• 한국기계가공학회지
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• 제11권6호
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• pp.82-87
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• 2012

The purpose of this study is to produce a side impact beam with high tensile steel using a roll forming process. The door side impact beam plays an important roll in a car because it protects passengers from external crash. The roll forming process is a continuous bending process wherein a long metal sheet is bended as it continuously passes several rolls. The characteristic of this study is that an impact beam is produced by a continuous process using a ultra high strength steel without a hardening heat treatment. A model was determined by analysing plasticity of a cross section shape considering high strength. Design parameters of the impact beam was determined by crash-analysing the model. Workpiece products were manufactured by designing dies for roll forming and setting them up in a following process line. Results of a bending test and a FEM analysis was considered and reviewed.

• 한국도로학회논문집
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• 제15권2호
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• pp.113-119
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• 2013

PURPOSES : The objectives of this study are to develop the eco-friendly pavement material using polyurethane binder and evaluate mechanical properties of the developed binder and concrete. METHODS : The bending beam test was conducted to select the sample candidates of polyurethane binder based on the bending strength. The characteristics of viscosity, curing time, and temperature change of sample binder was examined on different temperature conditions. The mechanical properties of polyurethane binder was estimated using the dynamic modulus testing. The indirect tensile strength test was conducted on polyurethane binder concrete with different gradation and binder content for evaluating the mechanical properties of concretes. RESULTS : Based on the beading beam test, four different binder samples were prepared for estimate the mechanical properties. The viscosity of polyurethane binder tends to increase with increase of liquid temperature and the hardening phenomenon begins 10 to 15 minutes at room temperature after mixing the resin and hardener. It is observed that the dynamic modulus of binder increases as loading frequency increases and change of modulus is found to be the highest in the PU-2I binder type. The PU-2I binder concretes shows the largest value of indirect tensile strength and indirect tensile energy. CONCLUSIONS : The use of polyurethane binder as pavement materials is capable of increasing the pavement performance and reducing the detrimental environmental effect during the highway construction.

• 대한기계학회논문집A
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• 제26권1호
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• Computers and Concrete
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• 제30권5호
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• pp.311-321
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• 2022

The interfacial bond strength of partially encased composite (PEC) structure tends to 0, therefore, the cast-in-place concrete theoretically cannot embody better composite effect than the fabricated structure. A total of 12 specimens were designed and experimented to investigate the energy dissipation and damage of fabricated PEC beam through unidirectional cyclic loading test. Because the concrete on both sides of the web was relatively independent, some specimens showed obvious asymmetric concrete damage, which led to specimens bearing torsion effect at the later stage of loading. Based on the concept of the ideal elastoplastic model of uniaxial tensile steel and the principle of equivalent energy dissipation, the energy dissipation ductility coefficient is proposed, which can simultaneously reflect the deformability and bearing capacity. In view of the whole deformation of the beam, the calculation formula of energy dissipation is put forward, and the energy dissipation and its proportion of shear-bending region and pure bending region are calculated respectively. The energy dissipation efficiency of the pure bending region is significantly higher than that of the shear-bending region. The setting of the screw arbors is conducive to improving the energy dissipation capacity of the specimens. Under the condition of setting the screw arbors and meeting the reasonable shear span ratio, reducing the concrete pouring thickness can lighten the deadweight of the component and improve the comprehensive benefit, and will not have an adverse impact on the energy dissipation capacity of the beam. A damage model is proposed to quantify the damage changes of PEC beams under cyclic load, which can accurately reflect the load damage and deformation damage.

• 콘크리트학회논문집
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• 제24권5호
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• pp.525-533
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• 2012

이 연구에서는 UHPCC에서 섬유혼입률에 따른 초기균열강도 및 휨인장강도의 변화를 0~5 vol.% 범위에서 조사하였으며, 노치의 여부에 따른 영향을 파악하기 위해 노치가 없는 보에 대한 4점 재하실험 및 노치 낸 보에 대한 3점 재하실험을 같이 실시하였다. 실험 결과로부터 섬유혼입률이 증가함에 따라 휨인장강도는 선형적으로 강도가 향상됨을 확인할 수 있었고, 초기균열강도의 경우에는 1 vol.% 이상에서는 강도향상을 나타내었으나 그 이하의 섬유혼입에서는 강도향상 효과가 거의 없는 것으로 나타났다. 노치 유무에 따른 휨 실험으로부터 구한 UHPCC의 초기균열발생강도 및 휨 인장강도를 비교했을 때, 섬유혼입률에 따라 노치의 영향이 변하는 것으로 나타났다. 섬유혼입률이 증가함에 따라 노치에서의 응력집중의 영향이 감소하여 강도 차이가 점차 줄어들었으며, 높은 섬유혼입률에서는 노치에 의한 응력집중효과는 없어지고 균열면의 상태 및 크기효과의 영향이 지배적으로 작용하여 노치낸 보의 강도가 좀 더 크게 나타났다.

• Steel and Composite Structures
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• 제18권6호
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• pp.1423-1450
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• 2015

The paper presents the details and results of an experimental study on bolted end-plate joints of industrial type steel building frames. The investigated joints are commonly used in Lindab-Astron industrial buildings and are optimized for manufacturing, erection and durability. The aim of the research was to provide an experimental background for the design model development by studying load-bearing capacity of joints, bolt force distribution, and end-plate deformations. Because of the special joint details, (i.e., joints with four bolts in one bolt-row and HammerHead arrangements), the Eurocode 3 standardized component model had to be improved and extended. The experimental programme included six different end-plate and bolt arrangements and covered sixteen specimens. The steel grade of test specimens was S355, the bolt diameter M20, whereas the bolt grade was 8.8 and 10.9 for the two series. The end-plate thickness varied between 12 mm and 24 mm. The specimens were investigated under pure bending conditions using a four-point-bending test arrangement. In all tests the typical displacements and the bolt force distribution were measured. The end-plate plastic deformations were measured after the tests by an automatic measuring device. The measured data were presented and evaluated by the moment-bolt-row force and moment-distance from centre of compression diagrams and by the deformed end-plate surfaces. From the results the typical failure modes and the joint behaviour were specified and presented. Furthermore the influence of the end-plate thickness and the pretension of the bolts on the behaviour of bolted joints were analysed.

• Composites Research
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• 제30권2호
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• pp.158-164
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• 2017

섬유금속적층판은 금속 판재와 섬유 강화 플라스틱을 적층한 하이브리드 소재 중 하나다. 섬유금속적층판은 부품 경량화 측면을 고려했을 시, 뛰어난 충격흡수능력을 가지고 있기 때문에 자동차 및 항공우주 산업에서 적용 및 연구를 진행하고 있는 추세다. 특히, 자동차의 측면 도어 임펙트 빔의 경우, 기존의 금속소재에서 복합재료로 대체하기 위한 연구가 활발히 진행 중이다. 본 연구에서는 자동차의 측면 도어 임펙트 빔을 금속소재와 자기 강화형 폴리프로필렌을 적층한 섬유금속적층판으로 대체하는 것이 목표다. 3가지 종류의 임펙트 빔의 3점 굽힘 시험 수치해석을 통해 단면적 대비 굽힘 저항력의 크기를 비교하였다. 그 후, 제작 실현성을 고려하여 굽힘 저항력이 우수한 이중모자형 임펙트 빔을 순수 DP 980과 섬유금속적층판으로 제작하여 자동차 측면 도어에 설치된 모델을 상정하고 충돌 해석을 수행하였다. 결과적으로 섬유금속적층판을 사용한 임펙트 빔은 기존의 DP 980보다 무게 대비 충격 에너지 흡수 능력이 약 7배 높음을 알 수 있었다.

• Composites Research
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• 제12권3호
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• pp.66-74
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• 1999

탄소/에폭시 복합재료 적층판의 혼합 모드 층간분리 연구를 위하여 수정 혼합 모드 굽힘시험이 수행되었다. 하중레버의 하중 부가점 위치와 시편에 작용하는 굽힘 하중점 위치를 변화시킴으로써 다양한 혼합 모드 비를 구할 수 있었다. 이론과 시험 및 유한요소 해석을 병행하여 변형에너지방출율을 구한 결과 이들은 잘 일치하여 일반적으로 사용될 수 있는 시험 방법으로 정립될 수 있음을 확인하였다.

• 한국해양공학회지
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• 제14권2호
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• pp.89-98
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• 2000

Using conventional textile techniques such as weaving braiding knitting and stitching it is possible to produce a wide range two and three dimensional fiber preforms, however so far only a limited attention has been given to knitted fabrics in composite industry. This is mainly due to the opinion that knitted fabric reinforced composites posses low mechanical properties owing to their looped fiber architecture. But it is possible to obtain desired mechanical properties by selecting proper knitted fabric structure, In this paper mechanical characteristics of kevlar plain weft knitted fabrics reinforced plastics(KFRP) are evaluated for th development of intrusion beam of car side door. Tensile bending impact properties of KFRP are measured experimentally and crush demands of Americal Federal Motor Vehicle Safety Standard No.214(FMVSS 214) compared with the bending load and displacement of KFRP by quasi-static test method. The applicability and limitation of bending load and displacement of KFRP according to specimen size has been discussed.

• Journal of Korean Vacuum Science & Technology
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• 제7권1호
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• pp.1-7
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• 2003

The pressure distributions in the test stand built for developing KSTAR NBI ion sources were obtained using a network system composed of conductance elements modeling the ion source, the neutralizer, and other beam line components. The allowable regime was defined on the coordinates of the gas supply rate to the ion source and the neutralizer, considering the proper conditions of the three critical parameters, the ion source pressure for good arc discharge, the pressure integral in the neutralizer for sufficient neutralization, and the chamber pressure for minimum neutral beam loss. The neutral beam evolution along the path from the ion source extraction grid to the calorimeter through the neutralizer, the bending magnet and the vacuum chamber was estimated for typical pressure distributions.