Yongcun Cui, Sier Deng, Haisheng Yang, Wenhu Zhang and Rongjun Niu
The purpose of this paper is to study the influence of the cage dynamic unbalance on the dynamic performances in cylindrical roller bearings.
Abstract
Purpose
The purpose of this paper is to study the influence of the cage dynamic unbalance on the dynamic performances in cylindrical roller bearings.
Design/methodology/approach
The dynamic analysis model which considering cage dynamic unbalance is presented, and the relationship between the cage dynamic unbalance and the cage stability, the cage slip ratio and the cage skew angle is investigated.
Findings
Cage dynamic unbalance has a great effect on the cage stability. The cage dynamic unbalance which in an axial excursion affects the cage characteristics is greater than that only in the radial direction. The cage slip ratio and the cage skew increases with the cage dynamic unbalance, especially with the axial excursion. The non-metal cage is more sensitive to the cage dynamic unbalance than that of the metal cage.
Originality/value
The analytical method and model can be applied by the bearing engineering designers.
Details
Keywords
Sier Deng, Jinfang Gu, Yongcun Cui and Wenhu Zhang
This study aims to analyze the roller dynamic characteristics and cage whirling of tapered roller bearing considering roller tilt and skew which provide a theoretical basis for…
Abstract
Purpose
This study aims to analyze the roller dynamic characteristics and cage whirling of tapered roller bearing considering roller tilt and skew which provide a theoretical basis for the design and application of tapered roller bearing.
Design/methodology/approach
Based on rolling bearing dynamic analysis, the dynamic differential equations of tapered roller bearing are established. Fine integral method and predict correct Adams–Bashforth–Moulton multi-step method are used to solve the dynamic differential equations of tapered roller bearings.
Findings
Friction at the flange contact between roller and large flange is the chief factor of roller skew. In comparison to cone speed, axial loads have more visible effect on roller skew, and proper speed or axial load is beneficial to sustain cage motion and decrease cage instability. Under the combined effort of axial load and radial load, the distribution of roller skew is correlated to the roller-flange contact load. In addition, roller skew angle in loaded zone is larger than that in unloaded zone; hence, it is helpful for cage stability if an extent radial load is applied. The pocket clearance of cage has very small influence on roller skew; therefore, a reasonable pocket clearance is suggested to assure minimum instability of cage. Friction coefficient of flange contact has a large effect on roller skew, and cage whirl is found to demonstrate a circular orbit with increasing friction coefficient.
Originality/value
The dynamic differential equations of tapered roller bearing considering roller large end/inner ring back face rib contact under various lubrication states were established. The impact of flange friction working conditions and cage pocket clearance on cage instability and roller skew were focused on. It is the first time that the ratio of the standard deviation of the cage-center translational speed to its mean value is used to access the instability of cage in tapered roller bearing.
Details
Keywords
Lu Zhang, Difang Wan, Wenhu Wang, Chen Shang and Fang Wan
The purpose of this paper is to analyze the role of four different incentives in improving hedging effectiveness and propose an alternative regulatory mechanism for China’s…
Abstract
Purpose
The purpose of this paper is to analyze the role of four different incentives in improving hedging effectiveness and propose an alternative regulatory mechanism for China’s futures market.
Design/methodology/approach
The research method that this study uses is a laboratory experiment, and this study follows the basic norms of experimental research. In addition, this paper designs and conducts a game experiment between hedgers and futures brokerage firms (FBFs) under different incentive mechanisms.
Findings
By analyzing the experimental data, it is found that compared with other incentive mechanisms, hedgers’ willingness to hedge and FBFs’ regulatory intention are both significantly higher for the dynamic linkage updating mechanism, indicating that hedgers have a stronger willingness to follow their hedging plan, and FBFs are more responsible for their regulatory behaviors. Additionally, the dynamic linkage updating mechanism has a long-term impact on effective hedging in the futures market.
Research limitations/implications
The findings suggest that the dynamic linkage updating mechanism is beneficial for effectively restricting both hedgers’ over-speculation and FBFs’ regulatory slack and improving the hedging efficiency of the futures market.
Practical implications
To solve the problem of inefficient hedging in China’s futures market, i.e., hedgers’ over-speculation and FBFs’ passive collusion with hedgers, the regulators of China’s futures market should reform the existing incentives and adopt a dynamic linkage updating mechanism to encourage all the participants to actively improve hedging effectiveness.
Originality/value
This paper analyzes and verifies, for the first time, the role of the dynamic linkage updating mechanism in the investing behaviors of hedgers and the regulatory behaviors of future brokerage firms. The futures market experiment that was designed and used in this study is a pioneering and exploratory experiment that applies game theory and mechanism design theory to the field of behavioral finance.
Details
Keywords
Song Li, Bo Fang, Tianzhi Yang, Yewei Zhang, Lijun Tan and Wenhu Huang
The purpose of this paper is to analyze a new, whole‐spacecraft isolator and its performance of vibration isolation, which has been designed to ensure spacecraft safety at the…
Abstract
Purpose
The purpose of this paper is to analyze a new, whole‐spacecraft isolator and its performance of vibration isolation, which has been designed to ensure spacecraft safety at the launching stage.
Design/methodology/approach
The design is based on the analysis of fractional derivative stress‐strain constitutive relationship of viscoelastic materials. First, the authors study the constitutive relationships for viscoelastic solid of the damping materials, then the authors introduce the results obtained to the equations of motion for the damped isolator.
Findings
By performing a series of transformation, the authors obtain the analytical solution of the equations. It is shown that the results compare favourably to the numerical simulations and experiments. In addition, a saturation phenomenon for the first order damping ratio is also discussed.
Practical implications
It is found that the constitutive relationships written in terms of the fractional calculus can be applied in the system function of the whole‐spacecraft vibration isolator. Such relationships, developed previously from a model analysis base, have been shown to be useful tools for engineering analyses.
Originality/value
Some suggestions are given to improve the design of viscoelastic whole‐spacecraft isolators. The establishment of a theoretical basis for the new fractional differential dynamical system enhances their value, as they may now be used with increased reliability of satellite.
Details
Keywords
Qiang Bian, Xiangyun Zhang, Bowen Jiao, Guang Zeng and Chunjiang Zhao
The purpose of this paper is to establish a dynamic analysis model of composite cylindrical roller bearings, investigate the effects of different working conditions on the…
Abstract
Purpose
The purpose of this paper is to establish a dynamic analysis model of composite cylindrical roller bearings, investigate the effects of different working conditions on the kinematic characteristics of composite bearings and compare the differences between them and solid roller bearings.
Design/methodology/approach
This paper establishes a dynamic analysis model for composite cylindrical roller bearings and proves the correctness of the established model by establishing dynamic vibration experiments and contact theory for composite roller bearings. Comparative analysis was conducted on the effects of coupling changes in rotational speed, load, number of rollers and filling ratio on parameters such as bearing static stiffness, contact stress and vibration acceleration.
Findings
The composite roller can enhance the bearing’s operational stability and minimize contact stress, but that a higher filling ratio is going to increase the bearing’s stiffness. The acceleration degree of bearing vibration, the load on the outer raceway nodes and the bearing stability all decrease as inner ring speed rises.
Originality/value
A dynamic calculation model of composite cylindrical roller bearings is established, and the influence of multiparameter coupling changes on bearing vibration and contact is studied, which lays a foundation for the structural improvement of the bearings.
Details
Keywords
Abstract
Purpose
This paper traces the incorporation of western educational histories in the development of normal-school curricula during the late Qing Dynasty and the Republic of China (1901–1944). It uses publication networks to show how the study of comparative educational history facilitated the international circulation of knowledge in the teaching profession, and how the “uses” of educational history were shaped by larger geopolitical forces.
Design/methodology/approach
This paper analyzes the international exchange of texts between normal schools in China and Japan and, subsequently, between normal schools in China and the United States. A database of 107 publications in the field of western educational history that were adopted in China reveals specific patterns of textual citation, cross-reference, and canon-formation in the field of educational historiography.
Findings
With conclusions derived from a combination of social network analysis and clustering analysis, this paper identifies three broad stages in China's development of normal-school curricula in comparative educational history: “Japan as Teacher,” “transitional period” and “America as Teacher.”
Research limitations/implications
Statistical analysis can reveal citation and reference patterns but not readers' understanding of the deeper meaning of texts – in this case, textbooks on the subject of western educational history. In addition, the types of publications analyzed in this study are relatively limited, the articles on the history of education in journals have not become the main objects of this study.
Originality/value
This paper uses both quantitative and qualitative methods to uncover the transnational circulation of knowledge in the field of comparative educational history during its formative period in China.