为了解决风电叶片双轴疲劳加载中叶片振动状态的检测的实际工程问题,设计了基于单目视觉的精准跟踪方案。通过在视频中选定包含特征标志圆的具有一定特征的ROI区域,设计了基于Mean Shift的图形跟踪算法跟踪视频的R O I区域。并在R O I...为了解决风电叶片双轴疲劳加载中叶片振动状态的检测的实际工程问题,设计了基于单目视觉的精准跟踪方案。通过在视频中选定包含特征标志圆的具有一定特征的ROI区域,设计了基于Mean Shift的图形跟踪算法跟踪视频的R O I区域。并在R O I区域中,应用HO UGH算法,对标志圆进行识别,并识别计算圆心位置。通过这样的算法设计,有效避免了跟踪算法在精确定位应用的不足以及HOUGH算法的误识别问题。在基于模拟视频的实验中,算法计算的特征位置与实际位置之间完全一致,并且满足实时性要求。展开更多
Failures due to high-cycle fatigue have led to a high cost in aerospace engineering over the past few decades.In this paper,the experimental results of the fatigue behavior of compressor blade specimen subjected to re...Failures due to high-cycle fatigue have led to a high cost in aerospace engineering over the past few decades.In this paper,the experimental results of the fatigue behavior of compressor blade specimen subjected to resonance and the effects of a damping hard coating on relieving the fatigue progress are presented.The crack initiation and propagation processes were observed under resonance of the first bending mode by using the resonant frequencies as the indicator.Significant nonlinear features were observed in the spectrum of the blade with a fatigue crack.The finite element model considering the breathing crack was established with nonlinear contact based on the crack localization and size,which was obtained by ultrasonic phased array technology.The simulation results of the vibration behavior of the cracked blade were obtained and consistent with the experimental results.A NiCrAlY coating was deposited on the blade,and increases in the fatigue life were observed under the same condition.The results of this paper can help to better understand the fatigue of a compressor blade subjected to resonance and provide a preference for the application of a damping hard coating on compressor blades.展开更多
Based on the nonlinear continuum damage model （CDM） developed by Chaboehe, a modified model for high cycle fatigue of TC4 alloy was proposed. Unsymmetrical cycle fatigue tests were conducted on rod specimens at room...Based on the nonlinear continuum damage model （CDM） developed by Chaboehe, a modified model for high cycle fatigue of TC4 alloy was proposed. Unsymmetrical cycle fatigue tests were conducted on rod specimens at room temperature. Then the material parameters needed in the CDM were obtained by the fatigue tests, and the stress distribution of the specimen was calculated by FE method. Compared with the linear damage model （LDM）, the dam- age results and the life prediction of the CDM show a better agreement with the test and they are more precise than the LDM. By applying the CDM developed in this study to the life prediction of aeroengine blades, it is concluded that the root is the most dangerous region of the whole blade and the shortest life is 58 211 cycles. Finally, the Cox propor- tional hazard model of survival analysis was applied to the analysis of the fatigue reliability. The Cox model takes the covariates into consideration, which include diameter, weight, mean stress and tensile strength. The result shows that the mean stress is the only factor that accelerates the fracture process.展开更多
In-service Very-High-Cycle-Fatigue(VHCF)regime of compressor vane and turbine rotor blades of the Al-based alloy VD-17and superalloy GS6K,respectively,was considered.Surface crack origination occurred at the lifetime ...In-service Very-High-Cycle-Fatigue(VHCF)regime of compressor vane and turbine rotor blades of the Al-based alloy VD-17and superalloy GS6K,respectively,was considered.Surface crack origination occurred at the lifetime more than 1500 hours for vanes and after 550 hours for turbine blades.Performed fractographic investigations have shown that subsurface crack origination in vanes took place inspite of corrosion pittings on the blade surface.This material behavior reflected lifetime limit that was reached by the criterion VHCF.In superalloy GS6K subsurface fatigue cracking took place with the appearance of flat facet.This phenomenon was discussed and compared with specimens cracking of the same superalloy but prepared by the powder technology.In turbine blades VHCF regime appeared because of resonance of blades under the influenced gas stream.Both cases of compressor-vanes and turbine blades in-service cracking were discussed with crack growth period and stress equivalent estimations.Recommendations to continue aircrafts airworthiness were made for in-service blades.展开更多
文摘为了解决风电叶片双轴疲劳加载中叶片振动状态的检测的实际工程问题,设计了基于单目视觉的精准跟踪方案。通过在视频中选定包含特征标志圆的具有一定特征的ROI区域,设计了基于Mean Shift的图形跟踪算法跟踪视频的R O I区域。并在R O I区域中,应用HO UGH算法,对标志圆进行识别,并识别计算圆心位置。通过这样的算法设计,有效避免了跟踪算法在精确定位应用的不足以及HOUGH算法的误识别问题。在基于模拟视频的实验中,算法计算的特征位置与实际位置之间完全一致,并且满足实时性要求。
基金Project(DUT20RC(3)014)supported by the Fundamental Research Funds for the Central Universities,China,Project(VCAME201801)supported by Key Laboratory of Vibration and Control of Aero-Propulsion System(Ministry of Education),ChinaProject(11472068)supported by the National Natural Science Foundation of China。
文摘Failures due to high-cycle fatigue have led to a high cost in aerospace engineering over the past few decades.In this paper,the experimental results of the fatigue behavior of compressor blade specimen subjected to resonance and the effects of a damping hard coating on relieving the fatigue progress are presented.The crack initiation and propagation processes were observed under resonance of the first bending mode by using the resonant frequencies as the indicator.Significant nonlinear features were observed in the spectrum of the blade with a fatigue crack.The finite element model considering the breathing crack was established with nonlinear contact based on the crack localization and size,which was obtained by ultrasonic phased array technology.The simulation results of the vibration behavior of the cracked blade were obtained and consistent with the experimental results.A NiCrAlY coating was deposited on the blade,and increases in the fatigue life were observed under the same condition.The results of this paper can help to better understand the fatigue of a compressor blade subjected to resonance and provide a preference for the application of a damping hard coating on compressor blades.
基金Supported by National Natural Science Foundation of China(No.60879002)Key Technologies R and D Program of Tianjin (No.10ZCKFGX03800)
文摘Based on the nonlinear continuum damage model （CDM） developed by Chaboehe, a modified model for high cycle fatigue of TC4 alloy was proposed. Unsymmetrical cycle fatigue tests were conducted on rod specimens at room temperature. Then the material parameters needed in the CDM were obtained by the fatigue tests, and the stress distribution of the specimen was calculated by FE method. Compared with the linear damage model （LDM）, the dam- age results and the life prediction of the CDM show a better agreement with the test and they are more precise than the LDM. By applying the CDM developed in this study to the life prediction of aeroengine blades, it is concluded that the root is the most dangerous region of the whole blade and the shortest life is 58 211 cycles. Finally, the Cox propor- tional hazard model of survival analysis was applied to the analysis of the fatigue reliability. The Cox model takes the covariates into consideration, which include diameter, weight, mean stress and tensile strength. The result shows that the mean stress is the only factor that accelerates the fracture process.
文摘In-service Very-High-Cycle-Fatigue(VHCF)regime of compressor vane and turbine rotor blades of the Al-based alloy VD-17and superalloy GS6K,respectively,was considered.Surface crack origination occurred at the lifetime more than 1500 hours for vanes and after 550 hours for turbine blades.Performed fractographic investigations have shown that subsurface crack origination in vanes took place inspite of corrosion pittings on the blade surface.This material behavior reflected lifetime limit that was reached by the criterion VHCF.In superalloy GS6K subsurface fatigue cracking took place with the appearance of flat facet.This phenomenon was discussed and compared with specimens cracking of the same superalloy but prepared by the powder technology.In turbine blades VHCF regime appeared because of resonance of blades under the influenced gas stream.Both cases of compressor-vanes and turbine blades in-service cracking were discussed with crack growth period and stress equivalent estimations.Recommendations to continue aircrafts airworthiness were made for in-service blades.
