A novel Helmholtz potential approach to predicting acoustic guided waves generated by fatigue crack

2018 ◽  
Author(s):  
Mohammad Faisal Haider Mohammad Faisal Haider
Keyword(s):  
Fatigue Crack ◽  
Guided Waves ◽  
Potential Approach ◽  
Helmholtz Potential

scholarly journals Fatigue crack detection in pipes with multiple mode nonlinear guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 180-192 ◽  
Author(s):  
Ruiqi Guan ◽  
Ye Lu ◽  
Kai Wang ◽  
Zhongqing Su
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Testing ◽  
Harmonic Wave ◽  
Guided Wave ◽  
Element Analysis ◽  
Fatigue Crack Detection ◽  
Wave Modes

This study elaborates fundamental differences in fatigue crack detection using nonlinear guided waves between plate and pipe structures and provides an effective approach for analysing nonlinearity in pipe structures. For this purpose, guided wave propagation and interaction with microcrack in a pipe structure, which introduced a contact acoustic nonlinearity, was analysed through a finite element analysis in which the material nonlinearity was also included. To validate the simulation results, experimental testing was performed using piezoelectric transducers to generate guided waves in a specimen with a fatigue crack. Both methods revealed that the second harmonic wave generated by the breathing behaviour of the microcrack in a pipe had multiple wave modes, unlike the plate scenario using nonlinear guided waves. Therefore, a proper index which considered all the generated wave modes due to the microcrack was developed to quantify the nonlinearity, facilitating the identification of microscale damage and further assessment of the severity of the damage in pipe structures.

scholarly journals Monitoring of Fatigue Crack Propagation by Damage Index of Ultrasonic Guided Waves Calculated by Various Acoustic Features

2019 ◽  
Vol 9 (20) ◽  
pp. 4254 ◽  
Author(s):  
Hashen Jin ◽  
Jiajia Yan ◽  
Weibin Li ◽  
Xinlin Qing
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Frequency Domain ◽  
Fatigue Crack Propagation ◽  
Guided Waves ◽  
Fatigue Cracks ◽  
Damage Index ◽  
Ultrasonic Guided Waves ◽  
Acoustic Features ◽  
Reliable Technique

Under cyclic and repetitive loads, fatigue cracks can be further propagated to a crucial level by accumulation, causing detrimental effects to structural integrity and potentially resulting in catastrophic consequences. Therefore, there is a demand to develop a reliable technique to monitor fatigue cracks quantitatively at an early stage. The objective of this paper is to characterize the propagation of fatigue cracks using the damage index (DI) calculated by various acoustic features of ultrasonic guided waves. A hybrid DI scheme for monitoring fatigue crack propagation is proposed using the linear fusion of damage indices (DIs) and differential fusion of DIs. An experiment is conducted on an SMA490BW steel plate-like structure to verify the proposed hybrid DIs scheme. The experimental results show that the hybrid DIs from various acoustic features can be used to quantitatively characterize the propagation of fatigue cracks, respectively. It is found that the fused DIs calculated by the acoustic features in the frequency domain have an improved reliable manner over those of the time domain. It is also clear that the linear and differential amplitude fusion DIs in the frequency domain are more promising to indicate the propagation of fatigue cracks quantitatively than other fused ones.

Fatigue crack detection under the vibration condition based on ultrasonic guided waves

2019 ◽  
pp. 147592171986077 ◽  
Author(s):  
Yanping Zhu ◽  
Fucai Li ◽  
Wenjie Bao
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Fatigue Testing ◽  
Ultrasonic Guided Waves ◽  
Testing Platform ◽  
Vibration Condition ◽  
Fatigue Crack Detection ◽  
The Difference ◽  
Index Value

Ultrasonic guided wave is an encouraging tool in structural health monitoring for civil, mechanical, ship, and aerospace devices. Most of heavy devices required a long-time running during the service, and the structure of these devices is under the vibration condition due to their inherent properties and working condition. This article mainly researches fatigue crack detection in vibration condition caused by operation using ultrasonic guided waves, aiming to study the application of ultrasonic guided waves in the field of structure dynamics. The detection method based on the difference index and the sequence curve of difference index between different states of crack is proposed to detect fatigue crack in vibration condition. The experiments are carried out on the fatigue testing platform and the vibration test-bed to investigate the relationship between opening states of fatigue crack and the difference index value of ultrasonic guided waves. In order to reduce the influence of loads applied by the fatigue testing platform on ultrasonic guided waves propagation, the initial experiment is first carried out to select the range of applied loads which have minimal influence on wave propagation. The results show that loads from 0 to 24 MPa have minimal effect on ultrasonic guided waves, and the difference index values of intact beam and cracked beam are in different orders of magnitude. Therefore, the method based on difference index value and sequence of difference index is credible to detect fatigue crack for structure in vibration condition.

Numerical Investigation of Nonlinear Lamb Wave Time Reversing for Fatigue Crack Detection

2019 ◽  
Author(s):  
Junzhen Wang ◽  
Yanfeng Shen
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Time Reversal ◽  
Lamb Wave ◽  
Crack Detection ◽  
Guided Waves ◽  
Fatigue Cracks ◽  
Contact Dynamics ◽  
Virtual Time ◽  
Fatigue Crack Detection

Abstract This paper presents a numerical study on nonlinear Lamb wave time reversing for fatigue crack detection. An analytical framework is initially presented, modeling Lamb wave generation, propagation, wave crack linear and nonlinear interaction, and reception. Subsequently, a 3D transient dynamic coupled-field finite element model is constructed to simulate the pitch-catch procedure in an aluminum plate using the commercial finite element software (ANSYS). The excitation frequency is carefully selected, where only single Lamb wave mode will be generated by the Piezoelectric Wafer Active Sensor (PWAS). The fatigue cracks are modelled nucleating from both sides of a rivet hole. In addition, contact dynamics are considered to capture the nonlinear interactions between guided waves and the fatigue cracks, which would induce Contact Acoustic Nonlinearity (CAN) into the guided waves. Then the conventional and virtual time reversal methods are realized by finite element simulation. Advanced signal processing techniques are used to extract the distinctive nonlinear features. Via the Fast Fourier Transform (FFT) and time-frequency spectral analysis, nonlinear superharmonic components are observed. The reconstructed signals attained from the conventional and virtual time reversal methods are compared and analyzed. Finally, various Damage Indices (DIs), based on the difference between the reconstructed signal and the excitation waveform as well as the amplitude ratio between the superharmonic and the fundamental frequency components are adopted to evaluate the fatigue crack severity. The DIs could provide quantitative diagnostic information for fatigue crack detection. This paper finishes with summary, concluding remarks, and suggestions for future work.

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