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Jin L.,South China University of Technology | Song F.F.,Application Technology of Electronic Component Laboratory | Wei G.Q.,South China University of Technology | Guo Q.,South China University of Technology
Advanced Materials Research | Year: 2013

A nonlinear transient three-dimensional finite element model for the laser welding process is developed to investigate the temperature and residual stress distribution. All the major physical phenomena associated to the laser welding process, including temperature dependent thermo-physical and mechanical properties are taken into account in the model. The heat input to the model is assumed to be a Gaussian heat source. Results show that the temperature distribution of laser welding is consistent with the actual, and along-welding line longitudinal stress and transverse stress are retained in the weld zone after laser welding and cooling to the room temperature. © (2013) Trans Tech Publications, Switzerland. Source

Wen P.Y.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Wen P.Y.,Chinese Academy of Sciences | Zhang S.M.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Zhang S.M.,Chinese Academy of Sciences | And 18 more authors.
Journal of Physics D: Applied Physics | Year: 2015

A comprehensive analysis of the degradation mechanism of blue InGaN/GaN laser diodes (LDs) is carried out by investigating the electrical and optical characteristics. The increase in the leakage current as well as decrease in the slope efficiency is observed. The luminescence properties of the active region at different aging stages are studied by means of cathodoluminescence. Significant degradation of the active region is observed on the room temperature cathodoluminescence while the low temperature cathodoluminescence shows almost no degradation, indicating that the degradation of the LDs is due to generation of low temperature frozen point defects. Furthermore, the generation of the defects follows a kinetic mechanism enhanced by electron-hole non-radiative recombination which explains the acceleration of time degradation in our LDs. © 2015 IOP Publishing Ltd. Source

Huang Q.W.,Application Technology of Electronic Component Laboratory | Li X.G.,Application Technology of Electronic Component Laboratory | Li X.G.,North University of China | Wang Y.H.,Application Technology of Electronic Component Laboratory
Applied Mechanics and Materials | Year: 2014

Fatigue of MEMS structures may occur after cyclic vibration loading, which can lead to the material degradation. A test bench was built for mechanical fatigue testing, especially for the structures that actuated by electrostatic force. A RF MEMS switch which was made of gold was tested; the material mechanical characteristic was monitored during the tests by means of the value of pull-in voltage, which is related to the change of the Young's modulus. The fatigue stress was produced by an alternating voltage, and the amplitude of which is from 15V to 65V. The excitation frequency and the actuation time were used as a counter for the number of cycles. The results show that there is no detectable mechanical fatigue after actuation up to one billion cycles. © (2014) Trans Tech Publications, Switzerland. Source

Yu L.,Jinan University | Yu L.,Application Technology of Electronic Component Laboratory | Zhu J.,Jinan University | Zhu J.,Application Technology of Electronic Component Laboratory | Zhu J.,China Electronic Product Reliability and Environmental Testing Research Institute
Applied Mathematics and Information Sciences | Year: 2015

Focused on the effects of environmental and operational variability on the structures, a novel procedure for structural linear and nonlinear damage detection is proposed based on the time series analysis and the higher statistical moments. The higher statistical moments of residual error of AR model, such as skewness and kurtosis, are then defined as the new damage-sensitive features to be a complimentary. Six integrated damage-sensitive features are further defined for vibration-based damage detection in terms of arithmetic and geometric mean of the residual errors. A series of experiments on a complicated truss bridge combined with a steel bridge plate have been conducted in laboratory. Damage was simulated by loosening the bolts of joints, and environmental variability were introduced by changing the shaker input level. 16 acceleration data of the bridge in each baseline and test state are measured and recorded for the structural damage detection. Based on these time series of acceleration data, the applicability of the proposed procedure is evaluated. Some valued conclusions are made and discussions suggested as well. © 2015 NSP Natural Sciences Publishing Cor. Source

Xu S.,South China University of Technology | Xu S.,Application Technology of Electronic Component Laboratory | Chen K.J.,South China University of Technology | Song F.F.,Application Technology of Electronic Component Laboratory
Applied Mechanics and Materials | Year: 2013

The pre-stressed modal and random vibration of electron gun are calculated by finite element software ANSYS Workbench. The results show that electron gun under the excitation of radial load (X direction) can be in danger of disable structure. Some measures can be taken to avoid electron gun failure due to resonance, such as replacing the materials, changing the structure of weak links and changing TWT installation to make external incentives along the axial direction (Y direction). The analysis results can provide effective reference and guidance for TWT development. © (2013) Trans Tech Publications, Switzerland. Source

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