Proceedings of the Institution of Mechanical Engineers,Part J: Journal of Engineering Tribology

Metal glass fibre reinforced composites which are considered as advanced composite materials play a significant role in aerospace, marine and automotive industries. In the current study, an attempt has been made to examine the tribological characteristics of glass fibre reinforced plastic (GFRP) composite filled with aluminium oxide (Al₂O₃) and silicon carbide (SiC) powder particles. Experiments were performed on pin-on-disc tribometer to evaluate the friction and wear rate as a function of normal load and sliding velocity under different conditions. For each composition of glass-epoxy composite filled with and without fillers, sliding tests were performed with normal load (20 N, 40 N, 60 N, 80 N 100 N) and sliding velocity (2.62 m/s, 4.18 m/s, 5.23 m/s, 6.85 m/s, 7.85 m/s) respectively. The metal GFRP composites were fabricated using hand-lay-up technique. The filler content (SiC & Al₂O₃) in epoxy-glass composite were varied. SiC was varied from 0 to 10% while Al₂O₃ was kept constant at 5%. To study the worn surface of glass-epoxy composite material scanning electronic microscopy is used. Before and after the experiment, weights of the composites (pin specimens) were studied on digital balance for wear loss. The present studies reported that the fabricated metal epoxy-fibre composite has performed excellent wear resistance when compared with epoxy-fibre composite without metal powders. The present work findings offer new insights into reinforcement in epoxy-glass composites with metal powders.

The study aim is to develop methods of efficiency enhancement for the antiwear additives in the lubricants based on hydrocarbon oils. The tribological properties of triaryl and trialkyl phosphorothionates with similar hydrocarbyl groups have been compared. The testing has been carried out in the contact unit of combined rolling and sliding friction. It has been shown that trioctyl phosphorothionate is considerably superior to tribenzyl phosphorothionate and triphenyl phosphorothionate in antifriction and antiwear properties. The obtained results validate the suggestion that for a given polar group contained in an antiwear additive molecule the maximal efficiency can be achieved with sufficiently great hydrocarbonyl groups, when their structures are similar to the prevailing structure of the lubricant hydrocarbon molecules.

The paper deals with the application of deep learning methods to rotating machines fault diagnosis. The main challenge is to design a fault diagnosis system connected with multisensory measurement system that will be sensitive and accurate enough in detecting weak changes in rotating machines. The experimental part of the research presents the test rig and results of high-speed multisensory measurements. Six states of a rotating machine, including a normal one and five states with loosened mounting bolts and small unbalancing of the shaft, are under study. The application of deep network architectures including multilayer perceptron, convolutional neural networks, residual networks, autoencoders and their combination was estimated. The deep learning methods allowed to identify the most informative sensors, then solve the anomaly detection and the multiclass classification problems. An autoencoder based on ResNet architecture demonstrated the best result in anomaly detection. The accuracy of the proposed network is up to 100% while the accuracy of an expert is up to 65%. A one-dimensional convolutional neural network combined with a multilayer perceptron that contains a pretrained encoder demonstrated the best result in multiclass classification. The detailed fault detection accuracy with the determination of the specific fault is 83.3%. The combinations of known deep network architectures and application of the proposed approach of pretraining of the encoders together with using a block of inputs for one prediction demonstrated high efficiency.

Wear of a friction pair of brake (brake disc and pads), in addition to reducing the active safety of vehicles, leads to the formation of particles that can affect the environment and human health. In addition to the technologies that are being developed for the collection of particles created by the wear of brakes during braking process, today new materials are being introduced, as well as various technologies for processing friction pairs with the aim of reducing brake wear and thus the formation of particles. Furthermore, today, technologies for coating (cladding) the friction surfaces of disc brakes with some materials are increasingly applied and researched, in order to reduce the wear intensity (wear rate) of disc brakes, i.e. the emission of particles created by wear of friction pairs. The aim of this paper is to analyse and review different deposition techniques and materials used for brake discs coatings, as well as the effect it has on the wear rate of friction pair. There are many coating deposition techniques, and special attention is paid to the technology of laser hardfacing of brake rotors.

A hardening of high velocity oxy-fuel sprayed Inconel 625 coating systems was performed by pulsed plasma nitriding treatment. After deposition of an Inconel 625 coating, samples were pulsed plasma nitrided at 520 °C for 12 h in a gas ratio of 3:1 N₂ and H₂ under a constant pressure of 2.5 × 10² Pa. Pulsed plasma nitriding improved the microhardness of the high velocity oxy-fuel sprayed Inconel 625 coating from 355 to 401 HV_0.05. The high velocity oxy-fuel-sprayed Inconel 625 coating after pulsed plasma nitriding process showed excellent corrosion resistance as well as a reduction of both the friction coefficient and wear rate during the sliding phase in a 3.5 wt.% NaCl solution against sliding action of Al₂O₃ ball.

The report presents the positron annihilation studies of subsurface zone generated in pure titanium exposed to a long period dry sliding test. The total depth of the subsurface zone induced is detected at about 250 µm. Only dislocations and vacancy clusters which consist of two or three vacancies are observed in this zone. Their concentration decreases with the depth, especially at the depth above 100 µm. Despite the long duration of the sliding test, no clear signs indicating the presence of a tribolayer were observed. This was confirmed also by observation of annealing of defects in this zone at different depths. The lack of the tribolayer is in contrast to the research done so far for other metals.

In the automotive industry, galling is a huge problem either for the tool life or the quality of the stamping metal component. Galling is a severe form of scuffing associated with gross damage to the surface or failure. This work aims to carry out a series of experiments of galling tests at different loads and similar roughness with 6061 aluminum and D2 steel, common materials used in automotive components and tools respectively. A tribometer was employed to generate Galling wear, the button-on-button configuration, according to the ASTM G-196-08 standard. The results show the threshold of minimum load without galling wear. Post-test-surface analysis of the specimens was conducted by confocal microscopy to identify the damage generated during the wear tests. Additionally, a couple of friction tests were carried only to illustrate the friction coefficient behavior under galling conditions.

This work investigates the effect of 3D-printing parameters on surface roughness in polylactic acid printed material by adopting Taguchi's design of experiments approach. The control parameters under study were: number of shells, printing temperature, infill rate, and printing pattern. As the response, mean surface roughness (Ra) was selected. The control parameters were assigned to an L9 orthogonal array to organize the experiments and obtain the mean surface roughness results. It is concluded that printing temperature is the dominant parameter that affects surface roughness when it comes to 3D printing of polylactic acid material followed by printing pattern, infill rate, and the number of shells.

Agricultural equipment is working in very high-stress conditions. However, it has a significant influence on the wear losses of soil processing parts. Chisel is operating at 30 cm working depth at a maximum of 12 km·h⁻¹ working speed. Due to unpredictable soil conditions, chisel tines suffer high wear losses. It leads to time consumption and cost expenses during the soil preparation period. Wear resistance, and agronomical requirements (working depth, loosening of soil) are the main criteria of agricultural equipment producers. The discrete element method is a solution that simulates soil as sphere shape particles with soil properties. Wear results reveal the change of parts shape, acting forces, and stresses during the simulation in the virtual soil bin. The used Rocky DEM software uses a parameter C (volume/shear work ratio) to describe wear intensity, which varies for different geometry. Chisel tine geometry should be divided into sections with varied parameter C according to stress acting on the surface. The test conditions can be used for future wear analysis of varied tool geometry and protection (sintered tungsten carbide plates, hard-faced surface, etc.) agricultural tools to compare its durability in different soil conditions.

A predictive analytics methodology is presented, utilizing machine learning algorithms to identify the performance state of marine journal bearings in terms of maximum pressure, minimum film thickness, Sommerfeld number, load and shaft speed. A dataset of different bearing operation states has been generated by solving numerically the Reynolds equation in the hydrodynamic lubrication regime, for steady-state loading conditions and assuming isothermal and isoviscous lubricant flow. The shaft has been modelled with four different values of misalignment angle, lying within the acceptable operating range, as defined in the existing regulatory framework. The journal bearing was modelled parametrically using generic geometric parameters of a marine stern tube bearing. The lift-off speed was estimated for each loading scenario to ensure operation in the hydrodynamic lubrication regime and the effect of shaft misalignment on lift-off speed has been evaluated. The generated dataset was utilised for training, testing and validation of several machine learning algorithms, as well as feature selection analysis, in order to solve several classification problems and identify the various bearing operational states.

Dynamic friction coefficient (COF) of the reciprocating sliding contact of the conventional UHMWPE, was investigated in four different environments (dry contact; distilled water; pure Ringer's solution and with PMMA particles), at five values of low normal load (0.1–1 N) and three values of sliding speed (4 - 12 mm/s). Significant differences of COF values occurred at the lowest load (0.1 N), whereas sliding speed did not influence COF values. Addition of PMMA particles in Ringer's solution produced significant increase of COF values, especially at the lowest load of 0.1 N. For the dry contact and the highest load (1 N), steady state was reached shortly after the beginning of the test and friction coefficient had uniform behaviour. In the case of wet environment and the lowest load, steady state was not reached and the friction coefficient exhibited non-reproducible random behaviour. According to the Hertz theory, 0.5 N load corresponded to the elastic stress of 48.7 MPa, thus surpassing the values of the elastic limits, hardness and true yield stress of the UHMWPE, and the behaviour of the friction coefficient was drastically different below and above this load value. It can be assumed that below the 0.5 N load, viscoelastic response, accompanied with plastic deformation is dominant, with transition to mainly plastic deformation for the higher loads.

Polymeric coatings reinforced with nanoparticles have recently occupied special focus by researchers and have been used in several industrial applications such as wind turbine manufacturing, oil and gas, aerospace and automotive industries. Yet, still more investigations are required to improve the tribological and mechanical properties of these coats and increase its service life. The effect of adding nano-silica/alumina to polyurethane coatings have been studied, however, their erosion resistance has not been investigated yet. The main purpose of this research is to investigate the erosion resistance of hybrid nano-silica/alumina polyurethane compositions with different weight fractions. To do this, erosion resistance experiments, scanning electron microscope and Zetasizer experiments to assess the agglomeration percentage were carried out. Results showed that the hybrid composition of nano-silica/alumina polyurethane significantly decreased the erosion rate and that the reduction in agglomeration was mirrored in much enhanced erosion resistance of the nanocomposites.

Steel ropes are widely used in material handling machines. The excessive wear of wires is often presented as a type of rope degradation. One of many indicators of the wear is abrasion, corrosion and fatigue cracks. Within this class of rope degradation, the main representation of wear is wire abrasion in the layers of the external wires. This is especially noticeable at the steel ropes which are operating in the drum devices with multilayer winding and in hoists of mining shafts. Over performed work cycles, the estimation of losses in rope cross-section is important for the calculation of the rope capacity. Abrasive wear of external wires is a relatively easy phenomenon to detect with a qualitative interpretation. However, it is a very difficult phenomenon to quantify. The aim of this article is to address this issue. A brief survey of usual methods for rope inspections is given, which can serve as practical guidance for the engineers in this field. With accompanying case study, it presented the advantages of magnetic method in rope inspections oriented towards measuring the changes of wires within the wear assessment.

The paper contains the results of the transient flow of piston ring conjunction of a single-cylinder motorbike engine. Calculations of piston ring forces, asperity contact and gas blow-by are determined in computational fluid dynamics. The stochastic model of Greenwood-Tripp approach is used to predict the load of asperities. The hydrodynamic friction is also calculated by means of computational fluid dynamics including the multi-phase flow through Rayleigh–Plesset equation and a discrete phase model for simulating nanoparticles interaction. The major contribution of this analysis is to specifically investigate the impact of the lubricant with additives and the corresponding transient effects such as hydrodynamic pressure, cavitation and lubricant film within the contact. The results indicate that to investigate realistic mechanisms of multi-phase flow in piston ring-liner contact, the contribution of nanoparticles should be matched with the type of lubricants. In addition, this advanced computational fluid dynamics model showed that nanoparticles motion is important in reciprocating line contacts, leading to lower boundary friction in the order of 8.8% than a simple model where cavitation and nanoparticles are ignored.

The tribological behavior of a steel/glass ball-on-flat contact was studied by synchronizing the friction measurements with an acoustic emission device and a vision system. The results highlight two distinct friction regimes identified with low and high friction values. Their transition is characterized by a modification of acoustic emission signals. In addition, two main damage and wear mechanisms are identified: the creation and propagation of Hertzian cracks visible on the glass surface and the constitution of an interfacial layer of debris. The different accommodation mechanisms, activated successively or simultaneously, are identified for acoustic emission frequencies between 300 and 700 kHz. Eventually, this approach allows a real-time wear mechanisms identification and gives better insights about acoustic emission signals in relation to tribological systems.