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  • 1.
    Li, Yiling
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Xi, Yinhu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Estimation of rolling friction coefficients in a tribosystem using optical measurements2018In: Industrial Lubrication and Tribology, ISSN 0036-8792, E-ISSN 1758-5775, Vol. 70, no 4, p. 680-686Article in journal (Refereed)
    Abstract [en]

    Purpose

    This paper presents a method to measure the rolling friction coefficient in an easy and fast way. The aim is to measure the rolling friction coefficient between a small steel ball and a cylindrical aluminum surface.

    Design/methodology/approach

    An analytical model of the tribosystem of a freely rolling ball and a cylindrical surface is established. The rolling friction coefficient is evaluated from images recorded by a high-speed camera. The coefficient between a 1.58 mm diameter steel ball and a cylindrical aluminum surface is measured. A background subtraction algorithm is used to determine the position of the small steel ball.

    Findings

    The angular positions of the ball are predicted using the analytical model, and good agreement is found between the experimental and theoretical results.

    Originality/value

    An optical method for evaluating the rolling friction coefficient is presented, and the value of this coefficient between a small steel ball and a cylindrical aluminum surface is evaluated.

  • 2.
    Wu, Jian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, China.
    Xi, Yinhu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University, China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Toward wear-resistive, highly durable and high performance triboelectric nanogenerator through interface liquid lubrication2020In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 72, article id 104659Article in journal (Refereed)
    Abstract [en]

    Triboelectric nanogenerator (TENG) has been proved as a powerful approach to harvest ambient mechanical energy for many technological applications. However, the service lifetime, stability and robustness of TENG are a challenge owing to the wearing and surface degradation. In this manuscript, liquid lubrication is introduced for the first time to increase the anti-wear property of TENG. The influence of the lubricant layer between the surfaces on TENG outputs is studied. It is surprising to find that proper liquid lubrication can not only provide a super wear-resistive TENG, but also can increase the electric outputs. In comparison to a slide-mode TENG with solid-solid contact, the service life of TENG can be greatly improved through liquid lubrication and there is no detected wear even after 36,000 cycles of operation. Specially, the open-circuit voltage and short-circuit current of squalane-lubricated TENG can be both more than 3 times of the unlubricated TENG. For unlubricated TENG, a transfer polymer film adheres to the harder material surface and reduces the contact effectiveness. Liquid lubrication is able to avoid the formation of the transfer film, increase the effective solid-solid contact area and squeeze the air at the interface, thus giving rise to higher electric outputs. Our study opens a new approach for extending the lifetime and stability of TENGs.

  • 3.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    A Complementarity Problem–Based Solution Procedure for 2D Steady-State Rolling Contacts with Dry Friction2016In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 59, no 6, p. 1031-1038Article in journal (Refereed)
    Abstract [en]

    The problem of steady-state rolling contact between two cylinders with dry friction was formulated into standard linear complementarity problems (LCPs) by using the explicit physical definition. For normal contact, the complementarity variables are the normal pressure and the gap. For the tangential contact, the traction distribution and relative slip are the variables obtained by solving the LCP. The frictional behavior is assumed to be governed by the Coulomb friction law, and LCP formulations of both similar elastic (Carter problem) and dissimilar elastic rolling contacts are presented in this work. Good agreement was found between the current LCP approach and publicly available software for both the rolling contact of similar elastic and dissimilar elastic cylinders. Moreover, the surface roughness was taken into account in this paper by the verified approach. The results show the initial slope of the traction - relative creepage curve decreases as the surface roughness increases.

  • 4.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor–Bearing System, Xi'an Jiaotong University.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Linear Complementarity Framework for 3D Steady-State Rolling Contact Problems Including Creepages with Isotropic and Anisotropic Friction for Circular Hertzian Contact2017In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 60, no 5, p. 832-844Article in journal (Refereed)
    Abstract [en]

    In this article, the problem of 3D steady-state rolling contacts with dry friction for circular Hertzian contacts is formulated mathematically as a linear complementarity problem (LCP). The complementarity variables are the traction and the relative slip of contact regions, in which a polyhedral friction law is employed. The present work uses the general expressions describing the surface deformations due to uniform traction over a rectangular area on an elastic half-space to derive the influence coefficient matrix for rolling contact problems. Three possible creepage types—that is, longitudinal, lateral, and spin creepage—are considered in this work. Firstly, the numerical results are verified against the existing numerical solutions and good agreement has been found. Secondly, the anisotropic friction is studied by the verified approach. Some numerical examples are provided to illustrate the current LCP method for both isotropic and anisotropic friction in which the combined effects of the three kinds of creepage on the traction distribution are shown.

  • 5.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Application of an inclined, spinning ball-on-rotating disc apparatus to simulate railway wheel and rail contact problems2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 374-375, p. 46-53Article in journal (Refereed)
    Abstract [en]

    Railway wheel-rail contacts involve various combinations of slip, rolling, and creepage. Traditionally, a twin-disc apparatus is used to simulate such problems. However, there are out of plane forces and motions involved in the actual situation. Therefore, the possibility of using a commercially-made, inclined-axis spinning ball-on-disc test rig was investigated to better simulate wheel and rail contact problems. By setting two angle parameters both the lateral and spin creepage can easily be applied to the contact. Traction measurements were conducted, and good agreement was found by comparing the present results with other available experimental data. The effects of the spin creepage on wear were studied in particular. An asymmetrical wear pattern was obtained from cases that applied a low longitudinal creepage and a spin creepage, corresponding to a rail running on a curved track. To the best of the authors' knowledge, this work is the first of its kind to be done using a laboratory-scale tribometer.

  • 6.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Traction formula for rolling-sliding contacts in consideration of roughness under low slide to roll ratios2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 104, p. 263-271Article in journal (Refereed)
    Abstract [en]

    Based on the numerical results of a wide range of parameters in terms of the linear complementarity framework, an easy-to-use formula is presented by using the regression analyses to estimate the traction coefficient for rolling-sliding contacts under low Slide-to-Roll Ratio (SRR) domain for dry condition. The parameters include geometry, surface roughness, SRR and friction coefficient and contact radius. The formula's predictions are in good agreement with measurements using a ball on disc test rig. The results indicate that for steel-steel contact, the effects of third body layer and plasticity on the traction can almost cancel each other out. In addition, by revising the expression proposed by Masjedi and Khonsari, the formula is extended to estimate the cases under mixed lubrication.

  • 7.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University, Xi'an, PR China.
    Hua, Jing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Noncontact Triboelectric Nanogenerator for Human Motion Monitoring and Energy Harvesting2020In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 69, article id 104390Article in journal (Refereed)
    Abstract [en]

    Monitoring human motion and harvesting its energy is an interesting and important topic. Triboelectric nanogenerators (TENGs) have shown their potential for signal detecting and energy harvesting. In this paper, a noncontact paper-based TENG is creatively proposed to be used as a self-powered human motion monitoring sensor and also to be used for human motion energy harvesting. The noncontact mode avoids the requirement of direct physical contact between the TENG and the human subject, which fascinates the application of TENG and can increase its service life. It is found that the walking gait cycle (leg raising and falling), moving direction, walking or running speed and moving path can be reflected by the output voltage signals directly and clearly. Noncontact human motion energy harvesting is also achieved by using this TENG with a rectification circuit. It is also surprisingly found that this TENG is able to detect human motion even through a building wall, and the output voltage is strong enough to be captured by a normal multimeter without any additional amplification circuit. This study opens up a new method for self-powered noncontact human movement detecting and monitoring.

  • 8.
    Xi, Yinhu
    et al.
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an, .
    Zhao, Yang
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an, .
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Time-dependent hysteresis friction behaviors of linear rolling bearings2018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, no 9-12, p. 3109-3116Article in journal (Refereed)
    Abstract [en]

    Hysteresis friction behaviors of linear rolling bearings (LRBs) are important for precision positioning applications, which are related to the displacement and the traversed trajectory history within pre-rolling friction region. Although these behaviors have been pointed out in literature, the time dependence of transient hysteresis friction behaviors has not been reported before. In this work, the effects of initial conditions induced by the applied forces prior to commencement of the hysteresis motion are considered, which are denoted by the differences between the magnitudes of positive endpoints and the magnitudes of negative endpoints of virgin curves for the obtained asymmetrical hysteresis loops. The evolution of the time dependence is denoted by the decaying of the differences with the increasing dwell time. The effects of the damping and the junction growth during the dwell time are used to explain the time-dependent hysteresis friction behaviors of the LRB. The experiments of higher preload and lubrication-free conditions have been implemented as well, and the results indicate that the conditions are positive to diminish the time-dependent hysteresis friction behaviors.

1 - 8 of 8
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