Macroscale Insight from Nanoscale Testing

Abstract

With a very large number of applications, macroscale behavior is based upon hypotheses or guesses about material or process behavior, with no direct experimental evidence to confirm or deny the hypothesis. This is clearly the case with most tribological phenomenon, such as abrasion-based friction and wear, as well as boundary lubrication. Design rules such as the Archard wear law do not explain the function or suggest the value of a wear coefficient, for example, which in effect regulates tribologists to empiricism. Often, nanoscale simulations with only experimental or theoretical components are equally limited, since parameters such as physical dimensions and material properties are chosen to conveniently match the researcher’s tools instead being correlated to a real problem.

This paper presents a summary of the research performed to date on single asperity plowing at depths and length scales that directly simulate real tribological contacts in manufacturing and machine design applications. Using a coupled experimental and theoretical approach, plausible and quantitative data is obtained to explain real-world, macroscale observations based on nanoscale phenomena. Applications emphasized in this paper are debris generation in metal forming, mechanisms of boundary lubrication, crystallographic anisotropy effects, and wear of polymers for orthopedic applications.