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Sliding friction of shale rock on dry quartz sand particles

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Friction 2019年第4期7卷 307-315页

作者： Huijie ZHANG shuhai liu Huaping XIAO College of Mechanical and Transportation Engineering China University of Petroleum-BeijingBeijing 102249China State Key Laboratory of Oil and Gas Resources and Engineering China University of Petroleum-BeijingBeijing 102249China

The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional performance of the shale rock–dry quartz sand contact was investigated using a self-developed testing device. The study showed that the coefficient of friction of the contact increases with nominal stress and that the corresponding friction force increases approximately linearly with nominal stress, which is directly related to the contact stress between each single sand particle and rock shale. An overall dynamic coefficient, γ, reflecting the response of friction force to nominal stress, first decreases and then increases with area ratio, which is determined by not only the contact stress but also the interparticle friction force. These have important repercussions for a preliminary understanding of the frictional properties of the shale rock–dry quartz sand contact in hydraulic fracturing and related industrial applications.

关键词： shale rock quartz sand frictional performance hydraulic fracturing

Fingerprint-inspired surface texture for the enhanced tip pinch performance of a soft robotic hand in lubricated conditions

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Friction 2023年第7期11卷 1349-1358页

作者： Tianze HAO Huaping XIAO shuhai liu Yibo liu College of Mechanical and Transportation Engineering China University of Petroleum-BeijingBeijing 102249China

The core capabilities of soft grippers/soft robotic hands are grasping and *** present,most related research often improves the grasping and manipulation performance by structural *** soft grippers rely on compressive force and friction to achieve grasping,the influence of the surface microstructure is also *** types of fingerprint-inspired textures with relatively regular patterns were prepared on a silicone rubber surface via mold casting by imitating the three basic shapes of fingerprint patterns(i.e.,whorls,loops,and arches).Tribological experiments and tip pinch tests were performed using fingerprint-like silicone rubber films rubbing against glass in dry and lubricated conditions to examine their *** addition to the textured surface,a smooth silicone rubber surface was used as a *** results indicated that the coefficient of friction(COF)of the smooth surface was much higher than that of films with fingerprint-like textures in dry and water-lubricated *** surface with fingerprint-inspired textures achieved a higher COF in oil-lubricated *** the fingerprint-like films to the soft robotic fingers improved the tip pinch gripping performance of the soft robotic hand in lubricated *** study demonstrated that the surface texture design provided an effective method for regulating the grasping capability of humanoid robotic hands.

关键词： fingerprint-like patterns surface engineering soft hand tip pinch

Linear polymer aqueous solutions in soft lubrication:From boundary to mixed lubrication

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Science China(Technological Sciences) 2013年第7期56卷 1709-1714页

作者： liu shuhai TAN GuiBin WANG DeGuo College of Mechanical and Transportation Engineering China University of Petroleum-Beijing

In order to better understand linear polymer aqueous solutions in soft lubrication from boundary to mixed lubrication,poly(ethylene glycol) and sodium hyaluronateare used as model polymers were investigated by using UMT-2 tribometer with the ball-on-disk mode. The relationship between the master Stribeck curves of the polymer aqueous solutions and the influence factors were investigated. Experimental results indicated that soft lubrication is determined by lubricant rheological properties and surface-lubricant interactions, e.g., wetting behavior of polymer aqueous solution on tribological surfaces.

关键词： soft contact lubrication linear polymer aqueous solutions mixed lubrication boundary lubrication

Carbon quantum dots: An innovative additive for water lubrication

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Science China(Technological Sciences) 2019年第4期62卷 587-596页

作者： XIAO HuaPing liu shuhai XU Quan ZHANG Hang College of Mechanical and Transportation Engineering China University of Petroleum-Beijing Institute of New Energy China University of Petroleum-Beijing

Water soluble carbon quantum dots(CQDs) were prepared and used as lubricant additives in deionized(DI) water. The impacts of CQDs on the tribological properties of water were evaluated for both Si_3N_4-on-steel and Si_3N_4-on-Si_3N_4 contacts. Experimental results show that the coefficient of friction(COF) reduced in the two types of tribopairs after the addition of *** reductions in COF were found to be 30% and 14% for the Si_3N_4-steel and Si_3N_4-Si_3N_4 contacts, respectively. In terms of wear behaviors, the CQDs notably improved tribofilm formation on the Si_3N_4 disk surface for the Si_3N_4-Si_3N_4 contacts,confirming that the nanoparticles increase friction while providing better protection from wear. This research will help to expand the application of CQDs as promising additives in water-based lubricants.

关键词： carbon quantum dot water lubrication lubricant additives ceramic tribopairs

Progress in experimental study of aqueous lubrication

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Chinese Science Bulletin 2012年第17期57卷 2062-2069页

作者： MA LiRan ZHANG ChenHui liu shuhai State Key Laboratory of Tribology Tsinghua University Beijing 100084 China

Aqueous lubrication is commonly regarded as friendly to the *** review current knowledge of the behaviors and mechanisms of aqueous *** methods for investigating aqueous lubrication are *** describe studies on both friction and film formation performance of various water-based lubricants,Additionally,we discuss possible underlying mechanisms of aqueous *** is also drawn to continuing topics of investigation and some unsolved problems.

关键词：水润滑实验可能机制水基润滑剂环境友好膜形成摩擦

Shear of molecular deposition films on glass substrates determined by tribometer

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Science China(Technological Sciences) 2011年第4期54卷 1005-1010页

作者： GUO YanBao WANG DeGuo liu shuhai ZHANG SiWei College of Mechanical and Transportation Engineering China University of PetroleumBeijing 102249China

The ultrathin polyelectrolyte molecular deposition films and polyelectrolyte composite nanoparticles molecular deposition films were prepared using layer-by-layer molecular deposition method and in situ growth method.A micro-tribometer has been developed to measure the shear response of those ultrathin molecular deposition *** using a smooth steel sphere in a ball-on-flat configuration,the shear force was determined for molecular deposition films on glass substrate for different *** results indicate that the shear behaviors of molecular deposition film were mainly determined with the contact area and film ***,the composite molecular deposition film with nanoparticles has better shear behaviors than the polyelectrolyte molecular deposition *** shear force of polyelectrolyte molecular deposition film is more dependent on the speed than that of composite nanoparticle molecular deposition film.

关键词： shear force molecular deposition film nanoparticles

Damages on the lubricated surfaces in bearings under the influence of weak electrical currents

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Science China(Technological Sciences) 2013年第12期56卷 2979-2987页

作者： XIE GuoXin LUO JianBin GUO Dan liu shuhai LI Gang State Key Laboratory of Tribology Tsinghua University

A special bearing tester was constructed to investigate the damage behavior on the lubricated surfaces in bearings with the passage of weak electrical currents as low as^1 *** results showed that when polar glycerine was used as the lubricant,many narrow and deep pits formed on the lubricated *** contrast,when the experimental conditions under the lubrication of the nonpolar paraffin oil were close to those under the lubrication of polar glycerine oil,damages on the lubricated surfaces were *** of microbubbles in polar lubricants with the passage of electrical currents was proposed to be responsible for the observed damages on the lubricated surfaces.

关键词： electro-damage bearings weak electrical current microbubbles

Frictional behaviors of rough soft contact on wet and dry pipeline surfaces:With application to deepwater pipelaying

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Science China(Technological Sciences) 2013年第12期56卷 3024-3032页

作者： TAN GuiBin WANG DeGuo liu shuhai WANG Hao ZHANG SiWei College of Mechanical and Transportation Engineering China University of Petroleum-Beijing

Elastic rubbers are widely used in nature and *** order to better understand soft rough contact under dry and wet conditions during deepwater pipelaying process,various polyurethane(PU)discs both in PU-pipe and PU-steel sliding combinations have been investigated by using self-developed *** tribological test results show that the friction coefficient can be clearly seen:PU90

关键词： rough soft contact tribological properties deepwater pipe-laying pipeline

A Fully Self-Healing Piezoelectric Nanogenerator for Self-Powered Pressure Sensing Electronic Skin

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Research 2021年第1期2021卷 876-884页

作者： Maosen Yang Jinmei liu Dong liu Jingyi Jiao Nuanyang Cui shuhai liu Qi Xu Long Gu Yong Qin School of Advanced Materials and Nanotechnology Xidian UniversityXi’an 710071China Institute of Nanoscience and Nanotechnology Lanzhou UniversityGansu 730000China

As an important way of converting mechanical energy into electric energy,a piezoelectric nanogenerator(PENG)has been widely applied in energy harvesting as well as self-powered sensors in recent ***,its robustness and durability are still severely challenged by frequent and inevitable mechanical impacts in real application ***,a fully selfhealing PENG(FS-PENG)as a self-powered pressure sensing electronic skin is *** self-healing piezoelectric composite and self-healing Ag NW electrode fabricated through mixing piezoelectric PZT particles and conductive Ag NWs into self-healing polydimethylsiloxane(H-PDMS)are assembled into the sandwich structure *** FS-PENG could not only effectively convert external stimulation into electrical signals with a linear response to the pressure but also retain the excellent self-healing and stable sensing property after multiple cycles of cutting and self-healing ***,a self-healing pressure sensor array composed of 9 FS-PENGs was attached on the back of the human hand to mimic the human skin,and accurate monitoring of the spatial position distribution and magnitude of the pressure was successfully realized.

关键词： piezoelectric healing generator