On the Cognitive Approach toward Classification of Dry Triboparticulates

Heshmat, H. and Brewe, D.E. “On the Cognitive Approach toward Classification of Dry Triboparticulates,” 20th Leeds-Lyon Symposium on Dissipative Processes in Tribology, Lyon, France, 7-10 September 1993, Dowson et al. (Editors), (1994) Elsevier Science B.V., Tribology Series 27, pp. 303-328.

To relate wear debris to a wear mechanism is a challenging task since one must describe the particle shape.  here, the “cognitive approach” is adapted to classify particles of powder, wear debris, and triboparticulate matter in general.  This method is considered to be not only convenient, but also the best method that the state of the art can provide over other known mathematical models, when complex particles are the subject of study.


This paper describes a procedure used to select suitable experiments to develop a fundamental understanding of packed/sheared dry particulate samples. As part of the triboparticulate characterization, packed samples of ten various dry powders were prepared for investigation.  Each pressed sample was then fractured diagonally and three sites (fractured, pressed and sheared) were examined).  This paper presents scanning electron photomicrographs (SEPs) of a particle ensemble from each site, along with a quantitative image analysis (QIA) of the individual particles, and the relationship between the powder property and average particle size. 

It has been postulated that solid particulates in an interface gap, when sheared, exhibit a molecular-like motion in liquid lubrication.  It is a widely accepted assumption, however, that these molecules, under mild shear stress, remain unbroken and unworn.  Fine solid triboparticulates, on the other hand, even under mild stress, undergo tribocomminution, i.e., they deform fracture, wear, agglomerate, and alter their physical and chemical states.  In other words, they do not remain in the precise condition, like molecules, in which they first began to exist or entered into the interface gap.  Since utilizing the cognitive approach to describe the shape of a particle itself is a matter of subjectivity rather than collectivity in terms of scientific approach, this paper discusses some of the pros and cons relevant to application of the cognitive approach toward classification of particulates in tribology. 

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