• Steel and Composite Structures
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• v.21 no.6
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• pp.1327-1345
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• 2016

$Al_2O_3$/SiC particulate reinforced (Metal Matrix Composites) MMCs which were produced by using stir casting process, bending strength and hardening behaviour were obtained using an analysis of variance (ANOVA) technique that uses full factorial design. Factor variables and their ranges were: particle size $2-60{\mu}m$; the stirring speed 450 rpm, 500 rpm and the stirring temperature $620^{\circ}C$, $650^{\circ}C$. An empirical equation was derived from test results to describe the relationship between the test parameters. This model for the tensile strength of the hybrid composite materials with $R^2$ adj = 80% for the bending strength $R^2$ adj = 89% were generated from the data. The regression coefficients of this model quantify the tensile strength and bending strengths of the effects of each of the factors. The interactions of all three factors do not present significant percentage contributions on the tensile strength and bending strengths of hybrid composite materials. Analysis of the residuals versus was predicted the tensile strength and bending strengths show a normalized distribution and thereby confirms the suitability of this model. Particle size was found to have the strongest influence on the tensile strength and bending strength.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.63-72
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• 2011

In recent years, hot-stamped components are more increasingly used in the automotive industry in order to reduce weight and to improve the strength of vehicles. In hot stamping process, blank is hot formed and press hardened in a tool. However, in hot stamping without cooling channel, temperature of the tool increases gradually in mass production thus cannot meet the critical cooling rate to obtain high strength over 1500MPa. Warpage occurs in the hot stamped component due to non-uniform stress state caused by unbalanced cooling. Therefore, tools should be uniformly as well as rapidly cooled down by the coolant which flows through cooling channel. In this paper, optimal design method of cooling channel to obtain uniform and high strength of the component is proposed. Optimized cooling channel is applied to the hot press V-bending process. As a result of measuring strength, hardness and microstructure of the hot formed parts, it is known that the design methodology of cooling channel is effective to the hot stamping process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.119-127
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• 1995

A process sequence in precison press forming of electronic components is investigated by the finite element method. Aperture, a key component of electronic gun, is formed through a wequence of about 15 operations, among which the beading & bending, the first coining, and the second coining operations are expected to be most critical in view of industrial experts' opinions. Thus, the analysis performed by a commercial code MARC focuses on the three operations, and comparisons are made between the results of the analysis and the measurement of experimental forming of the component, and it appears a sound agreement.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.76-84
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• 1997

A process sequence in precision press forming of electrnic components is investigated by the finite element method. Aperture, a key component of electronic gun, is formed through a sequence of about 15 operation, among which the beading & bending, the first piercing, the first coining, and the second coining operations are expected to be most critical in view of industrial experts opinions. Thus, the analysis per- formed by a commercial code MARC focuses on the three operations, and comparisons are made between the results of the analysis and the measurements of experimental forming of the component.

• Journal of Advanced Marine Engineering and Technology
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• v.14 no.3
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• pp.34-41
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• 1990

Mode Synthesis Method is applied to analyize the vibration characteristics of the press machine sold at present. Vibration analysis of the machine has not been done thoroughly as far, because of its complicated structure and much bigger unlinearity of its vibration characteristics. The press was disassembled by parts, and it was experimented by the exciting techniques and curve fitting methods, and analyzed by the Mode Synthesis Method. The 2 results were showed good agreements at each part. We confirming it, the machine was assembled, and experimented and analyzed by the same method. Also good agreements between 2 methods were obtained. In addition, impact responses of the actual moving press were agreed with the analyzed values by the Mode Synthesis Method. And we found that the first bending mode of the slide was ruling the vibration characteristics of the press.

• Structural Engineering and Mechanics
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• v.49 no.5
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• pp.661-672
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• 2014

Laminated Rectangular plates embedded in elastic foundations are used in many mechanical structures. This study presents an analytical approach for transverse bending analysis of an embedded symmetric laminated rectangular plate using Mindlin plate theory. The surrounding elastic medium is simulated using Pasternak foundation. Adopting the Mindlin plate theory, the governing equations are derived based on strain-displacement relation, energy method and Hamilton's principle. The exact analysis is performed for this case when all four ends are simply supported. The effects of the plate length, elastic medium and applied force on the plate transverse bending are shown. Results indicate that the maximum deflection of the laminated plate decreases when considering an elastic medium. In addition, the deflection of the laminated plate increases with increasing the plate width and length.

• Advances in aircraft and spacecraft science
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• v.5 no.1
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• pp.21-49
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• 2018

In this paper, geometric nonlinear bending characteristics of single wall carbon nanotube reinforced composite (SWCNTRC) doubly curved shell panels subjected to uniform transversely loadings are investigated. The nonlinear mathematical model is developed for doubly curved SWCNTRC shell panel on the basis of higher-order shear deformation theory and Green- Lagrange nonlinearity. All nonlinear higher order terms are included in the mathematical model. The effective material properties of SWCNTRC are estimated by using Eshelby-Mori-Tanaka micromechanical approach. The governing equation of the shell panel is obtained using the total potential energy principle and a Newton-Raphson iterative method is employed to compute the nonlinear displacement and stresses. The present results are compared with published literature. The effect of SWCNT volume fraction, width-to-thickness ratio, radius-to-width ratio (R/a), boundary condition, linear and nonlinear deflection, stresses and different types of shell geometry on nonlinear bending response is investigated.

• Structural Engineering and Mechanics
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• v.53 no.4
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• pp.661-679
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• 2015

In this article, nonlinear finite element solutions of bending responses of functionally graded spherical panels are presented. The material properties of functionally graded material are graded in thickness direction according to a power-law distribution of volume fractions. A general nonlinear mathematical shallow shell model has been developed based on higher order shear deformation theory by taking the geometric nonlinearity in Green-Lagrange sense. The model is discretised using finite element steps and the governing equations are obtained through variational principle. The nonlinear responses are evaluated through a direct iterative method. The model is validated by comparing the responses with the available published literatures. The efficacy of present model has also been established by demonstrating a simulation based nonlinear model developed in ANSYS environment. The effects of power-law indices, support conditions and different geometrical parameters on bending behaviour of functionally graded shells are obtained and discussed in detail.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.702-705
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• 2005

Metallic sandwich plates with Inner dimpled shell subjected to 3-point bending have been analyzed and then optimized for minimum weight. Inner dimpled shells can be easily fabricated by press or roll with high quality precision and bonded with same material skin sheets by resistance welding or adhesive bonding process. Optimized shape of inner dimple is a hemispherical shell to minimize weight without failure, including face yielding, face buckling and inner dimple buckling. It is demonstrated that bending stiffness of sandwich plate is 2 or 3 times than solid plates with same strength

• Structural Engineering and Mechanics
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• v.34 no.3
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• pp.367-376
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• 2010

In this paper, an experimental investigation of the mechanical behavior and buckling failure of sharp-notched circular tubes subjected to cyclic bending is discussed. The unnotched and sharp-notched circular tubes of SUS 304 stainless steel were tested under symmetric curvature-controlled cyclic bending. It was found from moment-curvature curves that the loops show cyclic hardening and gradually steady after a few cycles for all tested tubes. The ovalization-curvature curves show an unsymmetric, ratcheting and increasing manner with the number of cycles. In addition, it was found that six almost parallel lines corresponding to unnotched and five different notch-depth (0.2, 0.4, 0.6, 0.8 and 1.0 mm) tubes were noted from the experimental relationship between the cyclic controlled curvature and the number of cycles necessary to produce buckling on a log-log scale. An empirical formulation was proposed so that it could be used for simulating the aforementioned relationship. By comparing with the experimental finding, the simulation was in good agreement with the experimental data.