• Computers and Concrete
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• 제33권5호
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• pp.481-496
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• 2024

Internal erosion around pipes can lead to the failure of earth dams through various mechanisms. This study investigates the displacement patterns in earth dam models under three different failure modes due to internal erosion, using digital image correlation (DIC) methods. Three failure modes—erosion along a pipe (FM1), pipe leakage leading to soil erosion (FM2), and erosion in a pipe due to defects (FM3)—are analyzed using two- and three-dimensional image- processing techniques. The internal displacement of the cross-sectional area and the surface displacement of the downstream slope in the dam models are monitored using an image acquisition system. Physical model tests reveal that FM1 exhibits significant displacement on the upper surface of the downstream slope, FM2 shows focused displacement around the pipe defect, and FM3 demonstrates increased displacement on the upstream slope. The variations in internal and surface displacements with time depend on the segmented area and failure mode. Analyzing the relationships between internal and surface displacements using Pearson correlation coefficients reveals various displacement patterns for the segmented areas and failure modes. Therefore, the image-based characterization methods presented in this study may be useful for analyzing the displacement distribution and behavior of earth dams around pipes, and further, for understanding and predicting their failure mechanisms.

• 한국산학기술학회논문지
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• 제14권9호
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• pp.4111-4116
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• 2013

프로그레시브 금형은 다수의 공정을 순차적으로 이송시키면서 연속적으로 생산하는 능률적이고 품질이 우수한 가공법이다. 본 연구에서는 가스보일러 연소 배기관의 배기 효율과 불완전 연소의 원인이 되는 배기관을 용접할 때 발생하는 위치 정밀도를 확보하고, 생산성 증가를 목적으로, 제품 형상에 버링을 추가하여 프로그레시브금형을 제작하고, 금형을 분해하지 않고 버링펀치를 교환할 수 있도록 하며, 프로그레시브 금형에 의한 위치 정밀도와 생산성을 향상할 수 있도록 하였다.

• 소성∙가공
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• 제32권6호
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• pp.321-328
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• 2023

To ensure driver safety, high-strength steel pipes are utilized in the chassis and internal structures design of automobiles. ERW(electric resistance welding) pipes, fabricated through welding at joints using electrical resistance, form a Heat-Affected Zone (HAZ) during the welding process. Due to characteristics such as increased hardness and reduced ductility compared to the base material, HAZ poses challenges in finite element analysis (FEA) for pipe shapes. In this study, for FEA considering HAZ properties, mechanical properties were measured through uniaxial tensile testing and digital image correlation (DIC) techniques after specimen fabrication. These measurements were validated using reverse engineering methods. Furthermore, hardness measurements and gaussian functions were employed to ascertain the hardness distribution within the HAZ, serving as a basis for subdividing the HAZ and modeling the pipe shape. To validate the effectiveness of the HAZ modeling approach, models were interpreted incorporating only base material properties and models incorporating average-calculated HAZ properties. Comparative analysis was performed, revealing that the model subdividing the HAZ based on hardness measurements closely approximated experimental values. This validation offered a methodology for HAZ modeling in FEA.

• 소성∙가공
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• 제26권5호
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• pp.271-276
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• 2017

A tee is the most common pipefitting used to combine or divide fluid flow. Tees can connect pipes of different diameters or change the direction of a pipe run. To manufacture tee type of stainless steel pipe, combinations of punch piercing and burr forming have been widely used in the industry. However, such method is considerably time consuming with regard to performing empirical work necessary to attain process conditions to prevent upper end tearing of the tee product and meet target tee height. Numerous experiments have shown that the piercing profile is the main cause of defects mentioned above. Furthermore, the mold design is formed through trial and error according to pipe diameters and changes in requirements. Thus, the objective of this study was to perform piercing and burring process analysis via finite element analysis using DYNAFORM to resolve problems mentioned above. An optimization design method was used to determine the piercing punch profile. Three radii of the piercing punch (i.e., large, small, and joined radii) were selected as design variables to minimize thinning of a tee pipe. Based on results of correlation and multiple regression analyses, we developed a predictive approximation model to satisfy requirements for both thickness reduction and target height. The new piercing punch profile was then applied to actual tee forming using the developed prediction equation. Model results were found to be in good agreement with experimental results.

• 한국컴퓨터정보학회논문지
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• 제26권2호
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• pp.27-37
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• 2021

본 논문에서는 관로를 자동으로 검출하는 지하 관로 자동 탐색 시스템을 제안한다. 시간에 따른 지반변화, 관로 시공 불일치 등 여러 가지 요인으로 실제 관로의 위치가 지하 관로 도면과 일치하지 않는다. 이로 인하여 굴착공사나 관로 노후화에 의한 여러 사고가 발생한다. 사고를 방지하기 위해 GPR(지표 투과 레이더, Ground Penetrating Radar) 탐사를 통해 지하시설물을 찾아내는 작업이 이루어지고 있지만, 분석을 담당할 수 있는 전문가의 수가 부족하다. GPR 데이터는 매우 방대하며 분석과정에도 오랜 시간이 걸리기 때문이다. 이에 본 논문에서는 3D GPR 데이터를 자동으로 분석하기 위해 딥 러닝 기술인 3D 이미지 분할을 사용하고, 이에 적합한 데이터 생성 알고리즘을 제안한다. 또한 GPR 데이터 특성에 맞는 데이터 증강 기법, 데이터 전처리 모듈을 제안한다. 실험 결과를 통해 제안한 시스템은 F1 Score 40.4%의 성능을 보였으며 이를 통해 이미지 분할을 이용한 관로 분석의 가능성을 확인하였다.

• 한국지진공학회논문집
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• 제26권1호
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• pp.13-22
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• 2022

This study proposes a low-cycle fatigue life derived from measurement points on pipe elbows, which are components that are vulnerable to seismic load in the interface piping systems of nuclear power plants that use seismic isolation systems. In order to quantitatively define limit states regarding leakage, i.e., actual failure caused by low-cycle fatigue, in-plane cyclic loading tests were performed using a sine wave of constant amplitude. The test specimens consisted of SCH40 6-inch carbon steel pipe elbows and straight pipes, and an image processing method was used to measure the nonlinear behavior of the test specimens. The leakage lines caused by low-cycle fatigue and the low-cycle fatigue curves were compared and analyzed using the relationship between the relative deformation angles, which were measured based on each of the measurement points on the straight pipe, and the moment, which was measured at the center of the pipe elbow. Damage indices based on the combination of ductility and dissipation energy at each measurement point were used to quantitatively express the time at which leakage occurs due to through-wall cracking in the pipe elbow.

• Journal of Welding and Joining
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• 제27권1호
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• pp.71-78
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• 2009

In the circumferential welding of pipe, welding phenomenon changes with the position of pipe. Especially in the overhead position, back bead of vertical-up position would be sunk. To investigate the size of back bead and keyhole with the change of the flow rate of pilot and shield gas at each position, bead-on plate welds were conducted on 6mm thickness SS400 with inclined-up position. When the rest of welding conditions remained constant, the width of back bead was increased as the flow rate of pilot gas was increased. And back bead tended to convex as the flow rate of shield gas was increased.

• 한국생산제조학회지
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• 제26권2호
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• pp.251-256
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• 2017

This study developed an image processing system for detecting damages on underground spiral PVC pipes. The detection method is simple-identifying damaged areas by measuring circularity along the pipeline. This uses the assumption that damage parts will not make a circular shape. Conventional devices check the circular shape of the pipe along the pipeline by measuring the angles between 6 spring-connected legs on the device. The conventional device, however, requires the insertion of 3 different wires (electrical, communication, and camera lines) along with a guide wire for pulling the device. The developed system presented here has simplified this system, requiring only a camera line while maintaining reasonable accuracy in damage detection.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2016년도 춘계학술발표대회
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• pp.475-478
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• 2016

많은 embedded 소프트웨어는 전통적 절차적 언어인 C로 작성되며 embedded 시스템에 특화된 역할을 수행한다. 한편 기존 절차적 언어인 C는 현대의 객체지향적 개발 패러다임과 비교하면 코드의 확장성, 유지 보수성, 재사용성에 있어서 많은 어려움이 있으며 아직도 많이 사용하고 있지만 이 C의 유지 보수성과 확장성, 유연성을 확보하여 보다 생산적이고 유지 보수가 쉬운 패러다임으로서 함수 pooling이라는 개념과 이를 이용한 framework를 구현한다.

• 소성∙가공
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• 제31권3호
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• pp.143-150
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• 2022

The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.