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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…
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…
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…
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…
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.
Bearings in field applications with high dynamic loading, e.g. wind energy plants, suffer from sudden failure initiated by subsurface material transformation, known as…
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.