• 한국구조물진단유지관리공학회 논문집
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• 제15권2호
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• pp.98-106
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• 2011

강박스거더의 바닥틀은 바닥강판, 종방향 리브 및 횡방향 리브로 구성된다. 강바닥판 교량은 용접 접합부의 개소가 많고 중차량 접지하중과 반복응력의 증가에 의해 피로손상의 발생 가능성이 매우 높다. 일반적으로 강바닥판의 피로균열은 중차량 트럭하중의 반복적인 재하하중으로 인한 국부응력에 의하여 발생한다. 또한 중차량 통행량의 증가 및 통행차량의 대형화는 피로균열 발생 가능성을 촉진한다. 따라서 교량에 영향을 미치는 실제 통행 차량하중의 하중재하 패턴을 고려한 하중 접지면적에 따른 교량의 거동을 정확히 평가하는 것은 매우 중요하다. 본 연구는 강바닥판 교량에서 통행 차량의 접지면적과 하중재하 효과를 고려하여 설계하중에 의한 접지면적과 실제 통행 차량의 접지면적을 유한요소해석을 통하여 비교 평가하였다. 유한요소해석은 강바닥판 교량의 4가지 하중 재하패턴에 대하여 수행하였다, 또한 해석은 다이아프램의 설치 유무에 따른 통행트럭의 접지면적 영향을 비교 평가하였다. 유한요소해석 결과, 실제 싱글타이어의 하중재하면적이 설계하중의 접지면적보다 보다 큰 국부응력을 보였고, 바닥강판은 전륜하중인 싱글타이어 재하에 의해 가장 큰 영향을 받는 것으로 나타났다. 또한 다이아프램의 설치 유무는 탄성영역에서 다이아프램 설치가 강바닥판 가로리브와 세로리브 교차부의 피로저항에 대한 구조성능 개선에는 효과가 없는 것으로 나타났다.

• Journal of Welding and Joining
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• 제26권4호
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• pp.44-49
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• 2008

Generally, wear plate is steel plate having improved surface contact strength and impact strength by surface hardening which is welded using materials with good corrosion resistance, wear resistance and thermal resistance property. CFP GMAW(Compound Filler Plate Gas Metal Arc Welding) is the cladding method using GMAW with the CFP, which is bound with waterglass, on the substrate. It has advantages of reducing compound powder loss, uniform penetration, and preventing hardness decrease. To develope mass production technique of CFP GMAW process for production of high quality wear plate, the method for controling shallow penetration and increasing productivity is required. In this study, twin torch method applied to CFP GMAW process for increasing productivity. And the method was developed by controling penetration control, CFP dry time, gas formation flux and water glass concentration. As a result, applying twin torch method to CFP GMAW process was possible and high quality wide bead could be made without overlap joint.

• Steel and Composite Structures
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• 제12권3호
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• pp.249-260
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• 2012

In this study, stress and deflection behaviours of T-type welding joint applied to HE200M steel beam and column were investigated in finite element method (FEM) under different distributed loads. In the 3D-FEM modelling, glue option was used to contact between steel materials and weld nuggets. Geometrical model was designed as 3-dimensional solid in ANSYS software program. After that, homogeneous, linear and isotropic properties were used to design to materials of model. Solid-92 having 3-dimensional, 4 faced and 10-noded was selected as element type. In consequence of mesh operation, elements of 13285 and nodes of 28086 were occurred. Load distribution was applied to top surface of steel beam to determine behaviours of stress and deflection. As a result of FEM analysis applied with the loads of 55,000 N, 110,000 N and 220,000 N, maximum values were obtained as 116 N/$mm^2$, 232 N/$mm^2$ and 465 N/$mm^2$ for stress and obtainedas 1,083 mm, 2,166 mm and 4.332 mm for deflection, respectively. When modelling results and classical calculation values were compared, it was obtained difference of 10 % for stress values and 2.5% for deflection values.

• Steel and Composite Structures
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• 제31권4호
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• pp.361-372
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• 2019

In recent years, considerable attention has been paid to the research and development of high-strength steel plates, with particular emphasis on the enhancement of the seismic resistance of buildings and bridges. Many efforts have also been undertaken to improve the properties of high-strength bolts and weld materials. However, there are still different opinions on steel joints that combine high-strength bolts and fillet welds. Therefore, it is necessary to verify the design specifications and guidelines, especially for newly developed 1,400-MPa high-strength bolts, 570-MPa steel plates, and weld materials. This paper presents the results of literature reviews and experimental investigations. Test parameters include bolt strengths, weld orientations, and their combinations. The results show that advances in steel materials have increased the plastic deformation capacities of steel welds. That allows combination joints to gain their maximum strength before the welds have fracture failures. When in combination with longitudinal welds, high-strength bolts slip, come in contact with cover plates, and develop greater bearing strength before the joints reach their maximum strength. However, in the case of combinations with transverse welds, changes in crack angles cause the welds to provide additional strength. The combination joints can therefore develop strength greater than estimated by adding the strength of bolted joints in proportion to those of welded joints. Consequently, using the slip resistance as the available strength of high-strength bolts is recommended. That ensures a margin of safety in the strength design of combination joints.

• 한국안전학회지
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• 제15권1호
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• pp.140-145
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• 2000

강교량 부재인 십자연결형 접착부를 하중비전달형과 하중전달형으로 각각 제작하여 피로 강도 저감 정도와 응력비 변화에 따른 피로거동을 평가하였다. 또한, 필렛용접 비드의 기하학적 형상에 따른 응력집중을 확인하기 위하여 전산해석을 수행하였다. 피로실험 결과 시험편의 응력비가 피로 강도에 미치는 영향은 거의 없는 것으로 나타났으며, 하중전달형 시험편과 대부분의 밀착 시험편은 용접지단부에서 균열이 발생하여 모재가 파단됨을 알 수 있었다. 모재가 파단된 십자형 시험편의 피로강도는 ${\Delta}\sigma_c$=63.5 MPa로 하중 비전달형 시험편의 피로강도 ${\Delta}\sigma_c$=83.8 MPa보다 약 24% 작게 나타났다. 본 연구대상 시험편은 도로교 시방서상에 모재단면에 대한 응력으로 피로범주 C등급으로 규정하고 있으므로, 실험결과를 모재단면에 대한 응력으로 피로강도를 환산하면 78.27 MPa로 허용 피로강도보다 작은 것으로 나타났다.

• Earthquakes and Structures
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• 제14권2호
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• pp.167-178
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• 2018

A roller compacted concrete (RCC) dam should be analyzed under seismic ground motions for different conditions such as empty reservoir and full reservoir conditions. This study presents three-dimensional earthquake response and performance of a RCC dam considering materially non-linearity. For this purpose, Cine RCC dam constructed in Aydın, Turkey, is selected in applications. The three-dimensional finite element model of Cine RCC dam is obtained using ANSYS software. The Drucker-Prager material model is considered in the materially nonlinear time history analyses for concrete and foundation rock. Furthermore, hydrodynamic effect was investigated in linear and non-linear dynamic analyses. Researchers observe that how the tensile and compressive stresses change by hydrodynamic pressure effect. The hydrodynamic pressure of the reservoir water is modeled with the fluid finite elements based on the Lagrangian approach. In this study, dam body and foundation are modeled with welded contact. The displacements and principle stress components obtained from the linear and non-linear analyses with and without reservoir water are compared each other. Principle stresses during earthquake were obtained at the most critical point in the upstream face of dam body. Besides, the change of displacements and stresses by crest length were investigated. Moreover demand-capacity ratio criteria were also studied under linear dynamic and nonlinear analysis. Earthquake performance analyses were carried out for different cases and evaluated. According to linear and nonlinear analysis, hydrodynamic water effect is obvious in full reservoir situation. On the other hand, higher tensile stresses were observed in linear analyses and then non-linear analyses were performed and compared with each other.

• 한국산학기술학회논문지
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• 제20권7호
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• pp.166-172
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• 2019

금속 일체형 판재 도어 임팩트 빔 개발을 위해 단면 형상의 최적설계를 진행하였다. 기존의 도어 임팩트는 충격을 흡수하는 강관과 양쪽에 브라켓을 용접하여 자동차에 설치하는 구조로 이루어졌다. 하지만, 브라켓을 설치하기 위한 용접작업은 생산성을 떨어뜨리고 생산단가를 증가시키는 과정이다. 이러한 단점을 극복하기 위해 일체형 판재 도어 임팩트 빔의 개발은 반드시 필요한 공정이다. 본 논문에서는 일체형 판재 도어 임팩트의 단면 형상을 수치해석의 방법으로 제안하는 연구를 진행하였다. 외부 충격에 대한 반력 하중 및 생산성을 고려하여 엔지니어의 직관적인 설계 형상 6가지에 대하여 수치해석을 진행하였다. 객관적인 비교를 위해 3점 굽힘 하중 실험을 모사하는 유한요소해석을 진행하였다. 형상과 치수가 상이한 6가지의 단면 형상 중 최적의 형상을 선정하고, 상세 설계를 위해 단면형상의 높이와 폭의 치수를 변화시키며 해석을 진행하였다. 이를 통해, 일체형 판재 도어 임팩트의 최적의 단면 형상을 제안하였다.

• 대한금속재료학회지
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• 제48권3호
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• pp.203-209
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• 2010

An application of the instrumented indentation technique has been expanded from the measurements of hardness and elastic modulus to the analysis of residual stress. A slope of the indentation loading curve increases (or decreases) according to compressive (or tensile) residual stress. A theoretical equation has been established for quantifying residual stress from the slope change. However, a precise observation of the remnant indents is indispensible because the theoretical approach needs actual contact information. In addition, the conventional hardness test is still used for predicting the residual stress distribution of welded joints. Thus, we observed the three-dimensional morphologies of the remnant indents formed on artificial stress states and analyzed stress effects on morphological recovery of the indents. First, a depth recovery ratio, which has been regarded as a sensitive stress indicator, did not show a clear dependency with the residual stress. Thus an analysis on volumetric recovery was tried in this study and yielded a inverse proportional behavior with the residual stress. In addition, an elastic to plastic volume recovery ratio showed more significant correlation with the residual stress.

• 소성∙가공
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• 제32권1호
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• pp.12-19
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• 2023

The armature core is a part responsible for the skeleton of the steering wheel. Currently, in the case of commercial trucks, the main parts of the parts are manufactured separately and then the product is produced through welding. In the case of this production method, quality and cost problems of the welded parts occur, and an integrated armature core made of magnesium alloy is used in passenger vehicles. However, in the case of commercial trucks, there is no application case and research is insufficient. Therefore, this study aims to develop an all-in-one armature core that simultaneously applies a magnesium alloy material and a die casting method to reduce the weight and improve the quality of the existing steel armature core. The product was modeled based on the shape of a commercial product, and finite element analysis (FEA) was performed through Ls-dyna, a general-purpose analysis program. Through digital image correlation (DIC) and uniaxial tensile test, the accurate physical properties of the material were obtained and applied to the analysis. A total of four types of compression were applied by changing the angle and ground contact area of the product according to the actual reliability test conditions. analysis was carried out. As a result of FEA, it was confirmed that damage occurred in the spoke area, and spoke thickness (t_spoke), base thickness (t_base), and rim and spoke connection (R) were designated as design variables, and the total weight and maximum equivalent stress occurring in the armature core We specify an objective function that simultaneously minimizes . A prediction function was derived using the sequential response surface method to identify design variables that minimized the objective function, and it was confirmed that it was improved by 22%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.58.1-58.1
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• 2010

In solar cell module manufacturing, single solar cells has to be joined electrically to strings. Copper stripes coated with tin-silver-copper alloy are joined on screen printed silver of solar cells which is called busbar. The bus bar collects the electrons generated in solar cell and it is connected to the next cell in the conventional module manufacturing by a metal stringer using conventional hot air or infrared lamp soldering systems. For thin solar cells, both soldering methods have disadvantages, which heats up the whole cell to high temperatures. Because of the different thermal expansion coefficient, mechanical stresses are induced in the solar cell. Recently, the trend of solar cell is toward thinner thickness below 180um and thus the risk of breakage of solar cells is increasing. This has led to the demand for new joining processes with high productivity and reduced error rates. In our project, we have developed a new method to solder solar cells with a laser heating source. The soldering process using diode laser with wavelength of 980nm was examined. The diode laser used has a maximum power of 60W and a scanner system is used to solder dimension of 6" solar cell and the beam travel speed is optimized. For clamping copper stripe to solar cell, zirconia(ZrO)coated iron pin-spring system is used to clamp both joining parts during a scanner system is traveled. The hot plate temperature that solar cell is positioned during lasersoldering process is optimized. Also, conventional solder joints after $180^{\circ}C$ peel tests are compared to the laser soldering methods. Microstructures in welded zone shows that the diffusion zone between solar cell and metal stripes is better formed than inIR soldering method. It is analyzed that the laser solder joints show no damages to the silicon wafer and no cracks beneath the contact. Peel strength between 4N and 5N are measured, with much shorter joining time than IR solder joints and it is shown that the use of laser soldering reduced the degree of bending of solar cell much less than IR soldering.