Research on tribology in Southeastern Europe: A bibliometric study

In recent years there is a small but increasing number of articles presenting and/or analyzing the scientific production from discrete geographical regions on a certain scientific topic. These articles applied the so-called bibliometric methods in order to evaluate the contribution of different countries in a scientific research field. In the present work, the research output of all countries in Southeastern Europe (SEE) on the scientific field of tribology is presented by using bibliometric indices such as the total number of publications and citations as well as the h-index and the average number of citations per publication. Such a study is attempted, to the authors' knowledge, for the first time

Research on tribology in Southeastern Europe: A bibliometric study

In recent years there is a small but increasing number of articles presenting and/or analyzing the scientific production from discrete geographical regions on a certain scientific topic. These articles applied the so-called bibliometric methods in order to evaluate the contribution of different countries in a scientific research field. In the present work, the research output of all countries in Southeastern Europe (SEE) on the scientific field of tribology is presented by using bibliometric indices such as the total number of publications and citations as well as the h-index and the average number of citations per publication. Such a study is attempted, to the authors' knowledge, for the first time

Prediction of surface treatment effects on the tribological performance of tool steels using artificial neural networks

The present paper discussed the development of a reliable and robust artificial neural network (ANN) capable of predicting the tribological performance of three highly alloyed tool steel grades. Experimental results were obtained by performing plane-contact sliding tests under non-lubrication conditions on a pin-on-disk tribometer. The specimens were tested both in untreated state with different hardening levels, and after surface treatment of nitrocarburizing. We concluded that wear maps via ANN modeling were a user-friendly approach for the presentation of wear-related information, since they easily permitted the determination of areas under steady-state wear that were appropriate for use. Furthermore, the achieved optimum ANN model seemed to be a simple and helpful design/educational tool, which could assist both in educational seminars, as well as in the interpretation of the surface treatment effects on the tribological performance of tool steels

Wear and Degradation Modes in Selected Vehicle Tribosystems

The wear and degradation mechanisms of two principle vehicle tribosystems are presented to elucidate the main causes of their premature failure. The first case study concerns the malfunction of an automotive cast iron pressure plate operated in an automobile clutch system. The second is related to the unexpected failure of a stainless steel brake disk of a high performance motorcycle. Both components are designed to function under sliding friction conditions that lead to the severe wear of consumable non-metallic parts of the tribosystems: the clutch disk and the brake pad, respectively. However, in both cases it was the unexpected failure of the conjugate metallic parts that resulted in terminal system damage. The experimental approach to identify the root cause of failure involved both microstructure characterization, as well as observations of the metallic contact surfaces by means of optical and scanning electron microscopy, in conjunction with microhardness and surface topography measurements. For the case of the stainless steel brake disk in particular, Finite Element Analysis was employed to simulate the operating tribosystem, identify the site(s) prone for crack initiation and validate the failure mechanisms hypotheses

The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10–80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23–0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation

Rhodium nanoflowers stabilized by a nitrogen-rich PEG-tagged substrate as recyclable catalyst for the stereoselective hydrosilylation of internal alkynes

Morphology and size controllable rhodium nanoparticles stabilized by a nitrogen-rich polyoxyethylenated derivative have been prepared by reduction of RhCl3 with NaBH4 in water at room temperature and fully characterized. The flower-like Rh NPs are effective and recyclable catalysts for the stereoselective hydrosilylation of challenging internal alkynes and diynes, affording the (E)-vinylsilanes in quantitative yields for a wide range of substrates. The insolubility of the nanocatalyst in diethyl ether allows its easy separation and recycling

An Introduction to Wear Degradation Mechanisms of Surface-Protected Metallic Components

Despite the fact that ceramics and polymers have found numerous applications in several mechanical systems, metals and metallic alloys still remain the main materials family for manufacturing the bulk of parts and components of engineering assemblies. However, in cases of components that are serving as parts of a tribosystem, the application of surface modification techniques is required to ensure their unhampered function during operation. After a short introduction on fundamental aspects of tribology, this review article delves further into four representative case studies, where the inappropriate application of wear protection techniques has led to acceleration of the degradation of the quasi-protected metallic material. The first deals with the effects of the deficient lubrication of rolling bearings designed to function under oil lubrication conditions; the second is focused on the effects of overloading on sliding bearing surfaces, wear-protected via nitrocarburizing; the third concerns the application of welding techniques for producing hardfacing overlayers intended for the wear protection of heavily loaded, non-lubricated surfaces; the fourth deals with the degradation of thermal-sprayed ceramic coatings, commonly used as wear-resistant layers