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Chaoren Yan,Yan Chen,Ning Qian,Nan Guo,Yongqing Wang,Haojun Yang,Biao Zhao 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.8
Low frequency vibration-assisted drilling (LFVAD) of CFRP/Ti stacks is a promising method of one-shot drilling to increase efficiency and extend tool life while adaptive approaches are applied to adjust the cutting parameters in each layer. Thus, the interfacial recognition method is significant to automatically change the cutting parameters. In this paper, two recognition methods are proposed based on the analysis of the features of cutting forces under the LFVAD process in both time and frequency domains. With the recorded thrust force signals at different wear stages, both the proposed methods identify the transition point when the drill bit starts to contact the Ti layer within allowable time delay. Compared with the traditional threshold method, the time domain method and the frequency domain method respectively increase the identifying speed by 19.8% and 46.7%, besides the reduction of implementation cost. In contrast, the time domain method reduces the programming and calculation time, while the frequency domain method improves the average recognition speed. Furthermore, an adaptive drilling system embedded with the established time-domain method is designed and the accuracy of the method is proved of 100% in a drilling test of all 20 CFRP/Ti stack holes. Moreover, the effect of the adaptive LFVAD process in improving tool wear and increasing machining efficiency is verified by reducing the force growth rate by 11.7% and time decrease of 37% in a hole-making cycle compared with the traditional LFVAD process.
Yuhong Liang,Yan Chen,Binbin Chen,Baopeng Fan,Chaoren Yan,Yucan Fu 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.7
Ultrasonic vibration assisted grinding (UVAG) is an effective method for edge trimming to improve the mechanical integrity of carbon fiber reinforced polymer (CFRP). However, due to the high heat resistance, abrasiveness and powdery chip of CFRP, serious tool clogging, rapid tool wear and poor surface are still considerable problems to the industry. In this paper, monolayer brazed diamond grinding tools with defined grain distribution are designed in order to solve the above problems. The maximum undeformed chip thickness based on UVAG was analyzed. A mathematical grinding force model was established based on monolayer brazed diamond tools. The UVAG experiments using different grain inter-row spacing diamond tools were carried out. The grinding force and surface morphology were investigated and compared. It was found that the predicted grinding force values were consistent with the experimental results. Additionally, the force was strongly related to the grain inter-row spacing. When employing the tool with the grain inter-row spacing of 1.2 mm, the grinding force was highest and the roughness of the surface was better due to more active grits and interaction-overlap areas.