• Transactions of Materials Processing
• /
• v.22 no.6
• /
• pp.303-309
• /
• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.10a
• /
• pp.321-321
• /
• 2009

This paper presents quasi-zero-stiffness (QZS) characteristic of a passive isolator using flexures under compression force. The passive isolator consists of a positive stiffness element (a vertical coil spring) and a negative stiffness element (flexures under compression force), and their proper combination of the positive and negative stiffness elements can produce both substantial static and zero dynamic stiffness, so called QZS. Firstly, a nonlinear dimensionless expression of a flexure under compression force is derived. A dynamic model of the passive isolator is developed and numerical simulations of its time and frequency response are performed. Then, undesirable nonlinear vibration is quantified using a period doubling bifurcation diagram and a Poincare's map of the isolator under forced excitation. Finally, experiments are performed to validate the QZS characteristic of the passive isolator.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.11a
• /
• pp.261-264
• /
• 2000

The objective of this work was to characterize mechanical properties of thermoplastic composites for various forming condition in compression molding. Randomly oriented long glass fiber reinforced polypropylene(PP) was used in the work. The composite materials contained 20%, 30%, and 40% glass fiber by weight. Compression molding was conducted to make the test specimen. Dimensional stability was measured on each forming condition with the spring-forward angle. Tensile test was conducted to characterize mechanical properties of formed parts in various forming conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1993.04a
• /
• pp.147-147
• /
• 1993

All types of dynamic excitation, periodical, pulse or transient in vertical, horizontal or all three directions can be effectively reduced by vibration isolation systems. Typical elements for vibration isolation control are spring units consisting of a group of helical compression springs. In all cases of shock, transient or random excitation energy absorbing dampers have to be added to the spring units in order to reduce system response in the frequency range near the natural frequency of the isolation system. The same isolation system of spring units and viscos-dampers has been used since 1979 for passive protection of buildings and structures has been proved to by very advantageous for vibration and structure borne noise control. Not only because of high vertical flexibility of the spring units, compared for example with typical rubber or neoprene mounts out also because of the horizontal of flexibility, which can be adapted by modifying the spring dimensions to nearly every requirement. It is just normal to use the same basic elements for passive isolation as for active isolation.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2001.11a
• /
• pp.21-27
• /
• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.2
• /
• pp.671-686
• /
• 2020

Due to the long training time and high training cost of traditional surgical training methods, the emerging virtual surgical training method has gradually replaced it as the mainstream. However, the virtual surgical system suffers from poor authenticity and high computational cost problems. For overcoming the deficiency of these problems, we propose an optimized model for the local compression deformation of soft tissue. This model uses a simulated annealing algorithm to optimize the parameters of the soft tissue model to improve the authenticity of the simulation. Meanwhile, although the soft tissue deformation is divided into local deformation region and non-deformation region, our proposed model only needs to calculate and update the deformation region, which can improve the simulation real-time performance. Besides, we define a compensation strategy for the "superelastic" effect which often occurs with the mass-spring model. To verify the validity of the model, we carry out a compression simulation experiment of abdomen and human foot and compare it with other models. The experimental results indicate the proposed model is realistic and effective in soft tissue compression simulation, and it outperforms other models in accuracy and real-time performance.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.2
• /
• pp.250-255
• /
• 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 Hydrogen and New Energy
• /
• v.23 no.6
• /
• pp.619-627
• /
• 2012

This study was experimentally investigated on the effects of spring stiffness applied to linear compressor chambers. The springs prevented piston head from colliding with engine cover, stored the kinetic energy and regenerated the kinetic energy. The linear engine has two combustion chambers and four compressor chamber. The combustion chamber bore size was 30 mm, maximum stroke was 31 mm and effective stroke volume was 25.45 cc respectively. The spring stiffness was varied such as 0, 0.5, 1.00, 2.9 and 14.7 N/mm. The linear engine was fueled with premixed LPG (propane 99%) and air by pre-mixture device. As an experimental result, The stroke, piston velocity and the piston frequency were increased by high spring stiffness. Also, thermal efficiency was grown. because the increased stroke made the higher compression ratio. In conclusion, electric power and efficiency were improved.

• The korean journal of orthodontics
• /
• v.22 no.1
• /
• pp.135-146
• /
• 1992

It was the purpose of this study to analyze and compare the mechanical properties of ortho dontic open coil springs. Four variable factors were presented - wire diameter (.008", .009", .010"), lumen size (.030", .032", .036"), arch wire size and shape (.016" round, $ .016^{{\prime}{\prime}}{\times}.022^{{\prime}{\prime}}$ rect.) and alloy type (HiT II, Elgiloy, Sentalloy). The total 104 specimens were divided into 13 groups, and compression test was performed on an Instron test machine. The load deflection curve of each open coil spring was obtained, from which, the load-deflection relations, stiffnesses, percent recoveries were computed statistically. The results were obtained as follows: 1. When the lumen size of the coil spring remained constant, stiffness and percent recovery increased as the wire diameter increased. 2. When the wire diameter of the coil spring remained constant, stiffness and percent recovery decreased as the lumen size increased. 3. The effect of size and shape of arch wire on the coil spring was not statistically significant. 4. In alloy types, stiffness was the greatest in HiT II (55.21), Elgiloy (42.61) and Sentalloy (7.74) in that order. Sentalloy exhibited superior percent recovery and long range of action.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.422-427
• /
• 2008

This study is to illustrate the usefulness of Kriging Dimension Reduction Method(KDRM), which is to construct probability distribution of response function in the presence of the physical uncertainty of input variables. DRM has recently received increased attention due to its sensitivity-free nature and efficiency that considerable accuracy is obtained with only a few number of analyses. However, the DRM has a number of drawbacks such as instability and inaccuracy for functions with increased nonlinearity. As a remedy, Kriging interpolation technique is incorporated which is known as more accurate for nonlinear functions. The KDRM is applied and compared with MCS methods in a compression coil spring design problem. The effectiveness and accuracy of this method is verified.