当前期刊: Tribology international Go to current issue    加入关注   
显示样式:        排序: 导出
我的关注
我的收藏
您暂时未登录!
登录
  • A multi-technique characterization of the tribofilm formed by a fully formulated CVT fluid
    Tribol Int (IF 3.517) Pub Date : 2020-01-20
    Can Wang; Hubert Gojzewski; Dik J. Schipper

    In this work, the morphology, thickness, chemical composition and mechanical properties of the tribofilm formed by a fully formulated CVT fluid are investigated by multiple techniques and linked to the frictional and wear characteristics of a pin-on-disc tribosystem. It is found that the tribosystem shows higher friction and wear when tested at 150 °C than at 80 °C. The main reason is that although the morphology and thickness are similar, the tribofilms formed at different temperatures have different chemical compositions and mechanical properties. The tribofilm formed at 150 °C is Fe richer and has greater hardness and shear strength, which leads to a higher tribochemical wear rate and a greater interfacial shear force.

    更新日期:2020-01-21
  • Lubrication theory for Bingham plastics
    Tribol Int (IF 3.517) Pub Date : 2020-01-20
    Stefan G.E. Lampaert; Ron A.J. van Ostayen

    The rheological behavior of many lubricants used in hydrodynamic bearings can reasonably be modeled using the Bingham plastic material model. This behavior is characterized by a strong discontinuity, from a pure solid state to a viscous fluid state depending on the local shear stress. In literature three methods have been presented to model a Bingham plastic lubricated film. A full CFD and thus expensive, numerical simulation has been used. A general Reynolds equation based simulation has been used, however with a less accurate numerical regularization of the material discontinuity. Or a general Reynolds equation based simulation has been used, but with a severe reduction of the geometric complexity. In this paper, an ’exact’ thin film lubrication simulation for a Bingham plastic fluid is presented. The model is said to be exact in the sense that it requires no additional approximations to those used in the derivation of the general Reynolds equation, and requires no numerical regularization of the Bingham plastic fluid model and can still be used on any lubricating film geometry. Simulations on both infinite and finite journal bearings shows that the results of this new method are in good accordance with literature, demonstrating the validity of the method.

    更新日期:2020-01-21
  • Tribological behavior of shot peened/austempered AISI 5160 steel
    Tribol Int (IF 3.517) Pub Date : 2020-01-18
    Xue Han; Zhenpu Zhang; Jiayu Hou; Gary C. Barber; Feng Qiu

    In order to enhance component performance, material sustainability, and service life, this study presents the tribological behavior of different austempered AISI 5160 steel specimens with shot peening. All the specimens were austempered for 2 h, then followed by shot peening to study the effect of shot peening and bainite morphologies on the wear and friction behavior. The microstructures, hardness, and residual stress of specimens were studied by optical microscopy, scanning electron microscopy, Vickers micro-hardness, 3D-profiler, and X-ray diffraction. Shot peening produced higher hardness on soft austempered specimens, rather than on hard austempered specimens. Compared with non-shot peened austempered disk specimens, the wear reduction of disk specimens with shot peening is up to 73%.

    更新日期:2020-01-21
  • Auxiliary bearing squeeze film dampers for magnetic bearing supported rotors
    Tribol Int (IF 3.517) Pub Date : 2020-01-18
    Xiao Kang; Alan Palazzolo; Wan Zhong

    Auxiliary bearings (AB) support the rotor and protect the magnetic bearing (AMB) system when the AMB is disabled due to power loss or excessive loads. The paper demonstrates that installing a damping device along with the AB can yield extended AB fatigue life, protect the AMB, and reduce vibration, contact force and AB heating. A squeeze film damper (SFD) is an energy dissipation device that has been widely used in the turbo-machinery industry, and as demonstrated in the paper can also work effectively in combination with an AB. Usually, the SFD implements a supply groove to ensure adequate lubricant flow into the film lands. The supply groove can provide significant added mass coefficients and significantly influence the overall impedance of the SFD. Past literature has analyzed the transient response of the rotor dropping onto AB's with squeeze film dampers, none though have considered the influence of the SFD's center groove and its added mass effect on rotor's drop behavior. This paper develops a high fidelity finite element grooved SFD model considering the fluid inertia, and an effective groove clearance is used following the practice appearing in the literature. SFD force coefficients are benchmarked with results of a linear fluid inertia, bulk-flow model developed in the literature, before including them in the rotor – AB system model. The SFD model is integrated into a high fidelity nonlinear auxiliary bearing (angular contact ball bearing) model, which considers the movements, contact force, stress, and temperature of bearing balls, the inner race and outer race. The instantaneous reaction forces from the SFD are calculated with a finite element based solution of Reynold equation at each time step due to the intermittent and large sudden loads. The flexibility of the rotor is included utilizing a Timoshenko beam, finite element model. The fatigue life of the auxiliary bearing when integrated into the SFD is also calculated based on the rain flow counting method. The influence of the added mass of the SFD on the rotor's drop behavior is demonstrated showing that the added mass increases the contact force and peak temperature and reduces the fatigue life of the AB. Therefore, the added mass effect of the SFD should be considered to avoid over predicting the AB fatigue life. The influence of the SFD clearance on the rotor's drop behavior is also studied showing that an optimal clearance exists for increasing the AB fatigue life. Too small of a clearance will yield excessive damping making the effective stiffness too large, and causing high contact forces. Too large of a clearance lowers damping which may lead to a destructive backward whirl. This paper provides key guidelines for auxiliary bearing damper system design.

    更新日期:2020-01-21
  • Effects of sliding speed on the tribological behavior of AA 7075 petroleum casing in simulated drilling environment
    Tribol Int (IF 3.517) Pub Date : 2020-01-15
    Liangjie Mao; Mingjie Cai; Qingyou Liu; Yufa He

    This work investigated the effects of sliding speed on tribological behavior of AA 7075 petroleum casing in simulated drilling environment by pin-on-disc wear test. The main wear mechanism of AA 7075 disc at low sliding speed (0.0628 m/s and 0.157 m/s) was abrasive wear and oxidative wear at middle sliding speed (0.314 m/s). As sliding speed increases to higher sliding speed (0.471 m/s and 0.628 m/s), adhesive delamination wear dominated the wear process. The tribo oxides layer can efficiently protected the alloy substrate only at sliding speed of 0.314 m/s. At higher sliding speeds, tribo oxides layer were removed quickly once it was formed due to its internal fractures of tribo oxides and lower bonging strength with substrate.

    更新日期:2020-01-15
  • 更新日期:2020-01-15
  • Phosphonium-organophosphate modified graphene gel towards lubrication applications
    Tribol Int (IF 3.517) Pub Date : 2020-01-14
    Chaoliang Gan; Ting Liang; Duoli Chen; Wen Li; Xiaoqiang Fan; Guanxiong Tang; Bo Lin; Minhao Zhu
    更新日期:2020-01-14
  • Tribological performance of a novel wide-temperature applicable a-C/(WC/a-C) film against M50 steel
    Tribol Int (IF 3.517) Pub Date : 2020-01-13
    Zeqing Li; Honghong Zhang; Weifeng He; Chuansheng Ma; Guang'an Zhang; Xiangfan Nie; Yinghong Li

    To improve the wide-temperature applicability of amorphous carbon-based films, a novel a-C/(WC/a-C) film compositing of a-C nano-layers and super-latticed WC/a-C nano-multilayers was proposed and successfully fabricated on M50NiL substrate by an unbalanced magnetron sputtering system. For comparison, a monolayer a-C film and a super-latticed WC/a-C film were also prepared on the same substrates. The microstructures, mechanical properties and thermal stability of the as-deposited films were investigated. Particularly, the tribological behaviors of films against M50 counterpart were evaluated at the temperatures ranging from 25 °C to 350 °C. The results showed that because of the excellent thermal stability of super-latticed WC/a-C sublayers, the a-C/(WC/a-C) film has effectively overcome the poor tribological performance of a-C film at high temperatures (≥200 °C). While benefiting from the good toughness of a-C sublayers, the a-C/(WC/a-C) film showed significant better wear resistance than the WC/a-C film at the temperatures of 25–200 °C. The best wide-temperature applicability of the novel a-C/(WC/a-C) film should be attributed to the favorable mechanical properties, together with the formations of carbon-rich transfer film at 25–150 °C and WO3-rich transfer film at 200–350 °C.

    更新日期:2020-01-14
  • Linear complementarity solution of 2D boundary slip EHL contact
    Tribol Int (IF 3.517) Pub Date : 2020-01-13
    Y. Zhao; P.L. Wong; L. Guo

    Recent researches proved that bearing friction can be largely reduced with an oleophilic (no-slip) surface sliding against an oleophobic (slip) surface. The present work investigates the applicability of the slip/no-slip concept to 2D elastohydrodynamic lubrication (EHL) problems. Numerical analysis of isothermal EHL point contact is conducted under pure rolling conditions with the critical shear stress slip model. The challenge of determining the slip direction upon the attainment of the critical shear stress value in 2D problems is resolved by using a linear complementarity principle. The effect of boundary slip on bearing performance in terms of film thickness and friction is evaluated.

    更新日期:2020-01-13
  • Significance of third body rheology in friction at a dry sliding interface observed by a multibody meshfree model: Influence of cohesion between particles
    Tribol Int (IF 3.517) Pub Date : 2020-01-13
    Yinyin Zhang; Guilhem Mollon; Sylvie Descartes

    The third body approach deals with friction as a problem of third body rheology. Using a multibody meshfree model, we report influence of cohesion on third body rheology and friction at a dry sliding contact. With cohesion increasing from 0.0001 to 20 GPa, friction firstly increases linearly then transitions to a constant value, based on which three friction regimes are identified. Low cohesion (0.0001–1 GPa) is featured by lamellar flow; medium cohesion (1–5 GPa) triggers formation of strong inclined force chains; high cohesion (5–20 GPa) results in generation and rolling of agglomerates. How third bodies accommodate velocity gradient and transfer load are carefully examined. The results provide a possible novel approach of material design to monitor the coefficient of friction.

    更新日期:2020-01-13
  • The wear classification of MoDTC-derived particles on silicon and hydrogenated diamond-like carbon at room temperature
    Tribol Int (IF 3.517) Pub Date : 2020-01-13
    K.A.M. Kassim; T. Tokoroyama; M. Murashima; N. Umehara

    Molybdenum dithiocarbamate (MoDTC) is well-known as a friction-modifier in engine oil but has wear accelerating effects on DLC/steel sliding contact. Since MoDTC was reported degradable to other materials, the effect of each material on wear acceleration has not been clarified yet. Therefore, it is necessary to divide which Mo-derived compound has a major role to enhance wear. Thus, powder-type MoDTC, MoO3, Mo2C, MoS2, and Mo were dispersed into Poly-alpha-olefin (PAO), and tested on a-C:H and Si-DLC against steel ball at room temperature. For Mo2C, MoDTC, and MoO3, the specific wear rate of a-C:H was approximately 3.4 × 10−5, 3.2 × 10−6 and 1.5 × 10−6 mm3/Nm, respectively. MoDTC indicated higher affection than MoO3 regardless of the particles’ hardness. Si-DLC showed better wear prevention compared to a-C:H.

    更新日期:2020-01-13
  • Thrust bearing coupling effects on the lateral dynamics of turbochargers
    Tribol Int (IF 3.517) Pub Date : 2020-01-13
    Thales Freitas Peixoto; Katia Lucchesi Cavalca

    Nowadays tendency is the practice of engine downsizing with a turbocharger, to increase fuel economy and decrease emissions. For both design and analysis, a reliable rotor-bearing model is mandatory. In turbochargers, floating-ring bearings support the rotating shaft, with a double-acting thrust bearing, to support axial force imbalances from the compressor and turbine gas flows. The typical turbocharger is highly nonlinear due to the high rotational speeds achieved. Therefore, a turbocharger model, supported by floating-ring and thrust bearings, is developed, considering both bearings nonlinear behaviour, including temperature variations in oil films. The thrust bearing model contemplates a full thermo-hydrodynamic evaluation, while the floating-ring bearing investigation is somewhat simplified. The analysis focuses on the thrust bearing influence in the turbocharger lateral vibrations.

    更新日期:2020-01-13
  • Microstructure and tribological behavior of in situ synthesized (TiB+TiC)/Ti6Al4V (TiB/TiC=1/1) composites
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Bowen Zheng; Fuyu Dong; Xiaoguang Yuan; Hongjun Huang; Yue Zhang; Xiaojiao Zuo; Liangshun Luo; Liang Wang; Yanqing Su; Weidong Li; Peter K. Liaw; Xuan Wang

    To enhance wear properties of titanium alloys, in situ titanium matrix composites (TMCs) were synthesized by a melting cast method with (TiC + TiB) volume fractions of 0, 2, 4, 6, 8, and 10%. The results indicated that tribological properties of TMCs were increased owing to the dispersed distribution of (TiC + TiB) reinforcements, which improved the ability to resist the surface shear stress. Moreover, the stable transfer layer formed during wear reduced the shear strength and limited the direct interaction at tribo-pair interfaces to enhance surface hardness and wear resistance effectively. Consequently, the wear mechanism appeared to transitioned from the severe adhesive and oxidative wear gradually to the slight adhesion, abrasive, and oxidative wear along with reinforcements content increased.

    更新日期:2020-01-13
  • Partial-gross slip fretting transition of martensitic stainless steels
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    M. Lavella

    Based on critical reviews of the well-known dependence of fretting process upon the sliding amplitude, experiments were performed to verify this dependence. One of the main critical points is that the experiments which led to this result were performed controlling the imposed displacement amplitude instead of the real sliding amplitude. Therefore, the difference between the real displacement amplitude and the imposed amplitude due to compliances of the test rigs components was not considered. Fretting tests were performed using a high precision test rig. One of the main peculiarities of this test rig is that there is no difference between the imposed sliding amplitude and the real amplitude. The fretting process parameters of experiments were room temperature, two normal load (contact pressure 15, 25 MPa), four strokes (10, 15, 20, 50 μm), two martensitic stainless steels (X20Cr13, M152) and different durations from 15 to 160 M-cycles. Friction coefficient was computed using the hysteresis loops measured during the wear test. The worn surfaces were measured using an optical instrument based on focus variation. Wear volumes were accurately computed with a procedure that takes in to account the roughness of the surfaces. Results show that the friction coefficient is independent of slip amplitude, normal load and steel type if the hysteresis loops shape is parallelogrammatic and the contact surfaces are effectively conformal. When these conditions are not observed, the friction coefficient is dependent on normal load, even in contrast with its increase. Wear volume shows linear evolution in gross slip regime while it is non-linear in partial slip. Wear rate is independent of slip amplitude and normal load in partial slip regime at low ratio amplitude contact length. In contrast, wear rate depends on slip amplitude and exhibits a sharp increase near the transition partial-gross slip.

    更新日期:2020-01-13
  • A discussion on the capability of X-ray computed tomography for contact mechanics investigations
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Feikai Zhang; Jianhua Liu; Xiaoyu Ding; Zhimeng Yang

    The three-dimensional gap distribution and area of true contact significantly affect sealing performance and tribological properties between rough surfaces. Current experimental approaches are limited in their ability to predict the evolution of the gap distribution and real contact area on assembled rough interfaces, particularly on non-transparent surfaces. In our previous study [1], we presented a X-ray computed tomography method to obtain these parameters between non-transparent assembled rough interfaces experimentally. In this study, contacts of higher complexity than in our previous work are studied and accuracy as well as limitations of the experimental method are discussed. Additionally, the experimental procedure and data-processing methods are detailed to help other researchers reproduce this work.

    更新日期:2020-01-13
  • An analysis on the influence of air ingestion on vibration damping properties of squeeze film dampers
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Hai-lun Zhou; Xi Chen; Yu-qi Zhang; Yan-ting Ai; Dan Sun

    Considering the effect of air ingestion, a three-dimensional CFD model of open ends squeeze film damper (SFD) was established based on transient time step solution method and dynamic mesh technique. And the model was experimentally verified by bidirectional excitation experiment. Experiment and CFD simulation shows that air ingestion was caused by the pressure difference between oil film and external environment. With increasing precession frequency and eccentricity ratio, air ingestion area is gradually expanding resulting in increasing air volume, shrinking effective coverage of oil film and performance degradation of damper. Thereby, oil film damping shows the tendency to reduce. Compared with the case without considering air ingestion, the case considering air ingestion has obviously smaller peak pressure in the CFD simulation.

    更新日期:2020-01-13
  • Preparation and tribological behaviors of porous oil-containing polyimide/hollow mesoporous silica nanospheres composite films
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Weihong Jia; Shengrong Yang; Sili Ren; Limin Ma; Jinqing Wang
    更新日期:2020-01-13
  • Wear behavior of textured tools under graphene-assisted minimum quantity lubrication system in machining Ti-6al-4v alloy
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Rupinder Singh; J.S. Dureja; Manu Dogra; Munish Kumar Gupta; Mozammel Mia; Qinghua Song
    更新日期:2020-01-13
  • A coupled contact model of cartilage lubrication in the mixed-mode regime under static compression
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    JinJing Liao; David W. Smith; Saeed Miramini; Bruce S. Gardiner; Lihai Zhang

    This study presents a coupled cartilage contact model, in which the contact gap and cartilage tissue are modelled as two poroelastic systems, linked by pressure and normal flux continuity boundary conditions. Using a tibial plug under indentation as a proof-of-concept model, the predictions support the weeping lubrication theory under static compression. Specifically, that interstitial fluid would exude from the underlying cartilage into the contact gap to extend the mixed-mode duration by > 20-fold compared to a no fluid exudation counterpart. Moreover, the traditional contact model, that does not consider contact gap and cartilage fluid exchange, potentially overestimates the interstitial fluid pressure compared to the proposed coupled model. Parametric studies suggest that the increasing viscosity of synovial fluid prolongs the gap fluid pressure, while increasing the asperity stiffness reduces the gap fluid pressure but increases contact gap height.

    更新日期:2020-01-13
  • Flash temperature and anti-wear tribofilm growth mechanisms by asperity contact in top-ring/liner conjunction of IC engines
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Wei Pu; Qin Zhang; Wang Zhang; Si Ren; Zhe Chen; Tian Tian

    Understanding the growth mechanism of tribofilms at the top of the liner in IC engines is of great importance to protecting the sealing function of the top ring. In present study, the transient heat transfer is investigated between the ring and the liner in the top dead center (TDC) area with considerations of asperity contact pressure, boundary friction coefficient and reciprocating piston motion. A 3D transient model is developed to predict the evolutions of effective heat partition and conduction between the contact surfaces. It is revealed that the flash temperature in the asperity contact pairs of the top-ring/liner conjunction is remarkably higher than the steady-state liner temperature, therefore significantly enhancing the growth rate of anti-wear film formation based on a stress-activated Arrhenius model. The results show that the asperity contact model and the flash temperature model can be employed as an engineering tool for anti-wear tribofilm prediction in top-ring/liner conjunction of IC engines.

    更新日期:2020-01-13
  • Variation mechanism of the friction torque in a Cu-based wet clutch affected by operating parameters
    Tribol Int (IF 3.517) Pub Date : 2020-01-11
    Liang Yu; Biao Ma; Man Chen; Jiaqi Xue; Peiyao Zhao

    A comprehensive thermodynamic model is proposed to investigate the variation mechanism of friction torque in a Cu-based wet clutch affected by the operating parameters, which is verified by the bench test. The results show that the variation of friction torque is composed of three stages: preparation stage A, stable growth stage B and exponential growth stage C. Moreover, increasing the relative speed can reduce the growth rate of friction torque, so as to decrease its peak value; contrarily, increasing the applied pressure can effectively offset the decline of the friction torque slope caused by the rise of relative speed. Therefore, the relative speed and applied pressure should be reasonably matched to ensure a smooth and safe clutch engagement.

    更新日期:2020-01-13
  • Improved biotribological properties of polyetheretherketone composites for artificial joints with a ‘soft-on-hard’ structure and brushlike molecules
    Tribol Int (IF 3.517) Pub Date : 2020-01-09
    Yuntong Liu; Dangsheng Xiong; Xiaoduo Zhao

    On the purpose of improving the biotribological performance of polyetheretherketone (PEEK) for artificial joints, mimicking the ‘soft-on-hard’ contact mode of ‘cartilage-subchondral bone’ construction as well as the special brushlike structure of natural articular cartilage, a ‘soft-on-hard’ structure with a poly acrylic acid-poly acrylamide (PAA-PAAm) hydrogel layer connected onto a PEEK substrate was fabricated. Meanwhile, methacrylated sodium alginate (SAGMA) was introduced into the hydrogel layer to form molecular brushes. Compared to the friction coefficient of a pristine PEEK (0.22), that of the PEEK-hydrogel-molecular brush structure was significantly lower (0.02) benefiting from the synergistic effect of biphasic lubrication and boundary lubrication. This work develops a useful method to effectively improve the biotribological properties of artificial joints.

    更新日期:2020-01-11
  • Fabrication and cutting performance of bionic micro-serrated scalpels based on the miscanthus leaves
    Tribol Int (IF 3.517) Pub Date : 2020-01-09
    Juncheng Lu; Xingsheng Wang; Yuke Huang; Caiying Zhou; Bin Xu; Qiuqing Fu

    The purpose of this study is to improve the cutting performance of the scalpel by imitating the micro-structures of miscanthus leaves. Four different types of micro-serrated edges were designed, and these micro-serrations were then successfully processed on the edges of the scalpels by laser induced plasma micromachining (LIPMM). Subsequently, cutting tests were carried out to explore the effect of micro-serrations on the cutting performance. Compared to the unprocessed commercial scalpel, the micro-serrated scalpels could significantly reduce the cutting force and actual cutting depth. The type of blended serration without spacing scalpel had the best performance during cutting soft tissue due to the induced serration effect, which was also verified by the cutting process images and finite element simulation.

    更新日期:2020-01-11
  • Effects of foam copper on the mechanical properties and tribological properties of graphite/copper composites
    Tribol Int (IF 3.517) Pub Date : 2020-01-09
    Linying Zhu; Maozhong Yi; Liming Wang; Shengan Chen

    The foam copper with the thickness of 15–30 μm, the porosity of 97% was fabricated by electroless plating method. The graphite/copper composites were fabricated through the process of ball-milling,pressing and sintering. The effects of the foam copper on the mechanical properties and tribological properties of graphite/copper composites were studied in this paper. The results show that the hardness and bending strength of the graphite/copper with foam copper are improved, the friction coefficient and wear rate are decreased. The SEM(scanning electron microscope) images indicate that adding foam copper is helpful to weaken abrasive wear and form a relatively complete oxide film on the contact surface in the initial stage. TEM(transmission electron microscope) images show that there is much deformation occurred on the friction surface and in the area near friction surface of the graphite/copper composites, and the deformation zone can be divided into the friction layer with thickness of 200–300 nm, severely deformed area with thickness of 2–2.5 μm and slightly deformed area with the thickness of 1–1.5 μm.

    更新日期:2020-01-11
  • Predicting hydrodynamic conditions under worn shoes using the tapered-wedge solution of Reynolds equation
    Tribol Int (IF 3.517) Pub Date : 2020-01-08
    S.L. Hemler; D.N. Charbonneau; K.E. Beschorner

    Slips and falls are a leading cause of injuries in the workplace. The risk of slipping increases as shoe tread wears. The mechanics relating shoe wear to slip risk is needed to develop fall-prevention strategies. This research applies a rectangular, tapered-wedge bearing solution to worn shoes and compares the results to experimentally measured under-shoe fluid pressure results. Changes in the size of the shoe outsole worn region and fluid dispersion capabilities were recorded for four, slip-resistant shoes which were systematically abraded. The film thickness predicted by the solution correlated well with the measured force supported by the fluid. The results provide support that the tapered-wedge solution can be used to assess slip risk in worn shoes.

    更新日期:2020-01-09
  • Static and dynamic characteristics of high-speed water-lubricated spiral-groove thrust bearing considering cavitating and centrifugal effects
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    Shaowen Zhang; Shuyun Jiang; Xiaohui Lin

    The purpose of this paper is to investigate the static and dynamic characteristics of the high-speed water-lubricated spiral-groove thrust bearing (SGTB) considering cavitating and centrifugal effects. A turbulent flow lubrication model was established based on gas-liquid two phase flow, and the influence of cavitation and centrifugal force on the static and dynamic characteristics was analyzed for the SGTB. An experiment setup was developed to measure the static and dynamic characteristics of the SGTB. The result shows that the proposed model with cavitating and centrifugal effects is more accurate than that without those two effects, the effect of the cavitation and centrifugal force should be considered when the modified Reynolds number exceeds 0.3.

    更新日期:2020-01-07
  • Influence of fretting wear on bladed disks dynamic analysis
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    E. Lemoine; D. Nélias; F. Thouverez; C. Vincent

    Mastering physical phenomena taking place in aircraft engines is a key objective for manufacturers. Contact interfaces with dry friction in bladed-disks allows decreasing the dynamic response of the structure. Moreover, friction in the interfaces can induce fretting wear, decreasing even more the dynamic response. Combining harmonic balance method to study the dynamic behaviour, and a semi-analytical contact simulation method, allows to study the dynamic behaviour of the structure considering wear and dry friction in the interfaces. Furthermore, this method provides a computationally efficient tool to study the contact interfaces behaviour with accuracy and the dynamic response of the non-linear system.

    更新日期:2020-01-07
  • 1Influence of graphene oxide additive on the tribological and electrochemical corrosion properties of a PEO coating prepared on AZ31 magnesium alloy
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    Yulin Zhang; Fei Chen; You Zhang; Cuiwei Du

    Graphene oxide (GO) was incorporated into a plasma electrolytic oxidation (PEO)-based coating to further promote the tribological properties and corrosion resistance of AZ31 Mg alloys. The results demonstrated that the embedded GO additives reduced the surface roughness and porosity, promoted the formation of blocked pores and minor-sized structures, and enhanced the microhardness of the GO-containing coatings. The composite coating prepared with 20 mL L−1 GO additive was sufficient for sustaining a low and stable friction coefficient and high wear endurance. In addition, the inclusion of a GO additive in the composite coating could effectively decrease the corrosion rate and enhance the polarization resistance.

    更新日期:2020-01-07
  • Experimental and numerical roller skew in tapered roller bearings
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    Fida Majdoub; Ludovic Saunier; Christine Sidoroff-Coicaud; Bruno Mevel

    This work investigates the roller skew of a tapered roller bearing. An experimental setup has been built to measure the roller skew angle in tapered roller bearings thanks to two inductive proximity sensors (IPS). Using the roller skew measured values, a numerical friction law at the rib-roller end contact is defined. In order to validate this friction model, the calculated skew angles are compared to the experimental values. The roller skew angle is calculated after the kinematic equilibrium analysis at each roller. Moreover, the effect of the load, inner-raceway rotational speed, oil temperature, and lubricant type on the skew is examined.

    更新日期:2020-01-07
  • EHL/mixed transition of fully formulated environmentally acceptable gear oils
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    Reza Bayat; Arto Lehtovaara
    更新日期:2020-01-07
  • Enhanced lubricant replenishment by angled surface velocities in EHL contacts
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    X.M. Li; G.Y. Zhou; F. Guo; X.B. Wang; J.J. Zhang

    Effective lubricant replenishment to the lubrication track is highly expected for the purpose of lubricating film formation. In this paper, a novel lubricant replenishment mechanism is investigated. It is found that when velocities of the two bounding surfaces are angled, the lubricant adjacent to the track is efficiently moved back, and the inlet oil reservoir is enhanced considerably. The patterns of the inlet reservoir vary with disc revolutions, entrainment velocities, included angles of the surface velocities as well as lubricant feeding amount. The inlet lubricant supply and film formations by the grease are compared to those by its base oil, and the differences are analyzed from a perspective of lubricant transportations.

    更新日期:2020-01-07
  • Minimizing self-oscillation in belt drives: Surface texturing
    Tribol Int (IF 3.517) Pub Date : 2020-01-07
    Yingdan Wu; Michael J. Leamy; Michael Varenberg

    Detachment waves have recently been identified as one of the main sources for self-oscillation and accompanying energy losses in belt drive systems under low-speed and otherwise steady operation. In light of this, herein we explore mitigation of detachment wave-induced instabilities via regular and irregular texturing of the belt contact surface. The results document that surface texturing reduces the magnitude of belt drive oscillations, with the reduction being significantly more pronounced in the driver case than in the driven case. While both regular and irregular surface topographies are useful in minimizing the vibrations, regular patterns result in a stronger effect. The aspect ratio of surface projections is found to be the most important parameter, while excessive texturing of the belt surface is shown to result in belts losing their tractive capabilities.

    更新日期:2020-01-07
  • Generation mechanism of friction anisotropy by surface texturing under boundary lubrication
    Tribol Int (IF 3.517) Pub Date : 2019-02-10
    Shota Ito; Kenta Takahashi; Shinya Sasaki

    Continuously variable transmission (CVT) is commonly used in automobile to reduce fuel consumption and emission. Apart from wider gear ratio, reduction of friction loss in a radial direction of the pulley surface is an effective method of improving CVT efficiency. On the other hand, to improve torque transmission efficiency, high frictional force on circumferential direction of the pulley is necessary. Therefore, required frictional characteristics differ depending on sliding directions. To create friction anisotropy on belt-pulley contacts, laser surface texturing was proposed to improve friction characteristic and generates friction anisotropy on the surface. In this study, the relationship between surface texture and friction anisotropy was investigated under boundary lubrication by cylinder-on-disk type sliding test. The sliding test was conducted in four different directions, parallel, thirty degrees, sixty degrees, and perpendicular to the direction of the surface texture. Analysis of real contact area was conducted repeatedly in the sliding directions to evaluate change in interaction of asperities in sliding directions over time. The experimental results were then compared with result of the continuous analysis of real contact area. When a groove-type texture was created by a processing laser, texture pattern changes the sliding distance on the plateaus of the texture, which affects the level of metal contact on the surface, generating friction anisotropy. This hypothesis was supplemented by the continuous analysis of the real contact area, which confirmed that the sliding distance on the plateaus of the texture decreased as the sliding angle increased. Furthermore, clear correlation between sliding distance and friction force was observed, which suggests the possibility that friction anisotropy by surface texturing under boundary lubrication will be predicted by a friction force function.

    更新日期:2020-01-06
  • Lubrication characteristics and wear mechanism mapping for hybrid aluminium metal matrix composite sliding under surfactant functionalized MWCNT-oil
    Tribol Int (IF 3.517) Pub Date : 2019-12-27
    Harpreet Singh; Hiralal Bhowmick

    The friction-wear response of surfactant functionalized MWCNT-in-oil suspension under hybrid aluminium metal matrix composite/EN31 contact is presented. Composites were fabricated, characterized and tribological tests were performed with a pin-on-disc tribometer. Prior to tribological testing, thermophysical and stability analysis of the prepared lubricants were carried out. The operating regimes of the lubricants were predicted based on the estimated film thickness and friction responses. It is observed that the film thickness ratio for surfactant-MWCNT-oil is increased by 47% which helped in the shifting of lubrication towards the mixed regime. The findings of the study reveals that there is a remarkable enhancement in tribological behavior when surfactant functionalized MWCNT-in-oil is used. Finally, a wear map of the underlying wear mechanisms is also presented.

    更新日期:2020-01-04
  • Unique synergism between zinc dialkyldithiophosphates and Schiff base bridged phenolic diphenylamine antioxidants
    Tribol Int (IF 3.517) Pub Date : 2019-12-28
    Shengpei Wang; Shasha Yu; Bo Huang; Jianxiang Feng; Shenggao Liu

    The effects of four Schiff base bridged phenolic diphenylamine antioxidants (SSPDs) on the multifunctional properties of a traditional additive zinc dialkyldithiophosphate (ZDDP) were studied. Interestingly, it is observed that the cooperation between SSPDs and ZDDP improves the antioxidant, antiwear and extreme pressure of lubricant oil, but does not reduce its anticorrosive property. The EDS and XPS results indicated that a unique interaction was occurred between SSPDs and ZDDP. In addition, the synergistic effect was studied by NMR, which showed that SSPD selectively disintegrated the cage structures (basic form) of the ZDDP to afford a donor-acceptor complex via the coordination of nitrogen of imine to the zinc atom.

    更新日期:2020-01-04
  • Tool wear behavior of vitrified microcrystalline alumina wheels in creep feed profile grinding of turbine blade root of single crystal nickel-based superalloy
    Tribol Int (IF 3.517) Pub Date : 2019-12-26
    Qing Miao; Wenfeng Ding; Weijie Kuang; Jiuhua Xu

    Different aspects on the tool wear behavior of profiled vitrified microcrystalline alumina wheels during creep feed grinding of Ni alloy blade root were investigated. Experimental results indicate that the wheel peak regions had the higher wear values than the wheel valley regions by around 21.7%, 42.8%, 34.5%, in terms of the profile heights, circle radii and angles respectively. Furthermore, the wear flats, workpiece material adhesion, and the fractures of grains and bond bridges occurred in the wheel peak regions; while in the wheel valley regions, heavy wheel clogging, fractures of grains, and workpiece material adhesion were produced. Based on the experimental results, an analytical model with the average error of 17.3% to predict the wheel profile wear was finally developed.

    更新日期:2020-01-04
  • Fretting wear behavior of cobalt - Based superalloys at high temperature – A comparative study
    Tribol Int (IF 3.517) Pub Date : 2020-01-03
    Ahmed Korashy; Helmi Attia; Vince Thomson; Saeid Oskooei

    Superalloys are extensively used in the design of combustor components of aero engines because they can withstand high temperature oxidizing environments, while maintaining their strength. This investigation aims at assessing the tribological characteristic of some combustor components candidate cobalt-based and nickel-based superalloys. Three combinations of the alloys were tested at different operating conditions and temperatures; CP1 (Cobalt 1/Cobalt 2), CP2 (Cobalt 2/Nickel 1) and CP3 (Cobalt 1/Nickel 1). The investigation showed that the increase in temperature from 350 °C to 550 °C was associated with a decrease in the coefficient of friction for all tested contact pairs, a decrease in wear coefficient (wear damage) for CP1, and an increase in wear coefficient for CP2 and CP3. Samples analysis using SEM-EDS and Raman Spectroscopy showed that the least wear coefficient exhibited by CP1 at 550 °C, and by CP2 at 350 °C is due to the development of a compacted protective layer of chromium oxide Cr2O3, known for its favourable tribological characteristic, which contributes to load bearing, precludes the metal-metal contact, and reduces the friction and wear damage. On the other hand, the decrease in friction was associated with an increase in wear coefficient for CP2 and CP3 due to the formation of a porous oxide layer with high tungsten trioxide (WO3) content which makes the oxide softer, decreases friction and increases the wear damage in the oxide layer. Material selection maps are presented to aid aero-engine designers.

    更新日期:2020-01-04
  • The fretting fatigue performance of Ti–6Al–4V alloy influenced by microstructure of CuNiIn coating prepared via thermal spraying
    Tribol Int (IF 3.517) Pub Date : 2019-12-31
    Amin Ma; Daoxin Liu; Xiaohua Zhang; Guangyu He; Dan Liu; Chengsong Liu; Xingchen Xu

    Two types of CuNiIn coatings with different microstructures were successfully prepared on the surface of a Ti–6Al–4V alloy by means of high-velocity oxygen fuel (HVOF) and plasma spray (PS), respectively. The effect of the coating microstructure on the fretting fatigue (FF) resistance of the alloy as well as crack initiation and propagation was investigated. Compared with the HVOF-CuNiIn coating, the PS-CuNiIn coating was composed of a more significant lamellar microstructure and exhibited higher FF resistance. HVOF-CuNiIn possessed low resistance to crack initiation due to its low toughness, thus leading to a short FF life of the titanium alloy. The excellent FF resistance of the rotary flay peening (RFP)-treated sample resulted mainly from the large value of the compressive residual stress.

    更新日期:2020-01-04
  • Stability and Hopf bifurcations in rotor-bearing-foundation systems of turbines and generators
    Tribol Int (IF 3.517) Pub Date : 2019-12-30
    Athanasios Chasalevris

    The paper investigates the type of Hopf bifurcations existing in slender rotor systems of turbines and generators with respect to the design of bearings, foundations, and rotors. Two bearing profiles applied mostly in such rotor systems, the lemon bore and the partial arc bearing are considered in the analysis with nonlinear impedance. Simplistic models of single degree of freedom per direction are considered for the bearing pedestals. Part of the paper investigates the bifurcation type in simple Jeffcott rotor mounted on nonlinear lemon bore and partial arc bearings with resilient pedestals, aiming to raise design concerns which influence the type of bifurcation. The results highlight the need for nonlinear stability assessment in the standard design of turbines and generators.

    更新日期:2020-01-04
  • Improved examination and test procedure of tapping torque tests according to ASTM D5619 using coated forming taps and water-mixed metalworking fluids
    Tribol Int (IF 3.517) Pub Date : 2019-12-30
    A.L. Demmerling; D. Söffker

    Tapping torque test is a standardized (ASTM D5619-00) approach evaluating the lubricity of metalworking fluids. It was detected that running-in behaviors of taps and carryover effects caused by previously used fluids were not investigated. Further, it is detected that effects due to changed tap conditions or fluids are underestimated. The low number of measurements leads to deviations of torque means. In this contribution, the running-in phase of coated forming taps is evaluated by measuring tapping torque in AlMgSi1, C45E, and AlSi7Mg materials using water-mixed metalworking fluids. New tests and calculation methods considering tool wear are suggested. As outcome increased experimental significance at higher confidence levels, comparability between taps and test platforms, and better distinguishability of water-mixed metalworking fluids are obtained.

    更新日期:2020-01-04
  • 更新日期:2020-01-04
  • Real-time fretting loop regime transition identification using acoustic emissions
    Tribol Int (IF 3.517) Pub Date : 2019-12-28
    A. Wade; R. Copley; B. Clarke; A. Alsheikh Omar; A.R. Beadling; T. Liskiewicz; M. Bryant

    Acoustic emission (AE) has been successfully used to investigate the damage mechanisms of fretting contacts within different regimes. This study investigated the transition between fretting regimes using the relationship between AE and the mechanical response of a dry, steel-on-steel, ball-on-flat contact under different tangential displacements achieving the partial slip regime, mixed fretting regime and gross slip regime. Increased AE response occurred during gross-slip events and there was strong positive correlation between AE and fretting energy ratio. The relationship was strongest when gross sliding was experienced allowing identification of transition from the partial slip to the gross slip regime. This makes AE a good candidate to detect regime transition in-situ due to ease of integration and its non-destructive nature.

    更新日期:2020-01-04
  • Dry lubrication of ferritic stainless steel functionalised with crystalline aggregates of hexadecylphosphonic acid
    Tribol Int (IF 3.517) Pub Date : 2019-12-28
    Pierre-Henri Cornuault; Jean-Marie Melot; Xavier Roizard; Fabrice Lallemand

    This paper demonstrates the excellent tribological behaviour afforded by a new functionalisation technique based on the combination of chemisorption and physisorption of self-assembled hexadecylphosphonic acid for application in metal forming. Surface functionalisation of an X2TiCrNb18 ferritic stainless steel with this technique led to the growth of aggregates on the surface. Detailed analysis showed that crystalline aggregates were physisorbed on a chemisorbed molecular layer. Ball-on-plate linear reciprocating sliding tests were performed under high maximal contact pressures in the 0.5–1.1 GPa range using a 100Cr6 counterpart. Results revealed exceptional low-friction and low-wear afforded by a tribofilm originating from aggregates shearing. The tribofilm built up very quickly and presented the interesting feature of reducing the friction coefficient as the contact pressure increased.

    更新日期:2020-01-04
  • Role of ZrO2 oxide layer on the fretting wear resistance of a nuclear fuel rod
    Tribol Int (IF 3.517) Pub Date : 2019-12-27
    Young-Ho Lee; Il-Hyun Kim; Hyung-Kyu Kim; Hyun-Gil Kim

    The ZrO2 oxide layers of Zr-based fuel claddings have been intensively studied to unveil their oxidation mechanisms in high temperature pressurized water. Nevertheless, there has been insufficient research on their mechanical properties, which are key factors determining the resistance to grid-to-rod fretting damage in normal Pressurized Water Reactor (PWR) operation. An experimental approach was applied to examine the tribological behavior of time-dependent oxide layers on both Zr cladding and grid, which were prepared in simulated PWR conditions for up to 360 days. It was found that the wear rate of pre-oxidized Zr cladding suddenly dropped with increasing oxide thickness of both the cladding and grid. The increase of surface roughness with oxide growth on the Zr-based grid could result in a rapid increase of wear damage by third-body abrasion. The well-developed columnar structure of the ZrO2 oxide layer could have a detrimental effect on the resistance to plastic deformation due to the enlarged grain size and relaxation of compressive residual stress by tetragonal to monoclinic ZrO2 transformation and crack formation. Consequently, ZrO2 oxide layers formed on fuel cladding and spacer grid under high temperature pressurized water show sufficient ductility to accommodate plastic deformation, which results in enhanced fretting wear resistance.

    更新日期:2020-01-04
  • Optimization performance of plain journal bearings with partial wall slip
    Tribol Int (IF 3.517) Pub Date : 2019-12-27
    Shuhui Cui; Chuanwei Zhang; Michel Fillon; Le Gu

    In present work, in order to optimize partial slip zone for heavily loaded journal bearings, an isothermal hydrodynamic model considering wall slip occurring at oil-bush interface is built. Two-component slip model is utilized to calculate slip velocity. The performances of the journal bearing in different slip zone shapes and eccentricity ratios are evaluated. The optimal slip parameters in a range of eccentricity ratios are selected by considering their effects on hydrodynamic behavior, such as load carrying capacity and friction coefficient/torque. In addition, the application of optimal partial slip zone is presented. Results show that the optimal range of slip zone in high eccentricity ratio is quite restricted. The slip zone should be located at the convergent region of the film. The circumferential end of slip zone should locate at the convergent region and be close to the position of minimum film thickness. It is better to widen the axial length of slip zone, i.e. maximum rectangular shape could better improve bearing performance.

    更新日期:2020-01-04
  • Adhesion of lubricant on aluminium through adsorption of additive head-groups on γ-alumina: A DFT study
    Tribol Int (IF 3.517) Pub Date : 2019-12-26
    Sarah Blanck; Sophie Loehlé; Stephan N. Steinmann; Carine Michel
    更新日期:2020-01-04
  • Development mechanism of local corrosion pit in X80 pipeline steel under flow conditions
    Tribol Int (IF 3.517) Pub Date : 2019-12-26
    Zhuowei Tan; Dalei Zhang; Liuyang Yang; Zhenbo Wang; Frank Cheng; Mingyang Zhang; Youhai Jin; Shidong Zhu

    In this paper, local corrosion pits were stimulated by arc defect pits (ADP) of different sizes. The corrosion of specimens was tested in high-speed flow CO2-saturated NACE solution. Electrochemical corrosion characteristics were monitored online. The characteristics of corrosion scale were then investigated by SEM and Raman spectroscopy. The results showed deepening and expansion of corrosion pits will occur at the same time under flow conditions for shallow pits. The development of corrosion pits at certain depth led to formation of complete corrosion scale, which inhibited further corrosion. As corrosion pits deepened, expansion process decreased and deepening rates accelerated. In-depth analysis suggested that corrosion rates were mainly affected by mass transfer rate and integrity of formed corrosion scale.

    更新日期:2020-01-04
  • Atomic-scale study of vacancy defects in SiC affecting on removal mechanisms during nano-abrasion process
    Tribol Int (IF 3.517) Pub Date : 2019-12-24
    Piao Zhou; Tao Sun; Xunda Shi; Jun Li; Yongwei Zhu; Zikun Wang

    The mechanical properties of mono-crystalline SiC with vacancy defects in fixed abrasive polishing processes are not well known at the nanometric scale. In the molecular dynamic (MD) simulation, the removal mechanism of mono-crystalline SiC substrates with vacancy defects is investigated. So is the wear mechanism of diamond abrasives explored. The simulation result reveals that the increase of vacancy defects in SiC substrates leads to reduced von Mises Stress, however, to increased temperature of SiC substrates during nano-abrading process. More vacancy defects are found to lead higher removal efficiency and less subsurface damage on SiC substrates. Furthermore, the diamond abrasives are worn out through a combination of thermo-chemical wear, graphitization wear and abrasive wear in the simulation.

    更新日期:2020-01-04
  • Influence of lubricant on nonlinear vibration characteristics of linear rolling guideway
    Tribol Int (IF 3.517) Pub Date : 2019-12-18
    Yasunori Sakai; Tomohisa Tanaka

    Linear rolling guideways are widely used in precision mechanical systems such as robots and machine tools. Clarifying the natural vibration characteristics of a linear rolling guideway is important for improving the performance of mechanical systems, because the dynamic characteristics of the guideway strongly influence the dynamics and posture accuracy of mechanical systems. This study focuses on the natural vibration characteristics of linear rolling guideways. We discuss both the nonlinear relationship between friction and natural vibration, and the influence of the lubricant specification on the nonlinearity of nonlinear natural vibration. Additionally, the effects of the lubricant specifications on the damping ratio are different for different vibration modes, owing to the differences between the damping mechanisms.

    更新日期:2020-01-04
  • Cracks and degradation layers in large flat-on-flat fretting contact with steels and cast iron
    Tribol Int (IF 3.517) Pub Date : 2019-12-04
    Janne Juoksukangas; Verner Nurmi; Jouko Hintikka; Mari Honkanen; Minnamari Vippola; Arto Lehtovaara; Antti Mäntylä; Joona Vaara; Tero Frondelius

    Fretting may deteriorate contacts in terms of wear and cracking. Fretting-induced material degradation and frictional behaviour was studied experimentally in a large flat-on-flat fretting contact with a moderate nominal normal pressure and in different sliding conditions. The materials studied were cast iron, structural steel, and quenched and tempered steel. The results for all materials revealed a severely deformed microstructure, a tribologically transformed structure with high hardness, an oxidized third body layer and cracking. The initial peak in the coefficient of friction followed by stabilization occurred in all material pairs in gross sliding conditions. With low utilization of friction, only a limited amount of damage occurred. The results for each of these materials were compared.

    更新日期:2020-01-04
  • Tool wear and hole quality evaluation in cryogenic Drilling of Inconel 718 superalloy
    Tribol Int (IF 3.517) Pub Date : 2019-11-22
    Navneet Khanna; Chetan Agrawal; Munish Kumar Gupta; Qinghua Song

    In this paper, the research effforts have been made to discover the potential of cryogenic machining as a sustainable manufacturing process for drilling of Inconel 718 superalloy. The drilling performance is investigated in terms of thrust force, torque, tool wear, chip morphology and hole quality (circularity -CIR, cylindricity –CYL, and surface roughness - Ra values). The experimental result shows temperature-dependent tool wear drastically reduced under cryogenic drilling as compared to dry drilling, and this leads to a reduction in torque values up to 30%. Furthermore, the cryogenic drilling improves tool life up to 87.50% and produce better quality holes due to a decrease in CIR deviations (up to 51%), CYL deviations (up to 77%), and Ra values (up to 48%).

    更新日期:2020-01-04
  • Frictional characteristics of impregnated graphite with different graphitization degree versus chromium stainless steel under varying PV values
    Tribol Int (IF 3.517) Pub Date : 2019-11-07
    Jie Jin; Xudong Peng; Jinbo Jiang; Xiangkai Meng; Wenjing Zhao

    An experimental study was performed by employing a seal pair of phenolic resin impregnated graphite and high chromium martensitic stainless steel 9Cr18. A purpose-built test rig was designed and fabricated to study the effect of face temperature on the surface morphology of a seal ring made of phenolic resin impregnated graphite with different graphitization degrees for varying PV values (pressure × velocity). As revealed by the results, the effect of rotational speed on heat generation between the two mating surfaces was more significant than that of fluid pressure. The effects of surface frictional temperature between the two faces were found different when the phenolic resin impregnated graphite ring with different graphitization degrees. The worn surfaces of the phenolic resin impregnated graphite rings were examined with the assistance of scanning electron microscopy and 3D measuring laser microscopy to investigate the wear mechanism for these different mating rings. Both adhesive and abrasive wear mechanisms were discovered under the working conditions. It was found out that the phenolic resin impregnated graphite ring with a high degree of graphitization was worn more severely at high PV values. Under the conditions of high speeds or high PV values, the phenolic resin impregnated graphite with fine and compact graphite matrix particles, medium degree of graphitization, high thermal conductivity and hardness is the top choice.

    更新日期:2020-01-04
  • Replenishment of the EHL contacts in a grease lubricated ball bearing
    Tribol Int (IF 3.517) Pub Date : 2019-11-06
    Hui Cen; Piet M. Lugt

    The film thickness in grease lubricated bearings is usually calculated by assuming fully flooded conditions, using the base oil properties. This paper shows that, for sealed-for-life bearings, starvation already occurs at relatively low speeds, where the film thickness could be described by the product of speed, viscosity and Hertzian semi-contact width. It is shown that replenishment is not significant on the tracks in-between the balls but that it is a local phenomenon. The relation between film thickness and the product of speed, viscosity and contact size is different from what is found in single contacts. The film thickness decreases as a function of speed and viscosity, but the effect is only small leading to an almost constant film thickness with increasing product of viscosity and speed.

    更新日期:2020-01-04
  • Prediction of contact condition and surface damage by simulating variable friction coefficient and wear
    Tribol Int (IF 3.517) Pub Date : 2019-11-05
    A. Mäntylä; J. Hintikka; T. Frondelius; J. Vaara; A. Lehtovaara; J. Juoksukangas

    A simulation method to predict the reliability of clamped metal contacts under cyclic loading is presented. The main idea is to predict the development of contact condition of a joint by simulating a spatially variable coefficient of friction (COF) and wear. Frictional energy dissipation drives the COF evolution rule, and classic Archard's equation is employed as the evolution rule for wear depth. As both the COF and wear evolution are considered, the presented approach is capable of predicting changes in the contact condition over time. The approach is based on the Finite Element Method (FEM) and is generally applicable to industrial cases. The method is implemented as a subroutine to a FEM solver Abaqus to define a contact formulation in both normal and tangential directions. The subroutine allows full coupling between normal and tangential contact variables, which makes the approach robust also in complex industrial applications. As the effect of wear is described in the contact pressure calculation, there is no need for mesh modification. The presented approach was validated by simulating cylinder-on-plane configuration. The presented method provides similar results obtained with a simulation where geometry is updated due to wear. The results of the case study were qualitatively verified against a bolted joint type fretting experiment. The area of slip after stabilized COF distribution corresponds well with the experimental fretting scars. However, Archard's wear law seems to be limited, at least in partial slip cases, as it overestimates the amount of wear without considering entrapment of wear debris in the contact. A case study of medium speed combustion engine component is presented to show how the simulation method can be used in engine development to ensure reliable contact interfaces.

    更新日期:2020-01-04
  • On the peeling of elastic tapes from viscoelastic substrates: Designing materials for ultratough peeling
    Tribol Int (IF 3.517) Pub Date : 2019-11-04
    Elena Pierro; Luciano Afferrante; Giuseppe Carbone

    The present paper deals with the peeling of an elastic thin tape from a viscoelastic substrate. A previous investigation of the authors has disclosed several physical aspects of such phenomenon by focusing the attention on an ideal viscoelastic substrate with one-single relaxation time. However, for real viscoelastic solids, the spectrum of relaxation times may cover more than 10 decades. For this reason, it is of interest investigating the influence of the number of relaxation times on the peeling mechanism. More specifically, it is possible to enlarge the frequency range where the material shows significant damping and energy dissipation by increasing such number. This may help in properly designing viscoelastic materials with ultra-tough adhesion properties. As a practical example, a widespread viscoelastic material is considered, the PMMA (polymethyl methacrylate), which presents high damping at low-frequencies, thus making tough the peeling behavior at small velocities.

    更新日期:2020-01-04
  • Influences of solid and lubricant thermal conductivity on traction in an EHL circular contact
    Tribol Int (IF 3.517) Pub Date : 2019-11-03
    H.C. Liu; B.B. Zhang; N. Bader; G. Poll; C.H. Venner

    The influences of thermal conductivity of both the contacting solids and the lubricant on the traction in a rolling/sliding EHL contact have been studied numerically. For through-hardened AISI 52100 bearing steel (k was measured as 21W/mK by Reddyhoff et al. see Tribol Lett 67(1):22, 2019), with the improper but widely used thermal conductivity of 46W/mK in literature, the friction coefficient can be overestimated and the maximum temperature in the lubricating film would be underestimated. The effect of solid thermal conductivity on traction depends on the entrainment speed and the resulting film thickness. For the thermal conductivity of the lubricant, its pressure dependence affects the traction mainly at high speeds and/or at high sliding-to-rolling ratio (SRR) conditions.

    更新日期:2020-01-04
  • Production of a laser textured 316L stainless steel reinforced with CuCoBe + diamond composites by hot pressing: Influence of diamond particle size on the hardness and tribological behaviour
    Tribol Int (IF 3.517) Pub Date : 2019-11-03
    A. Cunha; R. Ferreira; B. Trindade; F.S. Silva; O. Carvalho

    Two composite blends of CuCoBe and synthetic diamond with different particle sizes, (0.1–0.5 μm and 40–60 μm), were obtained by mechanical alloying and were used as a reinforcement of a laser textured 316L stainless steel in this work. Consolidation/sintering of the powders was conducted by hot pressing. From all the samples studied, the 316L stainless steel reinforced with the CuCoBe + diamond (40–60 μm) composite presented the lowest values of specific wear rate and coefficient of friction (5.83 × 10−7 mm3/N.m and 0.14, respectively), showing the potential of this material in applications where good tribological behaviour is required, e.g. for the fabrication of improved automotive piston rings.

    更新日期:2020-01-04
  • A review of partial slip solutions for contacts represented by half-planes including bulk tension and moments
    Tribol Int (IF 3.517) Pub Date : 2019-11-02
    H. Andresen; D.A. Hills

    Solution procedures for establishing the regimes of stick and slip for frictional contacts capable of idealisation within the framework of half-plane elasticity and subject to complex loading regimes are reviewed, starting with the well known fundamental problems and going on to more complicated ones. These include problems where the normal load, shear force, applied moment and differential remote tensions all vary with time. Transient and steady state solutions are discussed.

    更新日期:2020-01-04
  • Impact-sliding wear behaviors of 304SS influenced by different impact kinetic energy and sliding velocity
    Tribol Int (IF 3.517) Pub Date : 2019-11-02
    Mei-gui Yin; Zhen-bing Cai; Yan-qing Yu; Min-hao Zhu

    Wear behaviors of materials in nuclear power stations are very complex, because they are rarely subject to just pure impact or sliding wear. This study uses a self-made impact-sliding wear test rig to study the influences of impact kinetic energy and sliding velocity on the energy absorption, mechanical response, interface deformation, and damage behavior of nuclear-grade 304 stainless steels (304SS). The results show that an increase in impact velocity causes an increase in absorbed energy, impact force, and friction force, while lowing the friction coefficient. The friction force and friction coefficient increase with an increase in the sliding velocity, whereas no obvious change is seen in impact force and absorbed energy. The dominant wear mechanism in test samples were delamination failure and friction oxidation. Furthermore, numerical study was performed to explain the effect of velocity on the mechanical response of 304SS.

    更新日期:2020-01-04
  • The effect of gas turbine lubricant base oil molecular structure on friction
    Tribol Int (IF 3.517) Pub Date : 2019-11-01
    Jake Airey; Matthew Spencer; Richard Greenwood; Mark Simmons

    The effect of molecular structure of lubricant polyol ester base oils on friction was studied. A Mini-Traction Machine was used to produce Stribeck curves under representative oil system conditions. The base oils were examined independent of viscosity to isolate the impact of the molecular structure. The effect of chain length, the number of ester groups and the effect of branching were investigated. Friction decreases as the chain length increases, as the number of ester groups increases and as the amount of branching decreases. The decrease in friction as the chain length and number of ester groups increases was attributed to improved packing efficiency and that longer chains can better separate surfaces. However, branching increases friction due to hindering packing efficiency.

    更新日期:2020-01-04
Contents have been reproduced by permission of the publishers.
导出
全部期刊列表>>
2020新春特辑
限时免费阅读临床医学内容
ACS材料视界
科学报告最新纳米科学与技术研究
清华大学化学系段昊泓
自然科研论文编辑服务
中国科学院大学楚甲祥
上海纽约大学William Glover
中国科学院化学研究所
课题组网站
X-MOL
北京大学分子工程苏南研究院
华东师范大学分子机器及功能材料
中山大学化学工程与技术学院
试剂库存
天合科研
down
wechat
bug