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Tan H.,Xi'an Jiaotong University | Tao T.,Xi'an Jiaotong University | Tao T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Xu G.,Xi'an Jiaotong University | And 3 more authors.
Experimental Thermal and Fluid Science | Year: 2014

This paper proposed a new defrosting method based on ultrasonic resonance mechanism, to solve the problem of the unknown mechanism of ultrasonic defrosting for a finned-tube evaporator. Dynamic microscopic process of frost crystals formation and growth under the natural frost condition was first investigated. According to the growth characteristics of the frost crystals, the natural frequencies of frost crystals with different height were calculated in COMSOL software. An ultrasonic transducer of 28. kHz/60. W was adopted as an executor to excite the evaporator, then ultrasonic defrosting experiments and laser vibrometer experiments were carried out under the excitation of the ultrasonic transducer. Finally, experiment of ultrasonic resonance based on intermittent operational was studied to optimize ultrasonic loading method. It was found that the height of the frost crystals were about 0.5. mm after growing for 4. min, the average natural frequency of the frost crystals were about 27.95. kHz, the evaporator and frost crystals on the fin surface were forced vibration at the frequency of 28.2. kHz, which was the actual working frequency of the ultrasonic transducer detected in laser vibrometer experiment, and most frost crystals with certain shape and size were immediately broken up when the ultrasonic vibration applied. The main mechanism of ultrasonic defrosting was the resonance effect of natural frequency of frost crystals and excitation frequency, and the optimal working mode of ultrasonic resonance defrosting was intermittent 4. min, vibration 1. min. The experiment's results also showed that ultrasonic shear stress and acceleration effect of ultrasonic also had defrosting performance, but they were not the main mechanism for ultrasonic defrosting. © 2013 Elsevier Inc.


Zhao X.,Xi'an Jiaotong University | Niu H.,Xi'an Jiaotong University | Zhang X.,Xi'an Jiaotong University | Zhang X.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System
2015 12th International Conference on Ubiquitous Robots and Ambient Intelligence, URAI 2015 | Year: 2015

With the rapid development of robot technology, more and more intelligent robots serve for people in many fields. The gear is important for many robots, teeth root bending stress is one of the gear strength indexes, so measuring teeth root bending stress is very important. Photo elastic method and electrical method have been generally applied. However, there are some disadvantages of those methods. The production and the installation technology of the photo elastic are complex. About electrical method, the sensor is too big to be pasted on the teeth root. In this paper, a new method measuring the bending stress of gear with Fiber Bragg Grating in robot is proposed. The feasibility of this method and the installation of the FBG probe are necessary to be considered. In reality, the probe is installed in a secure area of gear due to the structure of gear. Optimization of FBG probe installation is discussed in details and the best pasting angle is obtained in this work. Cantilever beam was used to instead of gear teeth because the overall stress distribution characteristics of gear are similar to cantilever beam. According to mechanics of materials theory, the relationship between quality/pasting angle and relative offset of FBG reflection wavelength is obtained. The experiment results are consistent with the simulation results. The proposed method with its superior ability was proved to be feasible. © 2015 IEEE.


Du Y.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Wu T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Cheng J.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System
2015 IEEE SENSORS - Proceedings | Year: 2015

Lubricating oil as the blood of machine carries profound information of the life-span performances. Naturally, oil degrades with serving time and cause severe wear. Therefore, it is very important to detect the age of lubricating oil, which can reveal lubrication conditions and wear conditions as well. To characterize oil performances quantitatively, the physical and chemical properties are monitored with an on-line oil property sensor focusing on viscosity and permittivity. Moreover, an online wear debris sensor is adopted to detect the wear along with oil deterioration. With these on-line sensors, an aging process of oil and the consequence of wear can be informatively understood. Experimentally, an oil aging test is carried out in a four-ball test rig with on-line sensors of oil properties and wear particles. Results show that the aging process of lubricating oil, which is comprehensive and uninvestigated, can be monitored with online sensors, and the accuracy for the detection is verified with off-line analysis. © 2015 IEEE.


Jiang K.,Xi'an Jiaotong University | Xu G.,Xi'an Jiaotong University | Liang L.,Xi'an Jiaotong University | Liang L.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | And 3 more authors.
Sensors (Switzerland) | Year: 2014

In this paper a stochastic resonance (SR)-based method for recovering weak impulsive signals is developed for quantitative diagnosis of faults in rotating machinery. It was shown in theory that weakimpulsive signals follow the mechanism of SR, but the SR produces a nonlinear distortion of the shape of the impulsive signal. To eliminate the distortion a moving least squares fitting method is introduced to reconstruct the signal from the output of the SR process. This proposed method is verified by comparing its detection results with that of a morphological filter based on both simulated and experimental signals. The experimental results show that the background noise is suppressed effectively and the key features of impulsive signals are reconstructed with a good degree of accuracy, which leads to an accurate diagnosis of faults in roller bearings in a run-to failure test. © 2014 by the authors; licensee MDPI, Basel, Switzerland.


Yan Y.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Zhu Y.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Zhang Y.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Qian S.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Chen Z.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System
5th World Tribology Congress, WTC 2013 | Year: 2014

Generally wear test is conducted under constant load. But the test results have great difference with the actual situation, because most of the parts and components are usually subjected to varying loads during the actual service. Therefore spectrum loading tests have to be performed when the wear behavior cannot be assessed based on simple constant load with the required level of confidence. For this purpose, wear load spectrum is first proposed in this paper. First, this paper details the method applied for collection and analysis of appropriate load data and generation of the wear load spectrum. The method may also serve as guidelines for those cases where new wear load spectra has to be created. Secondly in order to verify the feasibility of this method, a finite element-based method is presented for simulating the wear of a sliding bearing. The two-dimensional wear simulation model is based on Archard's equation. The simulation results proved the feasibility of this method. Finally the effect of the loading sequence on wear is studied. © Shell International Petroleum Company 2013.


Zeng Q.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Liu P.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Liu P.,China University of Technology | Peng R.,China University of Technology | And 4 more authors.
Corrosion Science and Protection Technology | Year: 2015

The electrochemical corrosion behavior of cast iron which are used as liner material of methanol gasoline engine cylinder and tungsten carbide coatings on cast iron were comparatively investigated in methanoic acid aqueous solution by means of polarization curves and electrochemical impedance spectroscopy. The experimental results show that the tungsten carbide coating exhibited higher free corrosion potential, lower free corrosion current density, as well as higher charge transfer resistance. Therefore, the tungsten carbide coating can inhibit the corrosion of cast iron effectively in methanoic acid solution. © 2015, Chinese Academy of Sciences. All rights reserved.


Tan H.,Xi'an Jiaotong University | Xu G.,Xi'an Jiaotong University | Tao T.,Xi'an Jiaotong University | Tao T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | And 2 more authors.
Applied Energy | Year: 2015

When an air-source heat pump (ASHP) was operated in heating mode under certain ambient conditions, frost always accumulated on the fin surface of its outdoor coil. Frosting may increase the energy consumption and deteriorate the performance of the ASHP, and hence, periodic defrosting is necessary. In this study, a new defrosting method using intermittent ultrasonic vibration was investigated. First, the vibration attenuation characteristics of a double-row outdoor coil and the frost growth characteristics under different ambient conditions were determined. Next, the average frost thickness with and without the application of intermittent ultrasonic vibration was calculated using MATLAB software. Finally, the decrease in defrosting energy consumption, the increase in heating capacity, and the increase in the coefficient of performance were analysed. The experimental results indicate that intermittent ultrasonic vibration could effectively remove the frost accumulated on the fin surface, and the effective defrosting area of an single ultrasonic transducer was 0.165m2 for a double-row finned-tube evaporator on which an ultrasonic transducer with a rated power of 50W and resonant frequency of 40kHz was applied. The defrosting energy consumption of the ASHP unit with ultrasonic vibration was 3.14-5.46% lower than that without ultrasonic vibration, whereas the heating capacity increased by 2.2-9.03% and the COP increased by 6.51-15.33%. In addition, the thermal comfort of the indoor side was clearly improved. © 2015.


Jiang K.,Xi'an Jiaotong University | Xu G.,Xi'an Jiaotong University | Tao T.,Xi'an Jiaotong University | Tao T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | Liang L.,Xi'an Jiaotong University
International Journal of Precision Engineering and Manufacturing | Year: 2015

Bearing defective inspection plays a vital role in bearing quality control. Unlike signals in the process of condition monitoring and fault diagnosis, the signal characteristic of defective bearings is much weaker and difficult to be quantified through the acceleration based techniques. In this paper, a novel system is developed to inspect automatically the small defects of roller bearings for on-line quality control. Rather than using acceleration based techniques the system employs a high sensitive eddy current sensor to measure the displacement profiles of the outer race for high signal to noise ratio. Furthermore, a morphological filter is used to enhance the feature signal which is subsequently measured by Kolmogorov complexity measure. Both simulated signals and measured data show that this system is able to diagnose defects including abnormal surface roundness, waviness, misaligned races which are typical quality problems in bearing manufacturing lines. © 2015, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.


Tan H.,Xi'an Jiaotong University | Xu G.,Xi'an Jiaotong University | Tao T.,Xi'an Jiaotong University | Tao T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | And 2 more authors.
Applied Thermal Engineering | Year: 2016

Frosting deposited on the outdoor coil of air-source heat pump (ASHP) units deteriorates the operational performance and energy efficiency. Therefore, periodic defrosting is necessary. First, the dispersion curves for the propagation mechanism of an ultrasonic guided wave in the evaporator are determined through numerical calculation. In addition, the shear stress and vibration characteristics under ultrasonic excitation are analysed using finite element method (FEM). Finally, the vibration amplitude and defrosting performance of ultrasonic vibration is analysed. The numerical calculation results indicate that three guided wave modes exist in the evaporator, including both A0 and S0 modes of the Lamb wave and SH0 mode of the SH wave, with the optimal defrosting mode being S0 of the Lamb wave. The FEM results show that the vibrational shapes of S0 mode and longitudinal mode clearly exists in the fin and tube, the torsional and flexural modes also exist in the tube, and the FEM results are consistent with the numerical calculation results. The impedance analysis and laser vibrometer results indicate that the resonance frequency shifting, electro-acoustic converting efficiency and vibration energy decrease is due to increasing external load. The ultrasonic defrosting experimental results indicate that ultrasonic vibration can suppress frost deposit on the fin surface. © 2016 Elsevier Ltd


Kuosheng J.,Xi'an Jiaotong University | Guanghua X.,Xi'an Jiaotong University | Tangfei T.,Xi'an Jiaotong University | Tangfei T.,Key Laboratory of Education Ministry for Modern Design and Rotor Bearing System | And 4 more authors.
Review of Scientific Instruments | Year: 2014

This paper presents the theory and implementation of a novel sensor system for measuring the angular speed (AS) of a shaft rotating at a very low speed range, nearly zero speed. The sensor system consists mainly of an eccentric sleeve rotating with the shaft on which the angular speed to be measured, and an eddy current displacement sensor to obtain the profile of the sleeve for AS calculation. When the shaft rotates at constant speed the profile will be a pure sinusoidal trace. However, the profile will be a phase modulated signal when the shaft speed is varied. By applying a demodulating procedure, the AS can be obtained in a straightforward manner. The sensor system was validated experimentally based on a gearbox test rig and the result shows that the AS obtained are consistent with that obtained by a conventional encoder. However, the new sensor gives very smooth and stable traces of the AS, demonstrating its higher accuracy and reliability in obtaining the AS of the low speed operations with speed-up and down transients. In addition, the experiment also shows that it is easy and cost-effective to be realised in different applications such as condition monitoring and process control. © 2014 AIP Publishing LLC.

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