Special Issue: Tribomechadynamics

Abstract

Tribomechadynamics is a nascent field of mechanical engineering that has emerged from the integration of tribology, contact mechanics, and structural and nonlinear dynamics. The principle challenge identified within the tribomechadynamics community is how to predict the nonlinear response of a structure with frictional interfaces. This challenge is exacerbated by frictional interfaces exhibiting wear and evolving, sometimes quite dramatically, over time, which can have profound effects on the nonlinear dynamic response of a structure (in particular, the hysteretic behavior and the amplitude-dependent natural frequencies and damping ratios of the structure). By necessity, tribomechadynamic studies span length scales from nanometers to decameters and time scales from microseconds to years. Consequently, this presents a number of formidable challenges for both experimentation and computational efforts, as detailed throughout this special issue.The origins of tribomechadynamics can be traced back to the Structural Dynamics 2000 workshop in 1999 [1] hosted by Los Alamos National Laboratories and a subsequent workshop on the Development of Methodologies for Constructing Predictive Models of Structures With Joints and Interfaces in 2000 [2] hosted by Sandia National Laboratories. At these two workshops, researchers in structural and nonlinear dynamics from the defense, aerospace, naval, automotive, and manufacturing communities (both in terms of industry, government, and academia) realized that the problems that each community had been grappling with isolation were common to the other communities as well. In each of these communities, the greatest impediment to improving system design was the inability to predict the response of a structure with frictional interfaces. Existing approaches focused on calibrated modeling efforts (e.g., Ref. [3]), in which a linear model was updated to include nonlinear contributions after test hardware had been fabricated and experimentally assessed. This approach, however, is nonsustainable as it incurs a high cost for design revisions since the frictional properties and wear cannot be predicted a priori. Further, the lack of a predictive model for friction and wear costs the global economy approximately $1 trillion per year [4] through design inefficiency (e.g., overdesigned joints that contribute extra mass to a structure and thus degrade its fuel efficiency), extraneous fabrication and testing to update and revise preliminary designs, and mechanical failures due to fretting fatigue or other joints-related issues.The realization that a predictive model of frictional interfaces was a common limiting factor for multiple communities led to a series of international workshops on joint mechanics [5–8]. In these workshops, researchers from scales spanning the atomic to deca-meters systems charted a roadmap for developing a predictive model of interfacial behavior. One consensus from these workshops was that there was insufficient integration, even within the same organizations, of tribology, contact mechanics, and structural and nonlinear dynamics. This led to the formal definition of tribomechadynamics in 2018 [9]. While the concept of integrating some elements of tribology, contact mechanics, and structural or nonlinear dynamics is not novel, the importance of defining the field of tribomechadynamics is that it is an intentional emphasis of the need for integrating these different disciplines. This intentional emphasis has already resonated through a wide set of communities (ranging from traveling waves in belt drives to violin string–bow interactions), as evidenced by the participation at the Tribomechadynamics 2020 Conference. Several of the best presentations from this conference, including the two best student paper award winners (Özge Akar of Friedrich-Alexander-Universität Erlangen-Nürnberg and Mengshi Jin of Tongji University), have been included in this special issue.