Study on Strain Energy Transfer and Efficiency in Spatial Micro-forming of Metal

Zhaojie Chen,Jin Xie,Quanpeng He,Dongsheng Ge,Kuo Lu,Chaolun Feng 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2

In spatial micro-fabrication on metallic surface, the mechanical machining consumes material shear deformation energy, while the laser machining energy is greatly converted into material melting heat energy. In production, the micron-scale material-removal machining requires the CNC system to long-time tool path interpolation for high energy-consumption. According to dynamics and kinematics of metallic plastic deformation, a strain energy transfer is proposed to deform micro-topographic shapes by differentiated surface stress. The objective is to realize the precision forming of spatial microstructure surface through the strain energy conversion and conservation. First, the energy transfer and strain variations were modelled in relation to die curvature radius, workpiece thickness, initial microstructure angle and depth. Then, the strain energy consumption was investigated in relation to material properties, die movement, and micro dimensions. Finally, it was applied to industrial cold-pressing. It is shown that the strain energy of a single microstructure formation transfers from centre to outer part. The spatial microstructure forming may change from diversified strain stage to uniform strain state with the highest energy efficiency at a critical strain energy, while the surface roughness remains unchanged. Under the strain energy transfer, the microstructure shape changes with increasing energy consumption to a critical value. The metal compressive strength, die curvature radius and workpiece thickness promotes energy consumption, while descending velocity promotes processing efficiency. By controlling the energy conversion, the spatial microstructure sizes may be fabricated with an error of about 1.0% and the energy consumption of about 10 mm3/J. In industrial production, it contributes high energy efficiency without coolant pollutant in contrast to mechanical machining and laser machining. As a result, the strain energy conversion and conservation may be regarded as an evaluation for an eco-friendly micro-fabrication.

In Situ Growth of MOF-Derived NaCoPO4@Carbon for Asymmetric Supercapacitive and Water Oxidation Electrocatalytic Performance

Peng Guo,Zhaojie Wang,Hongyu Chen,Shaohui Ge,Chen Chen,Haowei Wang,Jinbao Zhang,Minglei Hua,Shuxian Wei,Xiaoqing Lu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01

The increasing energy crisis promotes the study on novel electrode materials with high performance for supercapacitive storage and energy conversion. Transition metal phosphates have been reported as a potential candidate due to the unique coordination and corresponding electronic structure. Herein, we adopted a facile method for preparing NaCoPO4@C derived from a metal organic framework (MOF) as a bifunctional electrode. ZIF-67 was synthesized before a refluxing process with Na2HPO4 to form a precursor, which is transformed into the final product via calcination in different atmospheres. Specifically, the resultant NaCoPO4@C exhibits a high specific capacitance of 1178.7 F g -1 at a current density of 1 A g -1 for a supercapacitor. An asymmetric supercapacitor (ASC) assembled with active carbon displays a high capacitance of 163.7 F g -1 at 1 A g -1. In addition, as an oxygen evolution reaction (OER) catalyst, the NaCoPO4@C electrode requires only 299 mV to drive a current density of 10 mA cm -2. These results suggest that the rational design of MOF-derived NaCoPO4@C provides a variety of practical applications in electrochemical energy conversion and storage.

Experimental and analytical study on continuous GFRP concrete decks with steel bars

Zhaojie Tong,Yiyan Chen,Qiao Huang,Xiaodong Song,Bingqing Luo,Xiang Xu 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.6

A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

Unbalanced control strategy featuring inconsistent sub‑module voltage for modular multilevel converter–bidirectional DC–DC converter

Peng Chen,Fei Xiao,Jilong Liu,Zhichao Zhu,Zhaojie Huang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.5

Modular multilevel converter–bidirectional DC–DC converter (MMC–BDC) is a prospective solution for the bidirectional DC–DC power conversion between medium-voltage DC (MVDC) bus and distributed energy storage system. Researchers have studied its application in the shipboard power system. In face of distributed energy storage devices with discrepant state of charge (SOC), the sub-modules (SMs) of MMC–BDC should work under inconsistent power to unify the SOC level. The existing unbalanced SM power control strategies fail to consider unbalanced operation range and efficiency. Therefore, this study proposes a novel unbalanced control strategy based on the feedforward compensation method, which is characterized by inconsistent SM voltage. Comparisons are made to demonstrate the advantages of the proposed strategy over traditional ones, and the dynamic characteristics are analyzed. Simulation and experiment results illustrate the effectiveness of the proposed unbalanced operation strategy.

Controlled Synthesis of FeSe2 Nanoflakes Toward Advanced Sodium Storage Behavior Integrated with Ether-Based Electrolyte

Yalan Chen,Jingtong Zhang,Haijun Liu,Zhaojie Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.12

Sodium ion batteries based on the more sodium source reserve than that of lithium have been designed as promising alternatives to lithium ion batteries. However, several problems including unsatisfied specific capacity and serious cyclic stability must be solved before the reality. One of the effective approaches to solve the abovementioned problems is to search for suitable anode materials. In this work, we designed and prepared FeSe2 nanoflakes via a simple hydrothermal method which can be adjusted in composition by Fe precursor. As a potential anode for sodium storage, the optimized FeSe2 electrode was further evaluated in different electrolytes of NaClO4 in propylene carbonate/fluoroethylene carbonate and NaCF3SO3 in diethylene glycol dimethyl ether. The capacity was about 470 mA h g-1 and 535 mA h g -1 at 0.5 Ag-1, respectively, in the voltage between 0.5V and 2.9V in the cycle of stabilization phase. Superior performance both in capacity and in stability was obtained in ether-based electrolyte, which affords the property without plugging the intermediates of transition metal dichalcogenides during charge/discharge processes.

Control Strategy for Bidirectional DC-DC Converter Based on Cascade Connection of LC Filter and DAB Converter

Zhu Zhichao,Xiao Fei,Liu Jilong,Chen Peng,Ren Qiang,Huang Zhaojie 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3

The dual active bridge (DAB) DC-DC converter has broad prospects for use, for example, energy-storage systems, electric vehicles, and DC distribution network. To improve the quality of bus current, researchers often cascade fi lter inductors to the DC port of DAB converter. If so, the system may be instable and oscillate because the converter is turned into a cascaded structure of LC fi lter and DAB converter. In addition, it is found that the output current is used as the feedback variable for closed-loop control in bidirectional transmission, which will increase the number of sensors. And, the current of the energy storage unit (ESU) cannot be directly controlled when the ESU discharges. To solve these problem, this paper proposes a control strategy based on notch fi lter (NF) regulator. Regardless of whether power fl ows in the forward or reverse direction, the fi lter inductor current is always regarded as control objectives. For this purpose, NF regulator is introduced into the forward path of the current loop to suppress the oscillation of the LC fi lter inductor current. Finally, the eff ectiveness of the theoretical analysis and proposed strategy are verifi ed by simulations and experiments.

Optimal modulation strategy based on fundamental reactive power for dual‑active‑bridge converters

Zhichao Zhu,Fei Xiao,Jilong Liu,Peng Chen,Zhaojie Huang,Qiang Ren 전력전자학회 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.12

Dual-active-bridge (DAB) converters are widely used in bidirectional power transmission and voltage conversion. At present, phase-shift (PS) control is one of the most common and mature control methods for DAB converters. To improve the efficiency and performance of DAB converters, the soft switching and current stress are optimized by increasing the inner phaseshift ratio. However, under different PS controls, it is difficult to establish a unified mathematical model using the traditional instantaneous integral method. To solve this problem, based on the approximate equivalence of the fundamental component of a high-frequency link decomposed by Fourier series, an optimal fundamental modulation strategy is proposed, which takes the fundamental reactive power as the objective of optimization. The trajectories for each of the electrical parameters are analyzed intuitively through a vector diagram of the phasor. A practical optimal control strategy scheme for engineering is obtained. Finally, the effectiveness of the theoretical analysis and the proposed method are verified by experimental results.

Catalytic combustion of volatile aromatic compounds over CuO-CeO2 catalyst

Hongmei Xie,Qinxiang Du,Hui Li,Guilin Zhou,Shengming Chen,Zhaojie Jiao,Jianmin Ren 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.7

Ce1−xCuxO2 oxide solid solution catalysts with different Ce/Cu mole ratios were synthesized by the one-pot complex method. The prepared Ce1−xCuxO2 catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). Their catalytic properties were also investigated by catalytic combustion of phenyl volatile organic compounds (PVOCs: benzene, toluene, xylene, and ethylbenzene) in air. XRD analysis confirmed that the CuO species can fully dissolve into the CeO2 lattice to form CeCu oxide solid solutions. XPS and H2-TPR results indicated that the prepared Ce1−xCuxO2 catalysts contain abundant reactive oxygen species and superior reducibility. Furthermore, the physicochemical properties of the prepared Ce1−xCuxO2 catalysts are affected by the Ce/Cu mole ratio. The CeCu3 catalyst with Ce/Cu mole ratio of 3.0 contains abundant reactive oxygen species and exhibits superior catalytic combustion activity of PVOCs. Moreover, the ignitability of PVOCs is also affected by the respective physicochemical properties. The catalytic combustion conversions of ethylbenzene, xylene, toluene, and benzene are 99%, 98.9%, 94.3%, and 62.8% at 205, 220, 225, and 225 oC, respectively.