• Steel and Composite Structures
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• 제34권3호
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• pp.441-452
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• 2020

Within the French CIFRE research project COMINO, an innovative type of composite beam was developed for buildings that need fire resistance with no additional supports in construction stage. The developed solution is composed of a steel U-shaped beam acting as a formwork in construction stage for a reinforced concrete part that provides the fire resistance. In the exploitation stage, the steel and the reinforced concrete are acting together as a composite beam. This paper presents the investigation made on the load bearing capacity of this new developed steel-concrete composite section. A full-scale test has been carried out at the Laboratory of Structural Engineering of the University of Luxembourg. The paper presents the configuration of the specimen, the fabrication process and the obtained test results. The beam behaved compositely and exhibited high ductility and bending resistance. The shear connection in the tension zone was effective. The beam failed by a separation between the slab and the beam at high deformations, excessive shear forces conducted to a failure of the stirrups in this zone. The test results are then compared with good agreement to analytical methods of design based on EN 1994 and design guidelines are given.

• 한국정밀공학회지
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• 제27권1호
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• pp.113-118
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• 2010

A straight pipe is used after complicated bending work in a mechanical system. In this work process, the plastic deformation of the pipe produces residual stress in the pipe. This residual stress significantly affects the behavior of pipe fracture. For this reason, residual stress must be evaluated. Measuring the residual stress of a U-shaped pipe is difficult with existing destructive and nondestructive measurement methods. In this paper, the residual stress of a U-shaped aluminum pipe (99.7% pure aluminum) was evaluated from the Raman shift by Raman spectroscopy and FEM(Finite Element Method, FEM) analysis. The results of the stiffness test by FEM analysis are compared with those by experiments. The analyzed results of the Raman spectra showed a similar tendency with the results of the FEM analysis with respect to the residual stress distributions in U-shaped pipes. Also, the results of the bending tests showed resemblance to each other.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1507-1519
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• 1997

This paper aims to clarify the effects of grinding conditions on bending strength in surface grinding of various ferrites with the resin bond diamond wheel. The main conclusions obtained were as follows. At a constant material removal rate, the strength improves with increased wheel depth of cut and decreased workpiece speed. It is desirable to grind at higher peripheral wheel speed and under the critical workpiece speed presented in this paper. Grinding the ferrite of higher brittleness, the wheel depth of cut limited to hold 50% of their inherent strength becomes lower. The effect of various grinding conditions on bending strength becomes more larger in the order of Sr, Mn-Zn and Cu-Ni-Zn. When using the diamond grain of the lower toughness, the bending strength becomes higher, and the wheel wear occurs faster. Considering both bending strength and wheel wear rate, the best concentration of wheel is 100. The ground surfaces exhibit that the fracture process during grinding becomes more brittle in the order of Sr, Mn-Zn and Cu-Ni-Zn.

• E2M - 전기 전자와 첨단 소재
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• 제19권9호
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• pp.28-32
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• 2006

A 7.0-inch transmissive type plastic TFT-LCD was developed at the resolution of 640 $\times$ 3 $\times$ 480 lines (114ppi). All of the processed of TFT, color filter and LC were carried out below $130^{\circ}C$ on PES plastic films. The process conditions of TFT, color filter and LC were optimized for large area TFT-LCD on plastic substrate. The backplane and the color filter was strongly adhered while the panel was bending by using holding spacers.

• 한국환경과학회지
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• 제13권3호
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• pp.245-250
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• 2004

The SBR(Sequencing Batch Reactor) process is ideally suited to treat high loading wastewater due to its high dilution rate. SBR operates by a cycle of periods consisting of filling, reacting, settling, decanting and idling. The react phases such as aeration or non-aeration, organic oxidation, nitrification, denitrification and other bio-logical reactions can be achieved in a reactor. Although the whole reactions can be achieved in a SBR with time distributing, it is hard to manage the SBR as a normal condition without recognizing a present state. The present state can be observed with nutrient sensors such as ${NH_{4}}^{+}-N$, ${NO_{2}}^{-}-N$, ${NO_{3}}^{-}-N} and ${PO_{4}}^{ 3-}-P.$ However, there is still a disadvantage to use the nutrient sensors because of their high expense and inconvenience to manage. Therefore, it is very useful to use common on-line sensors such as DO, ORP and pH, which are less expensive and more convient. Moreover, the present states and unexpected changes of SBR might be predicted by using of them. This study was conducted to get basic materials for making an inference of SBR process from ORP(oxidation reduction potential) of synthetic wastewater. The profiles of ORP, DO, and pH were under normal nitrification and denitrification were obtained to compare abnormal condition. And also, nitrite and nitrate accumulation were investigated during reaction of SBR. The bending point on ORP profile was not entirely in the low COD/NOx ratio condition. In this case, NOx was not entirely removed, and minimum ORP value was presented over -300mV. Under suitable COD/NOx ratio which complete denitrification was achieved, ORP bending point was observed and minimum ORP value was under -300m V. Under high COD/NOx ratio, ORP bending point was not detected at the first subcycle because of the fast denitrification and minimum ORP value was under -300mV at the time.

• 한국정밀공학회지
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• 제27권4호
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• pp.79-86
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• 2010

Mechanical structures with power sources experience repeated force produced by motors. In result, the life of the pipes reduces and ultimately, the pipes collapse. Such pipes are formed into several shapes and particularly, the U-shape pipe is damaged frequently. In most cases, the U-shape pipe is made with a straight pipe by complicated bending work. During this work process, plastic deformation of the pipe produces residual stress in the pipe. This residual stress significantly affects the fracture behavior of the pipe and induces the change of the stress ratio (min. stress/Max. stress = R). For this reason, residual stress has to be evaluated. In this paper, the residual stress of a U-shaped pipe was evaluated by FEM analysis. In addition, fatigue tests of the U-shaped pipe were performed by using a uniaxial fatigue testing machine. The results of the fatigue test were modified with the results of FEM (Finite Element Method) analysis for residual stress. The modified fatigue test results of the U-shaped pipe were compared with those of a straight pipe.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.228-230
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• 2000

The multiforming progressive die are multiple operations performed by means of a die having above two stages, jon the each of stages performs a different operation as the sheet metal passes through the die hole. In the field of design and making tool for press working, the progressive die for sheet metal (SPC, thickness :2mm) is a specific division. In order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, i.e. theory an practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die components, know-how and so on. In this study, we designed and constructed a multiforming progressive die as a U-bending working of multi-stage and performed try out. out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the par 1 of this study we treated die design mostly.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.150-152
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• 2004

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

• 소성∙가공
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• 제8권3호
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• pp.306-312
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• 1999

In the recent sheet metal forming simulations, it increases to adopt the dynamic explicit method for an effective computation and the elastoplastic formulation for stress recovery. It is inevitable in the dynamic explicit method that some noises occur, which sometimes partly spoil results of simulations. This phenomenon becomes severer when complicate contact conditions are included in simulations. In commercial dynamic codes, the concept of contact damping is introduced. However, the formulation process of it is not revealed well. In this paper, a contact damping method is formulated in order for effectively suppressing noises occurring due to complicated contact conditions. This is checked by analyzing a simple sheet metal stamping process (U-draw bending). From the computational results, it is shown that the contact damping can effectively control the noises due to contacts, especially when considering the sheet thickness, and help to develop more reliable internal stress states, which result in more realistic shapes after springbank.

• 소성∙가공
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• 제15권4호
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• pp.295-303
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• 2006

Optimization is carried out to determine process parameters which reduce the amount of springback and improve shape accuracy of a deep drawn product in sheet metal forming process. The study uses the amount of stress deviation along the thickness direction in the deep drawn product as an indicator of springback instead of springback simulation. The scheme incorporates with an explicit elasto-plastic finite element method for calculation of the final shape and the stress deviation The optimization method adopts the response surface method in order to seek for the optimum condition of process parameters such as the blank holding force and the draw-bead force. The present scheme is applied to design of the variable blank holding force in an U-draw bending process and the application is further extend ε d to the design of draw-bead force in a front side member formed with advanced high strength steel (AHSS) sheets of DP60. Results show that design of process parameter is well performed to decrease the stress deviation through the thickness and to reduce the amount of springback. The present analysis provides a guideline in a design stage for controlling the springback based on the finite element simulation of the complicated parts.