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Evaluation Of Eddy-Current Probe Signals Due To Cracks In Fastener Holes, John R. Bowler, Theodoros P. Theodoulidis, Hui Xie, Yuan Ji
Evaluation Of Eddy-Current Probe Signals Due To Cracks In Fastener Holes, John R. Bowler, Theodoros P. Theodoulidis, Hui Xie, Yuan Ji
John R. Bowler
Cracks in conductors are detected through changes in the impedance of a coil that induces current in the material. In order to gain insight into the physics of the inspection, we have developed a theoretical and computational model that predicts the signals due to cracks in circular cylindrical holes using a boundary element calculation. In formulating the problem, the electromagnetic field is decomposed into transverse electric and transverse magnetic scalar modes. The effect of a planar crack in an electromagnetic field is represented by an electric current dipole layer orientated normal to the crack surface. The dipole density is determined …
Markov Chain Monte Carlo Defect Identification In Nde Images, Aleksandar Dogandžić, Benhong Zhang
Markov Chain Monte Carlo Defect Identification In Nde Images, Aleksandar Dogandžić, Benhong Zhang
Aleksandar Dogandžić
We derive a hierarchical Bayesian method for identifying elliptically‐shaped regions with elevated signal levels in NDE images. We adopt a simple elliptical parametric model for the shape of the defect region and assume that the defect signals within this region are random following a truncated Gaussian distribution. Our truncated‐Gaussian model ensures that the signals within the defect region are higher than the baseline level corresponding to the noise‐only case. We derive a closed‐form expression for the kernel of the posterior probability distribution of the location, shape, and defect‐signal distribution parameters (model parameters). This result is then used to develop Markov …
Ultrasonic Nondestructive Evaluation Of Fibre-Reinforced Composite Materials - A Review, Vikram K. Kinra, Vinay Dayal
Ultrasonic Nondestructive Evaluation Of Fibre-Reinforced Composite Materials - A Review, Vikram K. Kinra, Vinay Dayal
Vinay Dayal
This paper reviews various ultrasonic nondestructive evaluation techniques applicable to fibre-reinforced composites. The techniques are briefly described and key references are cited. Methods to evaluate the reduced stiffness of composites due to micro-damage are described. Results show that for composites through-the-thickness attenuation increases and stiffness does not change due to transverse cracks, but in-plane stiffness and attenuation changes are substantial and can be measured by the Lamb wave techniques.