The scientific corpus in technical fields such tribology is not immune from the harm resulting from unethical research behavior, whether intentional or unintentional. When combining this with an increasingly competitive and globalized scientific arena, the research environment can become quite fertile grounds for spawning unethical research behavior. At the same time, the increasing speed of the dissemination of research results due to the various online publication formats has highlighted the need for honest and transparent publications. Primarily developed from research conduct training modules created by the second author and his team at the Collaborative Institutional Training Initiative (CITI), this primer paper serves to illuminate the tenets of responsible research conduct for senior, mid-career and junior tribologists, in addition to scientists in related fields of engineering who want to know what it means to rigorously pursue scientific research in an ethical manner.

An in-house solver was created to simulate contact mechanics and hydrodynamic lubrication using smoothed particle hydrodynamics (SPH), SPH is a meshfree, particle-based method that can be used to solve continuum problems in solid and fluid mechanics. In this approach, the problem domain is represented by particles that move according to prescribed governing equations. Because smoothed particle methods have been shown to have the advantage of being able to model large deformations without concern of degradation in numerical accuracy, they have received recent interest for application to complex problems in tribology—the exploration of which is the focus of this study.

Polishing of a nominally flat aluminum substrate using a fluid jet, carrying abrasive particles, was investigated. The effects of jet orientation and polishing duration were studied, on a fixed spot on the aluminum substrate. Stylus profilometry was used to examine the final surface along different directions. It was seen that the final erosion contour is strongly dependent on the jet orientation. The surface roughness was found to be dependent on the slurry parameters. On average, the average roughness (R a ) of the aluminum surface was reduced from 430 nm to 139 nm. Best polishing was obtained with the jet orientation of 30°. The process was simulated by using computational fluid dynamics (CFD), and it was concluded that dynamic pressure is the main parameter affecting erosion. Results apply to erosion as well as polishing of metal surfaces.

Impact of a single copper particle in cold gas dynamic spray is simulated by finite element method by including the effects of high strain rates and temperature on material plasticity and failure. In order to predict stick behavior of the particle, cohesive forces that act between the particle and the substrate are included in the model by defining an interfacial cohesive strength parameter. Effect of this parameter on the deformation and stick/rebound behavior of the particle is studied. It is found that significant particle deformation, large area of contact between particle and substrate is needed to generate enough cohesive force to absorb the rebound energy of the particle and achieve sticking. As the impact velocity and assumed interfacial cohesive strength increases, particle is more likely to stick on to the substrate. Critical velocities in the same range with experimental results are predicted.

This presentation describes ongoing research performed on a simple shear cell apparatus, previously described [1]. As a complement, discrete particle simulations and continuum models have been used to predict normal and shear forces in the ongoing experiments. The trends and orders-of-magnitude of the models and experiment are in basic agreement. Theoretical models used are constructed with basic principles, rather than curve fitting, to obtain effective properties of the mixture such as viscosity or conductivity. The experiment itself serves to determine the effects of shear rate, packing fraction, particle size and film thickness on the load carrying normal stress. Additionally, the frictional shear stress can be investigated. The working particulate medium within the apparatus consists of glass of aluminum spheres, poly-dispersed over four size increments, all less than 1.00 mm diameter. The upper annular disk is held stationary in a rotational sense by a force transducer, and applies predetermined normal stress values which vary according to a system of interchangeable counterweights. The lower transfer surface and the sidewalls of the annular ring are rotated by applied mechanical torque. Experimental trials consist of shear initiation, after which the trough velocity, film thickness, supporting load, and frictional torque are measured. From these measurements one can calculate the average shear rate, the average load-carrying normal stress, the average frictional shear stress, and the solids volume fraction. Such third body granular flow may apply to some solid lubrication mechanisms, and to applications such as smart clutches and dampers. The continuum theory presented is unique in that it addresses solid-like behavior and its transition to fluidized behavior. The discrete particle dynamics rely on the conceptual models of Iordanoff and colleagues [2]. Our findings are that the two theoretical predictions agree reasonably with the experimental results, suggesting validity of the approach. These results are promising, and may be used to further develop high level predictive models. Furthermore, similar methods of small scale experimental particle simulation can be used to develop simpler more usable continuum approaches.

Granular flows continue to be a complex problem in nature and industrial sectors where solid particles exhibit solid, liquid, and gaseous behavior in a manner which is often unpredictable locally or globally. In tribology, they have also been proposed as lubricants because of their liquid-like behavior in sliding contacts, and due to their ability to carry loads and accommodate surface velocities. The present work attempts to model a granular Couette flow in an annular shear cell using a lattice-based cellular automata (CA) computational modeling approach. The CA framework has the flexibility to employ rule-based mathematics and/or first-principle physics to rapidly model physical processes. The model developed in this work incorporates dissipative effects due to friction between particles and boundaries, in addition to particle spin. This new model also includes a rigorous treatment of boundary-particle interactions. Additional work has been done to account for the transfer of momentum through particle chains, allowing for the modeling of transitional granular flows, which consist of both kinetic and contact flow regimes.

In this study, techniques for studying the Tribology of rock cutting are being developed using bit cutter-on-rock tribometry (BCORT). Tribo-testing is carried out on a slider pad-on-disk tribometer, retrofitted to include water-jet fabricated rock disks, a variable radius cutter assembly, and a system for the capture of in situ depth of cut. Preliminary findings for BCORT testing of O1 tool steel on Carthage marble are presented, in addition to verification of depth of cut measurements with a scanning white light optical interferometer. The interdependence of interfacial cutting friction, depth of cut rate, and disk speed are discussed in conjunction with experiments.

Pellets were formed by compacting MoS 2 powder. In the setup, the pellet is sheared against a disk surface while the slider pad rides on the MoS 2 partially-covered asperities, while depleting the lubricant. A volumetric fractional coverage (VFC) modeling approach was developed to predict the friction coefficients for the lubricated pellet/disk sliding contact by assuming that the friction coefficients at pellet/disk and slider/disk interfaces are functions of the fraction of lubricant occupying the control volume. This fractional coverage is a theoretical parameter for quantifying the amount of third body film covering the disk asperities as a function of time. The model can be applied to a deterministic surface, thus, the proposed theory can predict the behavior of friction coefficients between the pellet/disk and slider/disk interfaces for most topographies, whether they are deterministic (i.e., textured) or real (i.e., random).