• 소성∙가공
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• 제20권2호
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• pp.104-109
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• 2011

The metal front case of a mobile phone is manufactured by press forming and welding of thin metal sheets. Twisting of the frame after the forming process is one of main obstacle for the assembly with reinforcement by welding. This study introduces a method preventing twisting of the metal front case frame in press forming. The spring-back after forming produces twisting of the frame, which leads to a low structural stiffness. To reduce twisting, connectors are required to reinforce the structural stiffness of the frame. In this study, the twisting profile is evaluated using a finite element(FE) analysis for various connector shapes. The actual connector shape is determined by minimization of the frame twisting within the tolerance of the FE-analysis. To verify the validity of the proposed blank shape, a forming experiment is performed and the twisting profile is measured using a 3D laser scanning method. The dimensional accuracy is found to be within the tolerance and in good agreement with the FE-analysis.

• 한국정밀공학회지
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• 제17권8호
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• pp.100-105
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• 2000

In this study the structural design concepts of main parameters of a Cathode Ray Tube(CRT) such as frame spring and shadow mask were proposed to guarantee a failure-proof CRT under mechanical shock. With computer simulation and experiments some information on the structural design concept was obtained as followings: the frame and the shadow mask of the CRT needed designing to increase strength so double-beads shape at the corner of frame was newly designed for it, And the spring which interconnected frame with panel glass was required to deform elastically for the purpose of absorbing the shock energy in the direction of drop. A new type of spring 'twisting spring' was designed to achieve the flexibility in that direction. By using it the deformation energy of a shadow mask could reduced to some degree. To accomplish those simulations commerical codes Pam-Crash and I-DEAS were used and a typical CRT was analyzed as an example to prove the usefulness of this study.

• 한국기계기술학회지
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• 제13권2호
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• pp.71-78
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• 2011

A kart is a vehicle without the suspension system and the differential gear. The kart frame as an elastic body plays the role of a spring. By the cornering of a kart, rolling, pitching and twisting motions are induced in the kart frame. Also the slip or noncontact of the wheel and a permanent deformation of the kart frame can be induced. In order to examine closely this phenomenon, measurement on height-displacements with various sensors and tracking system and analysis on the kart frame twisting characteristics with the rolling and pitching angle are needed. According to the measurement result, while driving in a curve at high speed the kart frame is quite twisted. Analysis on the measurement results shows that a kart used primarily in high speed requires a frame with low torsional stiffness and a frame material with high tensile strength and large elongation.

• 한국기계가공학회지
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• 제12권1호
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• pp.77-83
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• 2013

This paper presents the feasibility on the application of composite coil spring, which has great interest in the automobile industry. In order to obtain much lighter weight of the composite spring, it will be necessary to optimize the design variables such as fiber angles and diameter of coil, etc. First of all, mechanical properties were measured to consider the effects of FVR and ply angles for carbon fiber composite material. And the shear modulus with respect to ply angles were derived based on twisting angles calculated by torsional beam model. Next we determined the design parameters of composite coil spring, which has equivalent spring rate to the steel coil spring. In order to assess the proposed method, finite element model of the composite spring was developed and analysed to obtain the spring constant. The results showed that static spring rate of the composite spring was in a good agreement with that of steel spring.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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• pp.21-27
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• 2001

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression, principle of virtual work is adapted The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants and stresses can be predicted by input of few factors.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.250-255
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• 2008

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression. principle of virtual work is adapted. And this theory was programming using MATLAB software. To compare FEM using MATLAB software was applied MSC. Nastran software. The geometry model for MSC. Patran was produced by 3-D design modeling software. Finite element model was produced by MSC. Patran. Finite element was applied tetra (CTETRA) having 10 node. The analysis results of the MATLAB and MSC. Nastran are fairly well agreed with those of various experiments. Using MATLAB program proposed in this paper and MSC. Nastran, spring constants and stresses can be predicted by input of few factors.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1130-1139
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• 2001

Springs are widely utilized in machine element. To find out stiffness of coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculated the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants can be predicted by input of few factors.

• Design & Manufacturing
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• 제12권3호
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• pp.13-18
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• 2018

Flexible display tends to grow every year, It tends to be larger, slimmer, and higher in image quality. Therefore, accuracy is required in the manufacturing process of each part. In the curved monitor, the bottom chassis has a structure to which other parts can be attached. The accuracy of the curvature which the bottom chassis of the curve monitor monitors has is important. If the curvature error is large, serious defects such as cracks, warpage, twisting and the like occur. Curvature was analyzed using 3D scanner. In the Forming process and Restriking process steps, spring go occurred, and spring back occurred in the Notching process and Bending process steps. Even in the same process, it was confirmed that the curvature value varied depending on the formed shape.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.121-129
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• 2000

this paper develops a computational model for the turning maneuver analysis of a cabover type heavy truck. The model having 42 degree-of-freedom is developed using ADAMS. Leaf springs used in the front and rear suspension systems are modeled by dividing it three links and joining them with joints. Force and displacement relationship showing nonlinear hysteric characteristics of the leaf spring is measured and modeled with an exponential function. A velocity and force relationship of a shock absorber is measured and modeled with a spline function. And a stabilizer bar is modeled using ADAMS beam element to consider a twisting and bending effect. To verify the developed model an actual vehicle test is performed in the double lane change course with 50kph and 60kph vehicle velocity. In the actual vehicle test lateral acceleration roll angle and yaw rate are measured, The tendency and peak-to-peak values of the actual vehicle test and simultion results are compared each other.

• 한국컴퓨터그래픽스학회논문지
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• 제12권1호
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• pp.21-25
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• 2006

This paper proposes a real-time simulation technique for thin shells undergoing large deformation. Thin shells are almost two-dimensional structures visually well approximated as surfaces, such as leaves, paper sheets, hats, aluminum cans. Unfortunately accurate simulation of these structures requires one of the most complex formulations in continuum mechanics, shell theory [4]. Moreover, there has not yet been any work reported to produce visually convincing animation of them while achieving real-time performance. Motivated by discrete shells [5] and modal warping [3], we formulate dynamics of thin shells using mass-spring models instead of finite element models, and then apply the modal warping technique to cope with large rotational deformation of thin shells. Experiments show that the proposed technique runs in real-time, and that it can simulate large bending and/or twisting deformations with acceptable realism.