• Journal of Welding and Joining
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• 제29권4호
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• pp.48-53
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• 2011

A thermal distortion analysis which takes strains directly as boundary conditions removed barrier of analysis time for the evaluation of welding distortion in a large shell structure like ship block. If the FE analysis time is dramatically reduced, the structure modeling time or the input-value calculating time will become a new issue. On the contrary to this, if the calculation time of analysis input-value is dramatically reduced and its results also are more meaningful, a little longer analysis time could be affirmative. In this study, instead of using inherent strain based on elastic analysis, a thermal strain based on elasto-plastic analysis is used as the boundary condition of weldments in order to evaluate the welding distortion. Here, the thermal strain at the weldment was established by using a stress-strain curve established from the test results. It is possible to automatically recognize the modeling induced-stiffness in the shrinkage direction of welded or heated region. The validity of elasto-plastic thermal distortion analysis was verified through the experiment results with various welding sequence.

• 한국농공학회지
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• 제44권4호
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• pp.99-106
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• 2002

This research was performed to study the actual behavior of 1-2W type pipe greenhouse under the influence of typhoon by measuring the various strains in structural materials. These results can eventually be utilized in the design criteria as well as in the modification of conventional equation for calculating more realistic wind loads. The first data under the influence of Typhoon Olga arrived in Jinju on Aug. 1999 were obtained by strain gage with 10 sensor points. According to the data obtained, the typical variation of strain depending on wind pattern could be observed. The strains in structural frame were fluctuated very sensitively depending on the direction and magnitude of wind velocity. But some of the data were lost or missed by system's failure. A kind of inherent vibration pattern of greenhouse pipe frame was observed from the plotted data, but this phenomenon is not so clear as to be separated from the overall fluctuation so far. This experimental research is expected to be continued as a long term project to measure and analyze the strain pattern of structural frame depending on the various locations and section characteristics by way of adopting more efficient instrument with sufficient number of measuring points and accuracy.

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1172-1178
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• 2006

Measurement of blade strain with sensors directly installed on the blade has one critical issue, how to send the sensor signal to the ground. Strain-gauges have been dominantly used to directly measure stress of a blade and either a slip ring or a telemetry system has to be used to send measured signal to the ground. However, both systems have many inherent problems and sometimes very severe limitations to be practically used. In this paper, new on-line strain monitoring method using. FBG(Fiber Bragg Grating) sensors and a beam coupler is introduced. Measurement of rotor stress using FBG sensors is nothing new, but unlike other system which installs all necessary instruments on the rotor and use telemetry system to send data to the ground, this system makes use of light's unique characteristic - light travels through space. In this new approach, single optical fiber with many FBG sensors is installed on the blade and all other necessary instruments can be installed at ground thereby giving tremendous advantages over slip ring or telemetry system. A reference sensor is also introduced to compensate the beam coupler's transmission loss change due to rotation. The suggested system's good performance is demonstrated with experiments.

• 한국지반공학회논문집
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• 제19권1호
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• pp.77-92
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• 2003

사질토에서의 한계상태정수 결정시 근본적인 물리적 과정들과 고유적 인 한계성들을 파악하기 위하여 일련의 표준삼축시험을 실시하였다. 시험결과에 의하면, 주어진 흙에 대하여 한계상태마찰각은 배수조건에 상관없이 일정한 반면에, e-log p＇공간상에서의 한계상태선은 주로 표준삼축시험에서 충분치 못하게 도달하는 변형률과 비배수시험에서의 변형률 국지화효과 때문에 배수조건에 따라 다른 결과를 보였다. 실내시험을 통하여 한계상태정수를 산정하는 최선의 방법은 균일하고 느슨하게 성형된 시료를 배수조건하에서 전단하는 것으로 나타났다. 더불어 배수시험에서 다일러턴 시효과나 변형률 국지화효과를 피할 수 있는 시험을 계획하기 위한 참고상태정수를 제시하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.452-465
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• 2015

This paper presents the simplified welding distortion analysis method to predict the welding deformation of both plate and stiffener in fillet welds. Currently, the methods based on equivalent thermal strain like Strain as Direct Boundary (SDB) has been widely used due to effective prediction of welding deformation. Regarding the fillet welding, however, those methods cannot represent deformation of both members at once since the temperature degree of freedom is shared at the intersection nodes in both members. In this paper, we propose new approach to simulate deformation of both members. The method can simulate fillet weld deformations by employing composite shell element and using different thermal expansion coefficients according to thickness direction with fixed temperature at intersection nodes. For verification purpose, we compare of result from experiments, 3D thermo elastic plastic analysis, SDB method and proposed method. Compared of experiments results, the proposed method can effectively predict welding deformation for fillet welds.

• Advances in Computational Design
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• 제7권4호
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• pp.281-295
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• 2022

Tensile property is one of the excellent properties of ultra-high performance concrete (UHPC), and uniaxial tensile test is an important and challenging mechanical performance test of UHPC. Traditional uniaxial tensile tests of concrete materials have inherent defects such as initial eccentricity, which often lead to cracks and failure in non-test zone, and affect the testing accuracy of tensile properties of materials. In this paper, an original integrated design scheme of mould and end fixture is proposed, which achieves seamless matching between the tension end of specimen and the test fixture, and minimizes the cumulative eccentricity caused by the difference in the matching between the tension end of specimen and the local stress concentration at the end. The stress analysis and optimization design are carried out by finite element method. The curve transition in the end of specimen is preferred compared to straight line transition. The rationality of the new integrated design is verified by uniaxial tensile test of strain hardening UHPC, in which the whole stress-strain curve was measured, including the elastic behavior before cracking,strain hardening behavior after cracking and strain softening behavior.

• 한국해양공학회지
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• 제17권1호
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• pp.80-85
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• 2003

In this study, we developed an analysis method of plate forming by induction heating, verifying the effectiveness of the present method through a series of experiments. The phenomena of the induction heating involves a 3D transient problem, coupled with electromagnetic, heat transfer, and elastoplastic large deformation analyses. To solve the problem, or present an appropriate model and an integrated system. Using the present analysis model, or can estimate the plate deformation in heating without experiments and simulate the plate bending process of induction heating.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2008년도 춘계학술발표대회 개요집
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• pp.28-28
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• 2008

• Elastomers and Composites
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• 제39권4호
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• pp.294-300
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• 2004

혼합폐플라스틱과 폐타이어분말을 혼합하여 복합체를 구성하고 그 기계적인 물성을 조사하였다. 수지-고무분말 사이의 계면접착력을 증대시키고자 두 요소와 친화성을 가질 것으로 예상되는 trans-octylene rubber(TOR)를 소량 첨가하였다. 고무분말의 투입량이 많아질수록 인장강도와 압축강도는 플라스틱자체보다 저하되었으며 파단신장률과 충격강도는 증가되었다. 상용화제 TOR이 첨가되면 인장강도와 충격강도 및 압축강도는 크게 향상되었으나 신장률은 변화가 없었다. 이러한 물성의 변화는 TOR의 화학적인 이중성에 기인한다고 여겨진다.

• 한국지반공학회논문집
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• 제19권5호
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• pp.199-210
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• 2003

흙이 변형하는 동안 전단지역 내에서 변형국지화가 자주 관찰된다. 사실상, 그 현상은 예외적이라기보다는 전형적으로 보인다. 개념적으로, 행해진 일의 증가가 음인 경우 변형국지화가 쉽게 발생한다. 이러한 현상을 검증하기 위해서, 본 연구에서는 배수상태의 조밀한 흙, 비배수상태의 느슨한 흙, 비배수전단하의 조밀한 흙에서의 공동화, 비균질한 흙, 판상형의 입자로 된 흙에서의 입자배열, 입자 깨짐을 가지는 흙, 그리고 낮은 함수비나 약한 시멘트결합이 된 흙 등 다양한 흙과 다양한 조건에 대하여 조사를 수행하였다. 이러한 경우들의 각각을 독립적으로 시험할 수 있도록 시료를 제작하였고 실험절차를 구상하였다. 실험결과에 의하면, 최고점후 변형연화거동을 가지는 흙은 변형국지화, 전단대형성, 그리고 점진적 파괴가 되기 쉽다. 응력상태, 흙밀도, 흙입자의 고유적인 역학적$.$지형학적인 특성, 저함수비, 그리고 비균질성이 변형국지화를 일으키는데 공헌을 하였다. 국지화가 가능한 모든 경우들을 고려해 볼 때, 실내시험으로부터 한계상태정수를 결정하는 최선의 방법은 배수전단하의 느슨하고 균일한 포화시료를 사용하는 것으로 나타났다.