On the influence of using a non-ideal element model to predict the generation of plane wave fronts for air-coupled concave arrays transducers used on Lamb waves NDT

2007 ◽  
Author(s):  
J. L. Prego Borges ◽  
Y. Yañez ◽  
J. A. Chávez ◽  
J. Salazar ◽  
A. Turó ◽  
...  
Keyword(s):  
Plane Wave ◽  
Lamb Waves ◽  
Element Model ◽  
Ideal Element ◽  
Wave Fronts

Lamb wave-based experimental and numerical studies for detection and sizing of corrosion damage in metallic plates

2018 ◽  
Vol 233 (6) ◽  
pp. 2107-2120 ◽  
Author(s):  
Adel Sedaghati ◽  
Farhang Honarvar ◽  
Anthony N Sinclair
Keyword(s):  
Guided Waves ◽  
Lamb Waves ◽  
Corrosion Damage ◽  
Element Model ◽  
Thin Plates ◽  
Aluminum Plate ◽  
Arrival Times ◽  
Numerical Studies ◽  
Corrosion Defects

Lamb waves are ultrasonic-guided waves with applications in inspection and monitoring of plate-like structures. These waves can be used for detecting, locating, and sizing of defects. In this paper, a new method is proposed for in situ measurement of the location and size of circle-like corrosion defects in thin plates. A novel technique for omnidirectional generation of Lamb waves is also proposed. The probe is placed on at least three different points around the defect and the arrival times of reflected echoes are measured. An algorithm then estimates the location and size of the defect based on the arrival times of reflected echoes. A finite element model is also developed for modeling the process and studying various aspects of the method. The proposed method is then tested on an aluminum plate. The center location and radius of a 5-mm hole in a 0.5-mm thick aluminum plate is estimated with uncertainties of ±1 mm (1%) and ±0.25 mm (5%), respectively. Various aspects of the proposed method are discussed, and uncertainties in measurements are estimated. Effectiveness of the proposed method is also assessed by sizing actual corrosion defects. The proposed method is fast, flexible, and portable and shows better accuracy in comparison to similar existing methods.

Time-domain topological energy imaging with ultrasonic Lamb waves considering multiple defects

2020 ◽  
Vol 62 (4) ◽  
pp. 208-215
Author(s):  
Wenfa Zhu ◽  
Yujie Zhang ◽  
Guopeng Fan ◽  
Haiyan Zhang ◽  
Shao Wei
Keyword(s):  
Numerical Simulation ◽  
Time Domain ◽  
Lamb Waves ◽  
Super Resolution ◽  
Element Model ◽  
Rayleigh Criterion ◽  
Multiple Defects ◽  
Reference Medium ◽  
Resolution Imaging ◽  
Imaging Resolution

This study presents a fast imaging approach with ultrasonic Lamb waves based on time-domain topological energy to identify multiple defects with defect spacing smaller than the threshold of the Rayleigh criterion in terms of imaging resolution. The direct acoustical field and time-domain topological energy of the two fields are used as imaging functions when considering the calculation of direct and adjoint acoustical fields in a non-defective reference medium on the basis of topological theory. The functions are not limited by acoustic diffraction and can achieve super-resolution imaging with multiple defects. First, a 3D finite element model is established. Transient acoustic field diagrams at different moments are used to show the focusing process of direct and adjoint acoustical fields clearly with multiple defects, thereby revealing the physical mechanism of time-domain topological energy imaging. Second, the effectiveness of the proposed approach to characterise multiple defects when the defect spacing is smaller than the imaging resolution threshold is verified through numerical simulation. Finally, the feasibility of super-resolution imaging considering multiple defects is proven by conducting experiments on aluminium plate samples with multiple defects under different defect spacing conditions. Numerical simulation and experimental results show that the proposed approach can overcome the problem of multiple defects with defect spacing smaller than the imaging resolution threshold by breaking the Rayleigh criterion constraint, while the accuracy presented is higher than that of the traditional delay-and-sum method.

Kinetic conditions for the existence of wave fronts in reaction-diffusion systems

1986 ◽  
Vol 103 (1-2) ◽  
pp. 161-177 ◽  
Author(s):  
José M. Fraile ◽  
José Sabina
Keyword(s):  
Plane Wave ◽  
Propagation Velocity ◽  
Reaction Diffusion ◽  
Wave Fronts ◽  
Reaction Diffusion Systems ◽  
Diffusion Systems ◽  
Partial Invariance

SynopsisThis paper deals with the existence of bounded plane wave fronts of reaction-diffusion systems. The main result ensures the partial invariance of a certain region, under kinetic conditions commonly used in the literature. This allows us to construct bounded plane wave fronts taking their values in that domain. We also give an estimate of the minimum permissible value of the propagation velocity of those plane wave fronts. Some examples are given.

Lamb Wave Based Damage Identification in Structures With Complex Geometry

2008 ◽  
Author(s):  
Xi Lu ◽  
Fucai Li ◽  
Guang Meng ◽  
Lin Ye ◽  
Ye Lu
Keyword(s):  
Finite Element ◽  
Lamb Wave ◽  
Damage Identification ◽  
Complex Geometry ◽  
Lamb Waves ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Element Model ◽  
Crack Location ◽  
Propagation Behavior

Structural health monitoring (SHM) plays a significant role in terms of fatigue life and damage accumulation prognostics. SHM for structures with complex geometry are much more practical in engineering applications. In this paper, complex aluminium alloy structures with “U” shape section were evaluated in terms of both finite element method (FEM)- and experiment-based Lamb wave analysis for the purpose of damage detection and identification. In the FEM-based analysis, three-dimensional finite element model was established to simulate the propagation behavior of Lamb wave in the structures. On the other hand, in the experiments, piezoelectric (PZT) wafers, functioning as both actuator and sensor, were used to generate Lamb waves propagating in the structures and collect the Lamb wave signals from the complex structures. Quantitative relationship between crack location and the reflection coefficient was constructed by taking advantage of continuous wavelet transform (CWT) and Hilbert transform (HT), which are based on the collected Lamb wave signals. Furthermore, the differences between simulated and experimental results in respect of crack severity evaluation and the reasons were discussed.

scholarly journals Propagation of Non-Linear Lamb Waves in Adhesive Joint with Micro-Cracks Distributing Randomly

2020 ◽  
Vol 10 (3) ◽  
pp. 741 ◽  
Author(s):  
Xiaoyang Li ◽  
Guoshuang Shui ◽  
Youxuan Zhao ◽  
Yue-Sheng Wang
Keyword(s):  
Adhesive Joint ◽  
Lamb Waves ◽  
Damage Zone ◽  
Adhesive Layer ◽  
Propagation Distance ◽  
Element Model ◽  
Matching Condition ◽  
Simulation Method ◽  
Micro Cracks ◽  
Non Linear

With the advantages of uniform stress transfer and weight reduction, adhesive joints are widely used in engineering. The propagation of non-linear Lamb waves in an adhesive joint with micro-cracks distributing in a random way is systematically investigated by using the numerical simulation method in this paper. A finite element model of the tri-layer adhesive structure with micro-cracks distributing randomly is established, and the Lamb wave mode pair with a matching condition of the phase velocity is chosen to examine the interaction of the micro-cracks with Lamb waves. The results show that the micro-cracks within the adhesive layer will lead to the generation of second harmonics. We also find that the Acoustic Non-linearity Parameters (ANP) increase with the propagation distance in the micro-crack damage zone and the density of the micro-cracks. However, ANPs are less concerned with the friction coefficients of the surface of micro-cracks. This numerical research reveals that non-linear Lamb waves can be employed to effectively characterize the micro-cracks related damages within an adhesive joint.

scholarly journals On the Directivity of Acoustic Waves Generated by the Angle Beam Wedge Actuator in Thin-Walled Structures

Actuators ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 64 ◽  
Author(s):  
Sergey Shevtsov ◽  
Valery Chebanenko ◽  
Maria Shevtsova ◽  
Evgenia Kirillova ◽  
Evgeny Rozhkov
Keyword(s):  
Experimental Study ◽  
Acoustic Waves ◽  
Lamb Waves ◽  
Oscillation Amplitude ◽  
Element Model ◽  
Propagation Length ◽  
Thin Walled Structures ◽  
Plastic Panel ◽  
Thin Walled ◽  
The Waves

The paper aims to develop improved acoustic-based structural health monitoring (SHM) and nondestructive evaluation (NDE) techniques, which provide the waves directivity emitted by the angle beam wedge actuators in thin-walled structures made of plastic materials and polymeric composites. Our investigation includes the dispersive analysis of the waves that can be excited in the studied plastic panel. Its results allowed to find two kinds of generated acoustic waves—anti-symmetric Lamb waves (A0) and shear horizontally polarized SH waves (SS0). The bounds of the chosen frequency range for the experimental and numerical studies were accepted as a compromise between the desire to obtain a high defect resolution by generating short waves, their adjustable directivity, and maximum propagation length. The finite element model for the transducer was built by using the results of an actuator structure experimental study. The frequency response functions for the actuator current and oscillation amplitude of the footprint surface demonstrated good agreement. The found eigenfrequencies of the actuator’s structure were used for the numerical and experimental study of the Lamb and SH wave generation and propagation in a thin-walled plastic panel. Our results convincingly demonstrated the satisfactory directivity of the actuated waves at their excitation on the frequencies that corresponded to the natural modes of the actuator oscillation. The authors assume that an efficient use of the proposed technique for other analyzed quasi-isotropic materials and applied actuators can be provided by preliminary research using a similar approach and methods presented in this article.

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