# Special Issue: Novel Approaches for Nondestructive Testing and Evaluation
## 8 Leaky Lamb Wave Radiation from a Waveguide Plate with Finite Width by [PERSON] et al. In this paper [7], leaky Lamb wave radiation from a waveguide plate with finite width was investigated to gain a basic understanding of the radiation characteristics of the plate-type waveguide sensor. Although the leaky Lamb wave behavior has already been theoretically revealed, most studies have only dealt with two-dimensional radiations of a single leaky Lamb wave mode in an infinitely wide plate, and the effect of the width modes (that are additionally formed by the lateral sides of the plate) on leaky Lamb wave radiation has not been fully addressed. This work aimed to explain the propagation behavior and characteristics of the Lamb waves induced by the existence of the width modes and to reveal their effects on leaky Lamb wave radiation for the performance improvement of the waveguide sensor. To investigate the effect of the width modes in a waveguide plate with finite width, propagation characteristics of the Lamb waves were analyzed by the semi-analytical finite element (SAFE) method. Then, the Lamb wave radiation was computationally modeled on the basis of the analyzed propagation characteristics and was also experimentally measured for comparison. From the modeled and measured results of the leaky radiation beam, it was found that the width modes could affect leaky Lamb waveradiation with the mode superposition, and radiation characteristics were significantly changed depending on the wave phase of the superposed modes on the radiation surface. Evaluation of Cracks on the Welding of Austenitic Stainless Steel Using Experimental and Numerical Techniques by [PERSON] et al. This paper [8] dealt with the investigation and characterization of weld circumferential thin cracks in austenitic stainless steel (AISI 304) pipe with eddy current nondestructive testing technique (EC-NDT). During the welding process, the heat source applied to the AISI 304 was not uniform, accompanied by a change in physical property. To take this change into consideration, the relative magnetic permeability was considered as a gradiently changed variable in the weld and heat-affected zone (HAZ), which was generated by the Monte Carlo method based on pseudo-random number generation (PRNG). Numerical simulations were performed by means of MATLAB software, using the 2D finite element method to solve the problem. To verify, results from the modeling works were conducted and contrasted with findings from experimental ones. Indeed, the results of the comparison agreed well. In addition, they showed that the consideration of this change in magnetic property allows distinguishing the thin cracks in the weld area. Measurement of Thinned Water-Cooled Wall in a Circulating Fluidized Bed Boiler Using Ultrasonic and Magnetic Methods by [PERSON] et al. In this paper [9], a nondestructive inspection system was proposed to detect and quantitatively evaluate the size of the near- and far-side damages on the tube, membrane, and weld of the water-cooled wall in a fluidized bed boiler. The shape and size of the surface damages were evaluated from the magnetic flux density distribution measured by the magnetic sensor array on one side from the center of the magnetizer. The magnetic sensors were arrayed on a curved shape probe according to the tube's cross-sectional shape, membrane, and weld. On the other hand, the couplant was doped to the water-cooled wall, and a thin film was formed thereon by polyethylene terephthalate. Then, the measured signal of the flexible ultrasonic probe was used to detect and evaluate the depth of the damages. The combination of magnetic and ultrasonic methods helped to detect and evaluate both near and far-side damages. Near-side damages with a minimum depth of 0.3 mm were detected, and the depth from the surface of the far-side damage was evaluated, with a standard deviation of 0.089 mm. Micromagnetic Characterization of Operation-Induced Damage in Charpy Specimens of RPV Steels by [PERSON] et al.