[en] A new method is presented for lifespan estimation of heat exchanger tube which was classically assumed by human experience. This report gives a new method for dealing with the problem of analysing pitting corrosion which has statistical characteristics.

[en] The vibration and deformation behavior of composite beams subjected to various transverse impacts has been investigated as a function of fiber orientation and void fraction. Theoretical results using the Euler-beam theory and mode superposition method were obtained along with the finite element analysis, which were compared with experimental ones.

[en] This paper examines the propagation of Lamb (or plate) waves in anisotropic laminated composite plates. The dispersion relations are explicitly derived using the classical plate theory (CLT), the first-order shear deformation theory (FSDT) and the exact solution (ES), Attention is paid to the lowest antisymmetric (flexural) and lowest symmetric(extensional) modes in the low frequency, long wavelength limit. Different values of shear correction factor were tested in FSDT and comparisons between flexural wave dispersion curves were made with exact results to asses the range of validity of approximate plate theories in the frequency domain.

[en] This proceedings contains articles of the Korean Society for Nondestructive Testing Spring Meeting, 1998. It was held on May.8-9, 1998 Yeungnam University in Daegu, Korea and subject of the Korean Society for Nondestructive Testing Spring Meeting 1998. This proceedings is comprised of 4 sessions.

[en] Development of Nondestructive Tester for industrial application to detect flaws in aluminum die-casted squirrel case rotor is reported in this paper. Electronic currents are supplied to the end-ring and Hall effect sensors are used to detect the variation of currents which flow in the bar of the rotor. Some signal processing techniques are introduced to classify the signals due to the defects in the bars

[en] In this study, an acoustic emission technique has been used to clarify the microscopic failure mechanisms of mortar under three point bending test. AE source location has also been done to monitor the activities of internal damage and the progress of microscopic failure path during the loading. The relationship between AE characteristic and microscopic failure mechanism is discussed.

[en] A new experimental method and principle were presented for the continuous measurement of the depth-dependant reflection coefficient of Rayleigh waves or their pulse interacting with various surface discontinuities. The method was to record the reflection-echo-amplitudes for varying depth during scanning the Rayleigh wave pulse with a small lateral beam width along a surface discontinuity with a small slope in depth. In the experiments using a declined slot and intensively focused Rayleigh waves, the coefficients were continuously measured with quite good reproducibility in the range of $0.05

[en] In this paper, the SH-wave scattering by multi-defects and inclusion using Boundary Element Method is studied. The effects of shape and distance of defects on transmitted and reflected fields are considered. The interaction of multi-defects in SH-wave scattering is also investigated. Numerical calculations by the BEM have been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results can be used to improve the detection sensitivity and pursue quantitative nondestructive evaluation for inverse problem.

[en] This paper examines the propagation of Lamb (or plate) waves in anisotropic laminated composite plates. The dispersion relations are explicitly derived using the classical plate theory (CLT), the first-order shear deformation theory (FSDT) and the exact solution (ES), Attention is paid to the lowest antisymmetric (flexural) and lowest symmetric(extensional) modes in the low frequency, long wavelength limit. Different values of shear correction factor were tested in FSDT and comparisons between flexural wave dispersion curves were made with exact results to asses the range of validity of approximate plate theories in the frequency domain.

[en] The study on the cylindrical guided wave was carried out to investigate its feasibility for nondestructive evaluation of tubular structures such as heat exchanger tubings of power industries and various pipings of chemical plants. The concept of wedge design and incident angle selection to optimize guided wave generation is presented based on the dispersion theory and the snell's law for the cylindrical guided wave. The brass tubes with artificial defects in the circumferential or axial direction were used for detect defection experiments. It was found that guided wave sensitivity for detecting an axial defect can be remarkably improved by using non-axisymmetrically launched guided waves. Through this study, it is expected that the guided wave can be successfully applied to tubular structure inspections as an more advanced and efficient NDE technique than a conventional point-by-point technique.