Abstract
Diamond fly cutting (DFC) is a technique which can accurately and efficiently generate shapes in the micro & nanometer scale. However, the miniaturization of parts and the small depth of cut make the materials removal or deformation in the DFC different from the common machining technology. It is difficult to investigate materials deformation or failure by means of pure macroscopic or microscopic scale method. Multiscale method can study material behavior across different length & temporal scale simultaneously which is helpful about uncover important properties and materials response in DFC and thus being employed in this work. The results show that several slipping-dislocation systems are generated with feeding of the cutting tool while most of them extend along the rake angle of cutting tool. The plastic deformation is a discrete process in the atomic scale while it is generally considered as continuum process in the macroscopic scale. The first slipping-band becomes the boundary of the following slipping process which leads to the different generation mechanism of the following dislocation. The dislocation density, cross-slip and junction increase with the increasing of strain rate. The dislocation density is gradually decreased far away from materials surface which justifies that most of the dislocation ought to be generated by the surface defects than by the internal defects. The dislocation can also be regenerated by the complicated dynamic behavior of the existing dislocations without external loading which lead to the complexity of the deformation process. The slipping-band can be considered as the green-channel of stress relaxation as the maximum stress is originated at the tool-workpiece contact area and gradually decreased in the further area.
Highlights
Diamond fly cutting (DFC) is a technique which can remove very small amount of materials and the generated surface or feature can be characterized by stringent tolerances on geometry characteristics
Several important features of DFC are the material removal volume, the depth of cut and the high cutting speed while the depth of cut lies in nanometer or micrometer length scale and the cutting speed can be as high as tens of meters per second
It is of great difficult to study the DFC using experiments because it is time consuming and expensive, model based numerical simulation provides an effective alternative for solving such problems
Summary
Minimum chip thickness effect, the surface generation in DFC is generally dominated by two processes: materials removal and ploughing/rubbing. Multiscale method offers the best choice for bridging the gap between experimental approach, theoretical analyzing and computational modeling on studying the behavior of materials under high strain rate. Understanding the fundamental physical mechanism behind DFC is a major scientific challenge and multiscale analysis is helpful about uncover the feature of DFC at different scale This is based on the judgment that multiscale method can be used to investigate the effects of hierarchy of internal structures on dynamic material behavior, making it realistic to understand fundamental mechanisms and avoid misunderstandings resulted by macroscopic observations and assumptions. Significant developments are acquired in materials simulation techniques, the goal of reliably predicting the properties and behaviors of materials processing (precision machining) has not yet been achieved This situation exists for several reasons which include lack of full understanding of material behavior at different scales, absence of scaling laws, computational limitations, and difficulties associated with experimental measurements of material properties at micro and nano scales. To uncover the initialization of materials removal and deformation in DFC and provide scientific guidance for process control
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