• Journal of the Korean Society for Heat Treatment
• /
• v.14 no.2
• /
• pp.110-117
• /
• 2001

Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. It was found that the carbides became coarser and spheroidized as aging time increased. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the ultrasonic attenuation and velocity measurements. Ultrasonic velocity was found essentially insensitive to the microstructural changes resulting from aging heat treatment. However, the ultrasonic attenuation was observed to increase with increasing aging time. Also, it was noticed that the change of ultrasonic attenuation with aging time was more sensitive at high frequency regions.

• Journal of Welding and Joining
• /
• v.12 no.3
• /
• pp.109-117
• /
• 1994

Spot welding has wide used with a high work efficiency in the automotive and aerospace industries. Up to the present, the technique mainly used to test spot welds on production lines has been entirely depended upon destructive chisel or peel testing. Therefore, it's being very important assignment to secure the NDE technique which can be evaluate spot weld quality with more efficiency and high reliability. This paper discusses the feasibility of UNDE techniques to evaluate spot weld quality. For the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of a the corona bond from nugget, ultrasonic c-scan image and distribution of reflective echo amplitude was measured by immersion method with the mechanical and the electronic scanning of point-focussed ultrasonic beam(25 MHz). As the results of this study, corona bond which is the most dangerous types of interface defects can be successfully detected, as well as expulsion and voids. Ultrasonic testing results were confirmed and compared by optical microscope and SAM(Scanning Acoustic Microscope) observation of the spot-weld cross section. The results show that the nugget diameter can be successfully measured with the accuracy of 0.8 mm.

• Advances in Computational Design
• /
• v.8 no.3
• /
• pp.219-236
• /
• 2023

In this paper, finite element modeling of the laser ultrasonics (LU) process in ablation regime is of interest. The momentum resulting from the removal of material from the specimen surface by the laser beam radiation in ablation regime is modeled as a pressure pulse. To model this pressure pulse, two equations are required: one for the spatial distribution and one for the temporal distribution of the pulse. Previous researchers have proposed various equations for the spatial and temporal distributions of the pressure pulse in different laser applications. All available equations are examined and the best combination of the temporal and spatial distributions of the pressure pulse that provides the most accurate results is identified. This combination of temporal and spatial distributions has never been used for modeling laser ultrasonics before. Then by using this new model, the effects of variations in pulse duration and laser spot radius on the shape, amplitude, and frequency spectrum of ultrasonic waves are studied. Furthermore, the LU in thermoelastic regime is simulated by this model and compared with LU in ablation regime. The interaction of ultrasonic waves with a defect is also investigated in the LU process in ablation regime. Good agreement of the results obtained from the new finite element model and available experimental data confirms the accuracy of the proposed model.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.45 no.5
• /
• pp.56-62
• /
• 2008

This paper proposes the use of decision tree classification for the measuring pattern recognition from industrial Computed Radiography(CR) images used in nondestructive evaluation(NDE) of steel-tubes. It appears that NDE problems are naturally desired to have machine learning techniques identify patterns and their classification. The attributes of decision tree are taken from NDE test procedure. Geometric features, such as radiative angle, gradient and distance, are estimated from the analysis of input image data. These factors are used to make it easy and accurate to classify an input object to one of the pre-specified classes on decision tree. This algerian is to simplify the characterization of NDE results and to facilitate the determination of features. The experimental results verify the usefulness of proposed algorithm.

• Journal of Magnetics
• /
• v.18 no.3
• /
• pp.348-351
• /
• 2013

Inconel 600 alloy, Ni base alloy, is widely used for steam generator tubings where sensitization occurs at grain boundaries and sensitization will induce tubing failures. This alloy has usually paramagnetic property, however, it transforms into ferromagnetic property along grain boundaries when sensitization occurs: this means NDE using magnetism for sensitization is possible. Therefore, in this study, Inconel 600 alloys were heat treated at 873 K from 0 to 400 hours so as to generate sensitization and their magnetic properties were investigated in detail. The saturation and the residual magnetization increase with increasing heat treatment time and take a maximum. On the other hand, the coercive force decreases with the increase in time of heat treatment. We confirmed that characteristics at only grain boundaries change into ferromagnetic phase by a MFM observation. As a trial for industrial application, heat treated Inconel 600 alloy was scanned by a magnetic field sensor, and the variations in magnetization were obtained nondestructively. The results indicate a feasibility of magnetic NDE for sensitization of Inconel 600 alloy.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.673-679
• /
• 2009

Nondestructive inspection(NDI) is a testing procedure used to easily inspect an object for internal defects, abnormalities, shape, and structure, etc. without destroying it. Typical candidates for NDI include buildings, railways, aircraft, bridges, underground pipelines and various types of factory equipment. Recent advances in nondestructive evaluation(NDE) technologies have led to improved methods for quality control and in-service inspection, and the development of new options for material diagnostics. This paper introduces the methods of a survey and assessment on NDI applications in Electric Multiple Units(EMU). The main objective of this paper was to obtain information on various applications of NDI technology in EMU.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.2
• /
• pp.163-168
• /
• 2001

Due to aging, adhesively bonded and riveted aircraft lap joints can contain distends, cracks around rivet holes, fatigue induced flaws, and corrosion. It is required for the safety of aircraft to inspect these defects through the whole region of mint in rapid speed. Bond quality or adhesively bonded and riveted aluminum lap splice joints is investigated using non-contact remote ultrasonic nondestructive evaluation (NDE). Non-contact ultrasonic tests are performed using laser generation and air-coupled transducer detection. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The Lamb wave is generated on one side of the lap splice joint, propagates along the plate, interacts with the joint and is detected on the other side by a micromachined air-coupled capacitance transducer. Analysis of recorded signals allows to evaluate the condition of the bond.

• Journal of Power System Engineering
• /
• v.15 no.1
• /
• pp.18-23
• /
• 2011

Image processing has provided powerful techniques to extract from the acoustic signals the desired information on evaluation for leakage existence, leakage rate, and searching for leakage location, etc. The imagery NDE data available can add additional and significant dimension in nondestructive evaluation(NDE) information and thus for exploiting in applications. To extract such information the use of advanced image processing techniques is much needed. In recent years, there has been much increased use of acoustic signal image processing techniques in acoustic NDE. This approach will increase the efficiency of inspection procedures and reduce inspection time. In this paper we are concerned only with This paper is concerned mainly with the use of advanced image processing techniques in valve leakage detection and advanced image restoration and enhancement methods, which attempt to evaluate promptly by a visualization method the acoustic sources while detecting the valve leakage.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.4
• /
• pp.311-317
• /
• 2014

The Pressurized water reactor owners group (PWROG) developed and applied a risk-informed in-service inspection (RI-ISI) program, as an alternative to the existing ASME Section XI' sampling inspection method. The RI-ISI programs enhance overall safety by focusing inspections of piping at high safety significance (HSS) locations where failure mechanisms are likely to be present. Additionally, the RI-ISI program can reduce nondestructive evaluation (NDE) exams, man-rem exposure for inspectors, and inspection time, among other benefits. The RI-ISI method of in-service piping inspection was applied to 3 units (KSNPs: Korea standard nuclear power plants) and is being deployed to the other units. In this paper, the results of RI-ISI for a Framatome type (France CPI) nuclear power plant are presented. It was concluded that application of RI-ISI to the plant could enhance and maintain plant safety, as well as provide the benefits of greater reliability.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.269-276
• /
• 2004

Deterioration analysis was performed on carbody and bogies of a shunting locomotive, which has been used for shunting works in steel making processes. In this investigation, various types of technical evaluation methods for the locomotive were employed to assess the current deterioration status. Corrosion test and nondestructive evaluation (NDE) techniques were employed to demonstrate the wear status of the carbody and bogie parts in the locomotive. Since the locomotive has been working under corrosive environment, the corrosion tests with x-ray analysis for exterior part of the locomotive were conducted to examine the evolution of corrosion reaction, and NDE techniques such as ultrasonic testing, magnetic particle testing, and x-ray radiography, were conducted on the carbody and bogies to inspect any possible inherent and/or in-service flaws. In this paper, the degree of deterioration in a shunting locomotive has been presented based on the analysis results.