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Greases are non‐Newtonian fluids with a special rheological and tribological behaviour. They have a wide range of applications, for example, ball bearings and gears. This paper reports a study of the reaction of model greases in a tribological contact. The influence of the grease topography has been measured in several tests and the tribological process is modelled. All investigations were done from an energy point of view.

Lubricants are very complex mixtures of components. To predict their behaviour over a long time it is necessary to make a lot of machinery element tests. This paper tries to give an insight into how lubricants can be estimated in their structure by IR‐microscopy and how this procedure could lead to a short prediction of their long‐time behaviour in time‐ and cost‐expansive machinery element testing.

Metal surfaces in machinery element test runs as well as in practical use seem to undergo a complex reaction scenery on the damage route. These processes were induced even at low temperatures (< 100úC) catalyzed by reactive intermediates which seem to be formed through water degradation on the iron surface. Oxygen as well as nitrogen seem to play an important role within this process. Organic material present as a lubricant is attacked heavily to give metabolites with oxygen and nitrogen incorporation. Some reactive intermediates formed in the mixed friction process are trapped by an experimental procedure.

Demand on for‐life lubrication needs to control all mechanisms being present in the tribocontact. Herein we present elementary chemical mechanisms supported by lubricants leading to effective destruction of machinery elements over long time. The chemical process may overtake all other essential mechanisms in for‐life lubrication. As far as known these mechanisms offer a fascination world of unknown reactions.

The purpose of this paper is to show how controlled exposure of electromagnetic fields toward bearing steel vulnerates the microstructure. The ability of Barkhausen Noise signal processing is used for detecting phenomena such as dislocation and subgrain formation processes as the beginning of later failures.

A Barkhausen noise signal measurement equipment is used for detecting subsurface distress of 100Cr6 as a function of the applied electromagnetic and mechanical stress. Barkhausen noise signal is mathematically processed by use of fractal dimension analysis.

The paper cleary reveals significant impact of electromagnetic field in junction with mechanical loading. Electromagnetic impact depends on the magnitude of the field.

Research limitations are given by the fact that in real field applications, e.g. wind power plants, bearings are exposed by multiple influences and the methodology is not applicable to those conditions.

The methodology can be applied to real field applications in condition monitoring systems. Up to now, no reasonable on‐line measurement is in use determining sub surface fatigue phenomena. The paper hence, reveals the possibility to raise condition monitoring into a new perspective.

The use of Barkhausen noise signal processing, as presented here, is original with respect to real field applications, such as wind power plants with a high demand in condition monitoring, especially off‐shore plants.

To prevent damages of machinery elements and enhancing life lubrication by using new surface engineering techniques.

A new “wet” coating technique offers an easy and promising route to modify steel surfaces. The design of surface coatings and the results of an official bearing test are presented.

Based on common bearing tests (e.g. DIN 51819), wear behaviour and tribological properties of modified surfaces are verified.

Our actual research proves an enhanced tribological behaviour in the case of improving surface properties. In contrast, to the common vapour deposition techniques the “wet” coating method seems to offer an alternative route to get surfaces with enhanced tribological properties.

The technique of “wet” coating offers an easy route to modify steel surfaces of all kinds of bearings.

Pre‐polymer coating provides a promising future technique for surface engineering.

This paper presents a tribological analysis of a grease lubricated contact with a consideration of the grease structure (density distribution).

This paper is concerned with the study of grease reaction by tribological stress. To observe the change of the viscoelastic properties by shearing the grease, rheometer tests were done. In addition to the flow behaviour, we investigated the friction process by using some tribometer. The tribological characteristics of the lubricant are determined with the help of energetic parameters. The interpretation of the results shows a correlation between viscoelastic properties and friction behaviour and an interesting dependence of storage modulus and shear stress. The results are considered to be useful information on the tribology of greases.

The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal lubrication state. The oil film thickness is a crucial parameter reflecting the lubrication status of bearings, directly influencing the operational state of bearing transmission systems. However, it is challenging to accurately measure the oil film thickness under traditional disassembly conditions due to factors such as bearing structure and working conditions. Therefore, there is an urgent need for a nondestructive testing method to measure the oil film thickness and its status.

This paper introduces methods for optically, electrically and acoustically measuring the oil film thickness and status of bearings. It discusses the adaptability and measurement accuracy of different bearing oil film measurement methods and the impact of varying measurement conditions on accuracy. In addition, it compares the application scenarios of other techniques and the influence of the environment on detection results.

Ultrasonic measurement stands out due to its widespread adaptability, making it suitable for oil film thickness detection in various states and monitoring continuous changes in oil film thickness. Different methods can be selected depending on the measurement environment to compensate for measurement accuracy and enhance detection effectiveness.

This paper reviews the basic principles and latest applications of optical, electrical and acoustic measurement of oil film thickness and status. It analyzes applicable measurement methods for oil film under different conditions. It discusses the future trends of detection methods, providing possible solutions for bearing oil film thickness detection in complex engineering environments.

Bearings in field applications with high dynamic loading, e.g. wind energy plants, suffer from sudden failure initiated by subsurface material transformation, known as white etching cracks in a typical scale of μm, preferably around the maximum Hertzian stress zone. Despite many investigations in this field no precise knowledge about the root cause of those failures is available, due to the fact that failure under real service conditions of wind energy plants differs from what is known from test rig results in terms of contact loading, lubrication or dynamics. The purpose of this paper is to apply Barkhausen noise measurement to a full bearing test ring running under conditions of elastohydrodynamic lubrication (EHL) with high radial preload.

Full bearing tests are carried out by use of DGBB (Deep Grove Ball Bearings) with 6206 specification, material set constant as 100Cr6, martensitic hardening, 10‐12 percent maximum retained austenite and radial preload of 3500 MPa. Speed is set 9000 rpm, temperature is self setting at 80°C by test conditions. For tests, synthetic hydrocarbon base oil (Poly‐α‐Olefine) with a 1 percent amount of molydenum‐dithiophosphate (organic chain given as 2‐ethylhexyl) was used.

Non‐destructive fractal dimension analyses by use of Barkhausen noise measurements is of versatile value in terms of recording bearing manufacturing processes, but can also be part of non‐destructive condition monitoring of bearings in field applications, where predictive reactive maintenance is crucial for availability of the plant.

Barkhausen noise signal recording may also be valuable for case studies related to microstructure changes of steel under operation conditions. Bearings are exposed in plenty of conditions to phenomena such as straying currents, subsequently straying magnetic fields. Hardly anything is known about how microstructure of bearing steel is susceptible to such conditions. This will be part of further studies.

Results given in the paper show that sudden bearing failure, according to formation of subsurface material property changes might be driven by activities of dislocations. Since those activities start with sequences of stress field‐induced formation of domains, later by formation of low‐angle subgrains, and at least phase transformation, recording of the Barkhausen signal would lead to real predictive condition monitoring in applications where a highly dynamic loading of the contact, even with low nominal contact pressure leads to sudden failure induced by white etching.