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Progress in Natural Science:Materials International 2023年第6期33卷 812-824页

作者： Yin Wang Yong Li Wei Yu Chen He Haiyao Wang Guangming Xu Jiadong Li State Key Laboratory of Rolling and Automation Northeastern University Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern University Guangxi Advanced Aluminum Processing Innovation Center Co.LTD Shenyang Institute of Automation Chinese Academy of Sciences

There are always microcracks and pores during the laser additive manufacturing of 7xxx aluminum alloy,which significantly limits its performance improvement and *** work uses additives to suppress defects and improve the alloy’s *** three alloys were prepared by the addition of silicon,TiN,or *** microstructure and mechanical properties were investigated in *** results show that silicon can inhibit the crack generation by reducing the solidification *** grain size is *** can refine the grain and it creates *** addition of both can restrain the defects,refine the grains and obtain good comprehensive ***,the hardness and wear resistance of A3 are slightly lower than A2 due to the brittle phase generated by the addition of *** yield strength,tensile strength,elongation,hardness and wear rate of A3 alloy treated by T6 are 214.8 MPa,262.8 MPa,2.59 %,130.9 HV and 2.24 × 10-3mm3/(N·m).

关键词： Laser additive manufacturing Metal matrix composites Al–Zn–Mg–Cu alloys Microstructure Tensile property friction property

Effect of Directional Stretching on Properties of PVA-HA-PAA Composite Hydrogel

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Journal of Bionic Engineering 2021年第5期18卷 1202-1214页

作者： Kai Chen Qin Chen Tian Zong Siyu Liu Xuehui Yang Yong Luo Dekun Zhang School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221116China Department of Mechanical Engineering Purdue School of Engineering and TechnologyIUPUIIndianapolisIN 46202USA

Polyvinyl alcohol(PVA)hydrogels with excellent characteristics are considered as promising cartilage replacement ***,there are still some main issues to be solved for PVA hydrogel,such as poor mechanical strength and disordered *** by the highly ordered structure of biological soft tissues such as articular cartilage,here,we prepared a high-strength but anisotropic polyvinyl alcohol-nanohydroxyapatite-polyacrylic acid(PVA-HA-PAA)composite hydrogel by directional stretching,freezing–thawing,and annealing *** of an as-prepared isotropic PVA-HA-PAA composite hydrogel leads to the orientation of PVA crystallites and PVA chains,which enables the formation of ordered structure and more hydrogen bonds via freezing under *** microstructure,water content,swelling and creep performance,tensile and bio-tribology properties of the composite hydrogel are studied,the results indicated that the properties of the hydrogel are aff ected by stretching due to the formation of ordered structure in the anisotropic *** instance,the elastic modulus and tensile strength of the anisotropic hydrogel reach 5.703 MPa and 18.958 MPa,respectively,which is significantly enhanced by comparing with isotropic ***,the friction property is anisotropic,and the Coefficient Of friction(COF)reduced in the parallel ***,this work provides a simple and practicable strategy to design strong and anisotropic hydrogels for potential applications in biomedical materials such as cartilage substitute.

关键词： PVA-HA-PAA hydrogel Directional stretching Anisotropic Mechanical properties friction property

Lyapunov　exponent　and　dimension　of　the　strange　attractor　of　elastic　frictional　system

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Acta Seismologica Sinica(English Edition) 1995年第4期8卷 575-584页

作者：牛志仁陈党民 1. Seismological Bureau of Shaanxi Province 710068 Xi’an China

In this paper, we have calculated the spectrum of Lyapunov exponent of the strange attractor for a single degree of freedom in elastic system with a two-state variable friction law via the method advanced by Wolf. The system is expressed by the following dimensionless equation:where,and f are dimensionless state variable, logarithm slip velocity and frictional stress, respectively;β1,β2,ρ,and K are dimensionless system *** state of this system is chaotic when dimensionless parameters are β1=1. 00, β2=0. 84, ρ=0. 048, =0. 198 85, K=0. *** Lyapunov exponent spectrum of its strange attractor has been calculated as follows:λ1=0. 0179, λ2=0, λ3=-0. 1578The dimension of this strange attractor has also been calculated as DL=D0=2.11where DL and D0 denote Lyapunov dimension and Kolmogorov dimension respectively.

关键词： friction property fractal dimension two-state variable Lyapunov exponent

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Structure and mechanical properties of pincers for freshwater lobster

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Science China(Technological Sciences) 2011年第3期54卷 650-658页

作者： WU ZhiWei ZHOU Fei Academy of Frontier Science Nanjing University of Aeronautics and Astronautics Nanjing 210016 China School of Mechanical Engineering Nanjing Forestry University Nanjing 21003Z China

The mineral phases and structure of pincer for the freshwater lobster were analyzed and observed by using X-ray diffraction and field-emission scanning electronic microscope with energy dispersive spectroscopy, and the mechanical properties of pincer were determined by using nano-indenter and micro-tribometer. The results showed that the pincers contained Ca, Mg, C, O, Na, etc. elements and there were many amorphous mineral phases in the lobster pincers. There were many concave hollows and convex domes with seta on the surface of pincer, and some spines were observed on the surface of seta, which exhibited non-smooth surface. The exoskeleton of pincer consisted of epicuticle, exocuticle and endocuticle, and the microstructure of exocuticle and endocuticle displayed the twisted plywood structure with chitin protein fibers. The mean hardness and elastic modulus on the surface of fresh pincers were 0.27 GPa and 5.28 GPa, respectively. With the increase in distance from the surface, the hardness and elastic modulus all decreased gradually. This indicated that the transition of hardness and elastic modulus occurred from exocuticle to endocuticle. When the heat treatment temperature was lower than 200°C, the values of hardness and elastic modulus fluctuated slightly, while they increased at the temperature beyond 200°C. As the pincers slid against Si3N4 balls in water and air, the friction coefficients in water were higher than those in air. The research could provide a bio-inspired basis for the structural design of composite materials and anti-friction surface.

关键词： lobster pincers mechanical properties bio-inspired composite materials friction property

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Molecular Dynamics Simulation on friction and Thermal Properties of FCC Copper in Nanoscale Sliding Contacts

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Journal of Harbin Institute of Technology(New Series) 2022年第2期29卷 24-33页

作者： Ruiting Tong Bin Han Tao Zhang Zefen Quan Geng Liu Shaanxi Engineering Laboratory for Transmissions and Controls Northwestern Polytechnical UniversityXi′an 710072China Jiangsu Automation Research Institute Jiangsu Lianyungang 222061China China Academy of Launch Vehicle Technology Beijing 100076China Shanghai Aircraft Design and Research Institute Shanghai 200232China

In nanoscale sliding contact,adhesion effects and adhesive force are predominant,and high friction force will be *** energy is mainly converted into heat,and the heat will make nanomaterials become soft to affect friction behaviors,so it is important to investigate the friction and thermal properties of the nanoscale sliding contacts.A model of a nanoscale sliding contact between a rigid cylindrical tip and an FCC copper substrate is developed by molecular dynamics *** thermal properties of the substrate and the friction behaviors are studied at different sliding velocities and different tip *** results show that at a low sliding velocity,the friction force fluctuation is mainly caused by material melting⁃solidification,while at a high sliding velocity the material melting is a main factor for the friction *** average friction forces increase at initial phase and then decrease with increasing sliding velocity,and the average temperature of the substrate increases as sliding velocity *** tip radius significantly increases the temperature,while the coupled effects of tip radius and temperature rise make friction force increase slightly.

关键词： molecular dynamics friction property thermal property nanoscale sliding contact

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Influence of Gender on the friction Properties between Fabric and Skin

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Influence of Gender on the Friction Properties between Fabri...