Papers by Author: Kyung Seok Song

Abstract: The NAUT technique allows non-contact ultrasonic testing in air. If the NAUT technique can be applied, not only ultrasonic testing in air with no couplant would be possible, but also the stable transmission and reception of ultrasonic waves, which would thus enable ultrasonic testing of hot or cold materials, or rough surfaces of specimens that could not be tested with conventional-contact ultrasonic testing techniques. By trying NAUT for CFRP (carbon fiber-reinforced plastic) specimens, the applicability of NAUT in these areas was observed, and the results from the waveforms of parts of the specimens were analyzed. To verify the usefulness of NAUT, first, artificially defective specimens were tested to investigate the defect detection ability of NAUT; and second, a test was conducted to select the test conditions, the ultrasonic propagation characteristics, and the mode conversion by the material thickness. Both the spot welding and CFRP specimens showed good applicability of NAUT. For the spot welding specimen, the ultrasonic transmittance was highest at the spot-welded part, regardless of the thickness and location of the specimen. For the CFRP specimen, the waveforms of a defective part and a defect-free part were compared, and the existence of delamination was discovered through the increase and decrease in the amplitude. These findings confirmed the practicality (usefulness) of NAUT.

Abstract: Importance on the detection of corrosion-related defect is undeniable from the fact that it can prevent significant economic loss and enhanced safety in mechanical equipments, pipes, ships, bridges, and other applications. Conventionally researched measurement methods for defect and thinning from corrosion are acoustic emission, EMAT using ultrasound, laser induced ultrasound, etc. However, these non-destructive testing methods have the shortcoming of accessibility to on-site. For instance, EMAT should be close to several millimeters to generate magnetic field in structure. For laser application, it can be applied to remote non-destructive testing, but some defect might not be possible to be detected by the surface condition of structure. In this study, infrared thermography camera is utilized to determine the degree of corrosion on paint-coated metal. In addition, fundamental researches to develop corrosion detection system for on-site metallic structure are conducted to provide the applicability of IR camera and possibility of thermal analysis method.

Abstract: Extrusion screw that is used on market of present extrusion molding catapult is divided by single-axle extrusion screw and multi-axles extrusion screw. Simulation technique of screw that is used in extrusion molding has become so far various. Consist of that analyze third dimension model and that analyze two-dimension model but most Analysis that display dynamic characteristic of screw inside of heat and flow in detail was not until present. Transfer of polymer site that typical single-axle extrusion screw that is analysis target of this treatise is mixed in most melting state is good, but has some controversial points. First melting transfer of balance that is not done difficult. Second melting causes effect that weaken mechanical special quality of screw by power excessive last month if heighten the screw speed to increase amount of done balance. Third Screw dynamic characteristic symptoms by thermal expansion that happen in screw of heater is fallen.

Abstract: In this investigation, we evaluated diagnoses of a defect concerning coating of land-base gas turbine using infrared thermography camera. In this camera method has a strong point which is able to save time and costs compared with former method. Because it can be long field acquire temperature distribution by using non-contact method. But it has a week point that method applies thermal load about inspection sample. Presently, Method used widely in detection of crack is ultrasonic inspection. But this method, There is problem in application in place that uneven surface. In order to check cracks on a blade coating of a gas turbine, a part with cracks in a waste blade disposed after having been used in the field was extracted to produce a sample. So we apply the method by a infrared thermography camera to the produced sample, the sample was heated by means of a halogen lamp. In this paper, we want to describe production of land-base turbine sample, a method of applying thermal load at produced sample, infrared thermography camera technique, an analysis technique of thermography, a defect analysis of coating of land-base gas turbine blades.

Abstract: After Industrial Revolution, energy has been recognized as an important factor which enhances the motive power for industry in the industrial society. However, recently the excessive consumption of energy pursuant to the rapid expansion of industry created serious problems of the exhaustion of fossil fuels as well as unusual change in the weather due to the mass discharge of carbon dioxide. We can say that after all proposals will boil down to the development of New & Renewable energy. The most suitable source of energy for this required change is solar energy. The advantages of solar energy are that it is renewable, infinite supplied and environmentally safe energy source, and the method of energy supply is in small scale and is decentralized. However, solar energy related products have the problems such as the limitation for installation, problems in maintenance and insufficient reliability, which have been the barrier to consumers to satisfy the purchase need for solar heat related products. In this research will perform thermodynamic analysis through the application of infrared ray thermal imaging camera and will discuss about the applicability of solar energy system and other fields as well.

Abstract: In this research, we used nondestructive test based on ultrasonic test as inspection method, and made up inspection robot in order to control of ultrasonic probe on the SWP surface, and programmed to signal processing code and pattern classifying code by user made programming code. For evaluation of flaw signal is reflected on welding flaw, user-made program codes are composed of signal processing and probability neural network (PNN) and backpropagation neural network (BPNN). And then, we actually confirmed to the theoretical advantage of each neural network method compared probability neural network with backpropagation neural network for classification and recognition rate. For the application of classifier to SWP inspection system, BPNN classifier is adequate in the first stage. And then, the application of PNN classifier is adequate as the next stage. Because of PNN application need enough sample data that is due to probabilistic density function.

Abstract: Contact type detection, one of UT for the detection of defects in welding area, has several weak-points. Proximity type ultrasonic inspection using laser is being studied these days to make up for the weak points of contact type ultrasonic inspection. In this paper, automatic inspection system of the welding area of spiral welding pipe has been developed, of which mechanical characteristic is better than that of circular directional pipes, and executed the proximity ultrasonic inspections using laser. The usefulness of proximity ultrasonic inspection using laser will be verified in this paper through the analysis of the inspection results.