Multiscale simulation and experimental study on ultrasonic vibration assisted machining of SiCp/Al composites considering acoustic softening

Ultrasonic vibration assisted machining (UVAM) is an attractive option to achieve high-quality and low-wear machining of the advanced composites. The scope of this paper is to evaluate the role of ultrasonic vibration on the microstructure and material removal mechanism for SiCp/Al composites. Firstly, an ultrasonic vibration assisted tension (UVAT) molecular dynamics (MD) simulation method for SiCp/Al composites is proposed. The simulation results verify the existence of acoustic softening effect for SiCp/Al composites under ultrasonic vibration loads. Furthermore, it is found that the acoustic softening originates from the dynamic evolution of the dislocations in the Al matrix. However, the acoustic softening is hardly mentioned in conventional finite element (FE) simulations depicting the microscopic removal mechanism of materials. In this paper, the constitutive correction method is adopted to realize it. The stress reduction of the Al matrix caused by acoustic softening is reverse-identified, and the maximum is 102 MPa. Finally, a novel FE model for UVAM of SiCp/Al composites considering acoustic softening is constructed, and the microscopic removal mechanism of SiCp/Al composites is revealed by the FE simulation and microscopic experimental results. On the one hand, the ultrasonic vibration enhances the stress relaxation of the Al matrix by reducing the dislocation density, and further enhances the deformation ability of SiCp/Al composites. On the other hand, the matrix tearing dominates the generation and propagation of shear band cracks in conventional machining (CM), while the dominant factor in UVAM is the finely broken SiC particles inside the shear band. This study enhances the understanding of the microscopic removal mechanism in UVAM for SiCp/Al composites.