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Three-dimensional finite element analysis of shallow indentation of rough strain-hardening surface

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Friction 2019年第6期7卷 587-602页

作者： chenghui gao Henry PROUDHON Ming LIU School of Mechanical Engineering and Automation Fuzhou UniversityFuzhou 350116China Centre des Matériaux MINES Paris TechEvry Cedex 91003France

Three-dimensional finite element modeling of the contact between a rigid spherical indenter and a rough surface is presented when considering both the loading and unloading phases. The relationships among the indentation load, displacement, contact area, and mean contact pressure for both loading and unloading are established through a curve fitting using sigmoid logistic and power law functions. The contact load is proportional to the contact area, and the mean contact pressure is related to the characteristic stress, which is dependent on the material properties. The residual displacement is proportional to the maximum indentation displacement. A proportional relationship also exists for plastically dissipated energy and work conducted during loading. The surface roughness results in an effective elastic modulus calculated from an initial unloading stiffness several times larger than the true value of elastic modulus. Nonetheless, the calculated modulus under a shallow spherical indentation can still be applied for a relative comparison.

关键词： finite element modeling surface analysis contact mechanics indentation spherical indenter

Fractal Surface Synthesis Based on Two Dimensional Discrete Fourier Transform

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1101-1108页

作者： ZHOU Chao gao chenghui HUANG Jianmeng School of Mechanical Engineering and Automation Fuzhou University Fujian Provincial Research Center of Digital Design for Manufacturing

The discrete Fourier transform（DFT） is used for fractional Brownian motion（FBM） surface synthesis in tribology（i.e., contact, sliding, and sealing, etc）. However, the relationship between fractal parameters（fractal dimension and scale factor） and traditional parameters, the influence of fractal parameters on surface appearance, have not been deeply discussed yet. These lead to some kind of difficulty to ensure the synthesized surfaces with ideal fractal characteristic, required traditional parameters and geometric appearance. A quantitative relationship between fractal parameters and the root mean square deviation of surface （Sq） is derived based on the energy conservation property between the space and frequency domain of DFT. Under the stability assumption, the power spectrum of a FBM surface is composed of concentric circles strictly, a series of FBM surfaces with prescribed Sq could be synthesized with given fractal dimension, scale factor, and sampling numbers, but the ten-point height（Sz）, the skewness（Ssk） and the kurtosis（Sku） are still in random, where the probability distributions of Sz and Ssk are approximately normal distribution. Furthermore, by iterative searching, a surface with desired Abbott-Firestone curve could be obtained among those surfaces. An intuitive explanation for the influence of fractal dimension and scale factor on surface appearance is obtained by discussing the effects on the ratio of energy between high and low frequency components. Based on the relationship between Sq and surface energy, a filtering method of surface with controllable Sq is proposed. The proposed research ensures the synthesized surfaces possess ideal FBM properties with prescribed Sq, offers a method for selecting desired Abbott-Firestone curve of synthesized fractal surfaces, and makes it possible to control the Sq of surfaces after filtering.

关键词： fractional Brownian motion discrete Fourier transform fractal surface power spectrum

3D Profile Filter Algorithm Based on Parallel Generalized B-spline Approximating Gaussian

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Chinese Journal of Mechanical Engineering 2015年第1期28卷 148-154页

作者： REN Zhiying gao chenghui SHEN Ding School of Mechanical Engineering and Automation Fuzhou University Tribology Research Institute Fuzhou University Fujian Institute of Metrology

Currently, the approximation methods of the Gaussian filter by some other spline filters have been developed. However, thesc methods are only suitable for the study of one-dimensional filtering, when these methods are used for three-dimensional filtering, it is found that a rounding error and quantization error would be passed to the next in every part. In this paper, a new and high-precision implementation approach for Gaussian filter is described, which is suitable for three-dimensional reference filtering. Based on the theory of generalized B-spline function and the variational principle, the transmission characteristics of a digital filter can be changed through the sensitivity of the parameters （t1, t2）, and which can also reduce the rounding error and quantization error by the filter in a parallel form instead of the cascade form, Finally, the approximation filter of Gaussian filter is obtained. In order to verify the feasibility of the new algorithm, the reference extraction of the conventional methods are also used and compared. The experiments are conducted on the measured optical surface, and the results show that the total calculation by the new algorithm only requires 0.07 s for 480×480 data points; the amplitude deviation between the reference of the parallel form filter and the Gaussian filter is smaller; the new method is closer to the characteristic of the Gaussian filter through the analysis of three-dimensional roughness parameters, comparing with the cascade generalized B-spline approximating Gaussian. So the new algorithm is also efficient and accurate for the implementation of Gaussian filter in the application of surface roughness measurement.

关键词： generalized B-spline Gaussian filter three-dimensional reference cascade characteristic parallel characteristic

Influence of CaCO_3 Whisker Content on Mechanical and Tribological Properties of Polyetheretherketone Composites

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Journal of Materials Science & Technology 2006年第5期22卷 584-588页

作者： Youxi LIN chenghui gao Ning LI College of Mechanical Engineering ＆ Automation Fuzhou University Fuzhou 350002 China

The mechanical and tribological properties of polyetheretherketone （PEEK） composites filled with CaCO3 whisker in various content of 0～45% （wt pct） were investigated. The composite specimens were prepared by compression molding. Tribological testing of composites in dry wear mode against carbon steel ring was carried out on a MM200 block-on-ring apparatus. Data on neat PEEK were also included for comparison. It was observed that inclusion of CaCO3 whisker affected the most mechanical properties and the friction and wear in a beneficial way. With an increase in CaCO3 whisker content, friction coefficient continuously decreased but the trends in wear performance varied. The specific wear rate showed minima as 1.28×10^-6 mm^3/Nm for 25% CaCO3 whisker inclusion followed by a slow increase for further CaCO3 whisker addition. In terms of friction applications, when the tribological and mechanical properties are combined, the optimal content of CaCO3 whisker in the filled PEEK should be recommended as 15% to 20%. Fairly good correlations are observed in friction coefficient vs bending modulus and wear rate vs bending strength, confirming that the bending properties prove to be the most important tribology controlling parameters in the present work.

关键词： CaCO3 whisker Polyetheretherketone (PEEK) Mechanical properties Tribological behaviour

A weak but inert hindered urethane bond for high-performance dynamic polyurethane polymers

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Chinese Chemical Letters 2024年第5期35卷 238-243页

作者： Fangzhou Wang Wentong gao chenghui Li State Key Laboratory of Coordination Chemistry School of Chemistry and Chemical EngineeringCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210023China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China

Covalent adaptable networks(CANs),which share the properties of both thermosets and thermoplastics at the same time,are desirable for many *** bulky substituents is a feasible way to design dynamic covalent bonds for constructing CANs,as evidenced by the successful implementation in CANs based on hindered urea bonds(HUBs).However,the dynamicity induced by introducing bulky substituents always come with low bond energy,resulting in low mechanical strength and poor stability of the ***,we designed a novel hindered urethane bond,which is weak in thermodynamic(K_(eq)=1701.23 L/mol at 25℃)and inert in kinetic at low temperature,but stable in thermodynamic(K_(eq)=1.54×10^(4) L/mol at 100℃)and active in kinetic at high temperature(k_(-1)=0.105 h^(-1) at 80℃ and 0.315 h^(-1) at 120℃).As a result,the polyurethane based on it exhibits high mechanical properties(with Youngs’modulus of 1011±29MPa and flexible modulus reached 1833±50MPa)and excellent reversibility(can be reprocessed at 60℃ under 100 kPa in 30 min and completely healed at 40℃ in 10 min).Moreover,unlike to many CANs based on hindered urea bonds,our dynamic polyurethanes are highly stable in humid environment or even water solutions due to the slow hydrolysis *** highperformance dynamic polyurethane polymers are attractive for many applications.

关键词： Covalent adaptable networks Urethane bond Kinetics Thermodynamics

Nitriding of Hard Fe Electrodepositionand Its Effects on Wear Resistance

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Journal of Materials Science & Technology 2001年第2期17卷 271-274页

作者： chenghui gao, Dajian CHEN and Baiyang ZHOU Department of Mechanical Engineering, Fuzhou University, Fujian, Fuzhou 350002, China Dept. of Mech. Eng. Fuzhou Univ. Fuzhou 350002 China

Nitriding is employed for the hard Fe electrodeposition to produce a hard-facing and antiwear coating. It only takes 1 h for the hard Fe coating, which is much shorter than nitriding the Fe and steel. The results showed that the nitriding can increase the microhardness, wear resistance of the coating, as well as the bonding strength of the coating with the substrate. Additionally it can eliminate the brittleness, turn the internal stress of the coating from tension to compression. The wear resistance of the nitrided Fe coating is 4.6 times as high as that of Cr coating. It is simple and economic to combine hard Fe electroplating and nitriding, which is a good technology of the tribological surface modification.

关键词： Fe Nitriding of Hard Fe Electrodepositionand Its Effects on Wear Resistance

Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties

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Journal of Materials Science & Technology 1997年第2期13卷 137-140页

作者： chenghui gao Baiyang ZHOU (Institute for Materials Research, Fuzhou University, Fuzhou 350002, China)(Manuscript received February 22, 1996, in revised form June 3, 1996) Institute for Materials Research Fuzhou University Fuzhou 350002 China

The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum H-c, B-r and P-h occur at 9.4 P (wt pet) content. Maximum H-c, B-r and P-h occur at the weight ratio of Fe to Ni equaling to 1/9.

关键词： Ni Fe Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties

分子动力学模拟剪切速度对纳米间隙中角鲨烷界面滑移的影响

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化工学报 2016年第4期67卷 1440-1447页

作者：潘伶高诚辉福州大学机械工程及自动化学院福建福州350108

采用聚合物一致性力场(PCFF),分别在7种剪切速度V和3种油膜厚度h下对纳米间隙中润滑剂角鲨烷进行分子动力学模拟,分析固液界面的密度、分子和流速的分布,探究纳米薄膜润滑的润滑机理和剪切速度对界面滑移的影响。结果表明,纳米间隙中润... 详细信息

采用聚合物一致性力场(PCFF),分别在7种剪切速度V和3种油膜厚度h下对纳米间隙中润滑剂角鲨烷进行分子动力学模拟,分析固液界面的密度、分子和流速的分布,探究纳米薄膜润滑的润滑机理和剪切速度对界面滑移的影响。结果表明,纳米间隙中润滑剂存在分层现象,各层间距相近,并非越远离固体壁面层间距越大,层间距约为角鲨烷分子单个C C键距离的3~4倍;随着油膜厚度的减小,纳米间隙中润滑剂层状分布越明显,固化层密度越大;当油膜厚度为3.44 nm时,固液界面滑移现象明显,滑移长度b值随着V先增大后减小,当V为22.8 m·s^(-1)时,b达到最大值4.35 nm;根据模拟和计算结果,给出滑移长度与剪切速度的关系公式。

关键词：分子模拟纳米结构聚合物界面滑移薄膜润滑角鲨烷

Performance Optimization of Fujian Digital Design and Manufacture Service Platform Based on AJAX

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武汉理工大学学报 2006年第S3期28卷 1107-1110页

作者： ZHU Xiaolin gao chenghui HE Bingwei School of Mechanical Engineering and Automation,Fuzhou University,Fuzhou 350002,China, School of Mechanical Engineering and Automation Fuzhou UniversityFuzhou 350002China

In this paper,the problem on the service platform,which existed on the traditional WEB application mode,are analyzed in *** shows that application of the AJAX technology can optimize the service *** the AJAX technology can supply the wonderful solution for the development of the high-performance WEB application by means of the WEB performance testing tool to test the network performance of the service platform.

关键词： AJAX web application service platform performance optimization