pu was simulated in this study,and the average number of gamma rays leaking from ^(240)Pu solid spheres with different masses was also *** simulation results show that there is a oneto-one correspondence between the average number of gamma rays and the mass of ^(240)Pu solid spheres in the range of 0.50–3.00 *** result provides a basis for using the average number of gamma rays to account for the mass of ^(240)Pu.

关键词： ^(240)Pu JMCT Gammaraymultiplicity Solid sphere mass Surface-to-volumeratio

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Broadband high-efficiency plasmonic metalens with negative dispersion characteristic

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Photonics research 2024年第4期12卷 813-820页

作者： YONG-QIANG LIU YONG ZHU HONGCHENG YIN JINHAI SUN YAN WANG YONGXING CHE National Key laboratory of Scattering and Radiation Beijing 100854China

Controlling the dispersion characteristic of metasurfaces(or metalenses) along a broad bandwidth is of great importance to develop high-performance broadband metadevices. Different from traditional lenses that rely on the material refractive index along the light trajectory, metasurfaces or metalenses provide a new regime of dispersion control via a sub-wavelength metastructure, which is known as negative chromatic ***, broadband metalenses design with high-performance focusing especially with a reduced device dimension is a significant challenge in society. Here, we design, fabricate, and demonstrate a broadband highperformance diffractive-type plasmonic metalens based on a circular split-ring resonator metasurface with a relative working bandwidth of 28.6%. The metalens thickness is only 0.09λ0(λ0is at the central wavelength),which is much thinner than previous broadband all-dielectric metalenses. The full-wave simulation results show that both high transmissive efficiency above 80%(the maximum is even above 90%) and high average focusing efficiency above 45%(the maximum is 56%) are achieved within the entire working bandwidth of 9–12 ***, an average high numerical aperture of 0.7(NA = 0.7) of high-efficiency microwave metalens is obtained in the simulations. The broadband high-performance metalens is also fabricated and experimental measurements verify its much higher average focusing efficiency of 55%(the maximum is above 65% within the broad bandwidth) and a moderate high NA of 0.6. The proposed plasmonic metalens can facilitate the development of wavelength-dependent broadband diffractive devices and is also meaningful to further studies on arbitrary dispersion control in diffractive optics based on plasmonic metasurfaces.

关键词： resonator dispersion high

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Nonlinear Impact Damage Evolution of Charpy Type and Analysis of Its Key Influencing Factors

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 254-264页

作者： Jianfeng Mao Qian Xu Jiadong Yang Chi Cao Dasheng Wang Fengping Zhong Mingya Chen Institute of Process Equipment and Control Engineering Zhejiang University of TechnologyHangzhou 310032China Taizhou Key laboratory of Advanced Manufacturing Technology Taizhou InstituteZhejiang University of TechnologyTaizhou 318014China State Key laboratory of Nuclear Power Safety Monitoring Technology and Equipment Shenzhen 518172China Zhejiang Academy of Special Equipment Science Hangzhou 310020China Suzhou Nuclear Power research Institute Suzhou 215004China

The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by *** with experiments,numerical simulation can study many problems with harsh ***,there are still few studies on the influence of geometric factors such as side *** this paper,the geometry of standard Charpy impact test is *** with different widths and side grooves are *** finite element model of Charpy impact was established by ABAQUS *** test results and simulation results to verify each *** effects of sample width,side groove depth and side groove bottom fillet on the impact fracture resistance of the sample were *** results show that the specimen width is positively correlated with the impact toughness of the *** side groove greatly reduces the impact toughness of the material;the toughness of side groove decreases with the increase of depth;the fracture toughness of side groove decreases with the increase of fillet at the bottom of side *** proportion of toughness energy to impact energy of samples was *** results show that the toughness energy accounts for about 70%of the impact energy of the sample,which has little to do with the geometric characteristics of the *** study presents a reliable method for studying Charpy impact *** influence of geometric parameters is obtained,which provides a reference method for the study of impact toughness of high toughness materials.

关键词： Johnson-Cook model Impact toughness Charpy impact

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numerical Analysis of Phase Change and Container materials for Thermal Energy Storage in the Storage Tank of Solar Water Heating System

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Journal of Thermal Science 2024年第2期33卷 408-421页

作者： SINGH Shailendra ANAND Abhishek SHUKLA Amritanshu SHARMA Atul Non-Conventional Energy laboratory Rajiv Gandhi Institute of Petroleum TechnologyJais Amethi229304India

This study evaluates the effectiveness of phase change materials(PCMs) inside a storage tank of warm water for solar water heating(SWH) system through the theoretical simulation based on the experimental model of *** et *** model is explained by five fundamental equations for the calculation of various parameters like the effectiveness of PCMs,the mass of hot water,total heat content,and duration of *** study simulated eleven PCMs to analyze their effectiveness like Sodium hydrogen phosphate dodecahydrate(SHPD),OM 37,N-Eicosane(NE),Lauric acid(LA),Paraffin wax(PW),OM 48,Paraffin wax C_(20-33)(PW-C20-33),Sodium acetate trihydrate(SAT),Palmitic acid(PA),Myristic acid(MA),and Stearic acid(SA).Among all PCMs,the SHPD has found the highest value of effectiveness factor of ***,it is the most recommended PCM for the storage tank of the SWH *** study also includes the melt fraction analysis of all enumerated PCMs corresponding to container materials of stainless steel,glass,aluminum mixed,tin,aluminum,and *** melt fraction analysis is performed by making a coding program in the FORTRAN programming *** the analysis,copper container material is found to have high melting rate for all PCMs so it is superior to other container materials.

关键词： theoretical model solar water heating system phase change material effectiveness factor melt fraction

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