Experimental and Numerical Investigation of the Tensile Performance and Failure Process of a Modified Portland Cement

Jianhang Chen,Kangming Tao,Banquan Zeng,Lei Liu,Hongbao Zhao,Junwen Zhang,Danqi Li 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.1

A better understanding of the tensile performance and tensile failure mechanism of cement paste is significant in preventing rock reinforcement failure. Therefore, this paper aims to reveal the tensile performance and failure mechanism of a modified Portland cement: Stratabinder HS cement. To achieve this objective, the split tensile test was conducted on specimens followed by simulating the failure mechanism numerically. The results indicated that the water–cement rate significantly influenced the tensile performance of the cement paste. When the water–cement rate increased from 0.35 to 0.42, the tensile strength declined from 1.9 MPa to 1.5 MPa. It was also observed that vertical tensile failure constantly occurred regardless of the water–cement rate. During the testing process, tensile cracks and shear cracks occurred. The increasing rate in the number of specimen cracks was dependent on the tensile stress state. Before the tensile stress reached the peak, the crack quantity increased slightly. After the peak, the crack quantity increased dramatically. During the vertical loading process, horizontal tensile stress occurred in the specimen. This horizontal tensile stress zone showed a diamond shape. The higher the tensile stress is, the larger the area of the horizontal tensile stress zone. When the tensile strength was reached, horizontal tensile stress mainly concentrated at the vertical centre of the specimen. This finally led to tensile failure of the specimen. This paper indicated that the water–cement rate was the key factor in evaluating the tensile strength of the Stratabinder HS cement.

회귀분석법에 의한 복합재료 적층판의 인장 파손특성 분석

이명건(Myoung Keon Lee),오광근(Kwang Keun Oh),김재훈(Jae Hoon Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Failure theory that is widely used in composit structure is first ply failure. It regards failure of a ply as laminate failure. This theory predicts correct failure by using strength characteristic of lamina. but, It is leading to conservative results because laminate can endure force when failing a lamina. Recently, advanced airline uses laminate failure theory that estimate strain of composit structure for airplanes. It is important to get value of mechanical fracture characteristic for the entire range of applicable layups (percentage of 0°, +/-45° and 90° plies) before appling laminate failure theory. This paper contains the results of tensile failure characteristics developed by using regression analysis method. The regression analysis is performed with the response variable being the laminate ultimate fracture strength and the regressor variables being two ply orientation(0° and ±45°) variables. Composit material is a 350°F(177°C) cured, carbon fiber reinforced plastic(CFRP) composite material system that incorporates an epoxy resin. The specimens used in this paper is designed with plies oriented only in four standard orientation of 0°, +45°, -45° and 90°. All specimens contain a minimum of 10% plies in each of the 0°, +45°, -45° and 90° orientations, thus ensuring that all test experienced a fiber failure mode without significant non-linearities in the load-strain response. A total of 149 tension tests were conducted on specimens from 14 distinct laminates and 3 material batches. ASTM-D-3039 was used for test method

국산 침엽수 철물접합부의 인장하중 특성

심국보,박정환,이준호 한국목재공학회 2003 목재공학 Vol.31 No.5

국산 주요 침엽수재인 소나무, 잣나무, 낙엽송의 철물접합부 인장하중 특성 구명을 위하여 본 연구를 수행하였다. 철물 접합부의 최대 인장하중은 AA형의 경우 소나무가 3,612 kgf로 낙엽송, 잣나무에 비해 각각 1.2배, 1.7배, EA형의 경우 2,704 k9f로 1.1배, 1.5배 우수하였다. 또한 AA형은 EA형에 비해 3 수종 모두 약 1.2배 이상 높은 인장하중을 나타내었다. 철물접합부의 파괴모드는 주로 이의 빠짐, 철물의 인장파괴와 목재의 전단파괴로 이루어지며, 특히 소나무 접합부는 철물의 인장파괴를 나타내었다. 철물접합부재의 인장하중-변위 특성은 Foschi 모형으로 정확하게 추정할 수 있었으며 , 철물접합부의 초기강성은 소나무 접합부재가 높게 나타났다. 국산 침엽수재의 철물접합부에 대한 설계하중은 소나무, 낙엽송, 잣나무의 순으로 높게 나타났으며, AA형의 경우 이당 설계하중이 소나무 25 kgf, 낙엽송 22 kgf, 잣나무 15 kgf이었으며, EA형의 경우 소나무 19 kgf, 낙엽송 17 kgf, 잣나무 13 kgf 이었다. This study was conducted to evaluate the tensile properties of metal plate connector for the domestic major softwoods, such as Korean red pine, Korean white pine, and Japanese larch. The maximum tensile load of Korean red pine was 3,612㎏f in AA type, it was 1.2 and 1.7 times higher load than that of Japanese larch and Korean white pine. In EA type, it was 2,704㎏f, and 1.1 and 1.5 times higher than the loads of Japanese larch and Korean white pine. The failure modes of metal plate connector were metal plate withdrawal, plate tensile failure, and wood shear block failure. The failure mode of Korean red pine connector was tensile failure of plate, that is reason of the high tensile load resistance for metal plate connections in Korean red pine. The mechanical properties of metal plate connector could be predicted by the Foschi model parameter. In the initial stage, the Korean red pine connector was stiffer than the other species. The design values for metal plate connector per tooth was 25, 22, and 15kgf for Korean red pine, Japanese larch, and Korean white pine in AA type and 19, 17, and 13㎏f in EA type.

새로운 형태의 선설치 인서트 앵커에 대한 단조 인장 및 전단강도 평가

전주성,김지훈,오창수,이창환,Jeon, Ju-Seong,Kim, Ji-Hoon,Oh, Chang-Soo,Lee, Chang-Hwan 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2

The damage to non-structural elements in buildings has been increasing due to earthquakes. In Korea, post-installed anchors produced overseas have been mainly used for seismic anchorage of non-structural components to structures. Recently, a new cast-in-place concrete insert anchor installed in concrete without drilling has been developed in Korea. In this paper, an experimental study was conducted to evaluate the tensile and shear strengths of the newly developed anchor under monotonic load. The failure modes of the tension specimens were divided into concrete breakout failure and steel failure, and all shear specimens showed steel failure. In both tension and shear, the maximum loads of specimens were greater than the nominal strengths predicted by the concrete design code (KDS 14 20 54). As a result, it is expected that the current code can also be used to calculate the strength of the developed cast-in anchor.

오픈 홀 인장 복합 재료 적층판에서 층간 및 내부 손상에 대한 점진적 손상 모델링

살만칼리드,김흥수 한국전산구조공학회 2019 한국전산구조공학회논문집 Vol.32 No.4

인장 강도는 복합 재료를 설계하기 위한 필수 변수이므로 개방 홀 인장 시험을 통해 복합 재료의 인장 강도를 측정한다. 그러나 인장 시험을 올바르게 모델링하는 것은 섬유와 매트릭스 손상, 층간분리 및 섬유와 매트릭스 사이의 손상 같은 다양한 손상을 수반하기 때문에 매우 어려운 과제다. 따라서 섬유와 매트릭스 사이의 면내 파괴 및 층간분리를 평가하기 위해 본 연구에서는 점진적 손상 모델을 개발하였다. 하신 손상 모델과 응집 영역 접근법을 층과 층간분리를 모델링하는데 사용하였다. 현재 모델의 결과를 이전에 발표된 실험 및 수치 결과와 비교하여 검증하였다. 이를 통해 유한요소해석에서 층간분리를 무시하면 인장 강도가 과대평가 된다는 것을 확인할 수 있었다. Open-hole tensile tests are usually performed to measure the tensile strengths of composites as they are an essential parameter for designing composite structures. However, correctly modeling the tensile test is extremely challenging as it involves various damages such as fiber and matrix damage, delamination, and debonding damage between the fiber and matrix. Therefore, a progressive damage model was developed in this study to estimate the in-plane failure and delamination between the fiber and matrix. The Hashin damage model and cohesive zone approach were used to model ply and delamination failures. The results of the present model were compared with previously published experimental and numerical findings. It was observed that neglecting delamination during finite element analysis led to overestimation of tensile strength.

Joinability and Mechanical Properties of Clinched Joints of Different Aluminum Alloys

Yue Zhang,Honghe Xu,Ruitao Peng,Yan Lu,Linwei Zhu 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.11

The joints of four aluminum alloy (7075, 5754, 6061, 1060) sheets were prepared using the clinching process with different die assemblies, and the forming and mechanical properties of the produced joints were evaluated using different testing procedures. The neck thickness, undercut values, bottom thickness, and joint dimensions of the joints were measured to investigate the joinability. The forming quality parameters, strength, failure displacement, failure mode, and energy absorption of the joints were investigated using the tensile shear test and peeling test. It was revealed that all four aluminum alloy sheets could form clinched joints with a suitable undercut, neck thickness and different die fits. A combination of SR5202 and SR703.12 dies resulted in an optimum joint quality for different sheets. Both neck thickness and the undercut amount played a major role in the determination of the strength of the joints. The best mechanical properties of the single-lap and cross joints were found for the sheets made from aluminum alloys 7075 and 6061. The aluminum alloy 5754 clinched joints exhibited slightly deteriorated mechanical properties but had the highest energy absorption capacity of the joints. However, the lower yield strength of aluminum alloy 1060 led to poor mechanical properties of these joints. All the single lap joints showed a tensile-shear failure mode of the upper sheet material, whereas the peel failure modes of the cross joints showed neck pull-off failure, neck fracture failure, and neck mixed failure.

알루미늄 및 용융아연도금강판의 다겹 Self-Piercing Rivet 접합특성에 관한 연구

권의표,이광진 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.3

Multiple galvanized steel and aluminium alloy sheets were joined by self-piercing rivet(SPR) and hybrid joining(SPR + adhesive bonding). In this study, tensile-shear load and fatigue properties of multi-layer SPR and hybrid joints were investigated. Moreover, tensile-shear deformation behavior of the joints under different specimen configurations was investigated. Depending on the specimen configurations either top sheet tearing failure mode or rivet tail pull-out failure mode was observed during the tensile-shear tests. The top sheet tearing failure mode resulted in low maximum tensile-shear load, but it led to larger displacement value as compared to that in the tail pull-out failure mode. Maximum tensile-shear load of hybrid joints was about four times higher than that of SPR joints. Also, fatigue limit of hybrid joints was about two times higher than that of SPR joints.

복합 정수장 구조물의 유한요소해석을 통한 내진성능 평가

조한민,허종완 한국복합신소재구조학회 2018 복합신소재구조학회 학술발표회 Vol.2018 No.04

In this study, finite element (FE) analysis was performed to evaluate the seismic performance of the water treatment plant, which is a major state of the art water treatment plant, to predict tensile cracks and compressive failure. The FE model simulation for two facilities of the water purification plant was made considering the initial conditions, boundary conditions and water effect. For the nonlinear dynamic analysis, seismic analysis was performed using ground acceleration. Tensile cracks and compressive failure are analyzed and the effects on the structures are analyzed. As a result of the analysis, tensile cracks can be predicted to occur in the main structure.

Up-Set Coupler 이음철근의 인장특성에 대한 실험적 연구

심종성,박철우,강태성,김태수 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 논문집 Vol.12 No.5

구조물이 초고층화, 대형화 되어감에 따라 철근의 이음방법에 대한 필요성이 증대되고 있다. 현재 일반적으로 건설현장에서는 겹이음을 많이 사용하고 있으나 굵은 직경을 사용한 구조부재의 경우 겹이음 사용 시 피복두께 확보의 어려움으로 부착파괴 및 접합부의 복잡한 배근으로 인한 콘크리트 타설의 시공성 저하 등이 문제가 되고 있다. 또한 압접이음은 철근의 단부를 국부적으로 가열하여 접합하는 방식으로 압접 후 철근의 취약부분이 발생할 수 있으므로 시공현장에서의 철저한 품질관리가 요구되는 단점이 있다. 이러한 단점을 해결하고자 새로운 개념의 Up-set Coupler를 적용하였다. 본 연구에서는 기계적 이음방법 중 철근 선조립공법이나 고강도, 대직경의 철근을 사용하는 PSC구조물의 접합부에서 주로 사용되는 대표적인 이음방법인 Screw Coupler와 Up-set Coupler, 그리고 이음이 없는 철근을 사용하여 각각의 인장특성과 사용성을 실험적으로 연구하고자 한다. As structures are getting super-rise and large-sized, introducing the construction methods such as prefabrication of bar-meshes and complex method are being actively discussed to pursue the high quality of reinforced concrete, the simplification of field works, and the reduction of duration, as well as the study on how to connect reinforcing rods, which occurs while applying the same methods, is in progress Also, the pressure welded joint is a kind of method that heats the ends of reinforced bars locally and joint them, and after the pressure welding, the vulnerable part in the reinforced bar occur. Thus, in the construction field, the throughout quality control is necessary because of the delayed duration and the lowered construct ability. In this study, of the traditional lap splice method and the mechanical splice one, the screw coupler, we tried to look into through experiments the prefabrication method of bar-meshes, a typical joint method usually used for the joint parts for PSC structures applying the reinforced bar with its big diameter, and a newly-developed up-set coupler method. And we also examined the characteristic of tensile.

드럼 세탁기 Spider의 피로수명 신뢰성 평가에 대한 연구

이성민(Seongmin Lee),조상봉(Sangbong Cho),조성진(Seongjin Jo),김영수(Youngsoo Kim),강동우(Dongwoo Kang),정연수(Younsu Jung),정보선(Bosun Chung) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

The spider of a drum washing machine receives the repeated fatigue loadings during laundering. Although the spider is designed statically safely, it often happens fatigue failure. Therefore it requires the safe design for fatigue and needs the prediction of quantitative fatigue life. The S-N diagram for a spider material is developed by fatigue test and statistical analysis. The stresses are measured directly from strain gages on the spider. To predict the fatigue life of spider, the rainflow counting method and Miner"s rule are used. The data for fatigue life are analyzed statistically. From these data, reliability estimation for fatigue life can be done and also, equivalent fatigue life can be obtained. It will be applied to make and improve to a short period for design and prototype test.