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Effect of shear-induced contact area and aperture variations on nonlinear flow behaviors in fractal rock fractures

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第2期15卷 309-322页

作者： Changsheng Wang Richeng Liu Yujing Jiang Gang Wang Hengjie Luan Shandong Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and TechnologyQingdao266590China State Key Laboratory of Mining Disaster Prevention and Control Co-founded By Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao266590China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China School of Engineering Nagasaki UniversityNagasaki852-8521Japan

This study experimentally analyzes the nonlinear flow characteristics and channelization of fluid through rough-walled fractures during the shear process using a shear-flow-visualization apparatus.A series of fluid flow and visualization tests is performed on four transparent fracture specimens with various shear displacements of 1 mm,3 mm,5 mm,7 mm and 10 mm under a normal stress of 0.5 *** granite fractures with different roughnesses are selected and quantified using variogram fractal *** obtained results show that the critical Reynolds number tends to increase with increasing shear displacement but decrease with increasing roughness of fracture *** flow paths are more tortuous at the beginning of shear because of the wide distribution of small contact *** the shear displacement continues to increase,preferential flow paths are more distinctly observed due to the decrease in the number of contact spots caused by shear dilation;yet the area of single contacts *** on the experimental results,an empirical mathematical equation is proposed to quantify the critical Reynolds number using the contact area ratio and fractal dimension.

关键词： Fracture Shear displacement Fractal dimension Nonlinear flow contact area Flow visualization

Simulation model optimization for bonnet polishing considering consistent contact area response

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Frontiers of Mechanical Engineering 2024年第4期19卷 87-105页

作者： Yanjun HAN Haiyang ZHANG Menghuan YU Jinzhou YANG Linmao QIAN School of Mechanical Engineering Southwest Jiaotong UniversityChengdu 610031China Institute of Data Science Maastricht UniversityMaastricht 6229ENthe Netherlands

Simulation model optimization plays a crucial role in the accurate prediction of material removal function in bonnet polishing processes,but model complexity often poses challenges to the practical implementation and efficiency of these *** paper presents an innovative method for optimizing simulation model parameters,focusing on achieving consistent contact area and the accurate prediction of the material removal function while preventing increase in model ***,controllable and uncontrollable factors in bonnet simulations are analyzed,and then a simplified contact model is developed and applied under constant force *** characterize the bonnet's contact performance,a contact area response curve is introduced,which can be obtained through a series of single spot contact ***,a rubber hyperelastic parameter optimization model based on a neural network is proposed to achieve optimal matching of the contact area between simulation and *** average deviation of the contact area under different conditions was reduced from 22.78%before optimization to 3.43%after optimization,preliminarily proving the effectiveness of the proposed simulation optimization ***,orthogonal experiments are further conducted to validate the proposed *** comparison between the experimental and predicted material removal functions reveals a high consistency,validating the accuracy and effectiveness of the proposed optimization method based on consistent contact *** research provides valuable insights into enhancing the reliability and effectiveness of bonnet polishing simulations with a simple and practical approach while mitigating the complexity of the model.

关键词： bonnet polishing simulation contact area tool influence function optimization

Analysis and Numerical Simulation of Rolling contact between Sphere and Cone

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Chinese Journal of Mechanical Engineering 2015年第3期28卷 521-529页

作者： ZHAO Yanling XIA Chengtao WANG Hongbo XUAN Jiaping XIANG Jingzhong LIU Xianli SU Xiangguo School of Mechanical and Power Engineering Harbin University of Science and Technology Shenyang Aerospace Mitsubishi Motors Engine Manufacturing Co. Ltd

In non-conforming rolling contact, the contact stress is highly concentrated in the contact area. However, there are some limitations of the special contact model and stress model used for the theoretical study of the phenomenon, and this has prevented in-depth analysis of the associated friction, wear, and failure. This paper is particularly aimed at investigating the area of rolling contact between a sphere and a cone, for which purpose the boundary is determined by the Hertz theory and the geometries of the non-conforming surfaces. The phenomenon of stick-slip contact is observed to occur in the contact area under the condition of no-full-slip（Q 〈 μ·P）. Using the two-dimensional rolling contact theory developed by CARTER, the relative positions of the stick and slip regions and the distribution of the tangential force over the contact area are analyzed. Furthermore, each stress component is calculated based on the Mc Ewen theory and the idea of narrow band. The stress equations for the three-dimensional rolling contact between the sphere and the cone are obtained by the principle of superposition, and are used to perform some numerical simulations. The results show that the stress components have a large gradient along the boundary between the stick and slip regions, and that the maximum stress is inversely proportional to the contact coefficient and proportional to the friction coefficient. A new method for investigating the stress during non-classical three-dimensional rolling contact is proposed as a theoretical foundation for the analysis of the associated friction, wear, and failure.

关键词： tractive rolling Hertz theory stick-slip contact contact area contact stress

Asperity-based modification on theory of contact mechanics and rubber friction for self-affine fractal surfaces

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Friction 2021年第6期9卷 1707-1725页

作者： Anahita EMAMI Seyedmeysam KHALEGHIAN Saied TAHERI Texas State University 601 University DriveSan MarcosTexas 78666USA Virginia Polytechnic Institute and State University 460 Old Turner Street BlacksburgBlacksburgVirginia 24061USA

Modeling the real contact area plays a key role in every tribological process,such as friction,adhesion,and *** between two solids does not necessarily occur everywhere within the apparent contact *** the multiscale nature of roughness,Persson proposed a theory of contact mechanics for a soft and smooth solid in contact with a rigid rough *** this theory,he assumed that the vertical displacement on the soft surface could be approximated by the height profile of the substrate *** this assumption gives an accurate pressure distribution at the interface for complete contact,when no gap exists between two surfaces,it results in an overestimation of elastic energy stored in the material for partial contact,which typically occurs in many practical *** issue was later addressed by Persson by including a correction factor obtained from the comparison of the theoretical results with molecular dynamics *** paper proposes a different approach to correct the overestimation of vertical displacement in Persson’s contact theory for rough surfaces with self-affine fractal *** results are compared with the correction factor proposed by *** main advantage of the proposed method is that it uses physical parameters such as the surface roughness characteristics,material properties,sliding velocity,and normal load to correct the *** method is also implemented in the theory of rubber *** results of the corrected friction model are compared with *** results confirm that the modified model predicts the friction coefficient as a function of sliding velocity more accurately than the original model.

关键词： contact area rubber friction self-affine fractals tribology surface roughness

Influence of Friction Interface contact on Ultrasonic Motor Efficiency Under Static Conditions

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Transactions of Nanjing University of Aeronautics and Astronautics 2015年第2期32卷 163-173页

作者：张毅锋张武肖爱武朱萌潘云华张小亚 Xi'an Chuang Lian Ultrasonic Technology Co Ltd School of Marine Science and Tchnology Northwest Polytechnical University Xi jing Electronic Corp Xi'an Modern Control Technology Research Institute

The friction interface matching plays a deterministic role in the motor efficiency,and the microcosmic contact status of friction interface should be investigated to improve the ultrasonic motor *** main purpose is to improve the effective output power of ultrasonic ***,one studies the contact condition of the friction interface of the ultrasonic motor,analyzes the micro condition of contact interface through finite element analysis,optimizes unreasonable structures,and compares the two different-structure ultrasonic motors through *** results reflect the necessity of *** optimization,the stator and rotor deform after pre-pressure and the contact interface of them full contact *** reaching heat balance the effective output of the motor is 37%,and the average effective output efficiency is 2.384 times higher than that of the *** can be seen that the total consumption of the ultrasonic motor system decreases ***,when using in certain system the consumption taken from the system will decreases largely,especially in the system with a strict consumption control.

关键词： ultrasonic motor friction interface contact area efficiency

Morphology and electric potential-induced mechanical behavior of metallic porous nanostructures

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Friction 2020年第3期8卷 604-612页

作者： Sunghan KIM Andreas APOLYCARPOU Hong LIANG School of Mechanical Engineering Chung Ang UniversinSeoul 06974Republic of Korea Department of Mechanical Engineering Texas A&M UniversiyCollege Sation 77843-3123USA

Understanding mechanical behaviors influenced by electric potential and tribological contacts is important for verifying the robustness and reliability of applications based on metallic porous nanostructures in electrical *** this work,nickel-based metallic porous nanostructures were studied to characterize their mechanical properties and morphologically dependent contact areas during application of an electric potential using a nanoindenter.W e observed that the indentation moduli of nickel-based metallic porous nanostructures were altered by pore size and application of electric *** addition,the structural aspects of the surface morphology of nickel-based porous nanostructures had a critical effect on the determination of contact area.W e suggest that the relation between electric potential and the mechanical behaviors of metallic porous nanostructures can be crucial for building mechanically robust functional devices,which are influenced by electric *** morphological shape characteristics of metallic porous nanostructures can be alternative decisive factors for manipulation of tribological performance through regulation of contact area.

关键词： mechanical properties nanoindentation metallic porous nanostructures contact area electric potentia

A Mathematical Modeling Method Elucidating the Integrated Gripping Performance of Ant Mandibles and Bio-inspired Grippers

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Journal of Bionic Engineering 2020年第4期17卷 732-746页

作者： Wei Zhang Zike He Yu Sun Jianing Wu Zhigang Wu School of Aeronautics and Astronautics Sun Yat-Sen UniversityGuangzhou 510006China

The ability to grip unhatched eggs is a skill exploited by the ants Harpegnathos venator,as they care their brood in tunneled nests,which is of extreme difficulty to keep the eggs intact while *** this paper we propose a mathematical modeling method to elucidate the mechanism of such a gripping behavior in the ant *** new method can be subdivided into following *** a preliminary,the concavity geometry and mandible kinematics are examined ***,coordinate transformation is used to predict the real-time spatial topology of the ***,we come up with a new method to quantify the workspace required to grip and the contact area between the concavity and ant *** model indicates that the biaxial rotation fashion with specialized concavities can reduce workspace by 40%and increase contact area by 53%on average compared with the uniaxial rotation pattern,which augments success rate of gentle *** methodology may have applications in evaluating mechanical performance in both natural and artificial grippers.

关键词： ant mandible bio-inspired grippers concavity kinematics workspace contact area

Experimental Study on Thermal Management of Cylindrical Li-ion Battery with Flexible Microchannel Plates

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Journal of Thermal Science 2020年第4期29卷 1001-1009页

作者： WEI Liting JIA Li AN Zhoujian DANG Chao Institute of Thermal Engineering School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing Key Laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale Beijing 100044China

A novel thermal management system of cylindrical Li-ion battery with the liquid cooling in flexible microchannel plate was established in the study. The experiments were conducted with R141 b in flexible microchannel plates. The cooling system with the flexible aluminum microchannels can effectively transfer heat from battery to the cooling refrigerant R141 b based on flow boiling. A battery module with five cells along flow channel was chosen to study the effects of contact surface area and mass flux on the thermal performance and electrochemical characteristics in the experiments. Three types of structure with different contact areas were studied and their performances were compared with the experiments without cooling structures. The experiments were carried out at the same discharge rate with the inlet mass flow rates of 0–10 kg/h. For the inlet mass flow rate of 5.98 kg/h, the surface temperature and temperature uniformity of battery were the best, and the output voltage and capacity of batteries were higher than those under other mass flow rates. With given inlet mass flow rates, the five series cells exhibited different electrochemical performances, including output voltage and discharge capacity, due to the different refrigerant flow states in the microchannels. Finally, an optimal design was presented with thermal performances, macroscopic electrochemical characteristics, inlet mass flow rates and cooling performance taken into consideration.

关键词： thermal management Li-ion battery flexible microchannels contact area

Crystal Structures of Urokinase-type Plasminogen Activator in Complex with 4-(Aminomethyl) Benzoic Acid and 4-(Aminomethyl-phenyl)-methanol

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Chinese Journal of Structural Chemistry 2009年第2期28卷 253-259页

作者：江龙光赵更香卞传兵袁彩黄子祥黄明东 State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter The Chinese Academy of SciencesFuzhou Fujian 350002 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China

Urokinase-type plasminogen activator （uPA） is a trypsin-like serine protease and plays a key role in several biological processes, including tissue remodeling, cell migration, and matrix degradation. The inhibitors of uPA have been shown to prevent the spread of metastasis and tumor growth, and accordingly uPA is widely recognized as a target for the treatment of cancer. In this work, we report the crystal structures of the complexes of uPA with its inhibitors： 4- （aminomethyl）-benzoic acid （AMBA） and 4-（aminomethyl-phenyl）-methanol （AMPM）, both at a resolution of 2.35 А. The inhibitory constants of these two inhibitors were measured by a chromogenic competitive assay, and it was found that AMBA is a better inhibitor for uPA （Ki = 2.68 mM） than AMPM （Ki = 13.99 mM）. The structural study shows that the binding mode of inhibitor AMBA on uPA is similar to that of AMPM on uPA, both docked into the active site S1 pocket of uPA. Structural details of these complexes are provided to explain the difference of inhibitory constants.

关键词： urokinase-type plasminogen activator 4-(aminomethyl)benzoic acid (4-aminomethyl-phenyl)-methanol enzyme inhibition assays contact area