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考虑不确定性因素的结构损伤检测方法 被引量:5
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作者 姜绍飞 周广师 +1 位作者 刘红兢 刘明 《沈阳建筑工程学院学报(自然科学版)》 2002年第2期85-87,共3页
结构损伤检测是当前国内外学术与工程界研究比较活跃的领域 ,如何将不确定性的因素与确定性的损伤检测方法相结合 ,并应用于实际的复杂工程结构中是当前亟需解决的课题 .在贝叶斯概率处理不确定性信息的基础上 ,提出了运用概率神经网络 ... 结构损伤检测是当前国内外学术与工程界研究比较活跃的领域 ,如何将不确定性的因素与确定性的损伤检测方法相结合 ,并应用于实际的复杂工程结构中是当前亟需解决的课题 .在贝叶斯概率处理不确定性信息的基础上 ,提出了运用概率神经网络 (PNN)进行复杂结构的损伤检测方法 ,并分别用传统PNN和自适应PNN对悬索桥的桥面板进行了损伤检测 ,以验证该方法的有效性 .研究表明 ,运用PNN进行损伤检测是可行、有效的 ,自适应PNN极大地优于传统PNN ,且随着噪声程度的增大 。 展开更多
关键词 损伤测检 概率神经网络 不确定性因素 贝叶斯决策 建筑结构 结构损伤
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Linear and Nonlinear Ultrasonic Detections of Impact Damage in Composite Laminate
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作者 WANG Rong WU Qi +1 位作者 ZHANG Guitao XIA Guochun 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2024年第5期599-608,共10页
The appearance and accumulation of internal impact damage seriously influence overall performance of carbon fiber reinforced plastic(CFRP).Thus,this study evaluates the change in impact damage number by using linear a... The appearance and accumulation of internal impact damage seriously influence overall performance of carbon fiber reinforced plastic(CFRP).Thus,this study evaluates the change in impact damage number by using linear and nonlinear ultrasonic Lamb wave detection methods,and compares these two detection results.An ultrasonic wave simulation model for composite structure with impact damage is established using the finite element method,and the interaction between impact damage and the ultrasonic wave is simulated.Simulation results demonstrate that the ultrasonic amplitude linearly decreases,and the relative nonlinear parameter linearly increases in proportion to the impact number,respectively.The linear-fitting slope of nonlinear parameter is 0.38 per impact number at an input frequency of 1.0 MHz.It is far higher than that of the linear ultrasonic amplitude,which is only-0.12.However,with the increase of impact damage,the linear growth of nonlinear parameters mainly depends on the decrease in ultrasonic amplitude rather than the accumulation of second harmonic amplitude.In the linear ultrasonic amplitude detection,the linear fitting slope at 1.1 MHz is-0.14,which is lower than those at 0.9 MHz and 1.0 MHz.Meanwhile,in the nonlinear ultrasonic parameter detection,the linear fitting slope at 1.1 MHz is 0.92,which is higher than those at 0.9 MHz and 1.0 MHz.The results show that higher frequencies lead to greater attenuation of ultrasonic amplitude and a larger increase in nonlinear parameters,which can enhance the sensitivity of both linear and nonlinear ultrasonic detections.The accuracy of simulation results is demonstrated through the low-velocity impact and ultrasonic experiments.The results show that compared with nonlinear ultrasonic technology,the linear ultrasonic technology is more suitable for impact damage assessment of carbon fiber reinforced plastic because of its simpler detection process and higher sensitivity. 展开更多
关键词 carbon fiber reinforced plastic(CFRP) nonlinear ultrasonic Lamb wave impact damage nondestructive testing
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DAMAGE CLASSIFICATION BY PROBABILISTIC NEURAL NETWORKS BASED ON LATENT COMPONENTS FOR TIME-VARYING SYSTEM 被引量:1
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作者 袁健 周燕 吕欣 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2009年第4期259-267,共9页
A new approach to damage classification for health monitoring of a time-varylng system is presented. The functional-series time-dependent auto regressive moving average (FS-TARMA) time series model is applied to the... A new approach to damage classification for health monitoring of a time-varylng system is presented. The functional-series time-dependent auto regressive moving average (FS-TARMA) time series model is applied to the vibration signal observed in the time-varying system for estimating the TAR/TMA parameters and the innovation variance. These parameters are the functions of the time, represented by a group of projection coefficients on the certain functional subspace with specific basis functions. The estimated TAR/TMA parameters and the innovation variance are further used to calculate the latent components (LCs) as the more informative data for health monitoring evaluation, based on an eigenvalue decomposition technique. LCs are then combined and reduced to numerical values (NVs) as feature sets, which are input to a probabilistic neural network (PNN) for the damage classification. For the evaluation of the proposed method, numerical simulations of the damage classification for a tlme-varylng system are used, in which different classes of damage are modeled by the mass or stiffness reductions. It is demonstrated that the method can identify the damages in the course of operation and the change of parameters on the time-varying background of the system. 展开更多
关键词 damage detection time-varying system feature extraction/reduction probabilistic neural networks
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Predictability of outcome of caustic ingestion by esophagogastroduodenoscopy in children 被引量:8
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作者 Abdulkerim Temiz Pelin Oguzkurt +2 位作者 Semire Serin Ezer Emine Ince Akgun Hicsonmez 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第10期1098-1103,共6页
AIM: To assess the necessity of esophagogastroduodenoscopy (EGD) to predict the outcome of caustic ingestion in children. METHODS: The study included 206 children who underwent EGD because of ingestion of caustic subs... AIM: To assess the necessity of esophagogastroduodenoscopy (EGD) to predict the outcome of caustic ingestion in children. METHODS: The study included 206 children who underwent EGD because of ingestion of caustic substances between January 2005 and August 2010. Retrospective analysis of data of the patients was performed. RESULTS: The male/female ratio was 1.6 and mean age was 38.1 ± 28.8 mo. The caustic substances were acidic in 72 (34.9%) cases, alkaline in 56 (27.2%), liquid household bleach in 62 (30.1%), and unknown in 16 (7.8%). Fifty-seven (27.7%) patients were symptom-free. Significant clinical findings were observed in 149 (72.3%) patients. Upper gastrointestinal endoscopy findings of esophageal injury were grade 0 in 86 (41.7%) patients, grade 1 in 49 (23.8%), grade 2a in 42 (20.4%), grade 2b in 28 (13.6%), and grade 3a in 1 (0.5%) patient. 35 patients with grade 2a, 2b, and 3a injuries underwent esophageal dilation at second week of ingestion. Esophageal stricture, which necessitated a regular dilation program developed in 13 of the aforementioned 35 patients. There is no statistically significant difference in the rate of development of esophageal stricture between the patients who ingested acidic (15.3%) and alkaline (8.9%) substances (P = 0.32). Severe gastric injury was detected in 38 (18.5%) patients. The rate of development of gastric injury was significantly higher in the acidic group (14%) than in the alkaline group (2.9%) (P = 0.001). Out of 149 patients with clinical findings, 49 (32.9%) patients had no esophageal injury and 117 (78.5%) patients had no gastric lesion. Esophageal and severe gastric injuries were detected in 20 (35.1%) and 8 (14%) of patients with no clinical findings respectively. Pyloric stenosis developed in 6 patients. Pyloric obstruction improved with balloon dilation in 2 patients. Mean hospitalization time were 1.2 ± 0.5 d for grade 0 and 2.3 ± 5 d for grade 1 and 6.3 ± 6.2 d for grade 2a and 15.8 ± 18.6 d for grade 2b. It was significantly longer for patients with grade 2a and 2b injuries (P = 0.000). CONCLUSION: Endoscopy is an effective technique for determining the presence of esophageal and gastric damage and to avoid unnecessary treatment in patients with no or mild injury. 展开更多
关键词 ENDOSCOPY CAUSTIC Injury ESOPHAGUS STOMACH
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Detecting damage to offshore platform structures using the time-domain data 被引量:1
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作者 程远胜 王真 《Journal of Marine Science and Application》 2008年第1期7-14,共8页
A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first... A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first constructed using the time-domain of noise data. A sensitivity matrix consisting of the first differential of the autoregressive coefficients of the time series models with respect to the stiffness of structural elements was then obtained based on time-domain response data. Locations and severity of damage may then be estimated by solving the damage vector whose components express the degrees of damage to the structural elements. A unique aspect of this detection method is that it requires acceleration history data from only one or a few sensors. This makes it feasible for a limited array of sensors to obtain sufficient data. The efficiency and reliability of the proposed method was demonstrated by applying it to a simplified offshore platform with damage to one element. Numerical simulations show that the use of a few sensors’ acceleration history data, when compared with recorded levels of noise, is capable of detecting damage efficiently. An increase in the number of sensors helps improve the diagnosis success rate. 展开更多
关键词 offshore platform damage detection time-domain response time series analysis sensitivity analysis autoregressive coefficient
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Modal Strain Energy Based Structural Damage Localization for Offshore Platform using Simulated and Measured Data 被引量:5
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作者 WANG Shuqing LIU Fushun ZHANG Min 《Journal of Ocean University of China》 SCIE CAS 2014年第3期397-406,共10页
Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to ve... Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to verify the damage detection algorithms. Only a few studies utilize modal testing data from 3D frame structures. Few studies conduct performance comparisons between two different modal strain energy based methods. The objective of this paper is to investigate and compare the effectiveness of a traditional modal strain energy method(Stubbs index) and a recently developed modal strain energy decomposition(MSED) method for damage localization, for such a purpose both simulated and measured data from an offshore platform model being used. Particularly, the mode shapes used in the damage localization are identified and synthesized from only two measurements of one damage scenario because of the limited number of sensors. The two methods were first briefly reviewed. Next, using a 3D offshore platform model, the damage detection algorithms were implemented with different levels of damage severities for both single damage and multiple damage cases. Finally, a physical model of an offshore steel platform was constructed for modal testing and for validating the applicability. Results indicate that the MSED method outperforms the Stubbs index method for structural damage detection. 展开更多
关键词 offshore platform damage localization strain energy mode shapes modal testing
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An Improved Modal Strain Energy Method for Damage Detection in Offshore Platform Structures 被引量:3
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作者 Yingchao Li Shuqing Wang +1 位作者 Min Zhang Chunmei Zheng 《Journal of Marine Science and Application》 CSCD 2016年第2期182-192,共11页
The development of robust damage detection methods for offshore structures is crucial to prevent catastrophes caused by structural failures. In this research, we developed an Improved Modal Strain Energy (IMSE) meth... The development of robust damage detection methods for offshore structures is crucial to prevent catastrophes caused by structural failures. In this research, we developed an Improved Modal Strain Energy (IMSE) method for detecting damage in offshore platform structures based on a traditional modal strain energy method (the Stubbs index method). The most significant difference from the Stubbs index method was the application of modal frequencies. The goal was to improve the robustness of the traditional method. To demonstrate the effectiveness and practicality of the proposed IMSE method, both numerical and experimental studies were conducted for different damage scenarios using a jacket platform structure. The results demonstrated the effectiveness of the IMSE method in damage location when only limited, spatially incomplete, and noise-polluted modal data is available. Comparative studies showed that the IMSE index outperformed the Stubbs index and exhibited stronger robustness, confirming the superiority of the proposed approach. 展开更多
关键词 damage detection modal strain energy offshoreplatform structure modal frequency mode shape
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Statistical Algorithm for Damage Detection of Concrete Beams Based on Piezoelectric Smart Aggregate 被引量:4
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作者 蒙彦宇 阎石 《Transactions of Tianjin University》 EI CAS 2012年第6期432-440,共9页
The functional piezoelectric ceramic smart aggregate(SA) sensors and actuators,based on piezoelectric ceramic materials such as lead zirconium titanate(PZT),were embedded into the reinforced concrete beams with three-... The functional piezoelectric ceramic smart aggregate(SA) sensors and actuators,based on piezoelectric ceramic materials such as lead zirconium titanate(PZT),were embedded into the reinforced concrete beams with three-point bending under static loading for purposes of damage detection.The SA actuators generated the desired sine sweep excitation signals online and the SA sensors received and detected real-time signals before and after damage.The wavelet analysis and statistical characteristics about damage signals were used as a signal processing and analysis tool to extract the optimal damage information and establish a statistical damage detection algorithm.The damage index-based wavelet analysis and damage probability-based probability and statistics were proposed by PZT wavebased theory and active health monitoring technology.The results showed that the existence of cracks inside largely attenuated the amplitude of active monitoring signal after the damage of beam and the attenuation was related to the severity degree of damage.The innovative statistical algorithm of damage pattern detection based PZT-SA can effectively determine damage probability and damage degree,and provide a prediction for the critical damage location of reinforced concrete structures.The developed method can be utilized for the structural health comprehensive monitoring and damage detection on line of various large-scale concrete structures. 展开更多
关键词 piezoelectric ceramic smart aggregate active health monitoring damage detection statistical analysis
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Damage Localization of Marine Risers Using Time Series of Vibration Signals 被引量:1
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作者 LIU Hao YANG Hezhen LIU Fushun 《Journal of Ocean University of China》 SCIE CAS 2014年第5期777-781,共5页
Based on dynamic response signals a damage detection algorithm is developed for marine risers. Damage detection methods based on numerous modal properties have encountered issues in the researches in offshore oil comm... Based on dynamic response signals a damage detection algorithm is developed for marine risers. Damage detection methods based on numerous modal properties have encountered issues in the researches in offshore oil community. For example, significant increase in structure mass due to marine plant/animal growth and changes in modal properties by equipment noise are not the result of damage for riser structures. In an attempt to eliminate the need to determine modal parameters, a data-based method is developed. The implementation of the method requires that vibration data are first standardized to remove the influence of different loading conditions and the autoregressive moving average(ARMA) model is used to fit vibration response signals. In addition, a damage feature factor is introduced based on the autoregressive(AR) parameters. After that, the Euclidean distance between ARMA models is subtracted as a damage indicator for damage detection and localization and a top tensioned riser simulation model with different damage scenarios is analyzed using the proposed method with dynamic acceleration responses of a marine riser as sensor data. Finally, the influence of measured noise is analyzed. According to the damage localization results, the proposed method provides accurate damage locations of risers and is robust to overcome noise effect. 展开更多
关键词 marine risers structure damage detection dynamic response autoregressive moving average model noise signal
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Experimental study of structural damage identification based on WPT and coupling NN 被引量:1
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作者 郭健 陈勇 孙炳楠 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2005年第7期663-669,共7页
Too many sensors and data information in structural health monitoring system raise the problem of how to realize multi-sensor information fusion. An experiment on a three-story frame structure was conducted to obtain ... Too many sensors and data information in structural health monitoring system raise the problem of how to realize multi-sensor information fusion. An experiment on a three-story frame structure was conducted to obtain vibration test data in 36damage cases. A coupling neural network (NN) based on multi-sensor information fusion is proposed to achieve identification of damage occurrence, damage localization and damage quantification, respectively. First, wavelet packet transform (WPT) is used to extract features of vibration test data from structure with different damage extent. Then, data fusion is conducted by assembling feature vectors of different type sensors. Finally, three sets of coupling NN are constructed to implement decision fusion and damage identification. The results of experimental study proved the validity and feasibility of the proposed methodology. 展开更多
关键词 Damage identification Experimental study Wavelet packet transform (WPT) Coupling neural network (NN)
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Damage Detection of Offshore Jacket Structures Using Frequency Domain Selective Measurements 被引量:1
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作者 M. Kianian A.A. Golafshani E. Ghodrati 《Journal of Marine Science and Application》 2013年第2期193-199,共7页
The development of damage detection techniques for offshore jacket structures is vital to prevent catastrophic events. This paper applies a frequency response based method for the purpose of structural health monitori... The development of damage detection techniques for offshore jacket structures is vital to prevent catastrophic events. This paper applies a frequency response based method for the purpose of structural health monitoring. In efforts to fulfill this task, concept of the minimum rank perturbation theory has been utilized. The present article introduces a promising methodology to select frequency points effectively. To achieve this goal, modal strain energy ratio of each member was evaluated at different natural frequencies of structure in order to identify the sensitive frequency domain for damage detection. The proposed methodology opens up the possibility of much greater detection efficiency. In addition, the performance of the proposed method was evaluated in relation to multiple damages. The aforementioned points are illustrated using the numerical study of a two dimensional jacket platform, and the results proved to be satisfactory utilizing the proposed methodology. 展开更多
关键词 damage detection structural health monitoring frequency response function offshore jacket platform minimum rank perturbation theory element modal strain energy ratio
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Experimental investigation of subsurface damage depth of lapped optics by fluorescent method 被引量:5
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作者 WANG Hong-xiang HOU Jing +2 位作者 WANG Jing-he ZHU Ben-wen ZHANG Yan-hu 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第7期1678-1689,共12页
Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica o... Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths. 展开更多
关键词 OPTICS subsurface defect nondestructive detection LAPPING subsurface damage
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Fatigue damage evaluation by metal magnetic memory testing 被引量:5
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作者 王慧鹏 董丽虹 +1 位作者 董世运 徐滨士 《Journal of Central South University》 SCIE EI CAS 2014年第1期65-70,共6页
Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of... Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of Hp(x),throughout the fatigue process were presented and analyzed.Abnormal peaks of Hp(y) and peak of Hp(x) reversed after loading; Hp(y) curves rotated clockwise and Hp(x) curves elevated significantly with the increase of fatigue cycle number at the first a few fatigue cycles,both Hp(y) and Hp(x) curves were stable after that,the amplitude of abnormal peaks of Hp(y) and peak value of Hp(x) increased more quickly after fatigue crack initiation.Abnormal peaks of Hp(y) and peak of Hp(x) at the notch reversed again after failure.The characteristics were found to exhibit consistent tendency in the whole fatigue life and behave differently in different stages of fatigue.In initial and crack developing stages,the characteristics increased significantly due to dislocations increase and crack propagation,respectively.In stable stage,the characteristics remained constant as a result of dislocation blocking,K value ranged from 20 to 30 A/(m·mm)-1,and Hp(x)M ranged from 270 to 300 A/m under the test parameters in this work.After failure,both abnormal peaks of Hp(y) and peak of Hp(x) reversed,K value was 133 A/(m·mm)-1 and Hp(x)M was-640 A/m.The results indicate that the characteristics of Hp(y) and Hp(x) signals were related to the accumulation of fatigue,so it is feasible and applicable to monitor fatigue damage of ferromagnetic components using metal magnetic memory testing(MMMT). 展开更多
关键词 metal magnetic memory testing MMMT signal tension-compression fatigue test feature extraction
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Molecular Dynamics of Nanometric Processing of Ion Implanted Monocrystalline Silicon Surfaces
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作者 陈耘辉 房丰洲 +1 位作者 张效栋 胡小唐 《Transactions of Tianjin University》 EI CAS 2014年第3期203-209,共7页
Three-dimensional molecular dynamics simulations are carried out to study the mechanism of nanometric processing of ion implanted monocrystalline silicon surfaces. Lattice transformation is observed during implantatio... Three-dimensional molecular dynamics simulations are carried out to study the mechanism of nanometric processing of ion implanted monocrystalline silicon surfaces. Lattice transformation is observed during implantation and nano-indentation using radial distribution function and geometric criterion damage detection. Nano-indentation is simulated to study the changes of mechanical property. Implantation analysis shows the existence of amorphous phase. Indentation process shows the lattice evolution, which is beneficial for reducing fractures during processing. The indentation results reveal the reduction of brittleness and hardness of the implanted surface. The ion fluence is in direct proportion to the damage, and inverse to the hardness of the material. Experiments of ion implar, tation, nanoindentation, nano-scratching and nanometric cutting were carried out to verify the simulation results. 展开更多
关键词 molecular dynamics ion implantation monocrystalline silicon nanometric cutting
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Experimental Damage Identification Using Modified Mode Shape Difference
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作者 Ahmed A. Elshafey H. Marzouk M. R. Haddara 《Journal of Marine Science and Application》 2011年第2期150-155,共6页
An experimental program was undertaken to test the feasibility to detect the occurrence of structural damage using a modified mode shape difference technique. The vibration response of a steel beam fixed at one end an... An experimental program was undertaken to test the feasibility to detect the occurrence of structural damage using a modified mode shape difference technique. The vibration response of a steel beam fixed at one end and hinged at the other was obtained for the intact and damage conditions. Modal analysis was performed to extract the frequencies and mode shapes. The method shows a good potential in detection of occurrence and location of damage. 展开更多
关键词 mode shape damage detection damage location modal analysis
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Computational Study of the A0 Scattered Field Due to an Edge Delamination
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作者 Nithurshan Nadarajah Benjamin Steven Vien +1 位作者 Wing Kong Chiu L. R. Francis Rose 《Journal of Mechanics Engineering and Automation》 2015年第4期229-236,共8页
Delamination detection presents a pertinent problem for SHM be no visible signs of the damage on the surface of the structure. (structural health monitoring), as in most cases, there may This study investigates the ... Delamination detection presents a pertinent problem for SHM be no visible signs of the damage on the surface of the structure. (structural health monitoring), as in most cases, there may This study investigates the scattering of a zeroth-order anti-symmetric (A0) Lamb wave mode by an edge delamination using the commercial FE (finite element) package ABAQUS. The Ao Lamb mode is chosen because the corresponding stress distribution is more sensitive to delamination than is the case for symmetric modes. The paper presents results for the scatter field for various angles of incidence, and for varying defect sizes. The regime of small defect size relative to the incident wavelength is of particular interest for SHM as it corresponds to early damage detection. It is shown that, in this regime the scattered field appears to originate from a point source at the origin of the delamination, and the corresponding amplitude is linearly proportional to area of the delamination. These results can be used to guide the use of Lamb waves to detect and quantify edge delamination in plate-like structures. 展开更多
关键词 Structural health monitoring Lamb waves wave scattering delamination damage.
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Data-based model free hysteresis identification for a nonlinear structure
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作者 Xu Bin He Jia +1 位作者 Zhou Ren Masri F. Sami 《Engineering Sciences》 EI 2010年第2期12-19,共8页
In the last two decades, the damage detection for civil engineering structures has been widely treated as a modal analysis problem and most of the currently available vibration-based system identification approaches a... In the last two decades, the damage detection for civil engineering structures has been widely treated as a modal analysis problem and most of the currently available vibration-based system identification approaches are based on modal parameters, namely the natural frequencies, mode shapes and damping ratios, and/or their derivations, which are suitable for linear systems. Nonlinearity is generic in engineering structures. For example, the initiation and development of cracks in civil engineering structures as typical structural damages are nonlinear process. One of the major challenges in damage detection, early warning and damage prognosis is to obtain reasonably accurate identification of nonlinear performance such as hysteresis which is the direct indicator of damage initiation and development under dynamic excitations. In this study, a general data-based identification approach for hysteretic performance in form of nonlinear restoring force using structural dynamic responses and complete and incomplete excitation measurement time series was proposed and validated with a 4-story frame structure equipped with smart devices of magneto-theological (MR) damper to simulate nonlinear performance. Firstly, as an optimization method, the least-squares technique was employed to identify the system matrices of an equivalent linear system of the nonlinear structure model basing on the exci- tation force and the corresponding vibration measurements with impact test when complete and incomplete excitations; and secondly, the nonlinear restoring force of the structure was identified and compared with the test measurements fi- nally. Results show that the proposed data-based approach is capable of identifying the nonlinear behavior of engineering structures and can be employed to evaluate the damage initiation and development of different structure under dynamic loads. 展开更多
关键词 nonlinear restoring force identification nonlinear systems 4-story structure impact force time series least-squares techniques MR damper
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An Improved Damage Identification Method Based on Mode Information
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作者 YANG Fengyan YANG Yongchun 《Journal of Ocean University of China》 SCIE CAS 2006年第3期273-277,共5页
This paper presents a new algorithm to predict locations and severities of damage in structures by changing modal parameters. An existing algorithm of damage detection is reviewed and the new algorithm is formulated t... This paper presents a new algorithm to predict locations and severities of damage in structures by changing modal parameters. An existing algorithm of damage detection is reviewed and the new algorithm is formulated to improve the accuracy of damage locating and severity estimation by eliminating the erratic assumptions and limits in the existing algorithm. The damage prediction accuracy is numerically assessed for each algorithm when applied to a two-dimensional frame structure for which pre-damage and post-damage modal parameters are available for only a few modes of vibration. The analysis results illustrate the improved accuracy of the new algorithm when compared to the existing algorithm. 展开更多
关键词 structural damage nondestructive detection damage identification modal analysis
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Dynamic Detection of Reinforced Concrete Bridge Damage by Finite Element Model Updating
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《Journal of Mechanics Engineering and Automation》 2014年第1期40-45,共6页
The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM (mathematical model updating method) from incomplete test data. A well suited finite element model of a repair... The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM (mathematical model updating method) from incomplete test data. A well suited finite element model of a repaired bridge is carried out. The diagnosis enables us to locate and detect the damage in a reinforced concrete bridge. Thus, developments of analytical predictions have been checked by modal testing techniques. Besides, the FTCS (finite time centered space) scheme is developed to solve the set of equations which can easily handle finite element matrices of a bridge model. It is shown in this study that the method is applied to detect damages as well as existing cracks in real time of a repaired bridge. To check the efficiency of the method, the repaired bridge of OuedOumazer in Algeria has been selected. It is proven that identification methods have been able to detect the exact location of damage areas to be corrected avoiding the inaccuracy from the finite element model for the mass, stiffness and loading. 展开更多
关键词 BRIDGES DAMAGE DETECTION MMUM finite elements FTCS correlation.
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The Role of Heat Shock Protein 70, IgE and MMP-9 in Detecting Early Minor Myocardial Damage and Evaluating the Efficacy of Coronary Artery Bypass Grafting (CABG)
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作者 Amal A. Baalash Hala E. Hamouda +2 位作者 Ghada M. Ismail Ibrahim K. Yassein Bedir M. Ibrahim 《Journal of Life Sciences》 2012年第3期260-267,共8页
The objective of this research was to identify levels of heat shock protein 70 (Hsp 70), total immunoglobulin E (IgE) and matrix metalloproteinase-9 (MMP-9) before and after coronary artery bypass grafting (CAB... The objective of this research was to identify levels of heat shock protein 70 (Hsp 70), total immunoglobulin E (IgE) and matrix metalloproteinase-9 (MMP-9) before and after coronary artery bypass grafting (CABG) surgery. Hsp 70, IgE, MMP-9, creatine phosphokinase-MB (CPK-MB), and lactate dehydrogenase (LDH) levels were measured in normal subjects (n = 20), and in patients with chronic stable angina pectoris who were referred for elective CABG, before and after performing CABG-surgery (n = 20). Compared with normal subjects, increased Hsp 70 and IgE levels, unchanged MMP-9 level, and activities of CPK-MB and LDH were found in the pre-operative patient group. Hsp 70 and IgE levels in the post-operative period were significantly reduced when compared to pre-operative period. Hsp 70 and IgE might be used as markers for detection of early minor myocardial damage, and coronary insufficiency with less overt damage than myocardial infarction, as significant changes in their levels appear before occurrence of in any changes in the levels of MMP-9, CPK-MB and LDH. Besides, Hsp 70, and IgE returning to the normal levels after CABG surgery, suggest that they could be helpful to evaluate the effect of CABG surgery. 展开更多
关键词 Heat shock protein IGE metaloproteinases MMP-9 myocardial ischemia coronary artery bypasses grafting.
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