Skip to main content

Research Repository

Advanced Search

Fractal Analysis on Machined Surface Morphologies of Soft-Brittle KDP Crystals Processed by Micro Ball-End Milling

Liu, Qi; Cheng, Jian; Liao, Zhirong; Liu, Mingyu; Chen, Mingjun; Zhao, Linjie; Lei, Hongqin; Ding, Wenyu

Fractal Analysis on Machined Surface Morphologies of Soft-Brittle KDP Crystals Processed by Micro Ball-End Milling Thumbnail


Authors

Qi Liu

Jian Cheng

Mingyu Liu

Mingjun Chen

Linjie Zhao

Hongqin Lei

Wenyu Ding



Abstract

The micro-defects on KH2PO4 (KDP) optic surfaces are mainly repaired by the micro-milling technique, while it is very easy to introduce brittle cracks on repaired surfaces, as KDP is soft and brittle. To estimate machined surface morphologies, the conventional method is surface roughness, but it fails to distinguish ductile-regime machining from brittle-regime machining directly. To achieve this objective, it is of great significance to explore new evaluation methods to further characterize machined surface morphologies. In this study, the fractal dimension (FD) was introduced to characterize the surface morphologies of soft-brittle KDP crystals machined by micro bell-end milling. The 3D and 2D fractal dimensions of the machined surfaces and their typical cross-sectional contours have been calculated, respectively, based on Box-counting methods, and were further discussed comprehensively by combining the analysis of surface quality and textures. The 3D FD is identified to have a negative correlation with surface roughness (Sa and Sq), meaning the worse the surface quality the smaller the FD. The circumferential 2D FD could quantitively characterize the anisotropy of micro-milled surfaces, which could not be analyzed by surface roughness. Normally, there is obvious symmetry of 2D FD and anisotropy on the micro ball-end milled surfaces generated by ductile-regime machining. However, once the 2D FD is distributed asymmetrically and the anisotropy becomes weaker, the assessed surface contours would be occupied by brittle cracks and fractures, and corresponding machining processes will be in a brittle regime. This fractal analysis would facilitate the accurate and efficient evaluation of the repaired KDP optics by micro-milling.

Citation

Liu, Q., Cheng, J., Liao, Z., Liu, M., Chen, M., Zhao, L., …Ding, W. (2023). Fractal Analysis on Machined Surface Morphologies of Soft-Brittle KDP Crystals Processed by Micro Ball-End Milling. Materials, 16(5), Article 1782. https://doi.org/10.3390/ma16051782

Journal Article Type Article
Acceptance Date Feb 16, 2023
Online Publication Date Feb 21, 2023
Publication Date 2023-03
Deposit Date May 11, 2023
Publicly Available Date May 12, 2023
Journal Materials
Electronic ISSN 1996-1944
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 16
Issue 5
Article Number 1782
DOI https://doi.org/10.3390/ma16051782
Keywords KDP crystal; fractal dimension; box-counting approach; brittle-to-ductile transition; surface morphology analysis; material removal modes
Public URL https://nottingham-repository.worktribe.com/output/17665692
Publisher URL https://www.mdpi.com/1996-1944/16/5/1782

Files





You might also like



Downloadable Citations