Download Identification of Damage Using Lamb Waves by Zhongqing Su, Lin Ye PDF
By Zhongqing Su, Lin Ye
Since the early Nineteen Nineties elevated curiosity within the use of Lamb waves (dynamic tension waves traveling in skinny plate/shell constructions) for selecting harm in engineering constructions has resulted in major advances in wisdom and know-how. Identification of wear utilizing Lamb Waves presents crucial knowledge for constructing Lamb-wave-based harm id innovations. It addresses basics reminiscent of the mechanisms of Lamb wave activation, propagation and acquisition, the choice of transducers and layout of lively sensor networks, and the advance of sign processing for de-noising, compression and have extraction within the time, frequency and joint time-frequency domain names. It additionally offers particular descriptions of varied sign fusion algorithms for the quantitative decision of wear parameters вЂ“ situation, orientation, measurement and severity. different key issues include:
вЂў finite point modelling and experimental innovations for Lamb waves;
вЂў energetic sensor community know-how utilizing numerous brokers, e.g., piezoelectric actuator/sensor and fibre Bragg grating sensor;
вЂў software-hardware structures for implementation of Lamb-wave-based harm id together with Lamb wave sign new release, acquisition and processing; and
вЂў consultant case reviews and numerous engineering applications.
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7. 7. 9 for each layer has four unknown constants, C1n , C2n , C3n and C4n ( n = 1, 2, A, N ). 0 SH0 2 6 4 8 (Thickness × frequency) / cT c Fig. 7. Dispersion curves of a. S i ; b. Ai ; and c. 4; cT =3170 m/s in aluminium alloy)  Fundamentals and Analysis of Lamb Waves ⎡ A11 ⎢ A ⎢ 21 ⎢ B ⎢ ⎢⎣ A( 4 N )1 A12 A22 B A( 4 N ) 2 31 A A1( 4 N ) ⎤ ⎡ C11 ⎤ ⎡0⎤ ⎢ ⎥ A A2( 4 N ) ⎥⎥ ⎢ C21 ⎥ ⎢0⎥ =⎢ ⎥. 17) [A] stands for the coefficient matrix. , ( ) A ω , k , λn , µ n , d n = 0 . , the dispersion equations of Lamb waves in multi-layered structures.
5 Attenuation of Lamb Waves It is common knowledge that the energy of Lamb waves dissipates with distance, a phenomenon known as attenuation, manifesting as the gradual reduction in magnitude of wave signals. With the existence of damage or inhomogeneity such as stiffeners or fasteners, the dissipation increases. For example, it has been observed that 52% of the total energy dissipates when Lamb waves pass through a damage area of 7 mm in diameter in a composite laminate (100 mm × 100 mm) .
23, subject to different incident angles ( θ i ), when the notch length is 20 and 40 mm, respectively. It is apparent that the reflection coefficient decreases while the 50 Identification of Damage Using Lamb Waves transmission coefficient increases substantially as θ i increases, showing strong angular dependence of the scattered Lamb waves. 2 0 15 30 45 60 Incident angle [degree] a 75 90 0 15 30 45 60 75 90 Incident angle [degree] b Fig. 23. a. Reflection; and b. 24 when θ i = 00 . This suggests that the notch length may not be defined solely by the reflection coefficient, since that may refer to two different notch lengths.