Undeformed chip thickness modeling in EUVAG considering wheel topography evolution

Abstract

To investigate the evolution of wheel topography and grinding performance under elliptical ultrasonic vibration-assisted grinding (EUVAG), silicon carbide (SiC) ceramics were selected as the material for processing. Comparative experiments involving wheel wear tests and grinding performance tests were conducted for both conventional grinding (CG) and EUVAG. This study proposes and establishes a novel method for determining the undeformed chip thickness distribution under EUVAG, utilizing it as a key parameter to link the evolution of wheel topography with grinding outcomes. The undeformed chip thickness model takes into account the dynamic effects of wheel and the unevenness of grain height, and is further modified by considering the material elastic-plastic micro deformation. First, to elucidate the influence of elliptical ultrasonic vibration on the evolution of wheel topography, the wear patterns of grains on wheel surface were characterized, including statistical analyses of the wear platform and cutting height of grains. Compared to CG, the occurrence of clearance surfaces and grain detachment is delayed in EUVAG, and there is an increase of 11.2 % to 25.1 % in the wear platform area A_uw. Subsequently, the coupled effects of wheel wear states, elliptical ultrasonic vibration parameters, and grinding process parameters on key grinding performance indicators were analyzed from the perspective of undeformed chip thickness distribution. The results demonstrated that increasing the wheel speed to reduce μ₂ is an effective approach for achieving lower grinding forces in EUVAG, the reduction amplitude is from 25 % to 46 %. Expanding the range of μ₂ can significantly reduce grinding specific energy. For applications requiring low surface roughness, controlling μ₂ at a lower mean value with a more uniform distribution can be achieved by increasing the wheel speed and decreasing the workpiece feed rate. The optimal surface roughness is 0.187 μm when v_s = 24 m/s. Reducing the range of μ₂ and the proportion of undeformed chip thickness facilitates a higher plastic removal ratio, while lowering μ₁ enhances plastic removal efficiency. The improvement in material removal rate achieved by EUVAG was observed to increase initially and then decrease with progressive wear of wheel, and the optimal improvement is 17.9 % achieved at wear state 4. Finally, by analyzing the mapping relationships between machining results and the distribution characteristics of undeformed chip thickness under various machining parameters, an efficient and low-damage prediction model for EUVAG of SiC ceramics was developed. It was found that the parameter combination [v_s=20 m/s, v_w=50 mm/min, a_p=10 µm, A_z=2.668 µm] provides an optimal balance between machining quality and efficiency, achieving the plastic removal with a small proportion of brittle removal, and the MRR of 37.6 × 10⁶ µm³/mm·s.