【作者】 何峰；

【导师】 余音； 夏利娟；

【作者基本信息】 上海交通大学 ， 船舶与海洋结构物设计与制造， 2008， 硕士

【摘要】 船舶在海洋上运营,长期处于一种恶劣环境之中,容易产生疲劳损伤,从而影响船舶结构的寿命。FRP (Fiber Reinforced Plastic)作为新型高效材料,因其比强度高、比模量大、抗疲劳性能好,已广泛应用于加强船舶结构的强度和刚度。然而FRP复合材料在制造和长期的使用过程中,可能产生脱层、裂纹等结构损伤,若不能即时发现,将导致结构的迅速破坏,造成灾难性事故。为保证船舶使用的安全和寿命,需要实时、有效的损伤检测方法对FRP复合材料的内在缺陷进行检测。本文探索了一种基于智能结构技术和小波分析的方法,分别对智能FRP复合材料夹层梁和夹层板的损伤检测进行了研究。对于复合材料夹层梁,分别对智能FRP夹层梁的脱层损伤和裂纹损伤进行了数值模拟计算和模型试验研究。通过在复合材料夹层梁内部埋入智能传感器,可以采集结构的应变响应信号;然后对应变响应信号进行复一阶高斯小波变换,通过分析小波变换系数中包含的奇点特征,对梁上的损伤信息进行了有效的识别,监测结构的损伤状况。研究了损伤发生在不同位置,以及不同的损伤程度时的小波变换方法识别。同时,对试验数据亦进行了同样的分析,以之验证数值模拟方法的有效性。对于复合材料夹层板,本文仅对智能FRP夹层板的脱层损伤进行数值模拟研究。采用有限元方法数值模拟智能FRP夹层板的应变响应信号,利用复高斯小波对其进行小波分析,通过分析小波变换系数中包含的奇点特征,可以有效的检测出夹层板是否存在脱层损伤、损伤的位置以及定性的判定板的损伤程度。更多还原

【Abstract】 Since an ocean-going ship is under expectable environment during its service life, it is vulnerable to fatigue damage. Fiber reinforced plastic (FRP) sandwich composite materials are widely used in the construction of marine structures. However, internal defects can occur, which if not identified on time, can lead to rapid structural degradation, and even cause catastrophe. In order to ensure marine safety and life-span, a simple fast and non-destructive damage evaluation method is required to assess and locate the internal defects in the FRP sandwich composite materials.Based upon intelligent structure technology and wavelet analysis, a method of damage monitoring was preliminary explored in the thesis, which was used to identify the damage on smart FRP sandwich beam and plate separately.For the smart FRP sandwich beam, a debond damage was monitored by numerically simulated calculation and experimental research separately, so was crack damage. Intelligent sensors could be used to monitor the strain response signals of sandwich beam, and then the first order complex Guassian wavelet transformation was applied to the strain response signals. By analyzing the singularity characteristics of wavelet transformation coefficients, the damage could be identified effectively. Damages with various sizes and in different positions were researched by the wavelet analysis. And the experimental data from sandwich beams was investigated also in order to demonstrate the validity of the numerically simulated calculation.For the smart FRP sandwich plate, just the debond damage was researched by numerically simulated calculation. Finite element method was used to simulate the strain response signals of FRP sandwich plate, and then the first order complex Guassian wavelet transformation was applied to the strain response signals. By analyzing the singularity characteristics of the wavelet transformation coefficients, the debond damage could be identified effectively. The study in this paper showed the validity of using wavelet analysis to identify whether there was any damage, where the damage was and the degree of damage.更多还原