Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> This letter presents experimental results on unlubricated friction, which suggests that stick–slip is described by self-organized criticality (SOC). The data, obtained with a pin-on-disc tribometer examines the variation of the friction force as a function of time—or sliding distance. This is the first time that standard tribological equipment has been used to examine the possibility of SOC. The materials were matching pins and discs of aluminium loaded with 250, 500 and 1000 g masses, and matching M50 steel couples loaded with a 1000 g mass. An analysis of the data shows that the probability distribution of slip sizes follows a power law. In addition, the frequency power spectrum follows a 1/fα pattern with α in the range 1.1–1.3. We perform a careful analysis of all the properties, beyond the two just mentioned, which are required to imply the presence of SOC. Our data strongly support the existence of SOC for stick–slip in dry sliding friction. <s> BIB001 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> The science base that underlies modelling and analysis of machine reliability has remained substantially unchanged for decades. Therefore, it is not surprising that a significant gap exists between available machinery technology and science to capture degradation dynamics for prediction of failure. Further, there is a lack of a systematic technique for the development of accelerated failure testing of machinery components. This article develops a thermodynamic characterization of degradation dynamics, which employs entropy, a measure of thermodynamic disorder, as the fundamental measure of degradation; this relates entropy generation to irreversible degradation and shows that components of material degradation can be related to the production of corresponding thermodynamic entropy by the irreversible dissipative processes that characterize the degradation. A theorem that relates entropy generation to irreversible degradation, via generalized thermodynamic forces and degradation forces, is constructed. This theorem provides the basis of a structured method for formulating degradation models consistent with the laws of thermodynamics. Applications of the theorem to problems involving sliding wear and fretting wear, caused by effects of friction and associated with tribological components, are presented. <s> BIB002 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> Despite the fact that self-organization during friction has received relatively little attention from tribologists so far, it has the potential for the creation of self-healing and self-lubricating materials, which are important for green or environment-friendly tribology. The principles of the thermodynamics of irreversible processes and of the nonlinear theory of dynamical systems are used to investigate the formation of spatial and temporal structures during friction. The transition to the self-organized state with low friction and wear occurs through destabilization of steady-state (stationary) sliding. The criterion for destabilization is formulated and several examples are discussed: the formation of a protective film, microtopography evolution and slip waves. The pattern formation may involve self-organized criticality and reaction-diffusion systems. A special self-healing mechanism may be embedded into the material by coupling the corresponding required forces. The analysis provides the structure-property relationship, which can be applied for the design optimization of composite self-lubricating and self-healing materials for various ecologically friendly applications and green tribology. <s> BIB003 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> The friction coefficient on rake face was calculated through the cutting forces tested in a series of cutting experiments. These experiments were performed for turning two kinds of hardened steel with four types of coating tool by orthogonal experimental method. The curves of the friction coefficient changing with the cutting process and its dependence on the cutting parameters were analyzed in detail. The results show that the friction coefficient on rake face decreases rapidly during the cutting progress and comes to a steady value, which could be an indication of the self-organization when turning hardened steel with coating tool. <s> BIB004 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> The paper discusses the concept of entropy as applied to friction and wear. Friction and wear are classical examples of irreversible dissipative processes, and it is widely recognized that entropy generation is their important quantitative measure. On the other hand, the use of thermodynamic methods in tribology remains controversial and questions about the practical usefulness of these methods are often asked. A significant part of entropic tribological research was conducted in Russia since the 1970s. Surprisingly, many of these studies are not available in English and still not well known in the West. The paper reviews various views on the role of entropy and self-organization in tribology and it discusses modern approaches to wear and friction, which use the thermodynamic entropic method as well as the application of the mathematical concept of entropy to the dynamic friction effects (e.g., the running-in transient process, stick-slip motion, etc.) and a possible connection between the thermodynamic and information approach. The paper also discusses non-equilibrium thermodynamic approach to friction, wear, and self-healing. In general, the objective of this paper is to answer the frequently asked question “is there any practical application of the thermodynamics in the study of friction and wear?” and to show that the thermodynamic methods have potential for both fundamental study of friction and wear and for the development of new (e.g., self-lubricating) materials. <s> BIB005 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> In self-organized sliding processes, the surfaces align to each other during sliding. This alignment leads to a more ordered contact state and significantly influences the frictional behavior. To understand the self-organization sliding processes, experiments were conducted on a pin-on-plate reciprocating sliding tester for various numbers of cycles. In the experiments, soft magnesium pins were slid against hard steel plates of various surface textures (undirectional, 8-ground, and random). Experimental results showed that the transfer layer formation on the steel plates increased with increasing number of cycles for all surfaces textures under both dry and lubricated conditions. The friction also increased with the number of cycles under dry conditions for all of the textures studied. During lubricated conditions, the friction decreased for unidirectional and 8-ground surfaces and increased for random surfaces with the number of cycles. Furthermore, the friction and transfer layer formation depend on the surface textures under both dry and lubricated conditions during the first few sliding cycles. Later on, it is less dependent of surface textures. The variation in the coefficient of friction under both dry and lubrication conditions were attributed to the self-organization process that occurred during repeated sliding. <s> BIB006 </s> Application of the Self-Organization Phenomenon in the Development of Wear Resistant Materials—A Review <s> Introduction <s> We experimentally investigate the non-equilibrium steady-state distribution of the work done by an external force on a mesoscopic system with many coupled degrees of freedom: a colloidal crystal mechanically driven across a commensurate periodic light field. Since this system mimics the spatiotemporal dynamics of a crystalline surface moving on a corrugated substrate, our results show general properties of the work distribution for atomically flat surfaces undergoing friction. We address the role of several parameters which can influence the shape of the work distribution, e.g. the number of particles used to locally probe the properties of the system and the time interval to measure the work. We find that, when tuning the control parameters to induce particle depinning from the substrate, there is an abrupt change of the shape of the work distribution. While in the completely static and sliding friction regimes the work distribution is Gaussian, non-Gaussian tails show up due to the spatiotemporal heterogeneity of the particle dynamics during the transition between these two regimes. <s> BIB007
Over the past several years there have been many scientific publications regarding the application of nonequilibrium thermodynamics and the theory of self-organization in tribology, for instance [1] BIB003    BIB006 BIB001 BIB004 BIB007 BIB002     BIB005  . Normally articles on nonequilibrium thermodynamics as applied to friction are divided into two types. One type of articles is typified by the detailed description of the theory without any practical recommendations and without any possibility of its practical application. The second type of articles is characterized by the detailed description of relevant experiments mentioning that the results of such experiments correspond to nonequilibrium thermodynamics. What is common with these two types of articles is lack of recommendations for the application of nonequilibrium thermodynamics, for instance, for the development of wear resistant materials, as well as their lack of explanations as to what the authors believe self-organization means. For example, in [1] it is declared that the phenomenon of self-organization exists in tribosystems, and it is concluded that surface energy is one of the most important parameters in self-organization of tribosystems. However, the authors of [1] fail to define what self-organization actually means. In BIB007 nonequilibrium stationary distribution of work performed by external forces over a mesoscopic system with multiple degrees of freedom is reviewed. The recommendations for applying the results achieved are not presented in BIB007 . In BIB002 it is proposed to use the second law of thermodynamics in order to determine the tribosystem's degradation (accumulation of defects and damages). The degradation is determined by growth in entropy, while production of entropy is determined by the velocity of accumulation of damages. However, the article does not review the phenomenon of self-organization which results in deceleration of the degradation. In BIB003 it is emphasized that self-organization leads to the reduction in friction force and intensity of wear, and that to proceed with self-organization, the tribosystem is required to lose thermodynamic stability.