It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced t...It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced technology and management methods andexpand the export-oriented economy.Since 1992,18 other developmentzones have been approved by the Council,increasing the number ofsuch zones to 32.展开更多
A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks...A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.展开更多
文摘It was approved by the State Council in I984 to establish economicand technological development zones in 14 coastal port cities tofunction as windows for those cities to attract foreign investment,introduce advanced technology and management methods andexpand the export-oriented economy.Since 1992,18 other developmentzones have been approved by the Council,increasing the number ofsuch zones to 32.
基金Supported by the Ministerial Level Advanced Research Foundation(051317030586)Ph.D.Programs Foundation of the Ministry of Education of China(20121101110018)
文摘A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.
