Damage Detection and Quantitative Assessment for the Cracked Beam Structures

2007 ◽  
Vol 353-358 ◽  
pp. 2431-2435 ◽  
Author(s):  
Yong Hong ◽  
Byung Jin Kim ◽  
Dong Pyo Hong ◽  
Young Moon Kim
Keyword(s):  
Frequency Shift ◽  
Quantitative Assessment ◽  
Evaluation Method ◽  
Mechanical Impedance ◽  
Peak Frequency ◽  
Beam Specimen ◽  
Cracked Beam ◽  
Beam Structures ◽  
Large Structures ◽  
Work Done

Beam structures are a common form in many large structures, and therefore the real-time condition monitoring and active control of beams will improve the reliability and safety of many structures. However, the incipient damage, i.e. cracks, is not easy to be detected with using the traditional methods, such as modal analysis, etc. Piezoceramic (PZT) sensors offer special opportunities for the health monitoring of structures constructed by beams. The change of mechanical impedance of structures along with the occurrence of damage is sensitively indicated by the change of electro-impedance of PZT sensors. This paper presents work done on developing and utilizing PZT sensors to detect and quantitatively assess the extent and locations of cracks occurred in simulated structures. The PZT sensors are conducted particularly to generate the longitudinal wave along the beam specimen, and systematic experiments conducted on statistical samples of incrementally damaged specimens were used to fully understand the method, the cracks with different length and location are simulated to indicate the feasibility of the detection and assessment. To estimate the damage conditions numerically, in this paper, we propose the evaluation method of impedance peak frequency shift F and CC (Correlation Coefficient), Cov (Covariance). The results of experiments verify that the impedance peak frequency shift Δ F uniformly assesses the location of cracks, and as well CC. and Cov assesses the size of cracks efficiently. The study presents the method that is satisfied for much higher frequencies, alternate power, and minute damages.

Evaluation Method for Seismic Fatigue Damage of Plant Pipeline

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Fumio Inada ◽  
Michiya Sakai ◽  
Ryo Morita ◽  
Ichiro Tamura ◽  
Shin-ichi Matsuura ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Nuclear Power ◽  
Power Plants ◽  
Evaluation Method ◽  
Response Spectrum ◽  
Damage Mechanism ◽  
Peak Frequency ◽  
Cumulative Damage ◽  
Cumulative Absolute Velocity ◽  
Seismic Index

Although acceleration and cumulative absolute velocity (CAV) are used as seismic indexes, their relationship with the damage mechanism is not yet understood. In this paper, a simplified evaluation method for seismic fatigue damage, which can be used as a seismic index for screening, is derived from the stress amplitude obtained from CAV for one cycle in accordance with the velocity criterion in ASME Operation and Maintenance of Nuclear Power Plants 2012, and the linear cumulative damage due to fatigue can be obtained from the linear cumulative damage rule. To verify the performance of the method, the vibration response of a cantilever pipe is calculated for four earthquake waves, and the cumulative fatigue damage is evaluated using the rain flow method. The result is in good agreement with the value obtained by the method based on the relative response. When the response spectrum obtained by the evaluation method is considered, the value obtained by the evaluation method has a peak at the peak frequency of the ground motion, and the value decreases with increasing natural frequency above the peak frequency. A higher peak frequency of the base leads to a higher value obtained by the evaluation method.

A Simulation Study on Welding Induced Distortion Control for Large Box Beam Structures

2004 ◽  
Author(s):  
Jun Xu ◽  
Wei Li
Keyword(s):  
Simulation Study ◽  
Welding Process ◽  
Three Dimensions ◽  
Beam Structures ◽  
Large Structures ◽  
Box Beam ◽  
Element Simulation ◽  
Distortion Control ◽  
Thermal Tensioning ◽  
Transient Thermal

Welding induced distortion in large structures is a major quality concern in industry. Many methods have been proposed in recent years to minimize the welding induced distortion. Among the available methods, transient thermal tensioning has been shown effective for minimizing the welding induced buckling distortion for T-joints. Due to the complexity of the welding process, different structures may require different strategies for distortion control. This paper presents a finite element simulation study on the distortion control for large box beam structures. The transient thermal tensioning method is applied through differential preheat on the two side plates of the beam. The effects of the preheating parameters including the average preheating temperature, temperature differential, and the preheating location are analyzed. It has been found that differential preheating control is effective in adjust the welding induced twist distortions. However, excessive differential preheating could generate bowing distortions. To determine an optimal preheating strategy, the distortions in all the three dimensions of a beam need to be considered simultaneously.

Estimation of quality factor based on peak frequency-shift method and redatuming operator: Application in real data set

Geophysics ◽  
2017 ◽  
Vol 82 (1) ◽  
pp. N1-N12 ◽  
Author(s):  
Francisco de S. Oliveira ◽  
Jose J. S. de Figueiredo ◽  
Andrei G. Oliveira ◽  
Jörg Schleicher ◽  
Iury C. S. Araújo
Keyword(s):  
Frequency Shift ◽  
Quality Factor ◽  
Real Data ◽  
Peak Frequency ◽  
Accurate Estimation ◽  
Layer By Layer ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Energy Dissipated ◽  
Factor Estimation

Quality factor estimation and correction are necessary to compensate the seismic energy dissipated during acoustic-/elastic-wave propagation in the earth. In this process, known as [Formula: see text]-filtering in the realm of seismic processing, the main goal is to improve the resolution of the seismic signal, as well as to recover part of the energy dissipated by the anelastic attenuation. We have found a way to improve [Formula: see text]-factor estimation from seismic reflection data. Our methodology is based on the combination of the peak-frequency-shift (PFS) method and the redatuming operator. Our innovation is in the way we correct traveltimes when the medium consists of many layers. In other words, the correction of the traveltime table used in the PFS method is performed using the redatuming operator. This operation, performed iteratively, allows a more accurate estimation of the [Formula: see text] factor layer by layer. Applications to synthetic and real data (Viking Graben) reveal the feasibility of our analysis.

scholarly journals Identification of Crack Location in Beam Structures Using Wavelet Transform and Fractal Dimension

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Yong-Ying Jiang ◽  
Bing Li ◽  
Zhou-Suo Zhang ◽  
Xue-Feng Chen
Keyword(s):  
Fractal Dimension ◽  
Wavelet Transform ◽  
Mode Shape ◽  
Practical Importance ◽  
Estimation Method ◽  
Experimental Investigations ◽  
Complex Structures ◽  
Cracked Beam ◽  
Beam Structures ◽  
Crack Location

Identification of structural crack location has become an intensely investigated subject due to its practical importance. In this paper, a hybrid method is presented to detect crack locations using wavelet transform and fractal dimension (FD) for beam structures. Wavelet transform is employed to decompose the mode shape of the cracked beam. In many cases, small crack location cannot be identified from approximation signal and detailed signals. And FD estimation method is applied to calculate FD parameters of detailed signals. The crack locations will be detected accurately by FD singularity of the detailed signals. The effectiveness of the proposed method is validated by numerical simulations and experimental investigations for a cantilever beam. The results indicate that the proposed method is feasible and can been extended to more complex structures.

Incipient Crack Identification in Beam Structures Using the Slope of the Anti-Resonance Curve

2007 ◽  
Vol 347 ◽  
pp. 601-606 ◽  
Author(s):  
Dan Sheng Wang ◽  
Hong Ping Zhu ◽  
Bo He
Keyword(s):  
Damage Identification ◽  
Mechanical Impedance ◽  
Resonance Curve ◽  
Crack Identification ◽  
Civil Structures ◽  
Cracked Beam ◽  
Impedance Characteristics ◽  
Simple Support ◽  
Rotational Spring Model ◽  
Incipient Crack

Crack damage brings a serious threat to the safety of mechanical and civil structures, and the problem of incipient damage identification of structures has been paying attention as a puzzle by many researchers in recent years. To seek for an alternative solution of the problem, a method for incipient crack localization using the slope of the anti-resonance curve is proposed in this paper. The method makes use of the driving-point mechanical impedance characteristics of cracked beams stimulated by harmonic force. To characterize the local discontinuity due to the presence of crack, a simplified rotational spring model is presented to model the crack. Subsequently, the proposed method is verified by a numerical example of cracked beam under simple support or cantilever boundary conditions.

scholarly journals Quality factor estimation based on the peak frequency shift method using a robust Fourier transform to VSP data

2019 ◽  
Vol 16 (6) ◽  
pp. 1061-1070 ◽  
Author(s):  
Rómulo Sandoval ◽  
José L Paredes ◽  
Flor A Vivas
Keyword(s):  
Fourier Transform ◽  
Frequency Shift ◽  
Quality Factor ◽  
Peak Frequency ◽  
Estimation Methods ◽  
Signal Spectrum ◽  
Q Factor ◽  
Shift Method ◽  
Vsp Data ◽  
Factor Estimation

Abstract Quality factor estimation (Q estimation) of vertical seismic profile (VSP) data are necessary for the process referred to as inverse Q-filtering, which is used, in turn, to improve the resolution of seismic signals. In general, the performances of Q estimation methods, based on the standard Fourier transform, are severely degraded in the presence of heavy-tailed distributed noise. In particular, these methods require a bandwidth detection which is difficult to estimate due to instabilities caused by outliers or gross errors, leading to an incorrect Q estimation. In this paper, an improvement of the Q-factor estimation based on the peak frequency shift method is proposed, where the signal spectrum is obtained using a robust transform algorithm. More precisely, the robust transform method assumes that the perturbations that contaminate the signal of interest can be characterized as random samples following a zero-mean Laplacian distribution, leading to the weighted median as the optimal operator for determining each transform coefficient. The proposed method is validated on synthetic datasets using different levels of noise and its performance is compared to those yielded by various methods based on the standard Fourier transform. Furthermore, a non-Gaussianity test is performed in order to characterize the noise distribution in real data. From the non-Gaussianity test, it can be observed that the underlying noise is better characterized using a Laplacian statistical model, and therefore, the proposed method is a suitable approach for computing the Q factor. Finally, the proposed methodology is applied to estimate the Q factors of real VSP data.

scholarly journals Energy Evolution and AE Failure Precursory Characteristics of Rocks with Different Rockburst Proneness

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Feng Pei ◽  
Hongguang Ji ◽  
Jiwei Zhao ◽  
Jingming Geng
Keyword(s):  
Evaluation Method ◽  
Comprehensive Evaluation ◽  
Failure Process ◽  
Effective Means ◽  
Testing Machine ◽  
Peak Stress ◽  
Peak Frequency ◽  
Energy Evolution ◽  
Comprehensive Evaluation Method ◽  
Precursory Information

Mastering the precursory information of rock failure is the basis of scientifically predicting rockburst, and AE technology is an effective means to solve this problem. The conventional uniaxial loading and cyclic loading/unloading tests of metagabbro and granite were carried out with GAW-2000 uniaxial electrohydraulic rigid testing machine to evaluate rockburst proneness. The energy evolution and AE characteristics of rocks with different rockburst proneness during loading are revealed. The results show that the rockburst proneness of granite is obviously stronger than that of metagabbro based on the comprehensive evaluation method of multiple rockburst proneness index. The reasons for different rockburst proneness are analyzed from the perspective of mineral composition and microstructure. Rockburst proneness is positively correlated with energy storage capacity. The elastic energy ratio of granite is obviously larger than that of metagabbro before peak stress. The intensity of AE signals generated in the failure process of strong rockburst rock (granite) is significantly higher than that of moderate rockburst rock (metagabbro). However, the peak frequency bands and amplitude all increase obviously before failure. The b-value and memory characteristics of rock with different rockburst proneness have obvious similar change rules.

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