AI for tribology:Present and future

With remarkable learning capabilities and swift operational speeds,artificial intelligence(AI)can assist researchers in swiftly extracting valuable patterns,trends,and associations from subjective information.Tribological behaviors are characterized by dependence on systems,evolution with time,and multidisciplinary coupling.The friction process involves a variety of phenomena,including mechanics,thermology,electricity,optics,magnetics,and so on.Hence,tribological information possesses the distinct characteristics of being multidisciplinary,multilevel,and multiscale,so that the application of AI in tribology is highly extensive.To delineate the scope,classification,and recent trends of AI implementation in tribology,this review embarks on exploration of the tribology research domain.It comprehensively outlines the utilization of AI in basic theory of tribology,intelligent tribology,component tribology,extreme tribology,bio-tribology,green tribology,and other fields.Finally,considering the emergence of"tribo-informatics"as a novel interdisciplinary field,which combines tribology with informatics,this review elucidates the future directions and research framework of"AI for tribology".In this paper,tribo-system information is divided into 5 categories:input information(I),system intrinsic information(S),output information(O),tribological state information(Ts),and derived state information(Ds).Then,a fusion method among 5 types of tribo-system information and different AI technologies(regression,classification,clustering,and dimension reduction)has been proposed,which enables tribo-informatics methods to solve common problems such as tribological behavior state monitoring,behavior prediction,and system optimization.The purpose of this review is to offer a systematic comprehension of tribo-informatics and to inspire new research ideas of tribo-informatics.Ultimately,it aspires to enhance the efficiency of problem-solving in tribology.

Tribo-informatics approaches in tribology research:A review

Tribology research mainly focuses on the friction,wear,and lubrication between interacting surfaces.With the continuous increase in the industrialization of human society,tribology research objects have become increasingly extensive.Tribology research methods have also gone through the stages of empirical science based on phenomena,theoretical science based on models,and computational science based on simulations.Tribology research has a strong engineering background.Owing to the intense coupling characteristics of tribology,tribological information includes subject information related to mathematics,physics,chemistry,materials,machinery,etc.Constantly emerging data and models are the basis for the development of tribology.The development of information technology has provided new and more efficient methods for generating,collecting,processing,and analyzing tribological data.As a result,the concept of"tribo-informatics(triboinformatics)"has been introduced.In this paper,guided by the framework of tribo-informatics,the application of tribo-informatics methods in tribology is reviewed.This article aims to provide helpful guidance for efficient and scientific tribology research using tribo-informatics approaches.

Tribo-informatics:Concept,architecture,and case study

Friction plays a vital role in energy dissipation,device failure,and even energy supply in modern society.After years of research,data and information on tribology research are becoming increasingly available.Because of the strong systematic and multi-disciplinary coupling characteristics of tribology,tribology information is scattered in various disciplines with different patterns,e.g.,technical documents,databases,and papers,thereby increasing the information entropy of the system,which is inconducive to the preservation and circulation of research information.With the development of computer and information science and technology,many subjects have begun to be combined with information technology,and multi-disciplinary informatics has been born.This paper describes the combination of information technology with tribology research,presenting the connotation and architecture of tribo-informatics,and providing a case study on implementing the proposed concept and architecture.The proposal and development of tribo-informatics described herein will improve the research efficiency and optimize the research process of tribology,which is of considerable significance to the development of this field.

New 9,19-cycloartane triterpenoid from the root of Cimicifuga foetida

AIM: To study the 9, 19-cycloartane triterpenes from the roots of Cimicifuga foetida. METHOD: Chromatographic separations by silica gel, C18 reversed phase silica gel, and high-performance liquid chromatography(HPLC) were used. All of the structures were elucidated on the basis of spectroscopic analysis and chemical methods. RESULTS: Five 9, 19-cycloartane triterpenes,(3β, 12β, 15α, 24R)-12, 2'-diacetoxy-24, 25-epoxy-15-hydroxy-16, 23-dione-3-O-α-L-arabinopyranoside(1), actein(2), 23-epi-26-deoxyactein(3), asiaticoside B(4), and 12β-hydroxycimigenol(5) were isolated from the roots of Cimicifuga foetida. CONCLUSION: Compound 1 is a new triterpene with two acetoxy groups at C-2' and C-12.

Multiscale analysis of friction behavior at fretting interfaces

Friction behavior at fretting interfaces is of fundamental interest in tribology and is important in material applications.However,friction has contact intervals,which can accurately determine the friction characteristics of a material;however,this has not been thoroughly investigated.Moreover,the fretting process with regard to different interfacial configurations have also not been systematically evaluated.To bridge these research gaps,molecular dynamics(MD)simulations on Al–Al,diamond–diamond,and diamond–silicon fretting interfaces were performed while considering bidirectional forces.This paper also proposes new energy theories,bonding principles,nanoscale friction laws,and wear rate analyses.With these models,semi-quantitative analyses of coefficient of friction(CoF)were made and simulation outcomes were examined.The results show that the differences in the hardness,stiffness modulus,and the material configuration have a considerable influence on the fretting process.This can potentially lead to the force generated during friction contact intervals along with changes in the CoF.The effect of surface separation can be of great significance in predicting the fretting process,selecting the material,and for optimization.

Iteration framework for solving mixed lubrication computation problems

The general discrete scheme of time-varying Reynolds equation loses the information of the previous step,which makes it unreasonable.A discretization formula of the Reynolds equation,which is based on the Crank-Nicolson method,is proposed considering the physical message of the previous step.Gauss-Seidel relaxation and distribution relaxation are adopted for the linear operators of pressure during the numerical solution procedure.In addition to the convergent criteria of pressure distribution and load,an estimation framework is developed to investigate the relative error of the most important term in the Reynolds equation.Smooth surface with frill contacts and mixed elastohydrodynamic lubrication is tested for validation.The asperity contact and sinusoidal wavy surface are examined by the proposed discrete scheme.Results show the precipitous decline in the boundary of the contact area.The relative error suggests that the pressure distribution is reliable and reflects the accuracy and effectiveness of the developed method.