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Time-dependent hysteresis friction behaviors of linear rolling bearings

INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2018年第9-12期94卷 3109-3116页

作者： Xi, Yinhu Zhao, Yang Larsson, Roland Mao, Junhong Xi An Jiao Tong Univ Theory Lubricat & Bearing Inst Key Lab Educ Minist Modern Design & Rotor Bearing Xian 710049 Shaanxi Peoples R China Lulea Univ Technol Div Machine Elements Dept Engn Sci & Math SE-97187 Lulea Sweden

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.

关键词： Hysteresis friction Pre-rolling Linear rolling bearings Time dependent

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The effective design of zirconia coping on titanium base in dental implant superstructure

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DENTAL MATERIALS JOURNAL 2018年第2期37卷 237-243页

作者： Mieda, Maiko Atsuta, Ikiru Matsushita, Yasuyuki Morita, Takehiro Ayukawa, Yasunori Tsukiyama, Yoshihiro Sawae, Yoshinori Koyano, Kiyoshi Kyushu Univ Fac Dent Sci Div Oral Rehabil Sect Implant & Rehabilitat DentHigashi Ku 3-1-1 Maidashi Fukuoka 8128582 Japan Kyushu Univ Dept Mech Engn Machine Elements & Design Engn Lab Nishi Ku 744 Motomachi Fukuoka 8190395 Japan

Zirconia exhibits good tissue compatibility and nontoxicity, making it a widely used esthetic replacement material for implant abutments. To avoid abutment-fracture, the parts composed of zirconia with a bonded metal component connected to the implant can be used. The purpose of this study was to design titanium and zirconia components with high fracture resistance at the zirconia component's edge line. Three edge line designs of the titanium base and zirconia sleeve were made: chamfer, shoulder, and back taper. To assess the strength of the abutment design, static loads were applied vertically and 30 degrees from the vertical axis. A test of tensile strength was also performed after chewing simulation. Conventional zirconia components mounted on a chamfer-type titanium base showed significantly lower fracture resistance than shoulder and back-taper types. This study suggests that to improve the durability of zirconia abutments with a titanium base, a back-tapered edge design is recommended.

关键词： Dental implant Zirconia sleeve Titanium base Structural durability Chewing simulator

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An effective device and method for enhanced cell growth in 3D scaffolds: Investigation of cell seeding and proliferation under static and dynamic conditions

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MATERIALS SCIENCE AND ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS 2020年 114卷 111060-111060页

作者： Theodoridis, Konstantinos Aggelidou, Eleni Manthou, Maria-Eleni Keklikoglou, Kleoniki Tsimponis, Antonios Demiri, Efterpi Bakopoulou, Athina Mihaildis, Athanasios Kritis, Aristeidis Aristotle Univ Thessaloniki AUTh Fac Hlth Sci Sch Med Dept Physiol & Pharmacol Thessaloniki 54124 Greece Aristotle Univ Thessaloniki AUTh Fac Hlth Sci Sch Med Dept Physiol & PharmacolcGMP Regenerat Med Facil Thessaloniki Greece Aristotle Univ Thessaloniki AUTh Fac Hlth Sci Sch Med Lab Histol Embryol & Anthropol Thessaloniki Greece Aristotle Univ Thessaloniki AUTh Papageorgiou Hosp Med Sch Dept Plast Surg Thessaloniki Greece Aristotle Univ Thessaloniki AUTh Lab Machine Elements & Machine Design Sch Mech Engn GR-54624 Thessaloniki Greece Hellen Ctr Marine Res HCMR Inst Marine Biol Biotechnol & Aquaculture Iraklion 71003 Crete Greece Aristotle Univ Thessaloniki AUTh Fac Hlth Sci Sch Dent Dept Prosthodont GR-54124 Thessaloniki Greece

Cell adhesion on 3D-scaffolds is a challenging task to succeed high cell densities and even cell distribution. We aimed to design a 3D-cell Culture Device (3D-CD) for static seeding and cultivation, to be used with any kind of scaffold, limiting cell loss and facilitating nutrient supply. 3D printing technology was used for both scaffold and device fabrication. Apart from testing the device, the purpose of this study was to assess and compare static and dynamic seeding and cultivation methods, of wet and dry scaffolds, under normoxic and hypoxic conditions and their effects on parameters such as cell seeding efficiency, cell distribution and cell proliferation. Human adipose tissue was harvested and cultured in 3D-printed poly(epsilon-caprolactone) scaffolds. Micro-CT scans were performed and projection images were reconstructed into cross section images. We created 3D images to visualize cell distribution and orientation inside the scaffolds. The group of prewetted scaffolds was the most favorable to cell attachment. The 3D-cell Culture Device (3D-CD) enhanced cell seeding efficiency with almost no cell loss. We suggest that the most favorable outcome can be produced with static seeding in the device for 24 h, followed either by static cultivation in the same device or by dynamic cultivation.

关键词： Cell seeding efficiency 3D cell culture Cell proliferation Cell distribution Static culture under normoxia/hypoxia Dynamic culture under normoxia/hypoxia

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Finite element method based analysis of planetary gear systems considering backlash and manufacturing deviations

Finite element method based analysis of planetary gear syste...

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International Conference on Gears

作者： Mihailidis, A. Korbetis, G. Drivakos, N. Nerantzis, I. Aristotle Univ Thessaloniki Lab Machine Elements & Machine Design Thessaloniki Greece BETA CAE Syst Thessaloniki Greece

ISBN: (纸本)9783180922942

The load carrying capacity of gear transmissions depends strongly on design, material and operation conditions. Modern analysis methods, such as the Finite Element Analysis, consider the above parameters with more or less sufficient accuracy. But it is still a challenging task to account for backlash and manufacturing errors although they have a crucial impact. There are several difficulties to overcome: First, the contact footprints as well as backlash and errors are some orders of magnitude smaller than the dimensions of the gears. Therefore, an extremely fine mesh is required. On the other hand, the total number of DOF's should be kept as small as possible to keep the computational effort manageable. Less stressed areas should be coarsely meshed, while the transition must be as smooth as possible. Moreover, in order to generate and mesh three-dimensional tooth flanks taking into considerations the above mentioned geometrical deviations is extremely time consuming. In this paper, new techniques and tools are introduced aiming to facilitate the modelling procedure. They include automatic generation of 3D gear flanks and selective meshing. A simple planetary gear system featuring helical gears with backlash and manufacturing errors is used to demonstrate the effectiveness of the proposed procedure, since it features multiple contacts and floating members. Results shown include stress distribution and deformation, as well as load sharing under quasi-static conditions.

关键词： Finite element method

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Calculation of the kinematics of hypoid gears towards developing a method for an equivalent crossed helical gear pair selection for use in tribological experimental evaluations

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART K-JOURNAL OF MULTI-BODY DYNAMICS 2017年第3期231卷 519-537页

作者： Athanasopoulos, E. Salpistis, C. Mohammadpour, M. Mihailidis, A. Theodossiades, S. Grekoussis, R. Aristotle Univ Thessaloniki Fac Engn Dept Mech Engn Lab Machine Elements & Machine Design Thessaloniki 54124 Greece Loughborough Univ Technol Wolfson Sch Mech Elect & Mfg Engn Loughborough Leics England

To experimentally verify power loss and friction for hypoid gears, measurements in a closed power-loop test rig are necessary. However, these are costly and mechanically complex, since they require additional spur gear reducers in the loop. ISO directives document the use of crossed helical gear pairs as virtual gears for hypoids to calculate the sliding velocity, since the flank geometry at the mean point can be precisely represented. The use of such pairs can be a cost effective and simpler alternative for testing purposes. However, the validity of this analogy regarding contact mechanics and tribology for the full mesh cycle has not been investigated hitherto. In the current study, a new method for calculating the sliding and rolling speed along the full path of contact of a hypoid gear pair is presented. Cutter kinematics are considered, for the accurate definition of the contact bodies. Using tooth contact analysis, the load distribution on the tooth under quasi-static conditions and the sliding velocity are calculated for comparison purposes. By applying a selection algorithm, a single experimental crossed helical gear pair is chosen aiming to simulate the contact conditions of hypoid gears. Two test scenarios are studied using elastohydrodynamic film thickness equations and friction models for evaluating the power loss. The contact is an elongated ellipse with varying directions of the sliding and sum velocities, which are considered in the model. The kinematic equivalence shows good agreement, while the tribological equivalence is achievable using a reduced input torque.

关键词： Hypoid gears crossed helical gears tribology kinematics flank velocity efficiency back-to-back gear test

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Surfactant-free electrochemical synthesis of fluoridated hydroxyapatite nanorods for biomedical applications

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CERAMICS INTERNATIONAL 2019年第14期45卷 17336-17343页

作者： Ge, Xiang Ren, Chengzu Lu, Xiong Li, Zhaoyang Chen, Guang Wang, Kefeng Ren, Fuzeng Wang, Qun Wang, Menghao An, Xinxin Qian, Bao Tianjin Univ Sch Mech Engn Key Lab Mech Theory & Equipment Design Minist Educ Tianjin 300354 Peoples R China Hong Kong Univ Sci & Technol Dept Mech & Aerosp Engn Kowloon Clear Water Bay Hong Kong Peoples R China Southwest Jiaotong Univ Sch Mat Sci & Engn Minist Educ Key Lab Adv Technol Mat Chengdu 610031 Sichuan Peoples R China Tianjin Univ Sch Mat Sci & Engn Tianjin Key Lab Composite & Funct Mat Tianjin 300354 Peoples R China Sichuan Univ Natl Engn Res Ctr Biomat Chengdu 610064 Sichuan Peoples R China Southern Univ Sci & Technol Dept Mat Sci & Engn Shenzhen 518055 Guangdong Peoples R China MianYang Teachers Coll Coll Life Sci & Biotechnol Mianyang 621006 Sichuan Peoples R China Tianjin Agr Univ Sch Humanities Tianjin 300384 Peoples R China Univ Kassel Dept Machine Elements & Engn Design D-34125 Kassel Germany

Fluoridated hydroxyapatite (FHA) [Ca-10(PO4)(6)FxOH)(2-x) x = 0-2] is believed to be a promising calcium phosphate (CaP) to replace pure hydroxyapatite (HA) for next-generation implants, owing to its better biocompatibility, higher antibacterial activity, and lower solubility. Notably, the shape and size of the CaP crystals play key roles in their performance and can influence their applications. One-dimensional (1D) FHA nanorods are important CaP materials which have been widely used in regenerative medicine applications such as restorative dentistry. Unfortunately, the traditional synthesis methods for FHA nanorods either employ surfactants or take a relatively long time. In this study, we aimed to propose a facile synthesis route to fabricate FHA nanorods without any surfactants using an electrochemical deposition method for the first time. This study focused on preparing FHA nanorods without the assistance of any surfactant, unlike the traditional synthesis methods, to avoid chemical impurities. FHA nanorods with lengths of 124-2606 nm, diameters of 28-211 nm, and aspect ratios of 4.4-21.8 were synthesized using the electrochemical method, followed by a heat treatment. For the as-synthesized FHA nanorods, the Ca/P ratio was 1.60 and the atomic concentration of F was 2.06 at.%. An ultrastructure examination revealed that each FHA nanorod possessed long-range order, good crystallinity, and a defect-free lattice with a certain crystallographic plane orientation along the whole rod. In short, we propose a novel, surfactant-free, cost-saving, and more efficient route to synthesize FHA nanorods which can be widely applied in multiple biomedical applications, including drug delivery, bone repair, and restorative dentistry.

关键词： Surfactant-free Electrochemical Fluoridated hydroxyapatite (FHA) Nanorods Transmission electron microscopy (TEM) High resolution TEM (HRTEM)

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Optimizing the development and manufacturing of 56SiCr7 leaf springs

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INTERNATIONAL JOURNAL OF FATIGUE 2017年 103卷 168-175页

作者： Fragoudakis, Roselita Savaidis, Georgios Michailidis, Nikolaos Merrimack Coll Dept Mech Engn N Andover MA 01845 USA Aristotle Univ Thessaloniki Dept Mech Engn Lab Machine Elements & Machine Design Thessaloniki 54124 Greece Aristotle Univ Thessaloniki Dept Mech Engn Met Phys Lab Thessaloniki 54124 Greece

This study investigates the microstructure, surface mechanical properties, and fatigue life of 56SiCr7 leaf specimens produced under serial conditions. The investigation occurs at different stages of the manufacturing process of the leaf springs;mainly heat treatment and surface treatment by shot peening. Macro hardness and micro-hardness measurements, at the Rockwell C and Vickers scales, respectively, are taken following the thermal treatment and surface shot peening treatment steps of the manufacturing process. Residual stress measurements accurately show the induction depth of the residual stresses in the material. The above measurements are used to determine how heat treatment and shot peening affect the mechanical properties of the surface and core of the spring material. Though the performed micro hardness measurements clearly indicate surface decarburization effects and quantify the decrease in strength, they do not reveal the insufficient martensitic transformation during the thermal treatment of selected specimens (protocol 1). The macro-hardness measurements are completely insensitive in revealing the surface decarburization and phase transformation phenomena that take place in the investigated case. Solely the microstructural investigations with the aid of a metallographic optical microscope revealed the degree of phase transformation achieved by the thermal treatment. The effect of the individual manufacturing processes, of thermal treatment and shot peening, on the fatigue life of the leaf springs is demonstrated by experimental Wohler curves at stress amplitudes between 250 MPa and 600 MPa. Two stress ratios are examined, R = 0 and R = 0.4, which reflect the stress ratios recommended by the automotive industry. The corresponding Haigh diagrams and mean stress sensitivity factors can be applied for fatigue life assessments of new leaf spring products produced using the suggested protocols. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Hardness Microstructure Fatigue life Residual stresses Leaf springs

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Micro/nano-structured TiO2 surface with dual-functional antibacterial effects for biomedical applications

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Bioactive Materials 2019年第1期4卷 346-357页

作者： Xiang Ge Chengzu Ren Yonghui Ding Guang Chen Xiong Lu Kefeng Wang Fuzeng Ren Meng Yang Zhuochen Wang Junlan Li Xinxin An Bao Qian Yang Leng Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education School of Mechanical EngineeringTianjin UniversityTianjin300354China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Center for Advanced Regenerative Engineering Northwestern UniversityEvanstonIL60208USA Department of Biomedical Engineering Northwestern UniversityEvanstonIL 60208USA Key Lab of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu610031China National Engineering Research Center for Biomaterials Sichuan UniversityChengdu610064China epartment of Materials Science and Engineering Southern University of Science and TechnologyShenzhenGuangdong518055China State Key Laboratory of Precision Measuring Technology and Instruments Tianjin UniversityTianjin300072China School of Humanities Tianjin Agricultural UniversityTianjin300384China Department of Machine Elements and Engineering Design University of KasselKassel34125Germany

Implant-associated infections are generally difficult to cure owing to the bacterial antibiotic resistance which is attributed to the widespread usage of *** the global threat and increasing influence of antibiotic resistance,there is an urgent demand to explore novel antibacterial strategies other than using ***,using a certain surface topography to provide a more persistent antibacterial solution attracts more and more ***,the clinical application of biomimetic nano-pillar array is not satisfactory,mainly because its antibacterial ability against Gram-positive strain is not good ***,the pillar array should be equipped with other antibacterial agents to fulfill the bacteriostatic and bactericidal requirements of clinical ***,we designed a novel model substrate which was a combination of periodic micro/nano-pillar array and TiO2 for basically understanding the topographical bacteriostatic effects of periodic micro/nano-pillar array and the photocatalytic bactericidal activity of *** innovation may potentially exert the synergistic effects by integrating the persistent topographical antibacterial activity and the non-invasive X-ray induced photocatalytic antibacterial property of TiO2 to combat against antibiotic-resistant implant-associated ***,to separately verify the topographical antibacterial activity of TiO2 periodic micro/nano-pillar array,we systematically investigated its effects on bacterial adhesion,growth,proliferation,and viability in the dark without involving the photocatalysis of *** pillar array with sub-micron motif size can significantly inhibit the adhesion,growth,and proliferation of Staphylococcus aureus(***)and Escherichia coli(***).Such antibacterial ability is mainly attributed to a spatial confinement size-effect and limited contact area availability generated by the special topography of pillar ***,the pillar array is not lethal to S

关键词： Titanium dioxide Micro/nano-structured surface Topographical bacteriostatic activity Photocatalytic bactericidal property Non-invasive treatment

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Linear Complementarity Framework for 3D Steady-State Rolling Contact Problems Including Creepages with Isotropic and Anisotropic Friction for Circular Hertzian Contact

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TRIBOLOGY TRANSACTIONS 2017年第5期60卷 832-844页

作者： Xi, Yinhu Almqvist, Andreas Shi, Yijun Mao, Junhong Larsson, Roland Xi An Jiao Tong Univ Theory Lubricat & Bearing Inst Key Lab Educ Minist Modern Design & Rotor Bearing Syst Xian Shaanxi Peoples R China Lulea Univ Technol Div Machine Elements Dept Engn Sci & Math Lulea Sweden

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.

关键词： Rolling contact creepage linear complementarity problem anisotropic friction

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Application of an inclined, spinning ball-on-rotating disc apparatus to simulate railway wheel and rail contact problems

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WEAR 2017年 374卷 46-53页

作者： Xi, Yinhu Bjorling, Marcus Shi, Yijun Mao, Junhong Larsson, Roland Xi An Jiao Tong Univ Theory Lubricat & Bearing Inst Key Lab Educ Minist Modern Design & Rotor Bearing Syst Xian 710049 Peoples R China Lulea Univ Technol Div Machine Elements Dept Engn Sci & Math SE-97187 Lulea Sweden

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. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Spinning ball-on-rotating disc apparatus Wheel and rail contact Lateral creepage Spin creepage

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