• Title/Summary/Keyword: Bending

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A Discussion on Measurement of Springback Ratio Using Winding Bend Rig (감아굽힘 장치를 이용한 스프링백 비의 측정에 대한 역학적 검토)

  • 김용우
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.2
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    • pp.1-9
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    • 2001
  • To measure springback ratio of thin sheet or plate, winding bend rig is made. It bends a specimen with keeping its curva-ture constant and measure the bending angles before and after release of bending load. To check the performance of the bend rig, we calculated the bending moment by two ways which are based on simple beam theory. One is that the bending moment is calculated by using the results of bending test, and the other is that the moment is calculated by using the results of tensile tests. The former may entails the effect of the other is that the moment is calculated by using the results of tensile tests. The former may entails the effect of the friction between bending pin of the rig and surface of specimen, but the latter does not contain any effects of the friction since the bending moment is obtained by using tensile tests. Never-theless, the values of the two bending moments shows the same level of bending moment, which implies that the friction does not influence on the presence of friction within the scope of the test performed in this experiment. This phenomenon is explained theoretically by using moment equilibrium.

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Bending moments in raft of a piled raft system using Winkler analysis

  • Jamil, Irfan;Ahmad, Irshad
    • Geomechanics and Engineering
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    • v.18 no.1
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    • pp.41-48
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    • 2019
  • Bending moments in the raft of a pile raft system is affected by pile-pile interaction and pile-raft interaction, amongst other factors. Three-Dimensional finite element program has to be used to evaluate these bending moments. Winkler type analysis is easy to use but it however ignores these interactions. This paper proposes a very simplified and novel method for finding bending moments in raft of a piled raft based on Winkler type where raft is supported on bed of springs considering pile-pile and pile-raft interaction entitled as "Winkler model for piled raft (WMPR)" The pile and raft spring stiffness are based on load share between pile and raft and average pile raft settlement proposed by Randolph (1994). To verify the results of WMPR, raft bending moments are compared with those obtained from PLAXIS 3D software. A total of sixty analysis have Performed varying different parameters. It is found that raft bending moments obtained from WMPR closely match with bending moments obtained from PLAXIS 3D. A comparison of bending moments ignoring any interaction in Winkler model is also made with PLAXIS-3D, which results in large difference of bending moments. Finally, bending moment results from eight different methods are compared with WMPR for a case study. The WMPR, though, a simple method yielded comparable raft bending moments with the most accurate analysis.

A Simplified Approach for Predicting Springback in U-Draw Bending of Sheet Metals (U 드로오 벤딩에서의 스프링백 예측을 위한 이론적 단순화)

  • 장성호;허영무;서대교
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10a
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    • pp.125-131
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    • 2003
  • The U-draw bending operation is known as a representative test method for springback evaluation of sheet metals since the sheet in U-draw bending operation undergoes stretching, bending and unbending deformations occurred at read stamping process. In this study, a simplified approach was proposed for predicting springback and side-wall curls in U-draw bending operations, using moment-curvature relationships derived for sheets undergoing stretching, bending and unbending deformation.

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Experimental Study on The Bending Collapse Characteristics of Al Rectangular Tubes (알루미늄 사각관의 굽힘붕괴특성에 관한 실험적 고찰)

  • 강신유;김창수;정태은
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.03a
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    • pp.265-272
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    • 1997
  • In this paper the bending collapse characteristics of 60 series Al rectangular tubes were studied with a pure bending collapse test rig which could apply the pure bending moment, there occured three kinds of bending collapse modes - local buckling, delayed buckling, tensile failure - depending on the b/t(width/thickness) ratio and material properties. Experiment results are compared with the results of finite element method.

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A Study on the U-bending of Rectangular Hollow Tube by the Eccentric Extrusion and Bending Process (편심압출굽힘가공법에 의한 사각형 단면을 가진 중공 튜브제품의 U형굽힘가공에 관한 연구)

  • Kim, Jin-Hoon;Jin, In-Tai
    • Transactions of Materials Processing
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    • v.7 no.5
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    • pp.496-504
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    • 1998
  • The eccentric extrusion and bending process for the forming of the curved rectangular hollow tube is newly developed. Generally the bending process of hollow tube is the secondary process followed by the extrusion process of the hollow tube from the round billet. So many defects such as wrinkling and the difference of wall thickness can be happened during the secondary bending process. In order to avoid the defects the new process named as "the eccentric extrusion and bending process" is suggested and applied to the U-bending of rectangular hollow tube. In this paper the kinematically admissible velocity field between the dies surface and the internal plug boundary surface s developed for the curving velocity. By the using of this curving velocity field the curvature of extruded products can be calculated with the parameters such as eccentricity dies length friction constant aspect ratio.

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Analysis on the Mechanism of Fluting in the Bending of Low Carbon Steels (저탄소강판을 이용한 굽힘 가공에서 발생하는 꺾임 현상에 대한 발생기구 해석)

  • Park, K.C.;Yoon, J.B.
    • Transactions of Materials Processing
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    • v.16 no.4 s.94
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    • pp.317-322
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    • 2007
  • In order to investigate the cause and condition of fluting in tangential bending of low carbon steel sheet, an analytic analysis, an experiment and a series of finite element analysis for bending process were done. The fluting in bended sheet was related with the yield point elongation of material. Due to the yield point elongation, unstable plastic hinge was occurred in course of bending of elastic perfectly plastic sheet. According to the analysis and computational results, lower yield point elongation than 5% was required to prevent fluting in 0.5-0.6t sheet in $15{\sim}25mm$ radius bending. The tendency of fluting occurrence was reduced as decreasing the radius of bending, increasing thickness of bended sheet, and removing irregularity in sheet and bending processes.

Effect of Water on the Bending Properties of Wool, Polyester, and Wool-Polyester Blended Fabrics (양모, 폴리에스테르 및 양모-폴리에스테르 혼방직물의 굽힘특성에 미치는 수분의 영향)

  • 김석근
    • Textile Science and Engineering
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    • v.22 no.3
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    • pp.43-52
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    • 1985
  • In this paper the bending behaviour of wool, polyester and wool-polyester blended fabrics in existence of water was investigated. The measurements of the bending properties of the fabrics were carried out at the various stages of water contents on the way of drying fabrics wetted by dipping in water. Relations between the bending parameters of fabrics, such as bending hysteresis and rigidity, and water contents were surveyed. For all the fabrics except polyester fabric, the bending hystereses were sharply increased untill water contents reached approximately the maximum moisture regain of wool and then plateaued at the higher water contents, while the bending hysteresis of polyester fabric was decreased with increas of water contents. The bending rigidity of polyester fabric was decreased, while those of other fabrics were increased slightly with the increase of water contents. The linear relationship was between the bending parameters and blend ratios of wool-shown at dry state. The same relation was not observed at wet state.

A Study on the Local Buckling Collapse Behavior of an Aluminum Square Tube Beam under a Bending Load (굽힘하중을 받는 알루미늄 사각관 보의 국부적 좌굴붕괴 거동에 관한 연구)

  • Lee, Sung-Hyuk;Choi, Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.12
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    • pp.2011-2018
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    • 2003
  • To analyze the bending collapse behavior of an aluminum square tube beam under a bending load, a finite element simulation for the four-point bending test has been performed. Using an aluminum tube beam specimen partly inserted with two steel bars, the local buckling deformation near the center of the tube beam was induced. The maximum bending load and the bending collapse behavior obtained from the numerical simulation were in good agreement with experimental results. Using a combination of the four-point bending test and its finite element simulation, analysis of the local buckling and the accompanied bending collapse behavior of aluminum tube beam could be quantitative accomplished.

New Bending System Using a Segmented Vacuum Chuck for Stressed Mirror Polishing of Thin Mirrors

  • Kang, Pilseong;Yang, Ho-Soon
    • Current Optics and Photonics
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    • v.1 no.6
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    • pp.618-625
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    • 2017
  • In the present research, a new bending system using a segmented vacuum chuck for Stressed Mirror Polishing (SMP) is developed. SMP is a special fabrication method for thin aspheric mirrors, where simple flat or spherical fabrication is applied while a mirror blank is deflected. Since a mirror blank is usually glued to a bending fixture in the conventional SMP process, there are drawbacks such as long curing time, inconvenience of mirror replacement, risk of mirror breakage, and stress concentration near the glued area. To resolve the drawbacks, a new bending system is designed to effectively hold a mirror blank by vacuum. For the developed bending system, the optimal bending load to achieve the designated mirror deflection is found by finite element analysis and an optimization algorithm. With the measurement results of the deflected mirror surfaces with the optimal bending loads, the feasibility of the developed bending system is investigated. As a result, it is shown that the bending system is appropriate for the SMP process.

Determination of winding diameter based on bending strain analysis for REBCO coated conductor tapes

  • Leon, M.B. De;Dedicatoria, M.J.;Shin, H.S.
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.2
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    • pp.8-11
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    • 2012
  • In order to recognize the allowable bending diameter in coils, the strain as function of diameters is evaluated. The irreversible strain limits of $I_c$ in the easy and hard bending modes were measured. Strains were calculated at the coating film in the easy bending and at outer edge or inner edge in the hard bending of the CC tape, respectively. The tape geometry subjected to bending procedures is considered from the current industrial spool winding operation. Through the linear superposition of strain induced in different bending modes regarding the expressions, the appropriate design for critical bending diameter is suggested. Results proved that the existence of buckling resulting from bending in hard direction when applied strain exceeded 0.6% is possible. The depicted results showed that the strain limit as a viable parameter should be considered for future purposes.