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RISS 인기검색어
- 검색키워드
- 저자 : Daochun Xu (검색결과 6 건)
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Deformation temperature and material constitutive model of cupronickel B10
Ning Lei,Daochun Xu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
Cupronickel B10—an important material used in aircraft carriers—exhibits excellent electrochemical and mechanical properties, such as high corrosion resistance and weldability. The Split-Hopkinson pressure bar (SHPB) test is a classical method to obtain the dynamic mechanical properties of solid materials. However, the deformation temperature has long been ignored in SHPB studies, which results in low accuracy of the material constitutive model. Thus, in this study, a new method for obtained the deformation temperature was proposed and the modified material equation was validated using experimental data. Quasi-static compression and SHPB experiments were conducted with a thermocouple. The results revealed that the deformation temperature of the quasi-static tests was nearly zero, whereas that of the SHPB experiments ranged from 40 to 90 °C. Therefore, the method developed to describe the deformation temperature can be used to improve the precision of SHPB experiments, as demonstrated for the case of cupronickel B10.
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Research on the sticking-sliding contact ratio in high-speed cutting of cupronickel B10
Miaoxuan Li,Daochun Xu,Ziyi Cui,Zhi Xie 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
Accurate understanding of the frictional behavior at the tool-chip interface is critical for the cutting process. To quantitatively analyze the ratio of the sticking contact length to tool-chip contact interface length, a concise calculation model was proposed. Orthogonal cutting experiments and friction experiments were conducted to acquire the friction coefficients for use as input parameters to the model. Calculations found that the ratio, the sliding contact length, and the tool-chip contact interface length showed downward tendencies with increasing cutting speed. The maximum value of the ratio was 63.2 %, achieved at 1000 m/min, whereas the minimum was 58.6 %, achieved at 800 m/min. Furthermore, as the cutting speed rises, the sliding and apparent friction coefficients decrease, while the sticking friction coefficient remains nearly constant. The findings are helpful to improve people's cognition of sticking-sliding contact, the quality of machining, and determine the thickness and length of the tool coating.
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Zhi Xie,Daochun Xu,Ziyi Cui,Miaoxuan Li 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3
Cupronickel B10—an important material widely used in the aero industry—has excellent mechanical and physical properties, such as corrosion resistance and ductility. The present study conducted a quasi-static test and split Hopkinson pressure bar (SHPB) test to obtain the quasi-static and dynamic mechanical properties of cupronickel B10, respectively. In these two experiments, the parameters needed for material constitutive models in cutting simulation are derived. However, the impact deformation temperature in the SHPB experiment has long been ignored, resulting in insufficient simulation accuracy. Hence, the impact deformation temperature is referenced to modify material constitutive models. Simulation results of the models are validated in orthogonal cutting experiments. Validation shows that Johnson-Cook class models are superior in simulating the chip form while Drucker-Prager class models are suitable for forecasting the cutting force and temperature. In particular, modified Drucker-Prager models can reduce the error of cutting force F C to 18.01 %.
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Cutting zone area and chip morphology in high-speed cutting of titanium alloy Ti-6Al-4V
Qingchan Ke,Daochun Xu,Danping Xiong 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
The titanium alloy Ti-6Al-4V has superior properties but poor machinability, yet is widely used in aerospace and biomedical industries. Chip formation and cutting zone area are important factors that have received limited attention. Thus, we propose a high-speed orthogonal cutting model for serrated chip formation. The high speed orthogonal cutting of Ti-6Al-4V was studied with a cutting speed of 10-160 m/min and a feed of 0.07- 0.11 mm/r. Using theoretical models and experimental results, parameters such as chip shape, serration level, slip angle, and shear slip distance were investigated. Cutting zone boundaries (tool-chip contact length, length of shear plane, and critical slip plane) and cutting zone area were obtained. The results showed that discontinuous, long-curling, and continuous chips were formed at low, medium, and high speeds, respectively. Serration level, shear slip distance, and slip angle rose with increasing cutting speed. The length of shear plane, tool-chip contact, and critical slip plane varied subtly with increased cutting speed, and rose noticeably with increased feed. Cutting zone area grew weakly with increased cutting speed, levelling off at high cutting speed; however, it rose noticeably with increased feed. This study furthers our understanding of the shear slip phenomenon and the mechanism of serrated chip formation.
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A Numerical Approach for Lightning Impulse Flashover Voltage Prediction of Typical Air Gaps
Qiu, Zhibin,Ruan, Jiangjun,Huang, Congpeng,Xu, Wenjie,Huang, Daochun The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
This paper proposes a numerical approach to predict the critical flashover voltages of air gaps under lightning impulses. For an air gap, the impulse voltage waveform features and electric field features are defined to characterize its energy storage status before the initiation of breakdown. These features are taken as the input parameters of the predictive model established by support vector machine (SVM). Given an applied voltage range, the golden section search method is used to compute the prediction results efficiently. This method was applied to predict the critical flashover voltages of rod-rod, rod-plane and sphere-plane gaps over a wide range of gap lengths and impulse voltage waveshapes. The predicted results coincide well with the experimental data, with the same trends and acceptable errors. The mean absolute percentage errors of 6 groups of test samples are within 4.6%, which demonstrates the validity and accuracy of the predictive model. This method provides an effectual way to obtain the critical flashover voltage and might be helpful to estimate the safe clearances of air gaps for insulation design.
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A Numerical Approach for Lightning Impulse Flashover Voltage Prediction of Typical Air Gaps
Zhibin Qiu,Jiangjun Ruan,Congpeng Huang,Wenjie Xu,Daochun Huang 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
This paper proposes a numerical approach to predict the critical flashover voltages of air gaps under lightning impulses. For an air gap, the impulse voltage waveform features and electric field features are defined to characterize its energy storage status before the initiation of breakdown. These features are taken as the input parameters of the predictive model established by support vector machine (SVM). Given an applied voltage range, the golden section search method is used to compute the prediction results efficiently. This method was applied to predict the critical flashover voltages of rod-rod, rod-plane and sphere-plane gaps over a wide range of gap lengths and impulse voltage waveshapes. The predicted results coincide well with the experimental data, with the same trends and acceptable errors. The mean absolute percentage errors of 6 groups of test samples are within 4.6%, which demonstrates the validity and accuracy of the predictive model. This method provides an effectual way to obtain the critical flashover voltage and might be helpful to estimate the safe clearances of air gaps for insulation design.
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