Machining defect suppression in ultrasonic grinding of C/SiC composites based on microscopic mechanical model

Fibre pull-out and interfacial debonding during the macro-brittle removal of C/SiC composites produce severe subsurface damage, compromising surface integrity. Ultrasound-assisted grinding enhances the support stiffness of equivalent homogeneous materials and reduces fibre bending deformation, improving machined surface quality. However, the influence of ultrasonic vibration on machining damage mechanisms from micro-scale mechanical models and material removal mechanisms has not been published. To suppress machining damage, this paper first conducts a comprehensive analysis of the high-frequency oscillatory cutting behaviour and separation effects of active abrasive grit within the grinding zone. Furthermore, the machining damages, including fibre pull-out and interfacial debonding, are mechanically modeled in terms of the interface crack deflection effect, fibre deformation, and fracture behaviour. Finally, the internal stresses, removal behaviour, and fracture modes of fibres with various ultrasonic amplitudes are predicted, and the optimal amplitude range to effectively suppress machining damage is acquired. Surface microstructure, grinding chips, roughness, and fractal dimension demonstrate that the machining damage suppression strategy can effectively inhibit fibre pull-out and interface debonding defects.