• 한국자동차공학회논문집
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• 제10권1호
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• pp.255-264
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• 2002

In this paper, the power transmitting mechanism for negative torque of the metal V-belt (MVB) CVT were investigated by theoretically analyzing variation of band tension, block compression forces for each of the primary and secondary pulleys. An experimental study was performed to investigate the speed ratio - thrust characteristics for negative torque. The experimental results are in good acoordance with the theoretical results. CVT line pressure control logic was suggested for negative torque based the speed radio - negative torque - thrust characteristics and the thrust ratio curves. The results of this study can be used as basic design materials for developing the CVT control system for negative torque.

• 소성∙가공
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• 제21권3호
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• pp.186-194
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• 2012

Hot stamping is a forming method that offers various advantages such as superior mechanical properties, good formability, and very small springback. However, relatively large-sized parts, such as front pillars, exhibit poor formability when hot stamped due to the limited material flow and thickness reduction imparted by the process. This reduction in thickness can also lead to cracks. One of the reasons is the relatively high friction between the sheet and the die. In this study, in order to obtain the optimal conditions for hot stamping of front pillars, various process parameters were studied and analyzed using the sheet forming software, J-STAMP. The effects of various parameters such as the die structure, blank shape, blank holding force, punch speed, clearance(upper and lower dies) and distance block were analyzed and compared.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.787-792
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• 2002

The voided slab have many advantages, light weight, high load-distribution capacity, low cost and beautiful appearance, etc. But they have also many cracks due to difficulties in designs and construction, analysis, shrinkage, installation and rising force of voided tube. This paper presents the retrofit effects with steel plate(SP)/carbon fiber sheet(CFS) of RC voided slab. As a results of this study, it proved that the strip pattern has to be profitable than full-face pattern in performance such as crack, ultimate loads, stiffness. Retrofit length has many influence on retrofit effects, as the length increases, performance and stability of end blocks higher. Also, it proved that the retrofit on full-section has to be profitable than voided-section in performance, and the overlay length of CFS is desirable to extent approximately and welding(V-cut) has to be efficient than anchors in SP connection. But the kinds of end block and anchor has not influence on retrofit effects.

• 한국정밀공학회지
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• 제20권11호
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• pp.55-63
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• 2003

In this study, an experimental research of grinding characteristics using super-abrasives for surface carburized and heat treated SCM415 materials, which were usually used to make a linear motion guide block and were comparatively hard-to-machine materials, was carried out. In order to conduct a high efficiency and a accuracy grinding of such materials, grinding processes using CBN (Cubic boron nitride) and 38P grinding wheels have been attempted on a surface grinding machine. The grindability according to each grinding conditions was evaluated by means of a grinding force, a surface roughness and a residual stress. The experimental methods and results were presented in this paper. And also, from a proposed truing method the CBN wheels that combined a copper and a break truer gave a full scope to the wheel's performance.

• Geomechanics and Engineering
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• 제13권2호
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• pp.217-235
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• 2017

The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.526-529
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• 2006

In this paper, flexure behavior of steel fiber reinforcement ultra high performance cementations composites (SFR-UHPCC) has been analyzed by equivalent stress block. Pulling-out tensile force of steel fiber with concrete matrix was induced. An appropriate flexure evaluation formula, i.e. semi-analytical formula, was established based on rectangular cross section beam for comparing with shear capacity and ultimate load of SFR-UHPCC beam. Finally, the semi-analytical formula has been simplified for the convenience of design work. Experimental results and theoretical shear strength are shown to compare with the formula proposed by this paper. The theory formula has a good prediction of failure type of SFR-UHPCC.

• 한국생산제조학회지
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• 제24권2호
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• pp.238-243
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• 2015

Recently, the use of assembled-type drills as environmentally friendly products has expanded because the shanks of drills can be reused by replacing the tip when the tools are worn or cut. In addition to their precision and endurable stiffness with respect to the cutting force, assembled-type drills need no stricture because of thermal deformation, which makes replacement easily. In this study, we developed novel assembled-type drills and compared their characteristics, such as the precision, stiffness, and thermal deformation, with those of conventional drills. The new drills exhibited a precision over IT 8 class and no changes in dimensions due to thermal deformation, such that we can change the assembly easily with durability.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.141-148
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• 2006

Concrete in a CFT(Concrete Filled Tube) column has enhanced strength and ductility because it is triaxially confined by a steel tube. But CFT columns are designed based on linear analyses by stress block method without the confining effect or the nonlinearity of the concrete. These make the significantly difference between the analysis results and the experimental results. Thus in this study, a nonlinear CFT column model was developed considering the confining effect on the concrete in a CFT column. This developed model was verified by experimental results from other researchers and compared with the results of various specifications. With the developed model, parametric studies were performed and the developed column model showed reasonable and accurate results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.767-770
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• 2000

A novel process is newly developed for building RP(Rapid Prototyping) parts using a sheet lamination technique. The build process of existing sheet lamination type RP machines consists of the following steps : feeding, lamination and cutting. In this process, the laminated part of an object is often scratched by a cutter or damaged by a laser beam due to the cutting operation preceded by lamination, In addition, decubing of the unused portion from the laminated block is difficult. In the new process, cutting operation is performed before lamination. The cutting operation takes place while a paper sheet is firmly attached on the plate using electrostatic force. Then liquid glue is applied to the calculated region of the given contour for lamination. The process aims to manufacture a $2k RP machine, what we call the Freeform Mater I, that can use A4 or latter-size used papers. A prototype machine that demonstrates the design concept is built and further research issues are discussed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.147-149
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• 2003

Many factors, such as welding current, welding time, force, electrode shape, the output stability of a welding machine, are closely related with micro spot series welding. Of those factors, the output stability evaluation of the welding machine would be checked first. in this study, we applied 6$\sigma$ to evaluation for the output stability of the welding machine. We estimated output stability and control stability of the welding machine by using Cp(process capability), Ppk and 4-block diagram. Therefore the problem as solved in micro spot series welding process and the problem of output control in welding machine by 6$\sigma$ tool.