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Dai Q.,Nanjing University of Aeronautics and Astronautics | Huang W.,Nanjing University of Aeronautics and Astronautics | Wang X.,Nanjing University of Aeronautics and Astronautics | Wang X.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology
Langmuir | Year: 2015

Thermo-capillary migration is a phenomenon in which surface thermal gradients drive a liquid to flow from warm to cold regions without external forces. It is important to prevent the migration of liquid lubricants on rubbing surfaces. In this paper, a pattern of microdimples was proposed to obstruct the liquid migration induced by an omnidirectional thermal gradient. Microdimple patterns were fabricated on the surfaces of SUS316 stainless steel. Experiments were performed to investigate the influence of microdimple patterns with different geometric parameters on the migration behavior of paraffin oil. In particular, this study focused on the interfacial flowing near the microdimples. The results demonstrated that microdimples have a significant obstructive effect on migration, whereas dimples have a retaining effect, and the adjacent dimples have an interacting effect. © 2015 American Chemical Society. Source


Zhu Y.,Nanjing University of Aeronautics and Astronautics | Zhu Y.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology | Fu J.,Nanjing University of Aeronautics and Astronautics | Ju Z.,Nanjing University of Aeronautics and Astronautics | And 2 more authors.
Nami Jishu yu Jingmi Gongcheng/Nanotechnology and Precision Engineering | Year: 2013

To study the impact of material characteristics on the machining performance of hydrophilic fixed abrasive pad (FAP), K9 optical glass and silicon wafers were chosen as the work-pieces to explore the effect of machining sequence on the acoustic emission signal and friction coefficient during lapping. Scanning electron microscope (SEM) was employed to analyze the size and morphology of debris. Results show that material removal rate (MRR) varies greatly with the change of the machining sequence. Compared with the direct lapping of silicon wafer, if the silicon wafer is lapped after the lapping of a K9 glass work-piece, its MRR will greatly decrease. In contrast, the MRR of K9 glass is almost the same no matter whether it is lapped directly or after the lapping of a silicon wafer. The average surface roughness of both directly lapped silicon wafer and K9 glass is lower than that of work-pieces which are lapped after the lapping of the other. The size of most silicon debris is about 600 nm-1.5 μm, with clear edge; while that of K9 glass is around 300 nm-500 nm, edgeless. The greater size and clear edge of debris created during the lapping of silicon wafer are helpful for the self-conditioning process of hydrophilic FAP. Therefore, brittle materials such as silicon are helpful for the self-conditioning behavior of FAP. Source


Dai M.,Nanjing University of Aeronautics and Astronautics | Dai M.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology | Tang D.,Nanjing University of Aeronautics and Astronautics | Tang D.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology | And 3 more authors.
Robotics and Computer-Integrated Manufacturing | Year: 2013

The traditional production scheduling problem considers performance indicators such as processing time, cost, and quality as optimization objectives in manufacturing systems; however, it does not take energy consumption or environmental impacts completely into account. Therefore, this paper proposes an energy-efficient model for flexible flow shop scheduling (FFS). First, a mathematical model for a FFS problem, which is based on an energy-efficient mechanism, is described to solve multi-objective optimization. Since FFS is well known as a NP-hard problem, an improved, genetic-simulated annealing algorithm is adopted to make a significant trade-off between the makespan and the total energy consumption to implement a feasible scheduling. Finally, a case study of a production scheduling problem for a metalworking workshop in a plant is simulated. The experimental results show that the relationship between the makespan and the energy consumption may be apparently conflicting. In addition, an energy-saving decision is performed in a feasible scheduling. Using the decision method, there could be significant potential for minimizing energy consumption. © 2013 Elsevier Ltd. Source


Qu N.S.,Nanjing University of Aeronautics and Astronautics | Qu N.S.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology | Ji H.J.,Nanjing University of Aeronautics and Astronautics | Zeng Y.B.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology
International Journal of Advanced Manufacturing Technology | Year: 2014

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness. © 2014 Springer-Verlag London. Source


Huang W.,Nanjing University of Aeronautics and Astronautics | Huang W.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology | Wang X.,Nanjing University of Aeronautics and Astronautics | Wang X.,Jiangsu Key Laboratory of Precision and Micro Manufacturing Technology
Bioinspiration and Biomimetics | Year: 2013

In this paper, an observation on the toe pad of a newt was carried out. It was found that the pad surface is covered with an array of polygonal cells separated by channels, similar to those of a tree frog's pad. With this micro-structure, a newt can move on wet and smooth surfaces without slipping. Inspired by the surface structure of newt toe pads, elastic micro-patterned surfaces were fabricated to understand the function of such micro-structures in friction systems. The tribological performance of the patterned surfaces was evaluated using a tribometer. Different tribological performances between micro-dimple and -pillar patterned surfaces were observed. The area density (r) of the micro-pattern is crucial for controlling the friction of the elastic surface. Distinguished from unpatterned and micro-dimple patterned surfaces, the pillar patterned surface with high area density can remain high friction at high sliding speed. It could be one of the reasons of such polygonal structures on newt's toe pads. © 2013 IOP Publishing Ltd. Source

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