Magnetically-actuated functional gradient nanocomposites can be locally programmed to generate unprecedented mechanical gradients applied to various bioinspired load-bearing materials.
This paper investigates the textured surface generation mechanism in vibration-assisted micro milling through modelling and experimental approaches. To decouple the effects of tool geometry and kinematics of vibration-assisted milling, a surface generation model based on homogenous matrices transformation is proposed. On this basis, series of simulations are performed to provide insights into the effects of various vibration parameters (frequency, amplitude and phase difference) on the generation mechanism of typical textured surfaces in 1D and 2D vibration-assisted milling. Furthermore, the wettability tests are performed on the machined surfaces with various surface texture topographies. The fish-scale textured surfaces are found to exhibit better wettability than those with wavy-structure. The results indicate that vibration-assisted milling is an effective method to generate certain surface textures with controllable wettability.
Large-scale molecular dynamics simulation is performed to study the nano-cutting process of single crystal copper realized by single-point diamond cutting tool in this paper. The centro-symmetry parameter is adopted to characterize the subsurface deformed layers and the distribution and evolution of the subsurface defect structures. Three-dimensional visualization and measurement technology are used to measure the depth of the subsurface deformed layers. The influence of cutting speed, cutting depth, cutting direction, and crystallographic orientation on the depth of subsurface deformed layers is systematically investigated. The results show that a lot of defect structures are formed in the subsurface of workpiece during nano-cutting process, for instance, stair-rod dislocations, stacking fault tetrahedron, atomic clusters, vacancy defects, point defects. In the process of nano-cutting, the depth of subsurface deformed layers increases with the cutting distance at the beginning, then decreases at stable cutting process, and basically remains unchanged when the cutting distance reaches up to 24 nm. The depth of subsurface deformed layers decreases with the increase in cutting speed between 50 and 300 m/s. The depth of subsurface deformed layer increases with cutting depth, proportionally, and basically remains unchanged when the cutting depth reaches over 6 nm.
This paper investigates the effect of vibration applied in feed direction on the burr generation mechanism in vibration-assisted micro milling. Kinematic analysis and finite element simulation are conducted for micro slot milling. Due to the vibration assistance in the feed direction, up milling and down milling takes place periodically on both of the cutting-in and cutting-out sides. This results in a reduction of burr formation. The results from both simulation and experiment confirm that the size of the top burrs in the down milling side of the slot are reduced significantly due to vibration assistance compared with conventional micro milling.
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