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1.
在冲击荷载作用下复合材料会产生断裂和分层等损伤。基于损伤数据对冲击工况进行识别,对改善复合材料的设计和确保其安全使用具有重要意义。基于此,本文提出一种基于深度学习和近场动力学(PD)理论的层合板冲击工况识别方法。首先使用改进的表面修正系数PD理论建立复合材料层合板刚体冲击损伤演化分析PD模型,PD模型数值模拟结果结合噪声数据增强技术构建层合板的冲击工况数据库;基于深度学习-卷积神经网络(CNN),对不同工况下的冲击损伤演化数据进行训练,实现对未知冲击工况的识别。结果显示,对于钢球冲击速度和角度的识别准确率均高于90%。  相似文献   

2.
结构构件出现缺口损伤时,伴随着结构质量的减小。为了更精确地识别结构损伤,以折减损伤单元截面积来模拟结构损伤,提出考虑结构质量变化的刚架结构损伤识别方法。该方法首先通过相对模态应变能指标对结构损伤进行准确定位;之后考虑梁单元截面特性变化的特点将单元刚度矩阵进行分解,以多个指标描述单元损伤,从而建立结构损伤程度识别方程,并用最小二乘方法对损伤指标进行求解。数值算例结果表明,本文方法能实现对刚架结构损伤位置的准确定位和损伤程度的精确识别,而且具有良好的抗噪性。  相似文献   

3.
本文介绍了射电偏振仪PПy—1的结构及其工作原理。该仪器是利用发射偏振的超高频无线电磁波透射复合材料构件,对接收到的信号进行分析来确定构件在工作状态下的应力应变值。本文还通过测试实例说明了仪器的使用及各种参数的确定方法。  相似文献   

4.
Lamb波具有传播范围远、对小损伤敏感等优点,适用于飞机机翼、壁板等大面积结构的损伤检测,然而Lamb波的频散和多模态特性使得单模态难以识别和解析信号。本文提出一种适用于板壳结构损伤检测的单模态提取方法,设计并使用一种同心压电传感器,根据所激励各模态的幅值比来分解信号并补偿时间差,从而提取出单一模态的信号。通过仿真分析和铝板实验验证,结果显示本方法能够有效提取单一A_0模态信号,并在实验中成功识别了隐藏的裂纹损伤反射回波信号,使信号相对于传统方法变得更易解释和分析。  相似文献   

5.
白象忠 Φ.   《实验力学》1995,10(3):210-217
本文介绍了射电偏振仪PIIY-1的结构及其工作原理。该仪器是利用发射偏振的超高频无线电磁波透射复合材料的构件,对接收到的信号进行分析来确定构件在工作状态下的应力应变值。本文还通过测试实例说明了仪器的使用及各种参数的确定方法。  相似文献   

6.
冯勇明  周丽 《爆炸与冲击》2012,32(3):259-266
基于Lamb波和匹配追踪算法,提出了一种损伤成像方法,对复合材料冲击损伤进行在线的连续 监测。首先针对Lamb波监测的特点,提出了匹配追踪方法的快速实现方案,将信号分解为多个Chirplet原 子的线性组合,建立了Lamb的弥散效应与Chirplet原子的调频斜率之间的关系,模拟结果表明Chirplet原 子能准确地匹配失真变形的窄带脉冲信号;根据损伤前与损伤后的信号差别,提出了一种基于Lamb波能量 特征差异提取的损伤指标;进一步采用改进的RAPID算法进行损伤成像,将损伤情况可视化。结果表明所 提方法可行和有效。  相似文献   

7.
结构动态特性的变化则预示结构出现损伤,基于Ritz线性近似,文中提出一种裂缝损伤识别的方法,用以识别结构裂缝损伤位置及损伤程度。该方法分两步:首先用模态子空间近似关系.消去模态应变能表达式中的整体刚度矩阵和整体质量矩阵,避免模型误差对识别结果的影响。再采用计算向量空间夹角的方法分离损伤位置与损伤程度的耦合影响,进而识别出单元裂缝损伤位置;其次,识别损伤程度采用二次线性规划方法,不再计算特征值灵敏度。线性约束条件保证了二次规划问题的解是唯一的。模拟筒支梁几种裂缝损伤情况进行数值计算与模态试验,利用所得模态参数对该算法程序进行了验证,识别出了裂缝损伤的确切位置及损伤程度,并进行了误差对比。结果表明,该算法由于不用整体结构的数值模型,从而避免了边界条件、连接条件及材料特性参数等因素对识别结果的干扰,识别精度得到提高,将其用于结构损伤识别是可行的。  相似文献   

8.
结构构件出现缺口损伤时,伴随着结构质量的减小。为了更精确地识别结构损伤,以折减损伤单元截面积来模拟结构损伤,提出考虑结构质量变化的刚架结构损伤识别方法。该方法首先通过相对模态应变能指标对结构损伤进行准确定位;之后考虑梁单元截面特性变化的特点将单元刚度矩阵进行分解,以多个指标描述单元损伤,从而建立结构损伤程度识别方程,并用最小二乘方法对损伤指标进行求解。数值算例结果表明,本文方法能实现对刚架结构损伤位置的准确定位和损伤程度的精确识别,而且具有良好的抗噪性。  相似文献   

9.
针对点阵夹芯结构的脱焊损伤,提出了一种基于高频激励下结构ODS(operational deflection shapes)的损伤检测方法。ODS包含结构的整体动态响应特性,尤其是高频激励下损伤区域的局部振动信息。首先通过仿真计算出损伤局部区域的特征频率,选取合适的高频宽频带激励损伤结构。然后,采用压电片与扫描式激光测振仪结合,检测高频稳态信号激励下损伤结构的动态响应,综合考虑频段内多个频率下的ODS,由损伤成像中共振峰的位置,直接定位损伤。仿真与试验均验证了该方法识别损伤的有效性。  相似文献   

10.
陈勇  陶宝祺  高亹 《实验力学》2000,15(4):441-447
飞机局部复合材料构件存在着因涡流作用诱发的弹性振动问题。本文首先研究了表面粘贴型压电元件对复合材料构件的传感和驱动原理;针对结构待控模态的要求,采用了D-准则优化确定同位压电传感/驱动器在构件中的布置方案;应用自适应振动前馈控制原理和方法,构造了闭环控制系统;分别利用正弦和方波信号激发气动声场,对玻纤/环氧圆筒构件进行激振和振动控制实验;结果表明:构件主要待控模态的振动得到了有效抑制,但也出现了高阶模态被激发的问题,导致结构辐射噪声上升。  相似文献   

11.
A two-stage damage detection approach is proposed and experimentally demonstrated on a complicated spatial model structure with a limited number of measurements. In the experiment,five known damage patterns,including 3 brace damage cases and 2 joint damage cases,were simulated by removing braces and weakening beam-column connections in the structure. The limited acceleration response data generated by hammer impact were used for system identification,and modal parameters were extracted by using the eigensystem realization algorithm. In the first stage,the possible damaged locations are determined by using the damage index and the characteristics of the analytical model itself,and the extent of damage for those substructures identified at stage I is estimated in the second stage by using a second-order eigen-sensitivity approximation method. The main contribution of this paper is to test the two-stage method by using the real dynamic data of a complicated spatial model structure with limited sensors. The analysis results indicate that the two-stage approach is ableto detect the location of both damage cases,only the severity of brace damage cases can be assessed,and the reasonable analytical model is critical for successful damage detection.  相似文献   

12.
Health monitoring and damage detection strategies for base-excited structures typically rely on accurate models of the system dynamics. Restoring forces in these structures can exhibit highly non-linear characteristics, thus accurate non-linear system identification is critical. Parametric system identification approaches are commonly used, but require a priori knowledge of restoring force characteristics. Non-parametric approaches do not require this a priori information, but they typically lack direct associations between the model and the system dynamics, providing limited utility for health monitoring and damage detection. In this paper a novel system identification approach, the intelligent parameter varying (IPV) method, is used to identify constitutive non-linearities in structures subject to seismic excitations. IPV overcomes the limitations of traditional parametric and non-parametric approaches, while preserving the unique benefits of each. It uses embedded radial basis function networks to estimate the constitutive characteristics of inelastic and hysteretic restoring forces in a multi-degree-of-freedom structure. Simulation results are compared to those of a traditional parametric approach, the prediction error method. These results demonstrate the effectiveness of IPV in identifying highly non-linear restoring forces, without a priori information, while preserving a direct association with the structural dynamics.  相似文献   

13.
提出了一种结合摄动法和L1正则化方法的随机梁式结构静力损伤识别方法。考虑初始模型误差和测量误差的影响,建立了关于随机损伤指数的控制方程,并将摄动法和L1正则化方法相结合,对随机损伤指数的控制方程进行求解,进而从概率的角度对结构的损伤进行识别。损伤试验结果表明,和传统的最小二乘求解法相比,本文方法能够更为准确地识别多处局部损伤的位置及大小,对实际结构损伤检测具有较好的参考价值。  相似文献   

14.
In this paper an on-going research effort aimed at detecting and localizing damage in plate-like structures by using mode shape curvature based damage detection algorithm is described. The proposed damage index uses exclusively mode shape curvature data from the damaged structure. This method was originally developed for beam-like structures. In this paper, the method is generalized to plate-like structures which are characterized by two-dimensional mode shape curvature. To calculate mode shape curvatures from the measured mode shapes, three approaches are proposed: the first one is the well-known central difference approximation, the other two are classical approaches based on Tikhonov's regularization technique with smoothing functional. The applicability and effectiveness of the proposed damage detection algorithms are demonstrated experimentally on an aluminium plate containing mill-cut damage. The validity of the method is assessed by comparing the identification results of the experimental test case to the results obtained from the simulated test case. The modal frequencies and the corresponding mode shapes of the aluminium plate are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer (SLV) for the experimental study.  相似文献   

15.
This paper presents a novel damage detection technique, tailored at the identification of structural surface damage on rail structures. The damage detection, proposed in this paper, exploits the wave propagation phenomena (P, S, Rayleigh and guided wave velocities) by identifying discrepancies, due to damage presence, in the dynamic behaviour of the structure. The uncorrelations are generated by waves reflected back to the sensor locations by the flaw surfaces. The peculiarity of the presented approach is the use of a time frequency coherence function for the identification of the arrivals of guided wave reflected back to the sensors by the damage surfaces.The damage detection methodology developed was divided into three steps. In the first step, the presence of the damage on the structure was assessed. In the second step, the arrival time of the reflected wave (or echo) was estimated using the continuous wavelet transform. Then, the detection algorithm was able, through a ray-tracing algorithm, to estimate the location of damage.A numerical investigation of two single damages was carried out. The damage was introduced on the railhead surface to simulate rolling contact fatigue defects. The results showed that the proposed methodology can be used successfully to localise the damage location, however, as expected, the localisation is strongly affected by the frequency range used. The results suggested that the separation and the characterisation of single modes are crucial for the identification of different types of rail defects. Further work is needed to establish the damage severity by relating the magnitude of the changes of the time frequency coherence to reflection and attenuation coefficients of each guided wave used and on the selection of the best range of frequency according to the type of damage to be identified.  相似文献   

16.
A reliable prediction of ductile failure in metals is still a wide-open matter of research. Several models are available in the literature, ranging from empirical criteria, porosity-based models and continuum damage mechanics (CDM). One major issue is the accurate identification of parameters which describe material behavior. For some damage models, parameter identification is more or less straightforward, being possible to perform experiments for their evaluation. For the others, direct calibration from laboratory tests is not possible, so that the approach of inverse methods is required for a proper identification. In material model calibration, the inverse approach consists in a non-linear iterative fitting of a parameter-dependent load–displacement curve (coming from a FEM simulation) on the experimental specimen response. The test is usually a tensile test on a round-notched cylindrical bar. The present paper shows a novel inverse procedure aimed to estimate the material parameters of the Gurson–Tvergaard–Needleman (GTN) porosity-based plastic damage model by means of experimental data collected using image analysis. The use of digital image processing allows to substitute the load–displacement curve with other global quantities resulting from the measuring of specimen profile during loading. The advantage of this analysis is that more data are available for calibration thus allowing a greater level of confidence and accuracy in model parameter evaluation.  相似文献   

17.
刘龙  黄海  孟光 《应用力学学报》2007,24(2):313-317
支持向量机是一种基于统计学习理论的机器学习算法,能够较好地解决小样本的学习问题。本文介绍了支持向量机分类和回归算法,提出了基于支持向量机的结构损伤分步识别方法:以模态频率作为损伤特征,首先根据支持向量机分类算法的概率估计确定可能的损伤位置,重新构造训练样本,然后利用支持向量机回归算法计算损伤位置;最后估计损伤程度。以梁的损伤识别为例进行了验证,结果表明该方法可以提高损伤识别的精度。  相似文献   

18.
IntroductionServiceloads,environmentalandaccidentalactionsmaycausedamagetostructures .Whenthestructuraldamageissmalloritisintheinteriorofthestructure,itsdetectioncannotbedonevisually.Inspectionofexistingbuildingsandbridgesaftercatastrophicevents,suchasearthquakesandhurricanes,aswellasundernormaloperatingconditions ,isoftentimeconsumingandcostlybecausecriticalmembersandconnectionsareconcealedundercladdingandotherarchitecturaldecorations.Formanyimportantstructures,suchashospitals,firestations,mi…  相似文献   

19.
基于不完备频响函数数据,结合概率统计方法,提出了一种能同时考虑模型参数不确定性和测试噪声影响的结构损伤统计识别方法。首先,基于频响函数某一行向量在不同频率下的幅值数据,利用矩阵拉直运算建立了关于损伤系数的确定性识别方程。其次,假设模型参数误差和测试噪声为零均值的高斯随机变量,根据摄动理论,推导了损伤后结构刚度参数的前二阶矩。随后,利用结构损伤前后的概率分布得到了结构损伤存在概率。最后,通过一个平面桁架结构模型验证了本文方法的有效性。数值算例的研究结果表明,损伤单元的损伤存在概率远大于非损伤单元;测试噪声对识别结果的影响比模型参数不确定性的影响更为显著。  相似文献   

20.
The present paper proposes a novel approach to the identification of the mechanical properties of individual component layers of a bimetallic sheet. In this approach, a set of material parameters in a constitutive model of cyclic elasto-plasticity are identified for the two layers of the sheet simultaneously by minimizing the difference between the experimental results and the corresponding results of numerical simulation. This method has an advantage of using the experimental data (tensile load vs strain curve in the uniaxial tension test and the bending moment vs curvature diagram in the cyclic bending test) for a whole bimetallic sheet but not for individual component layers. An optimization technique based on the iterative multipoint approximation concept is used for the identification of the material parameters. This paper describes the experimentation, the fundamentals and the technique of the identification, and the verification of this approach using two types of constitutive models (the Chaboche-Rousselier and the Prager models) for an aluminum clad stainless steel sheet.  相似文献   

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