• 한국자동차공학회논문집
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• 제4권6호
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• pp.27-38
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• 1996

A two-dimensional FEM program, which considers bending effects in the membrane fromulation, was developed under plane strain assumption for analyzing forming processes of an arbitrarily shaped draw-die of automotive panels. For the evaluation of bending effects with membrane elements, the bending equivalent forces and stiffnesses are calculated from the bending moment computed using the changes in curvature of the formed shape of two membrane ones. The curves depicted with 3 nodes are described by a circle, a quadratic equation, and a cubic equation, respectively, and in the simulation of the stretch/draw sections of an automotive inner panel, three different description results are compared each other. Also, the bending results are compared with membrane results and measurements in order to verify the validity of the developed program.

• 대한기계학회논문집A
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• 제22권3호
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• pp.493-503
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• 1998

The sectional forming analysis considering bending effects from the geometrically deformed shape of two linear membrane finite elements(called super element) was performed under plane strain assumption for analyzing forming processes of an arbitrarily shaped draw-die. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the changes in the interior angle at the middle node of super element, and are agumented to the membrane stretch forces. In order to verify the validity of the bending formulation, the simulation results for the stretch, draw, and bend sections were compared with membrane analysis results and measurements.

• 한국가구학회지
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• 제18권1호
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• pp.20-30
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• 2007

This experiment was carried out to investigate the effects of number and location of finger joints on the bending strength of glue-laminated lumbers. Urea resin adhesives were used in this experiment and the resin content was 70% for cold pressing. The lamina were edge-jointed and end-jointed. The specimen were composed of one or three layers. The obtained results are summarized as follows; The effects of finger joints on the decrease of bending strength of glue laminated woods were different according to the number and location of finger joints. The decrease of MOR was highest on the middle position of laminated woods. The effects of several arrangements of finger joints on the bending strength of glue laminated woods showed on Figure 7 and 8. The variance of thickness-laminating on the bending strength of glue laminated woods were larger than those of width-laminating.

• 소성∙가공
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• 제10권2호
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• pp.91-100
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• 2001

A sectional FEA program is developed lot analyzing forming processes of sandwich sheets, which are intensively used recently as a lightweight material of an automobile body. The aluminum sandwich sheet consists of two aluminum skins and a polyprophylen core in between. The aluminum sandwich sheet is dominantly effected by the bending effects in small radius of curvature, so that an appropriate description of bending effects is required to analyze the forming processes. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the curvature of the tool and are added to the membrane stretch forces. To verify the validity of the developed program the sectional FEA results in stretch/draw forming Processes of a square cup and draw forming Processes of an outer hood panel were compared with the measurements.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1580-1588
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• 1997

A modeling method for the flapwise bending vibration of a rotating cantilever beam which has small slenderness ratio is presented in this paper. It is shown that as the slenderness ratio decreases the shear and rotary inertia effects increase. Such effects become critical for the accurate estimation of the natural frequencies and modeshapes, especially higher frequencies and modes, as the angular speed increases. It is also shown that the flapwise bending natural frequencies are higher than the chordwise bending natural frequencies. The discrepancy between first natural frequencies are especially significant when the hub radius ratio is small.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.262-265
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• 2003

In the present study, subframe was developed using hydroforming technology. The manufacturing process for subframe consists of tube bending, pre-forming and hydroforming. The effects of bending process for manufacturing hydroformed subframe were researched. And the variables of bending process were studied by FEM simulation. The bending method is rotary draw bending that is the most popular, cost-effective bending method for thin walled tubes.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.59-66
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• 2008

This paper has proposed a new parameter to interpret the effects of plastic deformation in bending of strips in cylindrical die and punch. With reference to the parameter, we have provided an insight on the separation between strips and punches, the occurrence of the multi-point bending during the process of deformation, the final shapes of strips, and the springback ratios. Also using the parameter, we have considered the different effects between the bending deformation in the cylindrical die and the bending deformation due to pure bending.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.310-313
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• 2007

This paper covers finite element simulations to evaluate the bending limit of double pipe for tube-hydroforming. The tube-hydroforming process starts with a straight precut tube. The tube is often prebent in a rotary draw bending machine to fit the hydroforming tool. During the bending the tube undergoes significant deformation. So forming defects such as wrinkling, thinning and flattening are generated in the tube. Consequently we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters to minimize the forming defects using orthogonal arrays. The characteristic to evaluate the effects of the process parameters is the bending angle which wrinkling is generated, we define the bending angle at that time as bending limit. Of many process parameters, the process parameters of the bending process such as gab between inner and outer tube, boosting force, dimensions of mandrel were analyzed. And we observed the deformation modes of bent double pipe at specific bending angle in each parameter combination.

• Steel and Composite Structures
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• 제36권2호
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• pp.143-161
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• 2020

In nanosized structures as the surface area to the bulk volume ratio increases the classical continuum mechanics approaches fails to investigate the mechanical behavior of such structures. In perforated nanobeam structures, more decrease in the bulk volume is obtained due to perforation process thus nonclassical continuum approaches should be employed for reliable investigation of the mechanical behavior these structures. This article introduces an analytical methodology to investigate the size dependent, surface energy, and perforation impacts on the nonclassical bending behavior of regularly squared cutout nanobeam structures for the first time. To do this, geometrical model for both bulk and surface characteristics is developed for regularly squared perforated nanobeams. Based on the proposed geometrical model, the nonclassical Gurtin-Murdoch surface elasticity model is adopted and modified to incorporate the surface energy effects in perforated nanobeams. To investigate the effect of shear deformation associated with cutout process, both Euler-Bernoulli and Timoshenko beams theories are developed. Mathematical model for perforated nanobeam structure including surface energy effects are derived in comprehensive procedure and nonclassical boundary conditions are presented. Closed forms for the nonclassical bending and rotational displacements are derived for both theories considering all classical and nonclassical kinematics and kinetics boundary conditions. Additionally, both uniformly distributed and concentrated loads are considered. The developed methodology is verified and compared with the available results and an excellent agreement is noticed. Both classical and nonclassical bending profiles for both thin and thick perforated nanobeams are investigated. Numerical results are obtained to illustrate effects of beam filling ratio, the number of hole rows through the cross section, surface material characteristics, beam slenderness ratio as well as the boundary and loading conditions on the non-classical bending behavior of perforated nanobeams in the presence of surface effects. It is found that, the surface residual stress has more significant effect on the bending deflection compared with the corresponding effect of the surface elasticity, Es. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams.

• 한국방재학회 논문집
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• 제9권2호
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• pp.11-15
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• 2009

본 논문에서는 균일 모멘트 하중을 받는 박판 아치의 탄성 좌굴에 관한 연구를 수행하였다. 초기 곡률을 고려한 비선형 변형률-변위 관계식을 전체 포텐셜 에너지 방정식의 이차 변분에 대입하여 초기 곡률 효과를 포함하는 에너지 방정식을 유도하였다. 휨 모멘트에 의한 단면 내 법선 변형률이 선형으로 분포한다는 초기 곡률 효과에 대한 가정사항을 유도과정에 일관되게 적용하였다. 균일 모멘트 하중을 받는 아치의 휨-비틀림 좌굴하중에 관한 제차해를 제시하고 타 연구자의 결과와 비교하였다.