AWEARNESS Anti-Wear-Effectiveness of Additives using a Rabinowicz and Eyring based Simulation Scheme

• Applicants: Dr.-Ing. Florian Pape; Professor Dr. Lars Pastewka; Professor Dr.-Ing. Gerhard Poll; Professor Dr. Valentin L. Popov
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461911253

Engineering applications often involve lubricated systems. In the classical scenario, a lubricant layer of sufficient thickness effectively separates the surfaces of components moving in relation to each other. No wear occurs under such hydrodynamic lubrication conditions. However, many modern systems operate within the mixed lubrication regime. Surfaces, or their roughness peaks (asperities), come into direct contact, leading to wear and reduced component service life.Anti-wear additives eliminate base material wear by the formation of protective surface layers. In intimate contacts, such layers carry the mechanical shear and will experience wear. However, concurrent regeneration can lead to an equilibrium between layer removal and layer formation. Ultimately, the existence of this balance governs the achievability of effective anti-wear protection. This binary behavior corresponds to the distinction between mild and severe wear operating conditions in tribological experiments. The AWEARNESS project’s primary objective is to develop a robust prediction methodology on mild and severe wear modes for a lubricated tribological system in the presence of a chemical additive. The secondary objective is to estimate the quantitative wear rate as a function of the operating conditions within the severe wear regime.The AWEARNESS project will focus on Zinc dithiophosphates (ZDDPs), the most widely used family of anti-wear additives. ZDDPs form protective phosphate glass-based films on metal substrates. Recent studies proved the robustness of an Eyring model to describe ZDDP film formation kinetics. Here, ZDDP decomposition by stress-augmented thermal activation is assumed to constitute the rate-limiting reaction step. On the other hand, we assume a Rabinowicz criterion to determine film removal locally.AWEARNESS predictions will be ZDDP-specific, but the developed methodology will be widely applicable. Profound statements on the defining parameters for a system’s mild and severe wear operating conditions will be of great value to academia and industry alike. For this purpose, the applicants bring together the necessary expertise in physical and chemical modeling as well as first-hand experience in lubrication testing.

• DFG Programme: Research Grants