• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.102-105
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• 2001

The spring back taking place after the coiling process of steam generator tube leads to the dimensional inaccuracy. In order to reduce the spring back, tension force was applied to the one end of the tube during forming. In this work, parametric study using FEM was performed to find the appropriate magnitude of tension force. The force that induces minimum suing back was found by simultaneously taking account of suing back amount, cross-sectional ovality, and thickness of the tube wall after deformation. In addition, stress relieving by heat treatment was also simulated as an alternative to the former method. The latter was found to be more effective under the given constraints.

• 소성∙가공
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• 제11권3호
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• pp.238-245
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• 2002

The spring back taking place after the coiling process of steam generator tube leads to the dimensional inaccuracy. In order to reduce the spring back, tension force was applied to the one end of the tube during forming. In this work, parametric study using FEM was performed to find the appropriate magnitude of tension force. The force that induces minimum spring back was found by simultaneously taking account if spring back amount, cross-sectional ovality, and thickness of the tube wall after deformation. In addition, stress relieving by heat treatment was also simulated as an alternative to the former method. The latter was found to be more effective under the given constraints.

• 기술발표회
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• 통권2006호
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• pp.66-72
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• 2006

The ground anchoring has been utilized over 40 years. It is growing the application of the removal ground anchor with tension force for holding earth retaining constructions in the city. It transmits tension stress of prestressed steel wire through grouting to fixed the ground that is of great advantage adjacent ground stability. Nowadays, we can find the compression dispersion anchor on many site. But, it has some problems in behavior of anchors because of impossible to tense p.c strand uniformly under the existing equipment due to different length of p c strand. Hence, motive of this research was to study the application of the newly developed tension system, that analyze and compare with the current anchoring method build on the data of in-site test and laboratory test. As a result, in case of auto back tension system, it became clear that tension pressure was equally distributed among the steal wires but the existing tension system showed sign of instability by indicating stress deflection of about 30% compare with design load. This can cause an ultimate failure of the concentrated p.c strand and a shear failure of ground.

• 소성∙가공
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• 제25권3호
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• pp.189-194
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• 2016

In the current study, spring-back of DP980 steel sheet was numerically evaluated for U-bending using a yield function with a hardening model. For spring-back prediction, two types of yield functions - Hill'48 and Yld2000-2d - were considered. Additionally, isotropic hardening and the Yoshida-Uemori model were used to investigate the spring-back behavior. The parameters for each model were obtained from uniaxial tension, uniaxial tension-compression, uniaxial tension-unloading and hydraulic bulging tests. The numerical simulations were performed using the commercial software, PAM-STAMP 2G. The results were compared with experimental data from a U-bending process.

• 한국구조물진단유지관리공학회 논문집
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• 제27권5호
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• pp.120-129
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• 2023

행어케이블의 장력은 현수교의 건전성과 안전성을 확인할 수 있는 주요 응답 중 하나이다. 일반적으로 공용 중인 현수교에서 행어케이블의 장력을 추정하기 위해 진동법이 주로 사용되고 있다. 진동법은 행어케이블에서 고유진동수들을 측정하고 행어케이블의 형상 조건을 이용하여 간접적으로 장력을 추정하는 방법이다. 이 연구에서는 영상계측시스템을 이용하여 팔영대교의 행어케이블에 대하여 장력을 추정하였다. 영상계측시스템은 측정의 편의성과 경제성을 고려하여 디지털 캠코더와 삼각대를 사용하였다. 영상계측시스템을 이용하여 측정된 행어케이블의 응답은 변위 기반이므로 진동법을 적용하기 위한 고차모드의 고유진동수는 측정하기 어려울 수 있다. 이 연구에서는 저차모드의 고유 진동수를 이용하여 장력을 추정할 수 있는 역해석 기법을 적용하였다. 역해석 기법은 현장에서 측정된 행어케이블의 고유진동수들과 유한요소해석을 이용하여 산정된 고유진동수들의 오차를 목적함수로 정의하여 최적화를 수행하였다. 최적화 방법은 목적함수의 편미분이 필요 없는 직접탐색법을 적용하였다. 역해석 기법을 이용하여 산정된 장력과 진동법을 이용하여 추정된 장력을 비교 분석하여 역해석 기법에 대한 신뢰도와 정확도를 확인하였다. 그 결과 역해석 기법을 적용하면 저차모드의 고유진동수를 이용하여도 신뢰성 있는 장력의 추정이 가능하였다.

• 한국기계가공학회지
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• 제15권1호
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• pp.42-49
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• 2016

This study was analyed V-bending in order to analyze the spring-back phenomenon in the roll forming process. The material of forming sheet used in the roll forming process is high tension steel and the product name of sheet material is POSTEN 60. The most important variable is the number of roll passes (3-Pass, 4-Pass, 5-Pass, 6-Pass and 10-Pass) and other roll forming process variables were fixed. To determine the characteristics of the tension and compression, the forming sheet was analyzed by dividing the layer (Upper and Bottom) in the thickness direction from the center line. The results of FEM simulation analysis was derived to von-mises stress equivalent strain, and the spring-back value was calculated according to the final forming shape. The more number of the roll pass, von-mises stress and equivalent strain value of forming sheet were lowed. Also, spring-back values tended to decrease. The results of this study can be utilized for prediction and trend of spring-back value in the roll forming process applied to high tension steel sheet. So, development time and cost of the roll forming process is expected to be reduced.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.994-1000
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• 2004

It is growing the application of the removal ground anchor with tension force for earth retaining constructions in the downtown. Nowadays, we can find the compression dispersion anchor on many site. But, it is occur some probelems in behabior of anchors because of impossible to tense p.c strand uniformly with existing equipment due to different length of p.c strand. So we tried to tense each p.c strand uniformly with auto back equipment in-situ test. This study compared and analyzed in-situ test results of an existing equipment with those of auto back equipment by appling elastic theory. As a result of the test, It has been proved that differences of tension force in the existing equipment increases with increasing the number of p.c strands. This can cause the ultimate failure of the concentrated p.c strand and the shear failure of ground. So it has been proved that auto back equipment is necessary.

• 소성∙가공
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• 제11권2호
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• pp.147-154
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• 2002

The tension levelling Process is Performed to elongate the strip plastically In combination of tensile and bending strain so that all longitudinal fibers In the strip have an approximately equal amount ofn length and undesirable strip shapes are corrected to the flat shape. Thus paper is concerned with a simulation of the tension levelling process based on the analysis of tile unit model for the tension leveller. Analysis technique such as the sequential analysis of the unit model is suggested and verified with the assembly analysis of the unit model for the effective arts economic analysis of the full set of the tension leveller. Analysis of the full tension levelling Process using sequential unit models Is carried out for steel strips with the shape defect and provides the effect of the intermesh and optimum amount of the intermesh in tension levelling process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.201-204
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• 2001

The tension levelling process is performed to elongate the strip plastically in combination of tensile and bending strain so that all longitudinal fibers in the strip have an approximately equal amount of length and undesirable strip shapes are corrected to the flat shape. This paper is concerned with a simulation of the tension levelling process based on the analysis of the unit model for the tension leveller. Analysis technique such as the sequential analysis of the nit model is suggested and verified with the assembly analysis of the unit model for the effective and economic analysis of the full set of the tension leveller. Analysis of the full tension levelling process using sequential unit models is carried out and provides the effect of the intermesh and optimum amount of the intermesh in tension levelling process.

• 한국정밀공학회지
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• 제33권6호
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• pp.477-483
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• 2016

The spring-back and bow phenomenon in the roll forming process are important factors regarding the accuracy of evaluation of production goods. The purpose of this study was to determine the influence of spring-back and bow phenomenon according to the main variables (forming velocity and roll gap). The material of the forming sheet was high tension steel (SPFH 590), which has been used commonly in recent years. In order to accurately measure the spring-back and bow phenomenon, the forming sheet was formed into a V-shape. The study was applied to OFAT (One Factor at a Time) experimentation, with respect to the experimental variables (the forming speed and the roll gap). In the experimental results, the forming speed had a small influence on the spring-back and bow phenomenon. However, the roll gap had a greater influence on the springback and the bow phenomenon, as opposed to the forming speed.