Journal of Friction and Wear最新文献_第6页

Calculation of Fit Tolerance with Clearance to Increase Relative Wear Resistance of Joints 用间隙计算配合公差以提高接头的相对耐磨性

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-09-25 DOI: 10.3103/S1068366623030054

O. A. Leonov, N. Z. Shkaruba, G. N. Temasova, Y. G. Vergazova, P. V. Golinitskiy

{"title":"Calculation of Fit Tolerance with Clearance to Increase Relative Wear Resistance of Joints","authors":"O. A. Leonov, N. Z. Shkaruba, G. N. Temasova, Y. G. Vergazova, P. V. Golinitskiy","doi":"10.3103/S1068366623030054","DOIUrl":"10.3103/S1068366623030054","url":null,"abstract":"<p>The total resource of the assembly unit, as well as the post-repair resource of the unit, depend on the specified resource for critical joints. The main problem of calculating the joint accuracy is to determine the margin of accuracy or the margin of material for wear since an increase in the estimated fit tolerance will lead to a decrease in durability, and its decrease will entail an increase in costs due to an increase in rejects or the need to introduce a technological operation. In this regard, a method for calculating the joint fit tolerance depending on the specified or design wear characteristics was developed based on the analysis of the parametric failure model. When modeling various wear rates, it is recommended to use the relative wear resistance of the joint in the obtained dependences only if the wear function is approximated in a linear form. An expression for calculating the relative wear resistance of a joint is obtained depending on the wear resistance of the surfaces of the parts that form it. Using the example of calculating the fit tolerance of a rolling bearing operating under hydrodynamic friction conditions, the resulting fits are analyzed at a certain resource of no-failure operation of the joint for cases of increasing the wear resistance of the joint by 10 and 20%. The scientific novelty of the research lies in obtaining a theoretical relation between the fit tolerance and the probabilistic characteristics of the wear process at a specified probability of failure-free operation. The practical significance of research is expressed in the possibility of calculating the accuracy parameters of a particular joint at a specified resource.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41079705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Structural-Energy Aspect of the Friction Coefficient 摩擦系数的结构能量方面

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-09-25 DOI: 10.3103/S1068366623030042

S. V. Fedorov

{"title":"Structural-Energy Aspect of the Friction Coefficient","authors":"S. V. Fedorov","doi":"10.3103/S1068366623030042","DOIUrl":"10.3103/S1068366623030042","url":null,"abstract":"<p>Over five centuries, friction science used the friction coefficient as the main quantitative characteristic of the friction process. The concept of the friction coefficient as a characteristic of resistance to the movement of frictional surfaces in a latent form was formulated by Leonardo da Vinci. Two centuries later, already in an explicit form, as a formula, the friction coefficient appeared in the studies of Guillaume Amonton. Modern engineering believes that the friction coefficient has no physical meaning, it is merely a convenient friction parameter that can be easily determined in an experiment. What is the physical meaning of resistance to the movement of frictional surfaces? If we perform a thermodynamic analysis of the friction process, considering each deformable friction contact element as an independent transformer and dissipator of energy of the external relative displacement (motion) of surfaces, then it becomes possible to consider the friction coefficient in a new physical sense. The accumulation of the potential energy of a deformed structure (defects in the crystalline structure) by a friction contact is, in essence, a method of deceleration of frictional surfaces moving relative to each other. The static potential energy of the formed defects in the structure of the contact structure is a measure of the decrease in the kinetic energy of the relative motion of the frictional surfaces. The pragmatism of the energy (thermodynamic) approach of friction is organically embedded in the general problems of energy consumption and saving energy resources of modern tribology.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41079809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermal Diagnostics of Friction in Self-Lubricating Sliding Bearings with Swinging Movement of the Shaft 轴摆动自润滑滑动轴承摩擦的热诊断

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-09-25 DOI: 10.3103/S1068366623030108

N. P. Starostin, R. S. Tikhonov

{"title":"Thermal Diagnostics of Friction in Self-Lubricating Sliding Bearings with Swinging Movement of the Shaft","authors":"N. P. Starostin, R. S. Tikhonov","doi":"10.3103/S1068366623030108","DOIUrl":"10.3103/S1068366623030108","url":null,"abstract":"<div><div><h3>\u0000 <b>Abstract</b>—</h3><p>For thermal diagnostics of friction determining the time dependence of frictional heat generation and, accordingly, the moment of friction in self-lubricating sliding bearings using temperature data, an algorithm for solving the inverse problem of heat conduction by iterative regularization is proposed. The iterative regularization algorithm for restoring the frictional heat generation function from temperature data using a three-dimensional model of the thermal process and taking into account the speed of the swinging movement of the shaft is implemented. An assumption was made about the uniform distribution of specific heat generation along the length of the bearing to simplify the formulation of the problem. The numerical solution of the model problem was carried out with the shaft oscillating with a frequency of 1 Hz and amplitude of 7.5°. The time step was chosen from the Courant condition and was 0.1 s. The full-time interval was divided into local ones when solving the inverse problem in order to avoid storing large arrays of temperature data at each iteration. The solutions at the junctions of local intervals were glued. A condition for stopping the iterative process of restoring the frictional heat generation function is proposed, taking into account the total error in temperature measurements and calculations using local intervals. Calculations show that the accuracy of restoring the function of the specific intensity of frictional heat generation using the developed algorithm for solving the inverse problem of 9.9% is commensurate with the accuracy of 3.8% of specifying temperature information. The developed algorithm for determining frictional heat generation using a 3D model of the thermal process can be used to determine the friction torque from temperature data in real self-lubricating sliding bearings operating in the oscillation mode.</p></div></div>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41079813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental Evaluation of the Cross Roller Bearing Resistance Moment in Vacuum 真空中十字滚子轴承阻力矩的实验评定

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020095

M. V. Prozhega, E. O. Konstantinov, E. O. Reschikov, A. Yu. Albagachiev, N. I. Smirnov, N. N. Smirnov

{"title":"Experimental Evaluation of the Cross Roller Bearing Resistance Moment in Vacuum","authors":"M. V. Prozhega, E. O. Konstantinov, E. O. Reschikov, A. Yu. Albagachiev, N. I. Smirnov, N. N. Smirnov","doi":"10.3103/S1068366623020095","DOIUrl":"10.3103/S1068366623020095","url":null,"abstract":"<div><div><h3>\u0000 <b>Abstract</b>—</h3><p>Roller bearings with crossed rollers are actively used in the swivel mechanisms of manipulators and other units due to the combination of high rigidity and increased load capacity. When designing new mechanisms, an important characteristic is the resistance moment, the value of which can be significantly influenced by operating conditions, such as the environment, the amount and type of lubricant, load, etc. In the presented study, the resistance moment and the friction coefficient of a cross-roller bearing were investigated at various temperatures, pressure in the chamber, load, and amount of lubricant. To test a bearing with crossed rollers of size RA 6008 in the temperature range from –40 to +100°C in vacuum conditions, technological equipment was designed and manufactured, a method for measuring the resistance moment was developed, and a full factorial experiment was carried out to assess the degree of influence of various factors on the resistance moment at a fixed VNIINP-284 (AMETHYST) grease amount. The test results showed that the moment of resistance and the coefficient of friction decrease with an increase in the grease amount from 60 to 230 mg, a decrease in air pressure in the test chamber from 10<sup>5</sup> Pa to 1.33 × 10<sup>–3</sup> Pa leads to an increase in the friction coefficient and the resistance moment of the bearing, while an increase in temperature operation of a bearing with grease from 25 to 100°С leads to a decrease in the resistance moment and friction coefficient, and a decrease in temperature to –40°C leads to their increase.</p></div></div>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4561951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Forecasting of the Residual Life of Pavements on Highways Based on the Analysis of Energy Dissipation under the Dynamic Influence of Transport 基于交通动力影响下能量耗散分析的公路路面剩余寿命预测

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020113

A. N. Tiraturyan

{"title":"Forecasting of the Residual Life of Pavements on Highways Based on the Analysis of Energy Dissipation under the Dynamic Influence of Transport","authors":"A. N. Tiraturyan","doi":"10.3103/S1068366623020113","DOIUrl":"10.3103/S1068366623020113","url":null,"abstract":"<div><div><h3>\u0000 <b>Abstract</b>—</h3><p>The aim of the study is to develop a method for predicting the residual life of road surfaces on highways based on the analysis of energy dissipation under the dynamic influence of transport. To solve this problem, the method of analyzing its stress-strain state is applied, based on the exact solution of the dynamic Lame equation, which allows constructing the amplitude-time characteristics of displacements, strains, and stresses. Based on the constructed amplitude-time characteristics of stresses and strains, a dynamic hysteresis loop is constructed, the area of which corresponds to the volume of dissipation energy in the structure of the pavement for a single deformation cycle. Based on the presented computational approach, a method for determining the calculated total energy dissipation in the structure of the pavement over the service life was developed. Using the FWD shock loading unit and a mobile diagnostic laboratory, an experimental method for determining the total energy dissipation over the service life of the pavement was developed. Their comparison allows predicting wear and determining the residual life and service life of road coverings on highways as well as assigning corrective measures for their restoration.</p></div></div>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4561950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Extremely High Wear of Steel Surfaces in Polyorganosiloxane Mixtures Containing 10 wt % Hydrocarbon Oils 在含有10 wt %烃类油的聚有机硅氧烷混合物中，钢表面具有极高的磨损

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020071

G. F. Pavelko

{"title":"Extremely High Wear of Steel Surfaces in Polyorganosiloxane Mixtures Containing 10 wt % Hydrocarbon Oils","authors":"G. F. Pavelko","doi":"10.3103/S1068366623020071","DOIUrl":"10.3103/S1068366623020071","url":null,"abstract":"<p>The effect of 2,2,6,6-tetramethylpiperidine (TMP), <i>para</i>-cumylphenol (PCP), 2,6-di-<i>tert</i>-butyl-4-methylphenol (DTBMP), dicumyl peroxide (DCP), 2,2,6,6-tetramethylpiperidine-1-oxyl (TMPO), dodecantiol (DdSH), dibutyl disulfide (Bu<sub>2</sub>S<sub>2</sub>), didodecyl disulfide (Dd<sub>2</sub>S<sub>2</sub>), and molecular oxygen on the wear index (<i>W</i><sub><i>i</i></sub>) of purified Vaseline oil (PVO), hexadecane (HD), polyethylsiloxane (PES-5), and a mixture of PES-5 containing 10 wt % PVO or HD was studied for the first time. The reason for the extremely high wear of steel surfaces in a solution of PES-5 containing 10 wt % of hydrocarbon lubricants, consists in the antagonism of polyorganosiloxanes with hydrocarbon lubricants and in the lack of molecular oxygen necessary for the formation of a servovite film. The prospect of studying mixtures of polyorganosiloxanes and hydrocarbons is to find a mixture that would have synergism in the anti-wear area. Studies of additives and gaseous media can also be promising. The results of the study of mixtures of polyorganosiloxanes containing about 10% by weight of hydrogen lubricants can be effectively used to reduce the wear of steel surfaces operating in an oxygen atmosphere.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4562299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mathematical Modeling of Rotary Vane Compressors Taking into Account the Mutual Influence of Tribological and Operating Parameters 考虑摩擦参数和工作参数相互影响的旋片压缩机数学建模

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020101

N. A. Raykovskiy, G. I. Chernov, A. M. Kalashnikov

{"title":"Mathematical Modeling of Rotary Vane Compressors Taking into Account the Mutual Influence of Tribological and Operating Parameters","authors":"N. A. Raykovskiy, G. I. Chernov, A. M. Kalashnikov","doi":"10.3103/S1068366623020101","DOIUrl":"10.3103/S1068366623020101","url":null,"abstract":"<p>A mathematical model of an oilless rotary vane compressor is presented. The model takes into account the mutual influence of tribological and operating parameters of the stage. To specify conditions for the mathematical model to be unambiguous, experiments were carried out to determine the values of the friction coefficient and the maximum allowable sliding speed of promising self-lubricating materials as functions of the load and speed parameters of the compressor stage. Mathematical modeling of the integral energy characteristics of the oilless stage of the rotary vane type has shown the conceptual option to expand the range of its operation modes based on the justified use of self-lubricating materials in friction units and account of the mutual influence of tribological and operational factors. Theoretical studies have confirmed that the speed of the stage and the degree of pressure can be increased by a factor no less than 2 compared with those of commercially produced machines. However, setting the friction coefficient in modeling stages of a rotary vane type as a constant can lead to incorrect conclusions in designing in what regards the best operating and structural parameters of the stage. Increasing the speed of the oilless stage of the rotary vane type will enable a reduction in the production requirements for end clearances and an increase in the specific weight and size characteristics and the degree of pressure increase in the stage by a factor of 1.5–2 for the effective efficiency values of 0.8 or more. The proposed mathematical model makes it possible to more accurately predict the energy losses related to mechanical friction in the stages and the integral energy characteristics of the stage in a wide range of operating and design parameters.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4563536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study of the Anti-Wear Properties of Motor Oil during Thermostatization 温控过程中机油抗磨性能的研究

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S106836662302006X

N. N. Lysyannikova, V. G. Shram, Yu. N. Bezborodov, A. V. Lysyannikov, E. G. Kravtsova, M. A. Plakhotnikova, M. A. Kovaleva, E. A. Efremova, A. A. Ryabinin, Zh. S. Sharshembiev

{"title":"Study of the Anti-Wear Properties of Motor Oil during Thermostatization","authors":"N. N. Lysyannikova, V. G. Shram, Yu. N. Bezborodov, A. V. Lysyannikov, E. G. Kravtsova, M. A. Plakhotnikova, M. A. Kovaleva, E. A. Efremova, A. A. Ryabinin, Zh. S. Sharshembiev","doi":"10.3103/S106836662302006X","DOIUrl":"10.3103/S106836662302006X","url":null,"abstract":"<p>This paper discusses a method for determining the anti-wear properties of motor oils after temperature control in the temperature range from 160 to 280°C. Optical density, viscosity, and wear scar diameter are considered. The effect of degradation products on the anti-wear properties of the oils under study was evaluated. The degree of influence of degradation products on anti-wear properties is shown, which is determined by the dependence of the change of diameter of the wear spot of thermostated oils on the absorption coefficient of the light flux. It is noted that the decomposition products have an ambiguous effect on the anti-wear properties of motor oils, which vary from 0.32 to 0.26 mm, and significant changes occur at a coefficient of <i>K</i><sub>P</sub> = 0.05 of all studied oils, while the minimum diameter of the wear spot is characterized by mineral oil, partially synthetic and synthetic oils have values greater than 1.2 times and the reason for this is their heterogeneous composition, which depends on the quality of the additives used and their tendency to decomposition. As an assessment of anti-wear properties, a criterion is proposed that characterizes the concentration of degradation products and is recommended for classifying motor oils into groups of performance properties. The data obtained on the anti-wear properties of motor oils make it possible to compare oils of the same purpose and create a databank that will allow equipment designers to reasonably select oils depending on the temperature conditions of the tribocouples.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4564472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Wear of a Composite Based on Polyurethane, Polyfluorinated Alcohol, Montmorillonite, and Polytetrafluoroethylene 聚氨酯、聚氟醇、蒙脱土和聚四氟乙烯复合材料的磨损

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020046

S. V. Kudashev, A. A. Terekhov, V. A. Babkin, A. V. Nistratov, V. F. Zheltobryukhov, D. S. Andreev, A. V. Ignatov, V. N. Arisova, A. I. Bogdanov, N. V. Kuznetsova

引用次数: 0

Universal Dependences of Frictional Interaction Parameters during Elastic Wheel–Road Contact 弹性车轮-路面接触过程中摩擦相互作用参数的普遍依赖关系

IF 0.7 4区工程技术

Journal of Friction and Wear Pub Date : 2023-08-14 DOI: 10.3103/S1068366623020022

E. V. Balakina

{"title":"Universal Dependences of Frictional Interaction Parameters during Elastic Wheel–Road Contact","authors":"E. V. Balakina","doi":"10.3103/S1068366623020022","DOIUrl":"10.3103/S1068366623020022","url":null,"abstract":"<p>The questions of frictional interaction during the contact of a vehicle’s elastic wheel and a flat solid support surface under different loading conditions by force and moment are considered. The parameters of this interaction are investigated: the adhesion coefficient; its components by areas with static and sliding friction; static friction use coefficient; static friction proportionality coefficient; and relative coefficient of limiting realized static friction. Mathematical dependences in the form of smooth continuous functions are proposed for physically correct calculation of the specified parameters. Two options for loading an elastic wheel with a force and a moment are considered. It is shown that the adhesion coefficient for a given longitudinal wheel slip depends on the loading conditions: the lateral force along the wheel rotation axis and the moment in the rotation plane, as well as their sequence of occurrence. With the same values of force and moment, the adhesion coefficient can change at different sequences of their occurrence: up to 70% for high lateral forces (near to weight) and up to 12% for small lateral forces (up to 20% of weight). Three methods for calculating the adhesion coefficient in the contact of an elastic wheel with a flat solid support surface are proposed. When calculating the proposed characteristics of the methods, averaged zero diagrams were used in the absence of lateral wheel force for different elastic wheels and different types and conditions of road surfaces. To obtain them, the procedure of approximation of numerous experimental data of different researchers was carried out. The developed methods are valid for all elastic wheels and all types and conditions of solid supporting surfaces. The results of the work can be used with sufficient accuracy for practical calculations in the design modeling of the properties of stability, controllability, and braking dynamics of wheeled vehicles.</p>","PeriodicalId":633,"journal":{"name":"Journal of Friction and Wear","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4561949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0