Research on Electrostatic Monitoring of Tribo-Contacts with Dynamic Adaptive Fusion Method

Electrostatic monitoring is a unique and rapid developing technique applied in the prognostics and health management of the tribological system based on electrostatic charging and sensing phenomenon. It has considerable advantages in condition monitoring of tribo-contacts with high sensitivity and resolution. Unfortunately, the monitoring result can be affected due to the switch of operating conditions that reduces its accuracy. This paper presents a dynamic adaptive fusion approach, moving window local outlier factor based on electrostatic features to overcome the influence. Life cycle experiments of rolling bearings and railcar gearbox were carried out on an electrostatic monitoring platform. The MWLOF method was used to extract and analyze the experimental data, combined with the Pauta criterion to judge wear faults quantitatively, and compare with other feature extraction results. It is verified that the proposed method can overcome the influence of changes in working conditions on the monitoring results, improve the monitoring sensitivity, and provide an accurate reference for friction and wear faults.

Friction and Wear Behavior of Deep Drawing Tools Using Volatile Lubricants Injected Through Laser-Drilled Micro-Holes

In deep drawing processes, the use of lubricants is mandatory in order to prevent wear on tools and surface damage to the formed sheet metal components. Here, frequently used lubricants are synthetic and mineral oils, emulsions, and waxes. However, these conventional lubricants have to be applied to the sheet material prior to the forming operation and removed afterwards by cleaning processes. Additionally, the lubricants often contain substances that are harmful to the environment and to human health. To counteract these economic and ecological disadvantages, research is currently being conducted on a novel tribological system. For this, volatile media such as liquid carbon dioxide and gaseous nitrogen are being used, and are introduced directly into the friction zones between the tool and the sheet metal material during deep drawing under high pressure through special laser-drilled micro-holes. This paper covers the latest investigations and findings regarding the design of flow-optimized micro-holes, the laser drilling process, the friction characterization on tool radii, and the tool wear to be expected when using the lubrication medium CO2.

The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

The cold wiredrawing process constitutes a classical-tribological system in which a stationary tribe-element (die) is in contact with a tribe-element in relative motion (wire) and both interacting with the interfacial tribe-element (lubricant). This condition is reflected in the effect of friction as a function of the drawing speed and temperature, and directly affects the wearing of the surface into the die and the final quality on the drawn wire. The aim of this work has been to determine the best conditions to process ETP-copper using two different types of oil/water emulsion lubricants. For this purpose, six different die geometries have been proposed and a set of tests have been carried out at different speeds (between 1 and 21 m/s) to determine those combinations that give a lower value in the required drawing force (Fd). The experiments allowed to know the friction coefficient (µ), the temperature profile inside the drawing die and in the lubricant and also the mean roughness (Ra) in the drawn product. The results have shown that drawing speeds above 10 m/s significantly decrease the drawing force and, as a consequence, the friction effect on the interface. The best results have been achieved in the combinations of the lower die angle (2β = 14°) with drawing speeds between 17 and 18 m/s with both types of lubricants used, obtaining the lower values of the friction coefficient between µ = 0.10–0.15 with the lubricant type D (Agip S234-60 oil at 7% concentration). It has been found that those tests carried out with dies with a smaller approach angle have generally made it possible to obtain better qualities in the final product. Additionally, FEM simulations have been done to analyse those cases with the lower values of µ, throwing values of Fd that are consistent with those measured in the experimental setting and allowing to better understand the behavior of the material as it passes through the die.

Methods for determining the bearing capacity and extreme pressure properties of lubricants used in heavy-loaded tribodynamic couplings of metallurgical machines and units

To solve contact problems related to the study of the interaction between a lubricated or non-lubricated friction pair, we used standard equipment - friction machines and tribometers. However, the use of factory-made research equipment does not always allow us to accurately answer the questions concerning the tribotechnical characteristics of friction and wear processes under specific operating conditions. A review of the literature on the technical capabilities of testing machines showed that their main drawback is the inability to programmatically set the modes of acceleration of the tribological system and tracking slippage in real-time. The study revealed the need to develop a methodology for investigating the extreme pressure properties of liquid lubricants in the tribocoupling acceleration mode, which is caused primarily by the effect of high contact loads acting in the contact areas of friction pairs, e.g. gears, rolling bearings, etc. when technological machines and equipment start and reach the operating speed. The paper considers a modernized friction machine capable of programmatically setting acceleration modes and investigating tribodynamic processes of lubricated frictional couplings. We developed a technique that makes it possible to evaluate the efficiency of a liquid lubricant during acceleration and its effect on the wear of a lubricated contact based on the use of the modernized friction machine.

Development of comparative investigation method for timing chain wear analysis using oscillating tribometer

This paper presents the development of a test procedure to investigate timing chain components under abrasive stress on a tribometer. Engine developers use cost and time expensive engine dynamometer tests to investigate timing chain life expectancy under different conditions. Tribometer tests are fast and cost effective, but these use standardized specimen material and geometry that greatly differ from the original tribological system of the timing chain. Manufacturing specimens from the original chain material using the original technology is complicated; surface quality and hardness properties cannot be guaranteed. The aim of research was to develop a test method for rapid and cost-effective comparison of engine lubricants, timing chain materials or coatings, as well as to assess the wear resistance of the chain to contaminants. Various uncontaminated and carbon black blended lubricants were compared using standard-based ball-on-disc tribometer tests to tribometer tests using actual timing chain components (bush-on-pin test) of a Diesel engine. Lubricants were ranked in terms of coefficient of friction and wear. Results showed that bush-on-pin tests were comparably suitable for testing lubricants when evaluated against standard ball-on-disc tribometer tests.

Probing the Lubrication of Shear-Induced Self-Assembled Layer on Amorphous Carbon Films in Methane Atmosphere

Demand for reduction in friction and improvement in wear resistance of moving parts propels exploration in frictional origin for amorphous carbon (a-C) film lubricating properties based on the interfacial states. Methane, as an ideal energy carrier and industrial raw material, is one of active gas. Consequently, the relations between the tribological behaviors of a-C film under methane atmosphere and load or interfacial states were discussed based on experimental and theoretical methods. Experimental results illustrated that, as the load increased, tribological system exhibited various interfacial shear strength at a load of zero and pressure dependence of the shear strength for tribological systems. And then the origin was revealed with theoretical calculation and resulted from the distributions of adsorbates across the sliding interface.

Preliminary Study of the Superlubricity Behavior of Polyimide-Induced Liquid Crystal Alignment

We have studied the friction behavior based on liquid crystal (LC) alignment of a unique tribological system composed of a nematic LC and polyimide (PI). The LC was used as a lubricant and a tribological factor with molecular alignment ability. PI was used as both a rubbing pair part and a LC alignment agent. The LCs used as lubricants included the single LC 5CB and the mixed LCs 5CB–2UTPP3 and 3PEP5–3UTPP4. The PI used as the friction pair was 6FDA-ODA PI, and its counterpart was GCr15 steel. For this system, it was found that under the premise that the nematic phase temperature range of the selected LC meets the operating temperature of the friction test at a suitable ambient temperature, the operating speed and load are controlled to maintain a stable lubricating film thickness between the friction pairs during operation of the system. Moreover, by avoiding excessive or insufficient friction heat generated by the running speed being too high or too low to change the phase state of the LC, with the anchoring energy between the PI and the LC, the LC molecules will align in the rubbing direction, that is, they will arrange parallel to each other along the grooves, which can contribute to achieve superlubricity behavior.

METHODOLOGY FOR TESTING A JOINT CARTILAGE

A research method was developed to analyse the tribological properties of cartilage tissue. Based on the literature data and the possibility of obtaining samples of appropriate dimensions, the frequency and amplitude of friction tests were adopted. Based on the previously conducted preliminary tests, other test parameters were proposed, such as the frictional contact load and the number of test runs. It was assumed that the results of the research will be the friction coefficient and the wear intensity of the tribological system. According to the developed method, a series of verification tests was carried out in which the friction contact was lubricated in various ways with the selected lubricants. The results of tests of animal cartilage in nonlubricated contact were used as the reference basis for all the tested associations. The friction tests showed good method resolution and satisfactory repeatability. In the case of wear characteristics, a greater scatter of test results was observed. It is probably related to the varied geometrical structure of the cartilage surface as well as the elastic properties of the bone on which the tissue was placed. The correctness of the obtained results and a relatively good resolution of the tribological test method were found.

Einfluss von Silan-dotierten Umgebungsatmosphären auf tribologischen Eigenschaften von Titan

The production processes of the metalworking industry are usually carried out in the presence of oxygen. Par ticularly due to surface oxidation on tools and parts during production under normal atmosphere, high wear is observed in tribological systems. The focus of these investigations is the question to what extent the ambient atmosphere has an influence on the tribological system. For this purpose, the identification and characterization of wear mechanisms in an oxygen-free atmosphere is of high relevance. To analyse the influence of the ambi ent atmosphere on the tribological properties of titanium, ball-on-disc investigations are carried out on a univer sal tribometer (UMT) in an air, argon and silane-anodized atmosphere. By suppressing the oxidation under ex clusion of oxygen, a reduction of the tribochemical wear could be shown, which is accompanied by a reduction of the wear volume by a Factor of 4.5. However, due to the adhesion of both friction partners, which already occurs at low temperatures, caused by the omission of the friction-reducing cover layers, the friction coefficient increased. In addition, novel alloy formations at the interfaces were detected and analysed.

Fretting Wear Observation of Flat Contacts

With the instrumentality of a newly developed fretting test bench for planar contacts, a state-of-the-art method of inter-mediate imaging helps to understand fretting wear mechanisms of different materials and lubricants. The test bench uses application like planar surfaces unlike the usual point or elliptical contact in model testing (with the tribological test chain). Applications considered prone to fretting wear have large planar contacts – like bearing seats and shaft hub connections – and contact pressures normally perceiv ed as low or uncritical. This article examines a method to evaluate a targeted observation of the surfaces. The method uses a movable upper sample to open the contact and to document an interim status of the test by image recording. Among other things, this is to obtain time-lapse recordings of the progressive wear and tear. Just opening the contact can already influence the tribological system and the result of a test. It is shown whether and how this opening process has an impact on tests with continuous contact.