Mechanism of chip formation and surface-defects in orthogonal cutting of soft-brittle potassium dihydrogen phosphate crystals
Liu, Qi and Liao, Zhirong and Cheng, Jian and Xu, Dongdong and Chen, Mingjun (2021) Mechanism of chip formation and surface-defects in orthogonal cutting of soft-brittle potassium dihydrogen phosphate crystals. Materials and Design, 198. 109327. ISSN 0264-1275 (https://doi.org/10.1016/j.matdes.2020.109327)
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Abstract
Micromachining repair of surface defects on KH2PO4 (KDP) optics is an emerging technique in the construction of Inertial Confinement Fusion facilities for obtaining clean nuclear fusion energy. However, this method is yet facing considerable challenges owing to the soft-brittle nature of single-crystal KDP, hence it is necessary to understand its ductile-regime cutting mechanism to generate crack-free surfaces. This paper seeks to investigate the evolution of different cutting mechanism with the change of uncut chip thickness (UCT) in KDP orthogonal cutting processes. A transition of cutting modes from plastic cutting to shear-crack cutting and then fracture cutting with the rise of UCT has been revealed. To explain these cutting phenomena, a novel theoretical model was proposed by calculating the specific energy dissipation for crack/fracture propagations during cutting processes based on fracture mechanics. This analytical model was well validated by the analysis of cutting forces and machined surface quality. Nevertheless, three kinds of surface defects have been observed, i.e. micro pits, micro craters and edge chipping. These surface defects were caused by tearing and spalling of materials with elastic recovery, crack propagation along cleavage planes with ploughing effect, and the peeling away of large-size fracture, respectively. The presented results of great significance for promoting the application of micromachining processes in future engineering repair of KDP optics.
ORCID iDs
Liu, Qi ORCID: https://orcid.org/0000-0002-1960-7318, Liao, Zhirong, Cheng, Jian, Xu, Dongdong and Chen, Mingjun;-
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Item type: Article ID code: 81156 Dates: DateEvent15 January 2021Published13 November 2020Published Online11 November 2020AcceptedSubjects: Technology > Mechanical engineering and machinery Department: Faculty of Engineering > Design, Manufacture and Engineering Management Depositing user: Pure Administrator Date deposited: 17 Jun 2022 05:39 Last modified: 11 Nov 2024 13:31 URI: https://strathprints.strath.ac.uk/id/eprint/81156