Investigation of mechanical properties of bimetallic square tubes produced by shape rolling of Al/Cu circular pipes

Ali Tajyar,Abolfazl Masoumi 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

We investigated the effect of shape rolling process on the bond strength and mechanical properties of Al/Cu bimetal pipes. A bimetal circular pipe was fabricated by the explosive welding process. Then, the bimetal explosive-welded circular pipe was reshaped to a square tube by means of the shape rolling process. The mechanical properties of explosive welded pipes and shape-rolled tubes at the various stages of the rolling process were experimentally investigated by using the shear testing, micro hardness testing along the thicknesses and measurement of yield. The obtained results show that with the increase of roll gap reduction during the various stages, the hardness increases, while the shear strength decreases. However, their effects on hardness increase are not the same for both materials. Yield stress measurement results indicate that the average yield stress increases during explosive welding and also shape rolling process, but the rate of increase is more intensive in the explosive welding process. Moreover, the morphology of the interface before and after the Shape rolling was examined by Optical microscope (OM) and the presence of the intermetallic compounds at the interface was investigated by the electron microscope (SEM) and EDS analysis. Examination of the interfaces morphology revealed that, due to the brittle nature of the intermetallic compounds at the joining interface, the nucleation and propagation of micro cracks accelerated during the shape rolling process and the amount of micro cracks increases which makes the shear strength decrease.

Delamination evaluation on basalt FRP composite pipe by electrical potential change

Altabey, Wael A. Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.5

Since composite structures are widely used in structural engineering, delamination in such structures is an important issue of research. Delamination is one of a principal cause of failure in composites. In This study the electrical potential (EP) technique is applied to detect and locate delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). The proposed EP method is able to identify and localize hidden delamination inside composite layers without overlapping with other method data accumulated to achieve an overall identification of the delamination location/size in a composite, with high accuracy, easy and low-cost. Twelve electrodes are mounted on the outer surface of the pipe. Afterwards, the delamination is introduced into between the three layers (0º/90º/0º)s laminates pipe, split into twelve scenarios. The dielectric properties change in basalt FRP pipe is measured before and after delamination occurred using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to delamination, a finite element simulation model for delamination location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Response surfaces method (RSM) are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured electrical potential changes of all segments between electrodes. The results show good convergence between the finite element model (FEM) and estimated results. Also the results indicate that the proposed method successfully assesses the delamination location/size for basalt FRP laminate composite pipes. The illustrated results are in excellent agreement with the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.

CFRP 각관 드릴 결함을 억제하는 내부지지 지그 개발

김경재(Gyeong-Jae Kim),김성효(Seong-Hyo Kim),박송이(Song-Yi Park),민선혜(Seon-Hye Min),김수진(Su-Jin Kim) 한국기계가공학회 2024 한국기계가공학회지 Vol.23 No.7

To prevent burr and delamination defects that occur when drilling CFRP square pipes used in UAM aircraft fuselages, we developed an internal backup jig, with the burr area and delamination factors compared with a control group (with five holes drilled) and an experimental group. The experiments confirmed that delamination and burr occurrence reduced when the jig returned to the inside of the square pipe. The delamination factor decreased from 2.35 to 1.03, and the burr area factor decreased from 13.3% to 1.5% at the exit of the drill hole after applying the developed internal backup jig, thus highlighting its effectiveness in suppressing defects inside difficult-to-repair square pipes.

사각관로 초음파 유량계에 관한 연구

박덕우,김규식 대한전자공학회 2018 전자공학회논문지 Vol.55 No.2

물이나 기름과 같은 유체가 흐르고 있는 배관 내에 초음파를 보내면 유체의 흐름에 영향을 받아 흐름과 동일방향의 경우는 초음파 음속에 유속을 더한 속도로 전파되고, 반대방향으로 유체가 흐를 경우는 유속을 뺀 속도로 전달된다. 이 두 방향 전달시간의 차를 측정하여 유체의 속도를 측정할 수 있도록 한 것이 초음파 유량계이다. 이 초음파 유량계는 상하수도 구역 모니터링이나 산업용의 다양한 액체 유량 측정에 이용될 수 있다. 본 논문에서는 사각관로의 축소관으로 측정관로를 설계하여 유체측정 성능을 높였다. 또한, 다양한 실험을 통해, 유속 증대 효과, 축소관의 정류 성능 향상, 사각관로의 유체측정 성능 향상을 확인할 수 있었다. When an ultrasonic wave propagates in the fluid such as water or oil, its propagation speed increases to the amount of the fluid speed if their travels are of the same directions. On the other hand, the propagation speed of an ultrasonic wave decreases to the amount of the fluid speed if their travels are of the opposite directions. Ultrasonic wave flow meters can measure the fluid speed using the propagation time difference of two ultrasonic waves, which are of the opposite directions. They can be applied to measure and monitor the fluid flow rate of the water supply and drainage areas and widely used to a variety of industrial liquid flow measurement. In this paper, the fluid measuring performance could be improved by designing the rectangular conduit pipe for an ultrasonic wave flow meter. In addition, we could verify the performance improvement of fluid measurement such as the flow rate increasing effect, the rectifying effect of the shrink tube, the measuring error decrease of rectangular conduit pipe-type ultrasonic flow meters through a variety of experimental studies.

EPC method for delamination assessment of basalt FRP pipe: electrodes number effect

Altabey, Wael A. Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.1

Delamination is the most common failure mode in layered composite materials. The author have found that the electrical potential change (EPC) technique using response surfaces method is very effective in assessment delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). In the present study, the effect of the electrodes number on the method is investigated using FEM analyses for delamination location/size detection by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Three cases of electrodes number are analyzed here are eight, twelve and sixteen electrodes, afterwards, the delamination is introduced into between the three layers [$0^{\circ}/90^{\circ}/0^{\circ}$]s laminates pipe, split into eight, twelve and sixteen scenarios for cases of eight, twelve and sixteen electrodes respectively. Response surfaces are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured EPC of all segments between electrodes. As a result, it was revealed that the estimation performances of delamination location/size depends on the electrodes number. For ECS, the high number of electrodes is required to obtain high estimation performances of delamination location/size. The illustrated results are in excellent agreement with solutions available in the literature, thus validating the accuracy and reliability of the proposed technique.

각형강관을 이용한 슬림플로어 시스템의 층고절감효과 비교

조윤진 ( Cho Youn-jin ),임홍철 ( Rhim Hong-chul ),김대유 ( Kim Dae-you ),류승일 ( Yu Seung-il ),김도균 ( Kim Do-kyun ) 한국건축시공학회 2017 한국건축시공학회 학술발표대회 논문집 Vol.17 No.1

In recent years, new construction methods have been required to reduce the construction cost and increase the available area in an environment where construction work is frequently performed in a narrow urban area like Korea. As a result of these studies, slim floor composite beam has been suggested. Slim floor composite beam can reduce required depth because web of steel beam is embedded in the slab, so it is effective to reduce floor height and increase the available area. The purpose of this study is the floor height reduction evaluation by comparing system consisting of reinforced concrete, steel, and slim floor using square-shape steel pipe. After doing structural design for a typical plan, checked effectiveness by comparing each design plan. It is proven that slim floor composite beam can reduce required depth effectively comparing required materials of other system.

용접선 추적 비전장치를 이용한 원형-사각 파이프의 T형 조인트 레이저용접

손영일,박기영,이경돈 한국레이저가공학회 2008 한국레이저가공학회 학술대회 논문집 Vol.2008 No.-

Because of its fast and precise welding performance, laser welding is becoming a new excellent welding method. However, the precise focusing and robust seam tracking are required to apply laser welding to the practical fields. In order to laser welding of a type of T joint like a circular pipe on a square pipe, which could be met in the three dimensional structure such as an aluminum space frame, a visual sensor system was developed for automation of focusing and seam tracking. The developed sensor system consists of a digital CCD camera, a structured laser, and a vision processor. It is moved and positioned by a 2-axis motorized stage, which is attached to a 6 axis robot manipulator with a laser welding head. After stripe-type structured laser illuminates a target surface. images are captured through the digital CCD camera. From the image, seam error and defocusing error are calculated using image processing algorithms which includes efficient techniques handling continuously changed image patterns. These errors are corrected by the stage off-line during welding or teaching. Laser welding of a circular pipe on a square pipe was successful with the vision tracking system by reducing the path positioning and defocusing errors due to the robot teaching or a geometrical variation of specimens and jig holding.

내진 건축구조용 냉간성형 각형강관의 휨성능에 관한 실험적 연구

양일승(Yang, Il-Seung),정진안(Chung, Jin-An),이세정(Lee, Sae-Jung),정경수(Chung, Kyung-Soo) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.6

The use of SN steel in the building structure improved the reliability of the building. As a preceding study, the material properties of SPAR295 square pipes manufactured using SN400B plates were evaluated. The yield and ultimate strengths at the edges of SPAR295 square pipes did not satisfy the design codes based on the values at the sides. The bending tests of cold rolled steel square pipes for aseismatic building structures are performed. The main results show that: 1) the ultimate bending strength is much great, and the energy dissipation capacity is very well, which can make to consume great energy in earthquake. This SPAR295 can meet the need of seismic design very well. 2) The specimens are showed long yield platform after yielding, great cumulative energy-dissipating capacity and well ductility. 3) The fracture of specimens are caused by the local buckling and fracture of welding vicinity.

플라스틱 필름 온실용 구조재의 변위제한 검토

윤성욱,최만권,이시영,강동현,김현태,윤용철 경상대학교 농업생명과학연구원 2016 농업생명과학연구 Vol.50 No.1

In this study, after carrying out a bending test that targeted the frames of plastic filmgreenhouse, the load–displacement relationship was analyzed to be used as basic data to developgreenhouse construction and maintenance guidelines. As a result, regardless of the shapes of thespecimen, the yield and the maximum load increased as the size of the specimen increased. Thedisplacement also showed the same pattern. A steel pipe showed lower yield and maximum loadthan a square pipe, and the displacement was large. In the steel pipe case, the displacementunder the yield and maximum load was in the range of approximately 1.42–4.20mm and 5.80–24.13mm, respectively. In the square pipe case, the displacement under the yield and maximumload was in the range of approximately 1.62–3.00mm and 3.13–8.01mm, respectively. Further, a large difference was observed between the result of this test and the values calculated by aconventionally provided standard. In particular, not much difference was found from the resultof this test in the case of a purlin member from the values provided by previous researches. However, a large difference was observed in the column or main rafter members. Furthermore,when a wide-span and venlo type, which is a glasshouse, was used as a target(h/100 and h/80),the displacement under the yield and maximum load was approximately 28.0mm and 35.0mm,respectively, which showed a large difference compared with the Netherlands standard(14.0mm)of a glasshouse. Further, in the main rafter case, a large difference was observed in thedisplacement limit according to the width(i.e., span) of the greenhouse where members are used. Therefore, because the displacement limit can vary depending on various factors such as type,form, and size of a greenhouse, we determined that studies or tests that consider these factorsshould be carried out to reflect them in the construction and maintenance of greenhouses. 본 연구에서는 온실시공 및 유지관리 지침마련을 위한 기초자료로 사용하기 위하여 플라스틱 필름온실의 구조재를 대상으로 휨 시험을 실시한 후, 하중-변위의 관계를 검토하였다. 그 결과 시편의 형상에 관계없이 시편의 규격이 클수록 항복 및 최대하중이 큰 경향을 보였으며, 변위도 동일한 양상을 보였다. 강관이 각관보다 항복 및 최대하중은 적게 나타났으며, 변위는 크게 나타났으며, 강관의 경우는항복 및 최대하중 하에서의 변위는 각각 1.42~4.20mm 및 5.80~24.13mm정도의 범위에 있었다. 각관의 경우에 변위는 각각 1.62~3.00mm 및 3.13~8.01mm정도의 범위였다. 그리고 본 시험의 결과와 기존의 연구에서 제시한 기준 값들을 보면, 동일한 부재임에도 불구하고 부재들이 사용되는 온실형태나사용목적(예, 샛기둥)에 따라 큰 차이가 있음을 알 수 있었다. 또한 유리온실인 와이드 스팬 및 벤로 형을 대상으로 제시하고 있는 경우(, )에도 변형이 각각 28.0mm 및 35.0mm(기둥 길이280cm 적용)정도로서 네델란드의 유리온실 표준 기준(14.0mm)과 비교해도 큰 차이가 있었다. 스팬이 60cm인 경우, 주서까래나 도리 부재의 본 시험결과는 기존의 연구에서 제시한 값들 보다 각각55.7% 및 39.3%정도 크게 나타났다. 그리고 기둥의 경우, NEN의 기준 값인 14.0mm와 비교해서 본시험결과는 43.7%정도 적은 것으로 나타났다. 따라서 변위제한은 온실의 종류나 형태 및 규격 등 다양한 요인에 의해서 다를 수 있기 때문에 이들 요인들을 반영한 연구나 시험들을 진행하여 온실 시공 및유지관리 등에 반영할 수 있도록 하여야 할 것으로 판단되었다.

지하매설 배관의 부식성장 예측을 위한 Poisson Square Wave Process 모델링

김성준,김도현,김철만,김영표,김우식,최병학 한국품질경영학회 2020 한국품질경영학회 학술대회 Vol.2020 No.-

가스배관의 사용연수가 증가함에 따라 효율적인 유지보수와 안전성 확보에 대한 요구가 커지고 있다. 유럽연합의 한 보고서에 따르면, 장기사용 배관의 주요 고장원인은 부식이다. 부식은 배관의 중량손실을 야기하고 잔류강도를 악화시키기 때문이다. 가스배관의 고장은 치명적인 결과를 초래하므로 부식데이터의 체계적인 모니터링과 분석을 통해 고장예방에 힘써야 한다. 부식성장을 예측하는 문제는 배관 안전성 확보 및 유지보수 의사결정에 중요한 역할을 차지한다. 선형함수에 의한 부식성장 예측은 과대추정의 우려가 있으므로 현실적인 예측결과를 얻기 위해서는 비선형함수를 이용해야 한다. 하지만 매설환경의 다양함과 부식과정의 화학작용을 단일 함수로 묘사하는 것은 한계가 있다. 이에 Stochastic Process가 유용한 대안으로 관심의 대상이 되고 있다. 본 연구는 Poisson Square Wave Process(PSWP)를 이용한 부식성장 예측방안을 다룬다. PSWP는 펄스크기와 지속시간, 2가지 변수를 이용하여 다양한 형태의 부식성장을 모델링할 수 있다. 본 연구에서는 In-line Inspection을 통해 피깅데이터가 주어질 때, 적절한 펄스크기와 지속시간을 결정하는 절차를 제시하고 부식성장 예측치를 구하는 방안을 개발하고자 한다. 수치실험을 통해 확인한 결과, 제안된 기법은 선형 또는 비선형 함수를 이용했을 때에 비해 예측성능이 20-50% 정도 개선되는 것으로 나타났다. 여러 조건에서 부식성장 예측이 배관 신뢰도 계산에 미치는 영향 역시 연구내용에 포함될 것이다.