Lubricants

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14 pages, 1939 KiB

Open AccessArticle

A Brake System Coefficient of Friction Estimation Using 3D Friction Maps

by Francesco Varriale, Stefano Candeo, Gabriele Riva, Jens Wahlström and Yezhe Lyu

Lubricants 2022, 10(7), 134; https://doi.org/10.3390/lubricants10070134 - 23 Jun 2022

Cited by 3 | Viewed by 2352

Abstract

The coefficient of friction (COF) is one of the core factors in the evaluation of brake system performance. It is challenging to predict the COF, since it is strongly influenced by several parameters such as contact pressure (p), slip rate ( [...] Read more.

The coefficient of friction (COF) is one of the core factors in the evaluation of brake system performance. It is challenging to predict the COF, since it is strongly influenced by several parameters such as contact pressure (p), slip rate (v) and temperature (T) that depend on the driving conditions. There is a need for better models to describe how the brake friction varies under different driving conditions. The purpose of this research is to study the possibility of using 3D friction pvT-maps to estimate the COF of a disc brake system under different driving conditions. The 3D friction pvT-maps are created by filtering results of material tests conducted in a mini-dyno inertia bench. The COF measured under different driving cycles in an inertia dyno bench with the full brake system are compared with the COF estimated by the friction maps coming from the reduced scale dyno bench to investigate the validity of the simulation approach. This study shows that mini dyno bench is suitable to obtain a tribological characterization of the friction pad–disc rotor contact pair and is able to replace the full inertia dyno bench to investigate the brake system performance. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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21 pages, 1313 KiB

Open AccessArticle

Data-Driven Sliding Bearing Temperature Model for Condition Monitoring in Internal Combustion Engines

by Christian Laubichler, Constantin Kiesling, Matheus Marques da Silva, Andreas Wimmer and Gunther Hager

Lubricants 2022, 10(5), 103; https://doi.org/10.3390/lubricants10050103 - 22 May 2022

Cited by 7 | Viewed by 2680

Abstract

Condition monitoring of components in internal combustion engines is an essential tool for increasing engine durability and avoiding critical engine operation. If lubrication at the crankshaft main bearings is insufficient, metal-to-metal contacts become likely and thus wear can occur. Bearing temperature measurements with [...] Read more.

Condition monitoring of components in internal combustion engines is an essential tool for increasing engine durability and avoiding critical engine operation. If lubrication at the crankshaft main bearings is insufficient, metal-to-metal contacts become likely and thus wear can occur. Bearing temperature measurements with thermocouples serve as a reliable, fast responding, individual bearing-oriented method that is comparatively simple to apply. In combination with a corresponding reference model, such measurements could serve to monitor the bearing condition. Based on experimental data from an MAN D2676 LF51 heavy-duty diesel engine, the derivation of a data-driven model for the crankshaft main bearing temperatures under steady-state engine operation is discussed. A total of 313 temperature measurements per bearing are available for this task. Readily accessible engine operating data that represent the corresponding engine operating points serve as model inputs. Different machine learning methods are thoroughly tested in terms of their prediction error with the help of a repeated nested cross-validation. The methods include different linear regression approaches (i.e., with and without lasso regularization), gradient boosting regression and support vector regression. As the results show, support vector regression is best suited for the problem. In the final evaluation on unseen test data, this method yields a prediction error of less than 0.4 °C (root mean squared error). Considering the temperature range from approximately 76 °C to 112 °C, the results demonstrate that it is possible to reliably predict the bearing temperatures with the chosen approach. Therefore, the combination of a data-driven bearing temperature model and thermocouple-based temperature measurements forms a powerful tool for monitoring the condition of sliding bearings in internal combustion engines. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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14 pages, 3634 KiB

Open AccessArticle

Lubricating Oil Consumption Measurement on Large Gas Engines

by Bernhard Rossegger, Albrecht Leis, Martin Vareka, Michael Engelmayer and Andreas Wimmer

Lubricants 2022, 10(3), 40; https://doi.org/10.3390/lubricants10030040 - 08 Mar 2022

Cited by 4 | Viewed by 3950

Abstract

Increasing the reliability of combustion engines while further reducing emissions and life cycle costs are the main drivers for optimizing lubricating oil consumption (LOC). However, in order to reduce the lube oil consumption of an engine, it is crucial to measure it accurately. [...] Read more.

Increasing the reliability of combustion engines while further reducing emissions and life cycle costs are the main drivers for optimizing lubricating oil consumption (LOC). However, in order to reduce the lube oil consumption of an engine, it is crucial to measure it accurately. Therefore, a LOC measurement device based on the use of the stable isotope deuterium has been developed. Previous publications have focused on the use of passenger car engines. This publication describes the first application of this newly developed method on a large gas engine. This is of particular interest as large-bore engines might show different oil consumption behavior, much higher LOC in gram per hour and the bigger oil reservoir need larger amounts of tracer. Additionally, a different type of fuel has an effect on oil consumption measurement as well, as presented in this paper. The results showed this method can be applied to large gas engines as well after conducting minor changes to the measurement setup. However, other than liquid fuels, the origin and isotopic composition of the natural gas has to be monitored. Ideally, gas from large storage is used for carrying out these measurements. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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16 pages, 7298 KiB

Open AccessArticle

Tribological Properties of the Nanoscale Spherical Y₂O₃ Particles as Lubricant Additives in Automotive Application

by Álmos D. Tóth, Ádám I. Szabó, Máté Zs. Leskó, Jan Rohde-Brandenburger and Rajmund Kuti

Lubricants 2022, 10(2), 28; https://doi.org/10.3390/lubricants10020028 - 18 Feb 2022

Cited by 13 | Viewed by 2746

Abstract

The continuous tribological development of engine lubricants is becoming more and more vital due to its fuel efficiency improvement and lifetime increasing potential. The antiwear additives play a high role in the lubricants to protect the contacting surfaces even in the presence of [...] Read more.

The continuous tribological development of engine lubricants is becoming more and more vital due to its fuel efficiency improvement and lifetime increasing potential. The antiwear additives play a high role in the lubricants to protect the contacting surfaces even in the presence of thinner oil film. Nanoscale spherical particles in the lubricant may increase the necessary protecting effect. This paper presents the results of the experimental tribological investigation of nanoscale spherical Y₂O₃ (yttria) ceramic particles as an engine lubricant additive. The ball-on-disc tribological measurements have revealed an optimum concentration at 0.5 wt% with about 45% wear scar diameter and 90% wear volume decrease, compared to the reference, neat Group III base oil. The high-magnitude SEM analysis revealed the working mechanisms of yttria: the particles collected in the roughness valleys resulted in a smoother contacting surface, they were tribo-sintered and they have also caused slight plastic deformation of the outer layer of the metallic surface. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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14 pages, 2793 KiB

Open AccessArticle

Monitoring Tribological Events by Acoustic Emission Measurements for Bearing Contacts

by Philipp Renhart, Michael Maier, Christopher Strablegg, Florian Summer, Florian Grün and Andreas Eder

Lubricants 2021, 9(11), 109; https://doi.org/10.3390/lubricants9110109 - 10 Nov 2021

Cited by 8 | Viewed by 2543

Abstract

The measurement of acoustic emission data in experiments reveals informative details about the tribological contact. The required recording rate for conclusive datasets ranges up to several megahertz. Typically, this results in very large datasets for long-term measurements. This in return has the consequence, [...] Read more.

The measurement of acoustic emission data in experiments reveals informative details about the tribological contact. The required recording rate for conclusive datasets ranges up to several megahertz. Typically, this results in very large datasets for long-term measurements. This in return has the consequence, that acoustic emissions are mostly acquired at predefined cyclic time intervals, which leads to many blind spots. The following work shows methods for effective postprocessing and a feature based data acquisition method. Additionally, a two stage wear mechanism for bearings was found by the described method and could be substantiated by a numerical simulation. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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17 pages, 3789 KiB

Open AccessArticle

Understanding Friction in Cam–Tappet Contacts—An Application-Oriented Time-Dependent Simulation Approach Considering Surface Asperities and Edge Effects

by Christian Orgeldinger and Stephan Tremmel

Lubricants 2021, 9(11), 106; https://doi.org/10.3390/lubricants9110106 - 26 Oct 2021

Cited by 10 | Viewed by 5033

Abstract

With the increasing challenges of climate change and scarce resources, the development of sustainable and energy-efficient technical systems is becoming increasingly important. In many applications, the friction losses occurring in contacts have a decisive influence on the overall efficiency. At this point, tribological [...] Read more.

With the increasing challenges of climate change and scarce resources, the development of sustainable and energy-efficient technical systems is becoming increasingly important. In many applications, the friction losses occurring in contacts have a decisive influence on the overall efficiency. At this point, tribological contact optimization can make an important contribution to increasing the efficiency of technical systems. However, improvements are often associated with a considerable experimental effort. To reduce the development time, additional simulation models can be applied to predict the tribological behavior. This requires the closest possible approximation of the real contact within a numerical model. This paper presents a simulation approach for the time-dependent simulation of a cam–tappet contact. The simulation uses realistic operating conditions as they arise in the valve train of internal combustion engines. The influence of edge effects on the friction behavior is considered by a scaled calculation area and the influence of the surface roughness is investigated using stochastic asperity models. It is shown that the tribological behavior within the contact strongly depends on the surface properties and the load spectrum used. In addition, edge effects on the sides of the contact area have a clear influence on the pressure and film thickness distribution. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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17 pages, 3864 KiB

Open AccessArticle

Modelling of Frictional Conditions in the Wheel–Rail Interface Due to Application of Top-of-Rail Products

by Gerald Trummer, Zing Siang Lee, Roger Lewis and Klaus Six

Lubricants 2021, 9(10), 100; https://doi.org/10.3390/lubricants9100100 - 08 Oct 2021

Cited by 14 | Viewed by 3019

Abstract

The coefficient of friction between a wheel tread and the top of the rail should be maintained at intermediate levels to limit frictional tangential contact forces. This can be achieved by applying top-of-rail products. Reducing the coefficient of friction to intermediate levels reduces [...] Read more.

The coefficient of friction between a wheel tread and the top of the rail should be maintained at intermediate levels to limit frictional tangential contact forces. This can be achieved by applying top-of-rail products. Reducing the coefficient of friction to intermediate levels reduces energy consumption and fuel costs, as well as damage to the wheel and rail surfaces, such as, e.g., wear, rolling contact fatigue, and corrugation. This work describes a simulation model that predicts the evolution of the coefficient of friction as a function of the number of wheel passes and the distance from the application site for wayside application of top-of-rail products. The model considers the interplay of three mechanisms, namely the pick-up of product by the wheel at the application site, the repeated transfer of the product between the wheel and rail surfaces, and the product consumption. The model has been parameterized with data from small-scale twin disc rig experiments and full-scale wheel–rail rig experiments. Systematic investigations of the model behaviour for a railway operating scenario show that all three mechanisms may limit the achievable carry-on distance of the product. The developed simulation model assists in understanding the interplay of the mechanisms that govern the evolution of the coefficient of friction in the field. It may aid in finding optimal product application strategies with respect to application position, application amount, and application pattern depending on specific railway operating conditions. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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11 pages, 34316 KiB

Open AccessCommunication

Low Friction Powertrains: Current Advances in Lubricants and Coatings

by Peter Lee and Boris Zhmud

Lubricants 2021, 9(8), 74; https://doi.org/10.3390/lubricants9080074 - 27 Jul 2021

Cited by 9 | Viewed by 4733

Abstract

Improving fuel economy and reducing emissions is nowadays more important than ever. Apart from powertrain electrification, automotive manufacturers have constantly been seeking to improve the efficiency of the internal combustion engine. Downsizing and boosting have become common practice in the internal combustion engine [...] Read more.

Improving fuel economy and reducing emissions is nowadays more important than ever. Apart from powertrain electrification, automotive manufacturers have constantly been seeking to improve the efficiency of the internal combustion engine. Downsizing and boosting have become common practice in the internal combustion engine (ICE) design. Increased power density and torque output of modern boosted engines, in combination with the introduction of automatic stop-start systems and ultralow viscosity lubricants tends to stress the engine beyond the limits foreseen in the classical design. This leads to wear problems. Each engine component comes with a unique landscape of competing manufacturing technologies, among which advanced surface finishing and coating methods play an important role. This presentation provides an overview of different industrial trends related thereto. The role of lubricant on the engine tribology is studied for different engine designs. The importance of in-design “pairing” of low-viscosity motor oils with the engine characteristics is highlighted filling the gap in the understanding of complex interactions between the crankcase lubricant and engine mechanics. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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Review

Jump to: Research

14 pages, 1012 KiB

Open AccessReview

Energy Efficiency, Emissions, Tribological Challenges and Fluid Requirements of Electrified Passenger Car Vehicles

by Robert Ian Taylor

Lubricants 2021, 9(7), 66; https://doi.org/10.3390/lubricants9070066 - 22 Jun 2021

Cited by 10 | Viewed by 3600

Abstract

The motivations for the move to electrified vehicles are discussed with reference to their improved energy efficiency, their potential for lower CO₂ emissions (if the electricity system is decarbonized), their lower (or zero) NO_x/particulate matter (PM) tailpipe emissions, and the [...] Read more.

The motivations for the move to electrified vehicles are discussed with reference to their improved energy efficiency, their potential for lower CO₂ emissions (if the electricity system is decarbonized), their lower (or zero) NO_x/particulate matter (PM) tailpipe emissions, and the lower overall costs for owners. Some of the assumptions made in life-cycle CO₂ emissions calculations are discussed and the effect of these assumptions on the CO₂ benefits of electric vehicles are made clear. A number of new tribological challenges have emerged, particularly for hybrid vehicles that have both a conventional internal combustion engine and a battery, such as the need to protect against the much greater number of stop-starts that the engine will have during its lifetime. In addition, new lubricants are required for electric vehicle transmissions systems. Although full battery electric vehicles (BEVs) will not require engine oils (as there is no engine), they will require a system to cool the batteries—alternative cooling systems are discussed, and where these are fluid-based, the specific fluid requirements are outlined. Full article

(This article belongs to the Special Issue Tribology in Mobility)

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