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Nonlinear Analysis of Axial-load and Stress Distribution for Threaded Connection

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 869-875页

作者： LIAO Ridong SUN yujuan zhang Weizheng School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China

Analytical method for the distributions of axial-load and stress is based on elastic assumption, but the threaded connections are often in plastic deformation stage in practice. Meanwhile the strain in the threaded connection is difficult to measure. So it is necessary to study the reliable numerical method. At present neither the convergence analysis of the computational results nor the elastic-plastic analysis in the loading-unloading process are studied. In this paper, von Mises plasticity and kinematic hardening model is used to describe the material response. A new convergence criterion for nonlinear finite element analysis of the loading-unloading process is proposed. An axisymmetric finite element model according to the proposed convergence criterion is developed and used to analyze the distributions of axial-load and stress. It can be conclude that the stress distribution analysis is more dependent on the mesh density than the axial-load distribution analysis. The stress distribution result indicates that with increasing of applied load, the engaged threads close to the nut-bearing surface become plastic firstly. The axial-load distribution result reveals that the load percentage carried by single thread depends on the position of thread and load intensity. When the load is relatively small, the applied load is mainly carried by the engaged threads near the nut-bearing surface, when the load is larger, the differences of percentages for all threads become small. The proposed convergence analyzing procedure is applicable for other nonlinear analyses. The obtained distributions of axial-load and stress can be a reference of engineering application.

关键词： threaded connection finite element method (FEM) axial-load distribution stress distribution convergence criterion

Influences of deposition parameters on the microstructure and properties of nanostructural TiN films synthesized by filtered cathodic arc plasma

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Rare Metals 2005年第4期24卷 370-375页

作者： zhang yujuan YAN Pengxun WU Zhiguo zhang Pingyu Laboratory for Special Functional Materials Henan University Kaifeng 475001 China Department of Physics Lanzhou University Lanzhou 730000 China

Titanium nitride （TIN） films with nanostructure were prepared at ambient temperature on a （111） silicon substrate by the filtered cathodic arc plasma （FCAP） technology with an in-plane ＂S＂ filter. The effects of deposition parameters on the grain size, texture and nano-hardness of the films were systematically investigated. The grain size was obtained through calculation using the Scherrer formula and observed by TEM. The results of X-ray diffraction and electron diffraction indicated that increasing either negative substrate bias or argon flow promoted the formation of （111） preferred orientation. High argon flow leads to biaxial texture. The micro-hardness of the TIN films as a function of grain size showed a behavior according to the Hall-Petch relation under high argon flow.

关键词： inorganic nonmetallic materials titanium nitride deposition nanostructure

THE PERIODIC VOLTERRA MODEL WITH MUTUAL INTERFERENCE AND IMPULSIVE EFFECT

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International Journal of Biomathematics 2012年第3期5卷 77-91页

作者： yujuan zhang LANSUN CHEN Department of Mathematics Anshan Normal University Anshan Liaoning 114007 P. R. China Institute of MathematicsAcademy of Mathematics and System SciencesAcademia Sinia Beijing 100080 P. R. China

In this paper, a periodic Volterra model with mutual interference and impulsive effect is proposed and analyzed. By applying the Floquet theory of impulsive differential equa- tion, some conditions are obtained for the linear stability of semi-trivial periodic solution. Some sufficient conditions are also given for the permanence of the system. Further, stan- dard bifurcation theory is used to show the existence of coexistence state which arises near the semi-trivial periodic solution. Finally, theoretical results are confirmed by some special cases of the system.

关键词： Mutual interference impulsive effect extinction bifurcation permanence.

Study on the mechanism of rapid formation ofu ultra-thick tribofilm by CeO_(2)nano additive and ZDDP

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Friction 2023年第1期11卷 48-63页

作者： Xue LEI yujuan zhang Shengmao zhang Guangbin YANG Chunli zhang Pingyu zhang National&Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials Henan UniversityKaifeng 475004China

CeO_(2)nanoparticles are potential anti-wear additives because of their outstanding anti-wear and load-bearing ***,the shear-sintering tribo-film formation mechanism of oxide nanoparticles limits the tribo-film formation rate and thickness *** this study,by compounding with zinc dioctyl dithiophosphate(ZDDP),ultra-fine CeO_(2)nanoparticles modified with oleylamine(OM)can quickly form 2μm ultra-thick tribo-film,which is 10-15 times thicker than that of ZDDP and CeO_(2),*** ultra-thick tribo-film presents a nanocomposite structure with amorphous phosphate as binder and nano-CeO_(2)as filling phase,which leads to the highest loading capacity of composite *** results of adsorption experiments tested by dissipative quartz crystal microbalance(QCM-D)showed that the Ps value of additive has nothing to do with its equilibrium adsorption mass,but is directly proportional to its adsorption rate in 10 *** compound additive of CeO_(2)and ZDDP presented the co-deposition mode of ZDDP monolayer rigid adsorption and CeO_(2)viscoelastic adsorption on the metal surface,which showed the highest adsorption rate in 10 *** is found that the tribo-film must have high film forming rate and wear resistance at the same time in order to achieve super *** phosphate was formed from ZDDP and CeO,through tribochemistry reaction,which promotes the formation of an ultra-thick tribo-film with nanocomposite structure,which not only maintains the low friction characteristics of CeO,but also realizes high Pg and high load-carrying capacity.

关键词： CeO_(2)nanoadditives adsorption nanocomposite ultra-thick tribofilm zinc dioctyl dithiophosphate(7DDP)

Effects of magnetic ionic liquid as a lubricant on the friction and wear behavior of a steel-steel sliding contact under elevated temperatures

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Friction 2021年第1期9卷 61-74页

作者： Jiajia JIA Guangbin YANG Chunli zhang Shengmao zhang yujuan zhang Pingyu zhang Engineering Research Center for Nanomaterials Henan UniversityKaifeng 475004China Institute of Pharmacy Henan UniversityKaifeng 475004China

A magnetic ionic liquid(abridged as MIL)[C_(6)mim]_(5)[Dy(SCN)_(8)]was prepared and used as the magnetic lubricant of a steel-steel sliding *** tribological properties of the as-prepared MIL were evaluated with a commercially obtained magnetic fluid lubricant(abridged as MF;the mixture of dioctyl sebacate and Fe_(3)O_(4),denoted as DIOS-Fe_3O_4)as a *** lubrication mechanisms of the two types of magnetic lubricants were discussed in relation to worn surface analyses by SEM-EDS,XPS,and profilometry,as well as measurement of the electric contact resistance of the rubbed steel *** results revealed that the MIL exhibits better friction-reducing and antiwear performances than the as-received MF under varying test temperatures and *** is because the MIL participates in tribochemical reactions during the sliding process,and forms a boundary lubrication film composed of Dy_(2)O_(3),FeS,FeSO_(4),nitrogen-containing organics,and thioether on the rubbed disk surface,thereby reducing the friction and wear of the frictional ***,the MF is unable to form a lubricating film on the surface of the rubbed steel at 25°C,though it can form a boundary film consisting of Fe_(3)O_(4) and a small amount of organics under high ***,the excessive Fe_(3)O_(4) particulates that accumulate in the sliding zone may lead to enhanced abrasive wear of the sliding pair.

关键词： steel-steel sliding contact magnetic ionic liquid magnetic fluid lubricant tribological property lubrication mechanism

Self-dispersed molybdenum disulfide quantum dot/graphene crumpled ball as efficient high temperature lubricant additive

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Friction 2024年第8期12卷 1771-1784页

作者： Guiru DU yujuan zhang Shuguang FAN Ningning SONG Shengmao zhang Pingyu zhang Engineering Research Center for Nanomaterials Henan UniversityKaifeng 475004China

Inorganic nanoparticles have been proved as powerful lubricant additives at elevated ***,the tribological properties are inevitably impaired due to poor dispersion and insufficient high temperature resistance of organic matter modified ***,we prepare a self-dispersed molybdenum disulfide quantum dot/graphene crumpled ball(MGCB)comprising molybdenum disulfide quantum dot uniformly interspersed on the wrinkled graphene *** crumpled ball composite possesses excellent dispersity in polyalkylene glycol base oil without depending on surface *** with the conventional phosphate esters lubricant,our results indicate MGCB could vastly improve the lubrication performance of polyalkylene glycol with an extremely low concentration(0.05 wt%)at elevated temperature(150°C),showing a friction reduction of 47%and a wear reduction of 30%compared with the conventional phosphate esters lubricant(tricresyl phosphate,TCP).This is because crumpled ball potentiates synergistic lubrication effect within the boundary ***,we envision our designed self-dispersed MGCB has significant potential in tribological application at elevated temperature.

关键词： self-dispersed crumpled ball graphene molybdenum disulfide quantum dot high temperature tribological properties

Synthesis of water-soluble Cu nanoparticles and evaluation of their tribological properties and thermal conductivity as a water-based additive

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Friction 2019年第3期7卷 246-259页

作者： Junhua ZHAO Guangbin YANG Chunli zhang yujuan zhang Shengmao zhang Pingyu zhang Engineering Research Center for Nanomaterials Henan University

Efficient and sustainable use of water-based lubricants is essential for energy ***,the use of water-lubricated mechanical systems instead of conventional oil lubricants is extremely attractive from the viewpoint of resource *** this study,water-soluble Cu nanoparticles of size approximately 3 nm were prepared at room temperature(around 25 °C) via in-situ surface *** tribological behavior of the as-synthesized Cu nanoparticles as an additive in distilled water was evaluated using a universal *** results show that the as-synthesized Cu nanoparticles,as a water-based lubricant additive,can significantly improve the tribological properties of distilled *** particular,the lowest friction coefficient of 0.06 was obtained via lubrication with a concentration of 0.6 wt% of Cu nanoparticles in distilled water,which is a reduction of 80.6% compared with that obtained via lubrication with distilled water *** is considered that some Cu nanoparticles entered the contact area of the friction pairs to form a complex lubricating film and prevent direct contact of the friction ***,some Cu nanoparticles in the solution accelerate the heat transfer process,which also results in good tribological properties.

关键词： Cu nanoparticles water-soluble lubricant additive tribological properties

Synergistic tribological effect between polyisobutylene succinimide-modified molybdenum oxide nanoparticle and zinc dialkyldithiophosphate for reducing friction and wear of diamond-like carbon coating under boundary lubrication

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Friction 2023年第11期11卷 2021-2035页

作者： Shuoshuo CHEN Ningning SONG Shengmao zhang yujuan zhang Laigui YU Pingyu zhang National&Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials Henan UniversityKaifeng 475004China

Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate(MoDTC)can cause wear acceleration of diamond-like carbon(DLC)coating coupled with steel under boundary lubrication,which hinders its industrial ***,polyisobutylene succinimide(PIBS),an organo molybdenum amide,was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimidemolybdenum oxide nanoparticles(MPIBS-MONPs)with potential to prevent the wear acceleration of DLC *** thermal stability of MPIBS-MONPs was evaluated by thermogravimetric *** tribological properties as the additives in di-isooctyl sebacate(DIOS)were evaluated with MoDTC as a control;and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate(ZDDP)as well as worn surface *** indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating,being much superior to *** is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC ***,the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability;and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn *** as-formed composite tribofilm consisting of molybdenum oxide nanocrystal,amorphous polyphosphate,and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.

关键词： molybdenum oxide nanoparticle zinc dialkyldithiophosphate(ZDDP) synergistic tribological effect diamond-like carbon(DLC)coating boundary lubrication wear resistance

Phytoplankton community structure and environmental parameters in aquaculture areas of Daya Bay,South China Sea

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Journal of Environmental Sciences 2009年第9期21卷 1268-1275页

作者： WANG Zhaohui ZHAO Jiangang zhang yujuan CAO Yu Institute of Hydrobiology Jinan University Guangzhou 510632 China. Key Laboratory of Eutrophication and Red Tide Prevention Education Department of Guangdong Province Guangzhou 510632 China

Environmental characteristics and phytoplankton community structure were investigated in two aquaculture areas in Dapeng Cove of Daya Bay, South China Sea, between April 2005 and June 2006. Phytoplankton abundance ranged between 5.0 and 8877.5 cells/mL, with an average of 751.8 cells/mL. The seasonal cycle of phytoplankton were demonstrated by frequent oscillations, with recurrent high abundances from late spring to autumn and a peak stage in late winter. Diatoms were the predominant phytoplankton group, accounting for 93.21% of the total abundance. The next most abundant group was the dinoflagellates, which made up only 1.24% of total abundance. High concentrations of Alexandrium tamarense （Lebour） Balech with a maximum of 603.0 cells/mL were firstly recorded in this area known for high rates of paralytic shellfish poisoning （PSP） contamination. Temperatures and salinities were within the suitable values for the growth of phytoplankton, and were important in phytoplankton seasonal fluctuations. The operation of the Daya Bay Nuclear Power Station （DNPS） exerts influences on the phytoplankton community and resulted in the high abundances of toxic dinoflagellate species during the winter months. Dissolved inorganic nitrogen （DIN） and dissolved silicate （DSi） were sufficient, and rarely limited for the growth of phytoplankton. Dissolved inorganic phosphorus （DIP） was the most necessary element for phytoplankton growth. The enriched environments accelerated the growth of small diatoms, and made for the shift in predominant species from large diatom Rhizosolenia spp. to chain-forming diatoms such as Skeletonema costatum, Pseudo-nitzschia spp. and Thalassiosira subtilis.

关键词： phytoplankton environmental factor South China Sea aquaculture nuclear power station