• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.894-901
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• 2006

In general, the tension fores of hanger cable in suspension bridges play an important role in evaluating the bridge state. The vibration method, as a conventional one, has been widely applied to estimate the tension fores by using the measured frequencies on hanger cables. However, the vibration method is not applicable to short hanger cables because the frequency of short cables is severely sensitive to the flexural rigidity. Thus, in this study, the tension forces of short hanger cables, of which the length is shorter than 10meters, were estimated through back analysis of the cable frequencies measured from Gwang-An suspension bridge in Korea. Direct approach to rock analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method is able to search the optimal tension forces without regard to the initial ones and has a rapid convergence rate. To verify the feasibility of back analysis, the results from back analysis and vibration method are compared with the design tension forces. From the comparison, it can be inferred that back analysis results are more reasonable agreement with the design tension forces of short hanger cable. Therefore, it is concluded that back analysis applied in this study is an appropriate tool for estimating tension forces of short hanger cables.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.346-353
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• 2005

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.435-440
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• 2004

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• 소성∙가공
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• 제21권5호
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• pp.291-297
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• 2012

In this paper, the effect of back tension in multi-pass drawing or wiredrawing on the central bursting defect is investigated using finite element predictions. A rigid-plastic finite element method was used together with the McClintock damage model. Central bursting defects under different back tension stress values ranging from 0% to 20% of the yield strength of the material were predicted and they were compared to understand the effect of the back tension stress values on the central bursting defect. It is found that the level of back tension has a strong influence on the cumulative damage. Thus, higher back tension raises the possibility of the central bursting defect occurring, even though it decreases the interfacial pressure between the die and the work piece.

• 소성∙가공
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• 제20권6호
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• pp.461-467
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• 2011

An artificial body force method is presented to accurately simulate drawing processes in which back pressing is exerted. A rigid-plastic finite element method is applied together with a numerical scheme to eliminate the numerically incurred plastic deformation in rigid or elastic region, which significantly influences simulation results because it eventually changes reduction of area in drawing. Back tension or compression is applied by body force at the rear part of material to obtain numerically stable solution. Two typical examples are shown, a drawing process with back tension applied and a tube drawing with a fixed plug and back pressing applied.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.349-355
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• 1999

The texture inhomogeniety during rolling is one of the greatest problems. Especially, shear texture develops more easily during ferritic rolling of steel sheets at high temperatures due to friction between rolls and the material. In this study, the influence of front and back tensions on the texture development during ferritic rolling has been studied. The rolling textures were simulated using the full constrains Taylor-Bishiop-Hill model with the strain history obtained from finite element analysis. The calculated textures showed that the back tension rolling could reduce the shear component more effectively than front tension or rolling without tension. However, the experimental results showed that the lension effect was very small compared to our prediction. It might be attributed to initial texture and difference in frictions between simulation and experiments.

• 소성∙가공
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• 제22권6호
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• pp.303-309
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• 2013

Spring-back of MS1470 steel sheets was numerically predicted using a non-linear kinematic hardening material behavior based on the Yoshida-Uemori model. From uniaxial tension and uniaxial tension-compression-tension data as well as the uniaxial tension-unloading-tension data, the parameters of the Yoshida-Uemori model were obtained. For the numerical simulations, the Yoshida-Uemori model was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. The model performance was validated against the measured spring-back from the benchmark problems of NUMISHEET 2008 and NUMISHEET 2011, the 2-D draw bending test and the S-rail forming test, respectively.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.757-762
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• 2002

Many reports have been shown that the buoyancy, electromagnetic force, surface tension, and gas shear stress are the driving forces of weld pool circulation in arc welding. Among them, the surface tension of molten metal plays an important role in the flow in weld pool, which are clarified by the specially designed experiments with small particles as well as the numerical simulations. The surface tension is also related to the penetration in arc welding. Therefore, a quantitative evaluation of surface tension is demanded for the development of materials and arc process control. However, there are few available data published on the surface tension of molten metals, since it depends on the temperature and the composition of materials. In this study, a new method was proposed for the evaluation of surface tension and its temperature dependence, in which it is evaluated by the equilibrium condition of acting forces under a given surface geometry, especially back surface. When this method was applied to the water pool and to the back surface of molten pool in the stationary gas tungsten arc welding of thin plate, following results were obtained. In the evaluation of surface tension of water, it was shown that the back surface geometry was very sensitive to the evaluation of surface tension and the evaluated value coincided with the surface tension of water. In the measurement of molten pool in the stationary gas tungsten arc welding, it was also shown that the comparison between the surface tension and temperature distribution across the back surface gave the temperature dependent surface tension. Applying this method to the mild steel and stainless steel plates, the surface tension with negative gradient for temperature is obtained. The evaluated values are well matched with ones in the published papers.

• 한국운동역학회지
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• 제17권3호
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• pp.197-207
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• 2007

It has been reported that Back-Tension played a significant role in archery (Lee & Bondit, 2005; Kim, 2007) but there are a few researches related Back-Tension in Korea recently. Therefore, the purpose of this study was to investigate archery back tension technique for the second ranked archer in the World and to find ways to improve performance. A subject(height: 185cm, mass: 82kg, years: 21yrs, careers: 12yrs) who is a number of national team and the second ranked archer in the World authorized by FITA (Federation Internationale de Trial Arc) was perticipated in this experiment. When shooting 60 shots($12{\times}5$), shooting motions were recorded with 7 infrared cameras and 2 ultrahigh-speed cameras. A QTM and an Auto Track were used to acquire raw data. The sampling rates of both cameras were 200 Hz. and 1000 Hz. respectively and data were filtered using a fourth order Butterworth low pass filtering with a cutoff-frequency of 30Hz. The parameters were calculated with Matlab6.5 and analyzed with SPSS11.0. After Pearson's correlations between 8 parameters were analyzed, 5 parameters from 13parameters that affected records were analyzed with multiple regression analysis (Enter order: x1, x2, x3, x4, x5). The results were as follows: 1. Comparing between parameters according to scores, the patterns of horizontal and vertical angular velocity(av.) of scapular relative angle was different between 8 score and 9 or 10 scores. 2. The correlations of parameters that affected records were a horizontal av.(x1, p=.032<.05) and a vertical av.(x3, p=.033<.05) of scapular from release to delivery in KB back-tension (anchoring-delivery). 3. The decision coefficients(R2) of above two parameters and three parameters selected by experts that may affect record, that is, an absolute trunk angle(x4) from in KKC back-tension (anchoring-release) and a horizontal relative scapular angle(x2) and an absolute trunk angle(x5) from release to delivery in KB back-tension were 7.7%(x1), 0.1%(x2), 8.5%(x3), 0.7%(x4) and 0.9%(x5) in sequence. 4. The multiple regression equation was a y= -1.16E-2 x1 + 0.109 x2 + 3.437E-2 x3 + 6.139E-2 x4 + 0.117 x5 + 3.420 In conclusion, a total contribution was low, that is, R2(17.9%) suggested that on the one hand, Lim's motion may not depend on a certain factor because his postural factors affected shooting motion are some stable on the other hand, unknown factors may exist(e.g. psychological, physiological factors etc.). Further study of EMG patterns of muscles and anatomic consideration related to shoulder girdle and scapular bones may help to identify mechanism of Back-Tension.

• 한국지진공학회논문집
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• 제11권3호
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• pp.1-10
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• 2007

현수교 행어케이블의 장력은 현수교의 상태점검에 있어 중요한 요소이다. 현재 케이블의 장력 추정에는 여러 이론식에 의한 간접적인 방법들이 사용되고 있으며, 케이블의 가속도신호로부터 고유진동수를 측정한 후 고유진동수와 장력과의 관계로부터 케이블의 장력을 추정하는 진동법이 대표적이다. 하지만 운동방정식을 기반으로 하는 진동법은 휨강성의 영향이 큰 짧은 케이블의 장력추정에는 적합하지 않다. 본 논문에서는 10m 미만의 짧은 케이블에 대해서도 전기 가능한 새로운 장력 추정 방법으로 단변분탐색법과, 최적화 기법을 이용한 역해석 기법을 제시하였다. 이론에 대한 검증을 위해 국내에 사용 중인 광안대교 행어케이블을 대상으로, 역해석과 진동법에 의한 추정장력들과 설계장력을 상호 비교하였고, 이를 통해 역해석기법이 길이에 상관없이 장력추정에 유용하다는 결론을 얻었다.