Convective Heat Transfer Coeicient Model Under Nanoluid Minimum Quantity Lubrication Coupled with Cryogenic Air Grinding Ti–6Al–4V

Jianchao Zhang,Wentao Wu,Changhe Li,Min Yang,Yanbin Zhang,Dongzhou Jia,Yali Hou,Runze Li,Huajun Cao,Hafiz Muhammad Ali 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

Under the threat of serious environmental pollution and resource waste, sustainable development and green manufacturing have gradually become a new development trend. A new environmentally sustainable approach, namely, cryogenic air nanofluid minimum quantity lubrication (CNMQL), is proposed considering the unfavorable lubricating characteristic of cryogenic air (CA) and the deficient cooling performance of minimum quantity lubrication (MQL). However, the heat transfer mechanism of vortex tube cold air fraction by CNMQL remains unclear. The cold air fraction of vortex tubes influences the boiling heat transfer state and cooling heat transfer performance of nanofluids during the grinding process. Thus, a convective heat transfer coefficient model was established based on the theory of boiling heat transfer and conduction, and the numerical simulation of finite difference and temperature field in the grinding zone under different vortex tube cold air fractions was conducted. Simulation results demonstrated that the highest temperature initially declines and then rises with increasing cold air fraction. Afterward, this temperature reaches the lowest peak (192.7 °C) when the cold air fraction is 0.35. Experimental verification was conducted with Ti–6Al–4V to verify the convective heat transfer coefficient model. The results concluded that the low specific grinding energy (66.03 J/mm 3 ), high viscosity (267.8 cP), and large contact angle (54.01°) of nanofluids were obtained when the cold air fraction was 0.35. Meanwhile, the lowest temperature of the grinding zone was obtained (183.9 °C). Furthermore, the experimental results were consistent with the theoretical analysis, thereby verifying the reliability of the simulation model.

Superhydrophobic Ag–Cu Composite Metal Film as Surface-Enhanced Raman Scattering Substrate

Jianchao Wang,Hongsheng Luo,Xuliang Song,Xihong Zu,Jie Zhang,Yuxin Gu,Guobin Yi 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.7

In this paper, a superhydrophobic Ag–Cu composite metal film was fabricated as surface-enhanced Raman scattering substrate. Ag–Cu composite metal film was prepared from galvanic displacement on commercial copper foil. The prepared silver films were modified by PFDT to create a stable superhydrophobic SERS platform. Superhydrophobic substrates were characterized by a variety of characterization methods, including scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis, XPS and Raman spectra. The superhydrophobic substrate could enrich probing molecules with the volatilization of solvent. Mathematical model was presented and applied to investigate concentration factor of hydrophobic substrate. The measurements were in good agreement with the calculation results. The superhydrophobic Ag–Cu composite metal film can reduce the detection limits and provide a new way to prepare efficient SERS substrates for ultra-low concentration detection.

Application of Resonance Demodulation in Rolling Bearing Early Fault Feature Extraction Based on Electronic Resonance

Zhe Wu,Jianchao Zhang 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.12

Resonance demodulation is a commonly used rolling bearing fault diagnosis method, but resonance frequency of traditional resonance demodulation technology has a certain discreteness due to differences in terms of processing, testing and installation of sensor to collect fault information, so parameter of band-pass filter needs manual pre-determination. At the same time, as information of early bearing minor fault is often submerged in strong background noise, signal to noise ratio is low. Application of traditional resonance demodulation method to improve signal to noise ratio is with limited capability, and diagnosis effect is not obvious. This paper makes use of the equivalence of electrical resonance system and mechanical resonance system and gains resonance of sensor output signal through electrical resonator, which breaks through shortcomings of traditional method, achieve ultra narrow brand high-resolution detection, and improves signal to noise ratio of fault feature signal. Finally, verification is done through simulation fault bearing signal and actually collected fault signal. The results proves validity and effectiveness of the proposed method which has an important guiding significance for engineering

An analytical solution for one-dimensional contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries

Xibin Li,Jianchao Sheng,Zhiqing Zhang,Zhe Wang 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.4

An analytical method is proposed to solve the contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries. By virtue of the separation of variables scheme, the governing equation for contaminant diffusion is split into two ordinary differential equations, and the corresponding general solutions are obtained. By utilizing the initial, continuity and boundary conditions of the system, and the orthogonality of trigonometric functions, the analytical solution for contaminant concentration in the double-layered contaminated soil is derived, which can be further used to describe the average degree of diffusion. The reliability and accuracy of the developed solution is verified by comparing with the existing analytical solution and numerical simulation results. Selected numerical examples are further presented to analyze the influence of the imperfect diffusion boundaries on the spatial/time distribution of contaminant concentration, average degree of diffusion and mass flux. The results show that greater imperfect diffusion capacity coefficients lead to lower contaminant concentration distribution within the entire depth range and higher average degree of diffusion for a given time. Particularly, it only takes 23.32 years to complete the entire diffusion process when imperfect diffusion capacity coefficients are infinite. The developed solution can provide useful guidance for engineering practice.

Simulation and experiment study of burrs in micro-milling Zr-based metallic glass

Jiachun Wang,Zhenhong Zhang,Chuang Zhang,Jiabin Fu,Jianchao Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7

Metallic glass has been widely used in making micro parts and equipment due to its excellent physical and chemical performance. A large quantity of burrs is produced in the micro-milling process that is hard to remove and seriously affects the quality and precision of the parts. Burrs should be effectively restrained; however, the burrs’ type, position and the effect of milling parameters on burrs’ generation in micro-milling metallic glass have not been systematically studied. In this paper, by using 3-D FEM simulation and taking micro-milling experiments of Zr-based metallic glass (Vit1), the burrs in flat-end milling and ball-end milling micro grooves were investigated. The burrs’ type and position were observed and summarized, the formation process of various burrs was analyzed in detail, and the influence of cutting parameters on burrs was clarified. Comparing the simulation and experiment result, we could confirm that the top burr and the entrance burr were produced during the processing of the flatend milling cutter, and ball-end milling cutter effectively inhibits the production of the top burr but takes no actions on burrs’ generation at the entrance and the bottom of the groove. The main cause of the top burr is the extrusion of the tool, and the extrusion of the cutting layer metal and chip accumulation were the main reason for entrance and exit burrs. Reducing the axial cutting depth could effectively restrain the generation of burrs for both two kinds of milling tools.

Weathering Characteristics of White Marble Relics Around the Hall of Supreme Harmony (Taihe Dian) in the Forbidden City

Yang Wu,Bingjian Zhang,Jianchao Zhang,Kuanrong Zhai,Li Luo 대한토목학회 2023 KSCE JOURNAL OF CIVIL ENGINEERING Vol.27 No.2

Fangshan Hanbaiyu is a typical white marble in China that was mainly used in high-grade royal buildings represented by the Forbidden City. Over centuries of natural erosion, most marble artifacts have undergone a variety of deterioration. Based on the deterioration investigation of a total of 726 balusters, 559 dragon heads, and 698 frieze panels around the Hall of Supreme Harmony (Taihe Dian), nondestructive testing technology, including portable x-ray fluorescence, colorimeter, and surface hardness tester, were also used to evaluate the weathering degree and analyze the relationship between the deterioration patterns and the type and spatial distribution of marble components. The results show that the temperature difference stress caused by solar radiation and the erosion caused by rainwater are the main reasons for the weathering. This explains why the components facing the South and East are more deteriorated. In addition, an evaluation method for stone relics deterioration based on three indicators (surface integrity, surface color, and surface hardness) of stone relics was established, and the health index of 12 typical marble components was calculated by this method, the values showed a good linear correlation with the field survey, which can provide a useful reference for subsequent investigation and assessment of the deterioration of the marble relics.