Analytical force modeling for laser-assisted diamond machining of brittle materials

Abstract

Cutting force is a critical indicator that reflects material removal mechanisms and affects surface quality, making its accurate prediction essential. However, due to the superposition of multiple physical fields, predicting cutting force during laser-assisted diamond machining (LADM) remains highly challenging. This study establishes an advanced analytical force calculation framework to elucidate the material removal mechanisms in LADM of brittle materials, taking into account the effects of laser-induced temperature field on material removal behavior. Based on the temperature field simulations, the temperature-dependent mechanical properties influenced by the combined effects of cutting and laser parameters are evaluated through high-temperature nanoindentation. Furthermore, a novel groove fitting algorithm is proposed to provide unified criteria for determining the ductile-brittle transition depth (DBTD), and the dimensionless constants are identified using a genetic algorithm-based optimizer. The developed force model incorporates the elastic recovery on the flank face and the material removal behaviors of ploughing effect, plastic deformation, and brittle fracture on the rake face. Experimental validation on magnesium fluoride demonstrates excellent agreement between predicted and measured cutting forces in both conventional turning and LADM, with prediction errors within 8.62% across the commonly used parameter range of practical applications. The study also discusses how the overheating effect, caused by a mismatch between thermal softening zones and cutting regions under extreme laser conditions, impacts model accuracy. Theoretical and experimental results demonstrate that LADM can effectively reduce the hardness and Young’s modulus of brittle materials, enhance dislocation mobility and plastic deformation, and thereby improve ductile machinability. As a result, LADM leads to increased DBTD, lower cutting forces, and better surface quality compared to conventional machining. Overall, this work not only presents a robust theoretical framework for cutting force prediction, but also deepens the understanding of material removal and surface formation mechanisms in LADM of brittle materials.