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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 23, Issue 6 - Dec 2003
Volume 23, Issue 5 - Oct 2003
Volume 23, Issue 4 - Aug 2003
Volume 23, Issue 3 - Jun 2003
Volume 23, Issue 2 - Apr 2003
Volume 23, Issue 1 - Feb 2003
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A Structural Damage Identification Method Based on Spectral Element Model and Frequency Response Function
Lee, U-Sik ; Min, Seung-Gyu ; Kwon, Oh-Yang ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 559~565
A spectral element model-based structural damage identification method (SDIM) was derived in the previous study by using the damage-induced changes in frequency response functions. However the previous SDIM often provides poor damage identification results because the nonlinear effect of damage magnitude was not taken into account. Thus, this paper improves the previous SDIM by taking into account the nonlinear effect of damage magnitude. Accordingly an iterative solution method is used in this study to solve the nonlinear matrix equation for local damages distribution. The present SDIM is evaluated through the numerically simulated damage identification tests.
On Fiber Orientation Characterization of CERP Laminate Layups Using Ultrasonic Azimuthal Scanners
Im Kwang-Hee ; Hsu, David K. ; Sim Jae-Gi ; Yang, In-Young ; Song, Sung-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 566~576
Carbon-fiber reinforced plastics (CFRP) composite laminates often possess strong in-plane elastic anisotropy attributable to the fiber orientation and layup sequence. The layup orientation thus greatly influences its properties in a composite laminate. It could result in the part being rejected or discarded if the layup orientation of a ply is misaligned. A nondestructive technique would be very beneficial, which could be used to test the part after curing and to require less time than the optical test. In this paper, ultrasonic scanners were set out for different measurement modalities for acquiring ultrasonic signals as a function of in-plane azimuthal angle. The motorized scanner was built first for making transmission measurements using a pair of normal-incidence shear wave transducers. Another scanner was then built fer the acousto-ultrasonic configuration using contact transducers. A ply-by-ply vector decomposition model has been developed, simplified, and implemented for composite laminates fabricated from unidirectional plies. We have compared the test results with model data. It is found that strong agreement are shown between tests and the model developed in characterizing cured layups of the laminates.
Ultrasonic Measurement of Interfacial Layer Thickness of Sub-Quarter-Wavelength
Kim, No-Hyu ; Lee, Sang-Soon ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 577~582
This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process.
A Study for the Measurement of a fluid Density in a ripe Using Elastic Waves
Kim, Jin-Oh ; Hwang, Kyo-Kwang ; Bau, Haim-H. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 583~593
The effect of liquid confined in a pipe on elastic waves propagating in the pipe wall was studied theoretically and experimentally. The axisymmetric motion of the wave was modeled with the cylindrical membrane shell theory. The liquid pressure satisfying the axisymmetric wave equation was included in the governing equation as a radial load. The phase speed of the wave propagating in the axial direction was calculated, accounting for the apparent mass of the liquid. Experiments were performed in a pipe equipped with ring-shaped, piezoelectric transducers that were used for transmitting and receiving axisymmetric elastic waves in the pipe wall. The measured wave speeds were compared with the analytical ones. This work demonstrates the feasibility of using pipe waves for the determination of the density and, eventually, the flow rate of the liquid in a pipe.
Variable Angle Beam Guided Wave Probe Design for Tubing Based on Solid Mechanics
Cho, Youn-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 594~604
A State-of-art methodologies on implementing conventional piezoelectric and flexible PVDF elements for generating ultrasonic guided waves in a tubing are presented. Comb transducers with PVDF can be efficiently applied to selectively excite a guided wave mode by wrapping around any size pipe while a conventional immersion type piezo-elements can be also possibly used with a modification of transducer fabrication. Technical comparisons between the use of angle beam probe and comb one will be also discussed in detail. The presented technique can be easily applied to NDE for a long range inspection of tubular structures.
Transferring Distance-Amplitude Correction Curves - A Model-based Approach
Kim, Hak-Joon ; Schmerr Lester W. ; Song, Sung-Jin ; Sedov Alexander ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 605~615
In practice, it is common to manufacture reference blocks containing simple reflectors to obtain distance-amplitude correction (DAC) curves. However, the construction or DAC curves in this manner requires the use of a large number of specimens with appropriate curvatures and reference reflectors located at various depths. Therefore, less costly and quantitative procedures are strongly needed. To address such a need, in this study, we have developed model-based transfer curves to relate a DAC curve obtained in a particular reference configuration with that for a completely different configuration. An example of transferring DAC curves, using the proposed transfer curves, is given.
Comparison of Different Techniques for Measurement of Cold Work in Mild Steel
Badgujar, B.P. ; Jha, S.K. ; Goswami, G.L. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 616~621
There are various Non-Destructive Evaluation (NDE) techniques used for measurement of residual stresses in material, such as magnetic methods, X-ray diffraction, Ultrasonic velocity measurement etc. The capabilities, applications and limitations of these techniques for evaluation of cold work/plastic deformation were studied and compared. Mild steel plates were subjected to different degree of cold deformation and were analyzed by Magneto-mechanical Acoustic Emission (MAE), Barkhausen Noise (BN) and magnetic properties (hysteresis loop parameters analysis). Further, these specimens were analyzed by X-ray diffraction and ultrasonic velocity measurements. The microhardness measurement and microstructure studies of these cold worked plates were also carried out. The results of all these studies and comparison of different techniques are discussed in this paper.
Defect Shape Recovering by Parameter Estimation Arising in Eddy Current Testing
Kojima, Fumio ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 622~634
This paper is concerned with a computational method for recovering a crack shape of steam generator tubes of nuclear plants. Problems on the shape identification are discussed arising in the characterization of a structural defect in a conductor using data of eddy current inspection. A surface defect on the generator tube ran be detected as a probe impedance trajectory by scanning a pancake type coil. First, a mathematical model of the inspection process is derived from the Maxwell's equation. Second, the input and output relation is given by the approximate model by virtue of the hybrid use of the finite element and boundary element method. In that model, the crack shape is characterized by the unknown coefficients of the B-spline function which approximates the crack shape geometry. Finally, a parameter estimation technique is proposed for recovering the crack shape using data from the probe coil. The computational experiments were successfully tested with the laboratory data.
Analytical Beam Field Modeling Applied to Transducer Optimization and Inspection Simulation in Ultrasonic Nondestructive Testing
Spies, Martin ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 6, 2003, Pages 635~644
To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.