Simulation of wear in combustion engines

The “Sport” of Rough Contacts and the Fractal Paradox in Wear Laws

“…[7], but more in general, there is a more complex dependence (see Fig.1), in some cases even contradicting the Archard wear law inverse dependence on hardness, especially for very high hardness. The latter result may be connected to Kragelsky's [8] observation that catastrophic wear occurs when surface layers are harder than substrate, whereas the opposite is suggested for minimizing wear (see also Popov et al [9]). Therefore, even just looking at Fig.1 reveals that there is more in k than what -wear coefficient‖ constant suggests.…”

“…This constant value decreases if A * /λ s 2 increases, where λ s is the smallest wavelength in the roughness spectrum. This dependence (which is the counterpart of the dependence on the radius of the GW model) is not fully discussed in [9] but obviously means that the truncation of the fractal process is a very sensitive parameter also in the -refined‖ BEM models, as in the fractal limit, λ s →0 or R→0 and there is no longer predicted wear.…”

“…In this Section we discuss this aspect of the problem. Let us note that there also exist other approaches where the poorly defined notion of an asperity is avoided [9,22]. However, even within such a concept, the effective work of adhesion (which is proportional to the real contact area, which is also an ill-defined quantity [18]) does play a central role, and this area is also dependent on adhesion.…”

Adhesive Wear: Generalized Rabinowicz’ Criteria

“…This layer can be deposited to the surface artificially or it can appear naturally through mechanically induced chemical reactions of the base material with surrounding substances (lubricant, counter-body, air and so on) [9,10]. Assume that due to normal loading and tangential sliding a junction with the diameter D is formed, and that the Diameter D is much larger than the thickness of the layer (the opposite case corresponds to a homogeneous medium and is covered by Eq.(3)).…”

“…However, the surface region of contacts in most low-wear technical systems is not homogeneous. Through the work of Gerve et al [9] and in the last decade, especially by M. Scherge and co-workers [10], the role of very thin chemically modified surface layers has been demonstrated for systems with "minimal wear" (including, for example, combustion engines). Further, the Rabinowicz-Molinari criterion uses the notion of "asperity".…”