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Chip Control Analysis in Low-Frequency Vibration-Assisted Drilling of Ti–6Al–4V Titanium Alloys
Haojun Yang,Yan Chen,Jiuhua Xu,Mathieu Ladonne,Julian Lonfier,Wenfeng Ding 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.4
In this study, control research of chip morphology and removal is conducted theoretically and experimentally on the basis ofthe low-frequency vibration-assisted drilling process of titanium alloy. The chip morphology prediction model is establishedon the basis of the modifi ed kinematic model, in which the shear angle variation, critical cutting thickness, and stiff ness ofa vibration generator system are considered. In terms of chip removal monitoring, a new monitoring method based on highspeed camera is proposed in this paper. And the reliability of the new method is verifi ed by comparing the signals obtainedby the power sensor and the force sensor. An empirical prediction model for chip removal is also established on the basis ofthe modifi ed kinematical model, the chip morphology prediction model, and the force balance analysis of fragmental chips. Validation experiments show that the mean error of chip radian, which can refl ect the diff erence between the predicted chipmorphology and the experimental one, is 6%. The mean error of the predicted chip removal index compared with the experimentalone is 10.4%. The results obtained show that chip removal can be controlled eff ectively by low rotation speed, smallchip radian, light chip weight, high minimum quantity lubrication cooling pressure, and high oscillation frequency. On thebasis of the prediction model of chip removal, the eff ects of drilling parameters on chip removal behavior are analyzed, andthe optimal drilling parameter combination with highest processing effi ciency is given.
Haojun Fan,Ke Zeng,Qiao Guo,Shuai Gao,Dimeng Wu,Gang Yang 한국고분자학회 2012 Macromolecular Research Vol.20 No.1
A series of new asymmetric biphenyl dianhydrides, 2-phenoxy(o-methylphenoxy, m-methylphenoxy, and p-methylphenoxy)-4,4,5,5-biphenyltetracarboxylic dianhydrides, was readily synthesized using a five-step route. A new symmetric biphenyl dianhydride, 2,2-di(o-methylphenoxy)-4,4,5,5-biphenyltetracarboxylic dianhydride, was also synthesized using the similar procedure. The polyimides were prepared from such new dianhydrides and commercial diamines by high-temperature one-step polymerization. The asymmetric and symmetric substituent solubility and thermal property relationships of the resulting polyimides were investigated. Interestingly, the thermally reversible sol–gel transitions were observed for the polymer solutions of the polyimides derived from those asymmetric dianhydrides and 1,4-phenylenediamine (p-PDA). Unexpectedly, the polyimides derived from asymmetric dianhydrides did not show better organosolubility than those of the homologous polyimides derived from symmetric dianhydrides. The structures of the substituents (phenoxy, o-methylphenoxy, m-methylphenoxy and p-methylphenoxy)have a significant effect on both the solubility and the thermal properties of these polyimides. The polyimides derived from asymmetric dianhydrides show enhanced thermal properties relative to the symmetric dianhydridesderived polyimides. These results can be attributed to their different degrees of molecular packing revealed by wideangle X-ray diffraction measurements.
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.