• Title/Summary/Keyword: Spring-go

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Quantitative Analysis of Elastic Recovery Behavior after Bending of Ultra High Strength Steel Sheet: Spring-back or Spring-go (유한요소법을 이용한 초고강도 판재 굽힘에 따른 후변형의 정량적 분석: Spring-back or Spring-go)

  • Kwak, E.J.;Lee, K.;Suh, C.H.;Lim, Y.H.
    • Transactions of Materials Processing
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    • v.20 no.6
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    • pp.456-460
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    • 2011
  • A major source of difficulty in die design for high strength steel is the high level of elastic recovery during unloading. The degree of elastic recovery is affected by factors such as material strength, bending angle, punch's corner radius and sheet thickness. Finite Element Method was used in the present work to quantitatively analyze the elastic recovery for various combinations of these parameters. In some cases elastic recovery happened in reverse direction. This phenomenon, which we call spring-go, was explained via changes in stress distribution in the panel occurring in the forming process.

Experimental Analysis on the Effect of Grain Size of ZK60 Sheet on the Spring-Back Characteristics (마그네슘합금 ZK 60의 결정립 크기에 따른 스프링백 특성 분석)

  • Kang, S.H.;Kang, H.D.;Kwon, Y.N.;Lee, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.398-400
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    • 2008
  • In this work, an air-bending test using magnesium alloy ZK60 sheet was carried out at the various temperatures from room temperature to $300^{\circ}C$ in order to investigate the effect of grain size on the spring-back characteristic. It was found out from experiments that the amount of spring-back was nearly zero at all temperature range when the specimens with grain sizes of 14.66 and $60.71{\mu}m$ were bent by $90^{\circ}$. On the other hand, the spring-back amount dramatically increased at room temperature and phenomenon of spring-go was observed at high temperature when the specimen with submicro grain size of $0.98{\mu}m$ was bent by $90^{\circ}$. From this kind of different spring-back characteristics according to the grain size, it was confirmed that the grain size of material is one of the important factors which have an effect on the spring-back.

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Clustering Analysis with Spring Discharge Data and Evaluation of Groundwater System in Jeju Island (용천수 유출량 클러스터링 해석을 이용한 제주도 지하수 순환 해석)

  • Kim Tae-Hui;Mun Deok-Cheol;Park Won-Bae;Park Gi-Hwa;Go Gi-Won
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2005.04a
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    • pp.296-299
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    • 2005
  • Time series of spring discharge data in Jeju island can provide abundant information on the spatial groundwater system. In this study, the classification based on time series of spring discharge was performed with clustering analysis: discharge rate and EC. Peak discharges are mainly observed in august or september. However, double peaks and late peaks of discharge are also observed at a plenty of springs. Based on results of clustering analysis, it can be deduced that GH model is not appropriate for the conceptual model of Groundwater system in Jeju island. EC distributions in dry season are also support the conclusion.

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Interdecadal Variability and Future Change in Spring Precipitation over South Korea (한반도 봄철 강수량의 장기변동과 미래변화)

  • Kim, Go-Un;Ok, Jung;Seo, Kyong-Hwan;Han, Sang-Dae
    • Atmosphere
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    • v.22 no.4
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    • pp.449-454
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    • 2012
  • This study presents the long-term variability of spring precipitation over the Korean peninsula. It is found that the significant interdecadal change in the spring precipitation has occurred around year 1991. Over the Korean peninsula the precipitation for the post-1991 period increased by about 30 mm per year in CMAP and station-measured data compared to the precipitation prior to year 1991. Due to an increased baroclinicity during the later period, the low-level negative pressure anomaly has developed with its center over northern Japan. Korea is situated at the western end of the negative pressure anomaly, receiving moisture from westerly winds and producing more precipitation. Also, we estimate the change in the near future (years 2020~2040) spring precipitation using six best performing Coupled Model Intercomparison Project 3 (CMIP3) models. These best model ensemble mean shows that spring precipitation is anticipated to increase by about 4% due to the strengthened westerlies accompanied by the northwestern enhancement of the North Pacific subtropical high.

Design and Fabrication of a Mass-spring System for the Force-balance Servo Accelerometer (힘평형 서보 가속도계의 질량지지 장치 설계 및 제작)

  • Kim, Young-Dam;Go, Young-Jun;Nam, Hyo-Duk;Lee, Doo-Hee;Chang, Ho-Gyeong
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.5
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    • pp.14-20
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    • 2001
  • The mass-spring system with four arms for the force-balance servo accelerometer was designed and fabricated. The response characteristics of a mass-spring system was calculated with the change of arms thickness and seismic mass by the finite element method (FEM). Furthermore, the response characteristics of accelerometer was measured using the change of interference pattern and response voltage value by Michelson interferometer. The response characteristics with changing length and thickness of arm was changed drastically, and changing seismic mass was minor effect for the response characteristics of mass-spring system. The measured resonant frequencies have good agreement with that of numerical analysis within 5% range.

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FIV Analysis for a Rod Supported by Springs at Both Ends

  • H. S. Kang;K. N. Song;Kim, H. K.;K. H. Yoon
    • Nuclear Engineering and Technology
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    • v.33 no.6
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    • pp.619-625
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    • 2001
  • An axial-flow-induced vibration model was proposed for a rod supported by two translational springs at both ends. For developing the model, a one-mode approximation was made based on the assumption that the first mode was dominant in vibration behavior of the single span rod. The first natural frequency and mode shape functions for the flow-induced vibration, called the FIV model were derived by using Lagrange's method. The vibration displacements at reactor conditions were calculated by the proposed model for the spring-supported rod and by the previous model for the simple-supported(55) rod. As a result, the vibration displacement for the spring-supported rod was larger than that of the 55 rod, and the discrepancy between both displacements became much larger as flow velocity increased. The vibration displacement for the spring-supported rod appeared to decrease with the increase of the spring constant. AS flow velocity increased, the increase rate of vibration displacement was calculated to go linearly up, and that of the rod having the short span length was larger than that of the rod having the long span length although the displacement value itself of the long span rod was larger than that of the short one.

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Dynamic Modeling of Bolt Joints Using Lumped Mass-Spring Model (집중 질량-스프링 모델을 이용한 볼트 결합부 모델링)

  • Go, Gang-Ho;Lee, Jang-Mu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.3
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    • pp.495-501
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    • 2001
  • In this paper, a new technique which models the joints characteristics through reduction of DOFs of structures with joints using component mode synthesis (CMS) method is proposed. Bolt joints are modeled by mass-spring systems. Also generalized mass and stiffness matrices for this models are introduced. Because bolt joints have influence on eigenvalues of structures, exact eigenvalues from modal test are used. The results show that the behaviors of structures with bolt joints depend to a large extent on the translational DOFs and not on rotational DOFs of mass and stiffness matrices of bolts. Furthermore it is confirmed that lumped mass-spring systems as models of bolt joints are effective models considering the facts that joint characteristics converged to constant values in some iterations and eignevalues from proposed method are in good agreement with ones from modal test.