• JOURNAL OF ELECTRICAL WORLD
• /
• s.430
• /
• pp.88-89
• /
• 2012

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.1
• /
• pp.38-45
• /
• 2000

In this research, MFL technique has been studied for the inspection of storage tank floor. The reference specimens having 20%, 40%, 60% and 80% slot's are fabricated using the carbon steel plates of a 6mm and 10mm thick. Powerful permanent magnets and Hall effect sensors are used to this application. It is shown that our system is able to detect metal loss like a slot. Also, it is possible that slot diameter is measured using transverse type of Hall generator. It is demonstrated that MFL can not differentiate between the response from top side and bottom side slot. Flux leakage response from a bottom side indication is significantly lower in amplitude than that from an equivalent top side slot. It is essential to know this sensor lift-off distance because the MFL signal also changes considerably with the sensor lift-off distance.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.5
• /
• pp.363-368
• /
• 1999

Ultrasonic pulse-echo methods measuring the transit time through specimens have been widely used in determination of ultrasonic velocity and thickness of specimens. Usually, to determine the velocity of the ultrasonic. the transit time of the ultrasonic pulse through specimen is measured by using the ultrasonic measuring equipment such as the oscilloscope including ultrasonic pulser/receiver and the thickness of the specimen is measured by using the length measuring instrument such as micrometer or vernier calipers etc., i. e. each parameter is measured by using each measuring method. In the case of the measuring the thickness of a specimen by using the ultrasonics. the ultrasonic equipments, which measure the thickness, such as the ultrasonic thickness gauge must be calibrated by using the reference block of which the ultrasonic velocity is known beforehand. In the present work, we proposed a new method for simultaneous measurement of ultrasonic velocity and thickness without reference blocks. Experimental results for several specimens show that proposed method have good agreements with those by traditional ultrasonic method.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.6
• /
• pp.81-89
• /
• 1996

It is very important for ultrasonic test method to evaluate the integrity of the class I components in nuclear power plants. However, as the rltrasonic test is affected by internal structures and configurations of test materials, backscattering, that is, time invariant noise is generated in large grain size materials. Due to the above reason, the received signal results in low signal to noise(S/N) ratio. Split spectrum processing(SSP) technique is effective to suppress the grain noise. The conventional SSP technique. however, has been applied to unique algorithm. This paper shows that MPO(minimization and polarity threshold) algorithm which two algorithms are applied simulatancously, was utilized, the signal processing time was shorten by using the new constant-Q SSP with the FIR filter which frequency to bandwidth ratio is constant and the optimum parameters were analysed for the signal processing to longitudinal wave and shear wave with the same requirements of inspection on nuclear power plant site. Moreover, the new ultrasonic test instrument, the reference block of the same product form and material specification, stainless stell test specimens and copper test specimens block of the same fabricated for the application of new SSP technique. As the result of experimental test with new ultrasonic test instrument and test specimens, the signal to noise ratio was improved by appying the new SSP technique.

• Polymer(Korea)
• /
• v.38 no.1
• /
• pp.1-8
• /
• 2014

The effects of surface color and morphology on the mar behaviors of urethane-acrylate coated surfaces were examined. The superiority of mar resistance was observed in the order of white, red and black-colored samples. This can be explained by a contrast effect. In other words, in case of black colored sample, it takes place the defuse reflection of the incident light on the damaged region where mar damage exerts, leading to whitening phenomenon. Therefore, the damaged region is easily recognized by contrasting the black background. On the other hand, it is difficult for the white-colored sample to perceive the mar-damaged area by the white background acting as protecting coloration. As the gloss of urethane-acrylate coated surface increases, it is observed that there is an increase in the number of carbonyl (-C=O) function group, amount of ethylene and silica. The enhancements of surface rigidity by adding the silica particles and formation of carbonyl function groups by the surface oxidation lead to the increase in mar resistance, while the increase of polyethylene wax is responsible for the improved gloss and smooth-faced surface. Based on the above findings, technical approaches leading the improvement of mar resistance of the urethane-acrylate coated surface are discussed.

• Korean Journal of Materials Research
• /
• v.13 no.10
• /
• pp.651-657
• /
• 2003

Ultrasonic microscope has been used to detect the defects on surface or inner solid. Conventionally, it has used at a single operating frequency. The resolution and quality of the measured images are determined by a characteristic of the transducer of the ultrasonic microscope. The conventional ultrasonic microscope has been used envelope detector to detect the amplitude of reflected signal, but the changes in amplitude is not sensitive enough for specimen with microstructure that in phase. In this paper, we have studied multi-frequency depth resolution enhancement with ultrasonic reflection microscope for the reflectors of a stainless steel reference specimen and a reference calibration block to be used as the material in nuclear power plants for ISI, PSI. Increased depth resolution can be obtained by taking two, three-dimensional images at more that one frequency and numerically combining the results. As results of the experiment, we could get enhanced images with the rate of contrast in proportion and high quality signal distribution for the image to the changing rate of depth for the reflectors of the two kinds of specimens.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.2
• /
• pp.157-164
• /
• 2011

This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.

• Journal of Welding and Joining
• /
• v.16 no.3
• /
• pp.64-73
• /
• 1998

This paper is concerned with defects detection and evaluation of heat affected zone (HAZ) in austenitic stainless steel type 304 by ultrasonic wave and neural network. In experiment, the reflected ultrasonic defect signals from artificial defects (side hole, vertical hole, notch) of HAZ appears as beam distance of prove-defect, distance of probe-surface, depth of defect-surface on CRT. For defect classification simulation, neural network system was organized using total results of ultrasonic experiment. The organized neural network system was learned with the accuracy of 99%. Also it could be classified with the accuracy of 80% in side hole, and 100% in vertical hole, 90% in notch about ultrasonic pattern recognition. Simulation results of neural network agree fairly well with results of ultrasonic experiment. Thus were think that the constructed system (ultrasonic wave - neural network) in this work is useful for defects dection and classification such as holes and notches in HAZ of austenitic stainless steel 304.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.7
• /
• pp.149-159
• /
• 1998

The importance of soundness and safety evaluation in weld zone using by the ultrasonic wave has been recently increased rapidly because of the collapses of huge structures and safety accidents. Especially, the ultrasonic method that has been often used for a major non-destructive testing(NDT) technique in many engineering fields plays an important role as a volume test method. Hence, the defecting any defects of weld Bone in austenitic stainless steel type 304 using by ultrasonic wave and neural network is explored in this paper. In order to detect defects, a distance amplitude curve on standard scan sensitivity and preliminary scan sensitivity represented of the relation between ultrasonic probe, instrument, and materials was drawn based on a quantitative standard. Also, a total of 93％ of defect types by testing 30 defect patterns after organizing neural network system, which is learned with an accuracy of 99％, based on ultrasonic evaluation is distinguished in order to classify defects such as holes or notches in experimental results. Thus, the proposed ultrasonic wave and neural network is useful for defect detection and Ultrasonic Non-Destructive Evaluation(UNDE) of weld zone in austenitic stainless steel 304.

• Journal of the Korean Wood Science and Technology
• /
• v.43 no.6
• /
• pp.868-875
• /
• 2015

In order to replace existing slit type steel plate on the wooden structure joint, the FRP-reinforced laminated plates were produced. Four types of FRP-reinforced laminated plates were produced according to the type of reinforcement and adhesive, and before applying to the joint, the adhesion performance test according to KSF 3021 and KSF 2160 and the Compact Tension (CT) type fracture toughness test specified in ASTM D5045-99 were carried out. As a result of adhesion performance test, all GFRP textile, GFRP sheet, and GFRP Textile-Sheet type FRP-reinforced laminated plates satisfied the requirement of soaking delamination percentage with smaller than 5% based on KS standard. However, aramid type specimen satisfied the standard as the soaking delamination percentage of 4.8% but it did not satisfied the standard as the water proof soaking delamination percentage of 70%. As a result of fracture toughness test, the volume ratio of reinforcement to timber became 23% so that the strength of FRP-reinforced laminated plates increased by two to four times in comparison to the control specimen. It was confirmed that the GFRP Textile-Sheet type specimen was most resistant to the fracture most since the ratio of stress intensity factor compared with that of the control increased to 61% owing to the parallel arrangement of glass fiber to the load. As a result of tensile shear strength test using FRP-reinforced laminated plates and nonmetal dowels, it is about 12% lower than metal connectors.