Experimental and multiscale simulation analysis of the lubricant penetration in gear skiving

Cooling lubricants play essential roles in machining processes, namely cooling and lubricating contact surfaces, and facilitating the removal of chips that could compromise surface quality. A key question is how well the lubricant penetrates the cutting zone in complex interrupted cutting operations, such as gear skiving. This study tackles the challenge of analyzing the behavior of cooling lubricants across different scales by employing a combined experimental and multiscale simulation approach. The overall fluid flow is modeled using smoothed particle hydrodynamics, while chip formation is simulated with finite element methods. The cavitation behavior of the lubricant within the cutting wedge is examined using the Reynolds equation, and the tool’s indentation is investigated through molecular dynamics simulations. Finite element simulations are validated against experimental data from gear skiving tests using AISI 4140 steel, showing an average deviation of 6.6% in the maximum force values. Smoothed particle hydrodynamics simulations predict that the cooling lubricant can reach the meshing zone between the tool and the workpiece. For validation purposes, typical global flow characteristics from the simulation are compared with high-speed camera images, exhibiting good agreement. In typical gear skiving conditions, Reynolds calculations indicate that significant cavitation occurs, resulting in a substantial portion of the contact area remaining dry. We investigate the conditions that can help reduce cavitation. Molecular dynamics simulations reveal that nanocavities on the tool’s surface can improve the transport of lubricant molecules to the contact area.