Grinding force reduction mechanism for micro-dimple morphology in ultrasonic-assisted longitudinal-normal grinding

To meet the surface quality requirements of steel-based materials in high-precision machining, this study employs a tapered wheel to convert one-dimensional (1D) longitudinal ultrasonic vibration into two-dimensional (2D) longitudinal-normal coupled vibrations in a rotary ultrasonic-assisted grinding (RUAG) system. This method effectively produces a novel “non-contact intermittent grinding” behavior in abrasive grains, which reduces grinding forces and facilitates the formation of micro-dimples. To study the reduction mechanism of grinding force, a theoretical force prediction model of a single grain was proposed, which extended the framework of cutting deformation and friction forces by incorporating an impact force component. Systematic investigations revealed that grinding forces increased with vibration amplitude, decreased with rotational speed, and sharply rose with feed rate. Model predictions showed an error rate of less than 15% compared to experimental results. Experimental results of eccentric grinding wheel further confirmed that the frequent occurrence of non-contact grinding increased effective grain engagement, significantly reduced grinding depth and forces, and improved surface roughness compared to conventional grinding (CG) methods. This study provides theoretical models, simulated approaches, and practical guidelines for advancing 2D ultrasonic grinding technologies, with implications for enhanced precision and efficiency in industrial applications.