Nonlinear Ultrasonic Phased Array Imaging

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.

Ultrasonic phased array imaging of contact-acoustic nonlinearity

“…Closed cracks, which exhibit only a weak linear scattering response, have classically been difficult to detect using such methods. Recently, the authors reported a technique for imaging elastic nonlinearity using phased arrays through evaluation of diffuse energy [4]. This technique uses the principle of the subtraction of parallel and sequentially transmitted acoustic fields to separate linear and nonlinear propagation.…”

Decoupling Nonclassical Nonlinear Behavior of Elastic Wave Types

“…This result could lead to further understanding of the nonlinear mechanical phenomena that arise in natural systems as well as to the design and engineering of nonlinear acoustic metamaterials. DOI: 10.1103/PhysRevLett.116.115501 Nonlinear mesoscopic elastic materials [1] exhibit unique and interesting properties related to nonlinear and nonequilibrium dynamics that are relevant to various natural and industrial processes ranging in scales and applications, e.g., the onset of earthquakes and avalanches in geophysics [2][3][4], the aging of infrastructures in civil engineering [5,6], the failure of mechanical parts in industrial settings [7][8][9], bone fragility in the medical field [10][11][12], or the design of novel materials, including nonlinear metamaterials, for shock absorption, acoustic focusing, and energy-harversting systems [13]. These properties include the dependence of wave speed and damping parameters on strain amplitude [5,14,15], slow relaxation [16,17], and hysteresis with end-point memory [18][19][20].…”

Closed crack imaging using time reversal method based on fundamental and second harmonic scattering

“…The imaging strategy is that the response from linear scatterers is not affected by the vibration, whereas the response from nonlinear scatterers depends on the instantaneous stress level during the vibration cycle, so that by subtracting images obtained at the peak and at the trough of the vibration cycle, one is left with an image of only the nonlinear scatterers, because the image of linear scatterers would cancel out during the subtraction. A related strategy is proposed by Potter et al [56] who note that the response of a nonlinear scatterer to a parallel (i.e. simultaneous) transmission from a phased array, with appropriate time delays to focus on a chosen location, is different from the sum of the responses using sequential transmission, because the nonlinear response does not vary linearly with the amplitude of the input excitation.…”

“…Previous attempts at nonlinear ultrasonic imaging can be divided into two groups depending on whether the image reconstruction process involves (i) a point by point scanning of the ultrasonic response at every point (or pixel) within a prescribed imaging domain, usually (but not necessarily) using a laser vibrometer [36][37][38][39][40][41][42][43][44][45][46][47], or (ii) implementing an imaging algorithm that uses as input the measurements recorded by a sensor array deployed around and outside the imaging domain [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65]. The present work belongs to the second group, which is of greater interest for structural health monitoring based on built-in sensor arrays.…”