• 한국기계가공학회지
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• 제18권4호
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• pp.16-25
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• 2019

Recently, due to labor shortages in rural areas within South Korea, the demand for upland-field machinery is growing. In addition, there is a lack of development of systematic performance testing of upland-field machinery. Thus, this study examined structural safety and drawbar pull based on soil properties, as a first step for systematic performance testing on the test bed. First, the properties of soil samples from 10 spots within the experimental site were examined. Second, the strain was measured and converted into stress on 8 points of an onion harvester that are likely to fail. More specifically, the chosen parts are linked to the power, along with the drawbar pull, using a 6-component load cell equipped between the tractor and the onion harvester. The water content of the soil ranged between 5.7%-7.5%, and the strength between 250-1171 kPa. The test soil was subsequently classified into loam soil based on the size distribution ratio of the sieved soil. The onion harvester can be considered as structurally safe based on the derived safety factor and the drawbar pull of 115-1194 kgf, according to the working speed based on agricultural fieldwork.

• 한국철도학회논문집
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• 제20권1호
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• pp.85-98
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• 2017

일반적으로 철도궤도 상부노반 흙재료는 연속적인 열차의 동적하중을 받게 되어 증가-감소 단계의 응력을 경험하게 된다. 이와 같이 일정한 주기에 따라 반복적으로 재하되는 축차응력(${\sigma}_d$)과 반복재하회수가 증가하게 되어 발생하는 회복변형률(${\varepsilon}_r$)의 비를 이용, 회복탄성계수($M_R$)을 산정할 수 있다. 현재까지 철도궤도하부구조에 적용할 수 있는 통일된 회복탄성계수 측정 시험법이 제시된 바 없어, 본 연구에서는 철도궤도 하부구조에 적용 가능하며, 구속압, 응력조건 및 반복재하회수 등을 종합적으로 고려할 수 있는 반복삼축압축시험에 의한 잠정 회복탄성계수 측정시험법을 제시하였다. 또한 반복삼축압축시험에 의한 잠정 시험법을 통해 산정된 회복탄성계수($M_R$)와 중형공진주시험을 통해 측정한 전단탄성계수(G)와의 상관성분석을 실시하였다.

• 소성∙가공
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• 제4권1호
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• pp.9-16
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• 1995

Model material technique, which requires only the small space of experimental set-up and low cost for experiment, is used to estimate the deformed profile and the forging load in rotary forging. The materials and working conditions are determined to satisfy the similitude conditions between the model test and the prototype test. The model material of the so-called plasticine and the mild steel are chosen as specimens, and they represent almost the same value of strain gardening exponent in the stress-strain relationship. Lubricant in the model test is also carefully selected so that it gives the same frictional conditions at the tool-specimen interface. Experiments for two kinds of specimens are carried out in each testing equipment at room temperatue. From the experiments the deformed dimensions and the forging loads are measured and compared with each other by using the simulation coefficients. It is shown that there are good agreements between the model test and the prototype test. Finally, for verifying the availability of the model material technique this mathod is applied to forging of bevel gear product. the good result is obained which can demonstrate that the model material technique is very efficent for estimating or developing a new process.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.43-52
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• 2016

The degradation of the load-bearing capacity of reinforced concrete beams due to corrosion has a profoundly negative impact on the structural safety and integrity of a structure. The literature is limited with regard to models of bond characteristics that relate to the reinforcement corrosion percentage. In this study, uniaxial tensile tests were conducted on specimens with irregular corrosion of their reinforced concrete. The development of cracks in the corroded area was found to be dependent on the level of corrosion, and transverse cracks developed due to tensile loading. Based on this crack development, the average stress versus deformation in the rebar and concrete could be determined experimentally and numerically. The results, determined via finite element analysis, were calibrated using the experimental results. In addition, bond elements for reinforced concrete with corrosion are proposed in this paper along with a relationship between the shear stiffness and corrosion level of rebar.

• Structural Engineering and Mechanics
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• 제38권1호
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• pp.27-37
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• 2011

This paper presents the results of a study on the capability of nonlinear quasi-static finite element modelling in simulating the hysteretic behaviour of CFRP and GFRP-retrofitted RC exterior beam-column joints under cyclic loads. Four specimens including two plain and two CFRP/GFRP-strengthened beam-column joints tested by Mahini and Ronagh (2004) and other researchers are modelled using ANSYS. Concrete in compression is defined by the modified Hognestad model and anisotropic multi-linear model is employed for modelling the stress-strain relations in reinforcing bars while anisotropic plasticity is considered for the FRP composite. Both concrete and FRP are modelled using solid elements whereas space link elements are used for steel bars considering a perfect bond between materials. A step by step load increment procedure to simulate the cyclic loading regime employed in the testing. An automatically reforming stiffness matrix strategy is used in order to simulate the actual seismic performance of the RC concrete after cracking, steel yielding and concrete crushing during the push and pull loading cycles. The results show that the hysteretic simulation for all specimens is satisfactory and therefore suggest that the numerical model can be used as an inexpensive tool to design of FRP-strengthened RC beam-column joints under cyclic loads.

• 대한토목학회논문집
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• 제9권4호
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• pp.83-92
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• 1989

강성포장(剛性鋪裝)에 대하여 더 좋은 공용성능(供用性能) 기대를 위한 개발과 파손발생에 대한 파손과정에 관하여 포장상태를 조사하게 된다. 본 논문(論文)은 공용중(供用中)인 시멘트콘크리트 포장(鋪裝)의 피로거동(疲勞擧動)과 탄성특성(彈性特性)에 대한 연구결과이다. 공용중(供用中)인 각(各) 포장(鋪裝)의 평균인장강도(平均引張強度)를 측정하기 위하여 Indirect tensile시험을 실시한 것이다. 변형측정(變形測定)은 이러한 특성의 변화 및 콘크리트의 탄성특성(彈性特性)을 구하기 위한 피로(疲勞)시험을 통하여 이루어진 것이다.

• 한국생산제조학회지
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• 제23권2호
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• pp.145-151
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• 2014

Recently, the growing demand for weight reduction and improved structure durabilityfor commercial vehicles has led to active research into the development and application of suitablecomposite materials. This studysuggests abimaterial composite frame produced by apultrusion process to replace steel frames. We focused on the development of a composite frameconsisting of two types of materialsby mixing anorthotropic material with anisotropic material. The inside layer consisted of an aluminum pipe, and the outside layer was composed of a glass fiber pipe. To determine the strength and failure mechanisms of the composite material, tensile tests, shear tests, and three-point bending tests were conducted, followed by fatigue tests. After static testing, the fatigue tests were conducted at a load frequency of 5 Hz, a stress ratio (R) of 0.1, and an endurance limit of $10^6$ for the S-N curve. The resultsshowed that the failure modes were related to both the core design and the laminating conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.217-222
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• 2001

For the life evaluating of notched members, it is the best way that performing the real fatigue test of structure containing notch. But this method required generally much times and costs to evaluate fatigue life. So, generally we use the modified S-N curve or several methods to predict fatigue life. In this study, crack initiation life was evaluated by fatigue testing the SAE keyhole specimen and smooth specimen made of Al 7075-T6 alloys using the constant load then obtained S-N curve of smooth specimen and P-N curve of SAE keyhole specimen. And, fatigue lives of keyhole specimen are predicted using some life prediction methods (Nominal range I method, Nominal range II method, FEM analysis) for investigating experimented results, and that were compared with experimental data. Predicted fatigue lives by FEM analysis were corresponded with experimental data between 1/3times and 3times on the whole, and predicted fatigue lives using modified S-N curve (Nominal range I method, Nominal range II method) were nonconservative compared with that of FEM analysis.

• 한국해양공학회지
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• 제18권4호
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• pp.52-58
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• 2004

A Semi-Autonomous Underwater Vehicle (SAUV), capable of simple work on the seabed, is under development in KRISO-KORDI. This SAUV pressure vessel is composed of fiberglass reinforced plastic (FRP), and is also manufactured to carry electronic equipment. The objective of this paper is to describe the safety check for the pressure vessel. This is achieved fly conducting structural analysis and testing in a pressure tank. Strain and stress test results, under unit load, are obtained fly using ANSYS in linear structural analysis. Local buckling analysis are performed with NASTRAN at the middle oj the cylindrical hull. The first test, using linear structural analysis, is unsuccessful, as buckling occurred. During the second test, linear structural analysis, combined with local buckling analysis, is conducted. There is no buckling up to 250 m when both ANSYS and NASTRAN are used.

• 대한기계학회논문집
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• 제11권2호
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• pp.205-213
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• 1987

본 논문에서는 비압축 선형 점탄성재료를 원통체로 모델화하여 열하중에 대한 거동을 점유적 시간증분과정을 적용하여 수치해를 제시하고 원통체를 제작실험하여 변 형과 비파괴검사를 통해 측정하여 비교검토하였다. 또한 이론적 수치해와 시편과의 안전율을 각 파괴기준(failure criteria)에 적용하여 비파괴검사결과와 비교하였다.