The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scatt...The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.展开更多
多孔夹芯结构因优异的比强度、比刚度而广泛应用于爆炸冲击防护领域,然而目前与爆炸相关的研究主要集中在小当量爆炸加载下夹芯结构的失效机制,实际大当量加载场景下的吸能特征研究较为少见。为更好指导工程应用,设计了三种夹芯材料(泡...多孔夹芯结构因优异的比强度、比刚度而广泛应用于爆炸冲击防护领域,然而目前与爆炸相关的研究主要集中在小当量爆炸加载下夹芯结构的失效机制,实际大当量加载场景下的吸能特征研究较为少见。为更好指导工程应用,设计了三种夹芯材料(泡沫铝、边长3 mm及边长10 mm的蜂窝铝)在不同夹芯构型(单层夹芯、两层夹芯)及不同面板/夹层板/背板厚度下的十种夹芯结构,并对上述夹芯结构开展了0.5 kg TNT和1 kg TNT当量爆炸加载实验,分析了不同当量下夹芯结构的整体变形特征,探讨了夹芯材料、夹芯构型等因素对吸能防护的影响。实验结果表明:爆炸加载下,泡沫夹芯结构及蜂窝夹芯结构均可通过芯体材料的大幅压缩变形吸收转换能量,但整体而言蜂窝结构的变形均匀化更好;芯体吸能效率的发挥一方面与自身的比压缩强度相关,另一方面也与表层面/背板的强度及刚度相关,在实际应用时需优化匹配芯体的压缩强度与面/背板的强度及刚度,保证芯体材料可获得最大程度的压缩,发挥其吸能优势;实验中发现双层夹芯结构在吸能防护性能上优于等面密度的单层夹芯结构,即在等面密度的情形下,通过对内部芯体的合理结构优化是提升结构整体吸能防护效果的有效途径。该研究可以为实际应用中的防护结构设计提供更多参考数据。展开更多
The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this...The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this purpose,the influences of structural parameters on the SAP of acoustic metamaterials were investigated by using experimental testing and a validated theoretical model.In addition,the sandwich structure was optimized by the genetic algorithm.The research shows that the panel thickness and micro-orifice diameter mainly affect the second resonant frequency and second peak sound absorption coefficient(SAC)of the structure.The unit cell size is found to influence the first and second resonant frequencies and two peaks of the SAC.An extremely low side-length of the honeycomb core decreases the SAP of the structure for low-frequency noise signals.Additionally,the sandwich structure presents a better SAP when the diameter of micro-orifices on the front micro-perforated panel(MPP)exceeds that of the back MPP.The sandwich structure shows better noise reduction performance after the optimization aiming at the noise frequency outside trains.展开更多
基金supported by the National Key Research and Development Program of China(No.2018YFA0702800)the National Natural Science Foundation of China(No.12072056)supported by National Defense Fundamental Scientific Research Project(XXXX2018204BXXX).
文摘The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.
文摘多孔夹芯结构因优异的比强度、比刚度而广泛应用于爆炸冲击防护领域,然而目前与爆炸相关的研究主要集中在小当量爆炸加载下夹芯结构的失效机制,实际大当量加载场景下的吸能特征研究较为少见。为更好指导工程应用,设计了三种夹芯材料(泡沫铝、边长3 mm及边长10 mm的蜂窝铝)在不同夹芯构型(单层夹芯、两层夹芯)及不同面板/夹层板/背板厚度下的十种夹芯结构,并对上述夹芯结构开展了0.5 kg TNT和1 kg TNT当量爆炸加载实验,分析了不同当量下夹芯结构的整体变形特征,探讨了夹芯材料、夹芯构型等因素对吸能防护的影响。实验结果表明:爆炸加载下,泡沫夹芯结构及蜂窝夹芯结构均可通过芯体材料的大幅压缩变形吸收转换能量,但整体而言蜂窝结构的变形均匀化更好;芯体吸能效率的发挥一方面与自身的比压缩强度相关,另一方面也与表层面/背板的强度及刚度相关,在实际应用时需优化匹配芯体的压缩强度与面/背板的强度及刚度,保证芯体材料可获得最大程度的压缩,发挥其吸能优势;实验中发现双层夹芯结构在吸能防护性能上优于等面密度的单层夹芯结构,即在等面密度的情形下,通过对内部芯体的合理结构优化是提升结构整体吸能防护效果的有效途径。该研究可以为实际应用中的防护结构设计提供更多参考数据。
基金Project(51775558)supported by the National Natural Science Foundation of ChinaProject(2019 JJ 30034)supported by the Natural Science Foundation for Excellent Youth Scholars of Hunan Province,ChinaProject(20181053303 gg)supported by the Training Objects of Young-Middle-Aged Backbone Teacher in Ordinary Universities of Hunan Province,China。
文摘The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this purpose,the influences of structural parameters on the SAP of acoustic metamaterials were investigated by using experimental testing and a validated theoretical model.In addition,the sandwich structure was optimized by the genetic algorithm.The research shows that the panel thickness and micro-orifice diameter mainly affect the second resonant frequency and second peak sound absorption coefficient(SAC)of the structure.The unit cell size is found to influence the first and second resonant frequencies and two peaks of the SAC.An extremely low side-length of the honeycomb core decreases the SAP of the structure for low-frequency noise signals.Additionally,the sandwich structure presents a better SAP when the diameter of micro-orifices on the front micro-perforated panel(MPP)exceeds that of the back MPP.The sandwich structure shows better noise reduction performance after the optimization aiming at the noise frequency outside trains.
