• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.3
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• pp.271-277
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• 2011

This study presents a nondestructive test for underwater PVC pipes. To use guided ultrasonic waves, specially denoted by cylindrical Lamb waves, a test setup was made in a water tank using the pitch and catch mode and specimens were made to give artificial cutouts located in the circumferential direction of the pipes. Total three states of damaged levels were considered to see how the guided waves interact with the defects. For the experimental adjustments, three different pipe diameters (60, 90, 114 mm) were tested, and two factors - incident angle (10 and $40^{\circ}$) and distance (50 and 200 mm) - were tried. From the results, regardless of the diameters and two experimental factors, it is shown that the degrees of defects were recognized through amplitude and arrived time of the very first part of the received cylindrical Lamb waves. Between amplitude and arrived time, it is found that the amplitude gives more sensitive results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1371-1374
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• 2007

A few intake stations have vibration problems caused by pipes. The vibration transffered from pipes excites building severely. Therefore, the crack is generated on building wall and people who work at intake station are damaged. In this paper, the vibration is measured and analysis is carried out for pipes at intake station in order to identify the usefulness and effectiveness of the solution proposed for pipe resonance avoidance. According to the result of analysis, bellows is reduced the vibration of pipes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.681-686
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• 2008

In this paper, we estimated the degree of pipe thinning by using two accelerometers. It uses measured velocity of flexural wave traveling along the pipes. If the thickness of the wall decreases because of pipe thinning, flexural stiffness of the pipes decreases and accordingly, traveling velocity of flexural wave decreases. Thus, if we install two vibration sensors outside of the pipes and measures traveling velocity of flexural waves regularly, we can estimate and monitor the degree of pipe thinning quickly. In order to test the method we experimented with pipes, and get the result that group velocity varies according to the degree of pipe thinning. It verified this method can be used to monitor the pipe thinning.

• Proceedings of the KWS Conference
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• v.43
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• pp.150-152
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• 2004

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1766-1771
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• 2007

This paper presents plastic limit loads and approximate J-integral estimates for circumferential part-through surface crack at the interface between elbows and pipes. Based on finite element limit analyses using elastic-perfectly plastic materials, plastic limit moments under in-plane bending are obtained and it is found that they are similar those for circumferential part-through surface cracks in the center of elbow. Based on present FE results, closed-form limit load solutions are proposed. Welds are not explicitly considered and all materials are assumed to be homogeneous. And the method to estimate the elastic-plastic J-integral for circumferential part-through surface cracks at the interface between elbows and straight pipes is proposed based on the reference stress approach, which was compared with corresponding solutions for straight pipes.

• Journal of KSNVE
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• v.9 no.4
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• pp.795-805
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• 1999

Rubber mounts so called grommets and pipes are two major paths of vibration transmission from a compressor, an important vibration source in an air conditioner, to the whole unit. A procedure of configuring the suction and discharge pipes of the compressor was developed in this paper so as to reduce the vibration transmission through the pipes as well as the grommets. Through investigating the effects of shapes and connecting disrections of pipe elements on vibration transmission, a guideline to configure the pipe layout, which enables to reduce vibration transmission, was proposed. The initial pipe layout by the guideline was optimized with the objective function, minimization of boty vibration transmission and the cost, and with the constraints to yield the final dimensions of the pipes. The procedure not only minimizes the transmitted force to the circumferential devices but enables to eliminate rubber blocks or dampers, which are generally used to avoid resonances of the pipe system.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.197-204
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• 1993

Pipe drainage is one of the effective slope protein works that can be adopted practically. As fine soil particles are suspended in percolating water, the strainer structure of under drain pipes in necessary to prevent the immediate clogging by soil suspension flow. This study deals with the effective strainer structure of under drain pipes for slope protection. The effective strainer structure of under pipes is the funneled strainer in which pore radius is enlarged toward flow direction. It is designed from the rheological properties of soil suspension flow which prevents the immediate clogging. Experimental results showed that the pipe drain discharge through the funneled strainers was larger than that through the constant pore radius strainers. This theorectial and experimental results indicate that the strainer with enlarged pore radius toward flow direction, is more effective than the strainer with constant pore radius.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.271-274
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• 2001

Experiments on the yield strength of pipe connectors made of metal wire, joint pins, pole pipes, multi span insertion joints, and T-clamp joints used in pipe houses were conducted. The strength of connections of a pipe connector made of metal wire was adequate but it had a big difference according to loading direction. The collapse load of pipes connected with a joint pin was lower than that of single pipes. Also experimental results showed that pole pipes for use in a part of frame buried under the ground were safe, and the strength of multi span insertion joints should be increased. The resistant moment of T-clamp was about 13.7% of a single pipe.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.97-106
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• 2012

To investigate the application of corrosion inhibitor on water supply pipes, turbidity, magnitude of corrosion, composition of scale and concentration of metals from an old steel pipe were analysed under inhibitor addition. The concentration of turbidity, iron and copper from the pipes under inhibitor application was 12 ~ 14% of the case which no inhibitor was applied, which suggests the application of inhibitor was very effective for internal corrosion control. In addition, SEM, EDX, XRD and XRF test results showed that application of inhibitor was effective for the decrease of iron concentration and increase of oxygen, phosphorus and calcium concentration, which suggested the existence of protective layer. Therefore, the occurrence of red water will be significantly decreased when inhibitor was applied to the old steel pipes.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.61-66
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• 2001

Fracture behaviors of pipes with local wall thinning is very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe drosion-corrosion damage. However, effect of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization, ovalization+cracking, local buckling and local buckling+cracking. Also, maximum load was successfully evaluated.