High-performance carbon fiber-reinforced polyether-ether-ketone(CF/PEEK)has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance.The drymac...High-performance carbon fiber-reinforced polyether-ether-ketone(CF/PEEK)has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance.The drymachining requirement tends to cause the cutting temperature to surpass the glass transition temperature(Tg),leading to poor surface quality,which is the bottleneck for dry milling of CF/PEEK.Temperature suppression has become an important breakthrough in the feasibility of high-speed dry(HSD)milling of CF/PEEK.However,heat partitioning and jet heat transfer mechanisms pose strong challenges for temperature suppression analytical modeling.To address this gap,an innovative temperature suppression analytical model based on heat partitioning and jet heat transfer mechanisms is first developed for suppressing workpiece temperature via the first-time implementation of an air jet cooling process in the HSD milling of UD-CF/PEEK.Then,verification experiments of the HSD milling of UD-CF/PEEK with four fiber orientations are performed for dry and air jet cooling conditions.The chip morphologies are characterized to reveal the formation mechanism and heat-carrying capacity of the chip.The milling force model can obtain the force coefficients and the total cutting heat.The workpiece temperature increase model is validated to elucidate the machined surface temperature evolution and heat partition characteristics.On this basis,an analytical model is verified to predict the workpiece temperature of air jet cooling HSD milled with UD-CF/PEEK with a prediction accuracy greater than 90%.Compared with those under dry conditions,the machined surface temperatures for the four fiber orientations decreased by 30%–50%and were suppressed within the Tg range under air jet cooling conditions,resulting in better surface quality.This work describes a feasible process for the HSD milling of CF/PEEK.展开更多
This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike...This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB3206700)the Fundamental Research Funds for the Central Universities,China(Grant No.2023CDJYXTD-003)the Natural Science Foundation of Chongqing,China(Grant No.2022NSCQMSX2038).
文摘High-performance carbon fiber-reinforced polyether-ether-ketone(CF/PEEK)has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance.The drymachining requirement tends to cause the cutting temperature to surpass the glass transition temperature(Tg),leading to poor surface quality,which is the bottleneck for dry milling of CF/PEEK.Temperature suppression has become an important breakthrough in the feasibility of high-speed dry(HSD)milling of CF/PEEK.However,heat partitioning and jet heat transfer mechanisms pose strong challenges for temperature suppression analytical modeling.To address this gap,an innovative temperature suppression analytical model based on heat partitioning and jet heat transfer mechanisms is first developed for suppressing workpiece temperature via the first-time implementation of an air jet cooling process in the HSD milling of UD-CF/PEEK.Then,verification experiments of the HSD milling of UD-CF/PEEK with four fiber orientations are performed for dry and air jet cooling conditions.The chip morphologies are characterized to reveal the formation mechanism and heat-carrying capacity of the chip.The milling force model can obtain the force coefficients and the total cutting heat.The workpiece temperature increase model is validated to elucidate the machined surface temperature evolution and heat partition characteristics.On this basis,an analytical model is verified to predict the workpiece temperature of air jet cooling HSD milled with UD-CF/PEEK with a prediction accuracy greater than 90%.Compared with those under dry conditions,the machined surface temperatures for the four fiber orientations decreased by 30%–50%and were suppressed within the Tg range under air jet cooling conditions,resulting in better surface quality.This work describes a feasible process for the HSD milling of CF/PEEK.
基金supported in part by the National Key Research and Development Program of China under Grant 2022YFB3207301Shandong Provincial Natural Science Foundation under Grant No.ZR2024ZD08.
文摘This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.
