Ultrasonic imaging for non-destructive evaluation of standing trees: effect of anisotropy on image reconstruction

Espinosa, Luis; Prieto, Flavio; Brancheriau, Loïc

doi:10.1117/12.2266757

Cited by 3 publications

(4 citation statements)

References 17 publications

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“…1. When taking into account the anisotropy of wood in the transverse cross section of a tree, the propagation paths of acoustic waves are curved, and not straight rays as they are for an isotropic material (Espinosa et al 2017). As a result, the notion of wave velocity (considered as an intrinsic parameter of the material) associated with one pixel of the tomogram has no sense for anisotropic material, because the velocity depends on the direction of propagation.…”

Section: Resultsmentioning

confidence: 98%

“…This problem is solved assuming that the transverse cross section of trees is quasi-isotropic. The hypothesis of isotropy blurs the image and makes it difficult to characterize the mechanical state of wood and the presence of a defect (Arciniegas et al 2014;Espinosa et al 2017). A way to overcome this problem is to consider the cross section of a standing tree as being cylindrically orthotropic in the process of inversion, such that the 4 elastic constants of wood for each pixel in the radialtangential plane could be determined.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of Ultrasonic Wave Velocity Estimation Using the Christoffel Equation for Wood Non-Destructive Characterization

Espinosa¹,

Brancheriau²,

Prieto³

et al. 2017

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To perform a non-destructive evaluation of wood, the Christoffel equation is frequently used to describe the relationship between the ultrasonic wave velocity and the mechanical parameters. In the context of acoustical tomography imaging of standing trees, the key contribution of this numerical study is to determine the influence of mechanical parameters of the wood radial-tangential plane on the wave velocity computation using the Christoffel equation. Mechanical parameters from six species were selected. A sensitivity analysis was carried out by increasing and decreasing every parameter by a given percentage, and then by computing the variation of velocity for a set of wave direction of propagations. The evolution of the wave velocity, according to the direction of propagation, depended on the considered species; there was a difference between the softwoods and the hardwoods. The sensitivity analysis showed a bigger influence of the Young's moduli, followed by the Poisson's ratio, and finally by the shear modulus. However, these last two parameters cannot be neglected when using the Christoffel equation to solve the inverse problem of standing tree tomography. A proposed solution involves determining the propagation paths using the Young's moduli as variables and then inversing the set of equations in accordance with the overall parameters.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Sensitivity of Ultrasonic Wave Velocity Estimation Using the Christoffel Equation for Wood Non-Destructive Characterization

Espinosa¹,

Brancheriau²,

Prieto³

et al. 2017

BioResources

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“…The excitation signal used for testing is directly related to the precision of the TOF estimation, affecting the image reconstruction method [13,14]. This image reconstruction method must be adapted to the wood anisotropy condition, in order to avoid the bias introduced by the isotropic hypothesis considering straight-line trajectories [15,16]. For wood, the ray paths between the ultrasonic transmitter and the receivers are not straight as for isotropic media; therefore, the image reconstruction method should be adapted to deal with curved rays.…”

Section: Introductionmentioning

confidence: 99%

“…For wood, the ray paths between the ultrasonic transmitter and the receivers are not straight as for isotropic media; therefore, the image reconstruction method should be adapted to deal with curved rays. The defect position is other factor influencing the detection, with eccentric defects being more difficult to locate [16]. Other factor is related to the definition of the tree geometry, considering that most of the cases the cross-section will differ from a perfect circle, and these variations will modify the image construction.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic imaging of standing trees: factors influencing the decay detection

Espinosa

Prieto

Brancheriau

et al. 2019

2019 XXII Symposium on Image, Signal Processing and Artificial Vision (STSIVA)

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Ultrasound Computed Tomography is a widely used technique for nondestructive control of materials. One application is the evaluation of the inner state of standing trees in urban areas. The quality of the tomographic image depends on several factors, such as the number of probes used and the image reconstruction algorithm. Here we are interested in evaluating the influence of using a reconstruction algorithm adapted to wood anisotropy, compared to the classic methods using an isotropic model, and the effect of numerically increasing the number of sensors and the time-of-flight measurements using an interpolation method, known as sinogram interpolation. A numerical configuration was tested, simulating the presence of an eccentric defect in a wood section. Reconstructed images were compared before and after the interpolation process, and a thresholding was applied to quantify the decay area estimation. A more detailed defect identification was obtained with the reconstruction algorithm adapted to wood anisotropy and the interpolation of the sensors.

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Effect of wood anisotropy in ultrasonic wave propagation: A ray-tracing approach

et al. 2019

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Ultrasonic imaging for non-destructive evaluation of standing trees: effect of anisotropy on image reconstruction

Cited by 3 publications

References 17 publications

Sensitivity of Ultrasonic Wave Velocity Estimation Using the Christoffel Equation for Wood Non-Destructive Characterization

Sensitivity of Ultrasonic Wave Velocity Estimation Using the Christoffel Equation for Wood Non-Destructive Characterization

Ultrasonic imaging of standing trees: factors influencing the decay detection

Effect of wood anisotropy in ultrasonic wave propagation: A ray-tracing approach

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