Meixian Zhang, Yiding Ou, Haibing Yuan, Junlin Pan and Lei Ma
The purpose of this paper is to examine the practicability of the self-designed ambient humidity controllable pin-disc/rolling multifunctional friction and wear test device and to…
Abstract
Purpose
The purpose of this paper is to examine the practicability of the self-designed ambient humidity controllable pin-disc/rolling multifunctional friction and wear test device and to evaluate the friction and wear characteristics of materials under diverse ambient humidity conditions in different contact forms.
Design/methodology/approach
The practicability of the self-designed multifunctional friction tester was examined by the friction and wear tests of materials under different ambient humidity conditions [65%RH, 98%RH (relative humidity)] in diverse contact forms (pin/disc and rolling). Meanwhile, the friction and wear properties of pin/disc samples also rolling samples were assessed from three aspects: average friction coefficient, wear mass and wear morphology.
Findings
The results prove that the self-designed multifunctional friction tester has practicability. Therefore, it can be used to simulate the friction and wear tests of materials under diverse ambient humidity conditions in different contact forms. Besides, it is evident that the wear damage of pin/disc and rolling samples are greatly improved under high ambient humidity conditions. And when other conditions are identical, the higher the ambient humidity, the smaller the average friction coefficient, wear mass and wear damage degree of pin/disc also rolling samples.
Originality/value
This paper offers a self-designed multifunctional friction and wear test device. And the tester not only can realize the control of test ambient humidity, but also achieve the wear test of pin/disc or rolling contact forms. The design and production of the tester can offer convenience for the research of tribology, and provide fundamental guidance for the study of materials under high humidity condition in diverse contact forms.
Details
Keywords
Lei Ma, Hanbo Shi, Siyuan Ding, Chao Zhang, Haibing Yuan and Junlin Pan
The purpose of this paper is to study the wear of railway brake disc/pad in low-temperature environment and to explore the damage form of brake disc/pad materials and the law of…
Abstract
Purpose
The purpose of this paper is to study the wear of railway brake disc/pad in low-temperature environment and to explore the damage form of brake disc/pad materials and the law of temperature rise in braking process and its influence on friction pair material damage.
Design/methodology/approach
The influence of ambient temperature on tribological properties of brake materials was studied by using low-temperature environment simulation device and MM-1000 high-speed brake testing machine. The law of temperature rise in the braking process was simulated by temperature field module of COMSOL.
Findings
The damage of disc sample increases with the decrease of ambient temperature, and the main damage form is furrow. With the decrease of ambient temperature, pitting corrosion, wear, spalling and cracks appear successively. The maximum temperature of brake disc decreases linearly with the decrease of ambient temperature. However, when the ambient temperature is 0 in the experiment, the surface temperature of the disc will increase abnormally because of the increase of abrasive particles caused by the toughening and brittleness transformation of the material.
Originality/value
In this paper, through the study of train braking in low-temperature environment, the damage mechanism and law of train braking pair in low-temperature environment are found, which provide some basis for the development of high-speed railway in low-temperature environment.
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Tatiana Andrea Gélvez Rubio and Juan Carlos Gachúz Maya
This paper enquires into general trends of China's International Development Cooperation over the past decade in Latin America and provides insights into the challenges with the…
Abstract
Purpose
This paper enquires into general trends of China's International Development Cooperation over the past decade in Latin America and provides insights into the challenges with the Belt and Road Initiative.
Design/methodology/approach
This paper analyses quantitative data for Chinese Official Development Assistance (ODA) and Other Official Flows (OOF) for projects in Latin America based on recent data contributions including Bluhm et al. (2018) and Gallagher & Myers (2019).
Findings
Based on the data available, it can be concluded that the cooperation between China and Latin America has been increasing. For instance, the value of China's cooperation increased by 4.5% per year on average from 2000 to 2014. Moreover, China's economic and political motivations in the region indicate that the cooperative relationship has been changing from a South–South to a North–South framework. Two main factors are involved in this transition: the evolution of China from a developing country to a global emerging power and the implementation of the Belt and Road Initiative to strengthen political and economic ties with the governments of the region.
Practical implications
This investigation suggests that the increasing number of loans in the region and Beijing's growing interest in trade and natural resources are structural factors that guide the Chinese foreign policy.
Originality/value
There are few analyses of China's cooperation for development in Latin America that involve the evaluation of concessional and non-concessional loans for projects in the region in the last decade. This paper also analyses the challenges and opportunities that the implementation of the Belt and Road Initiative represents for the region.