• Proceedings of the KWS Conference
• /
• 2005.11a
• /
• pp.91-93
• /
• 2005

The purpose of this study is to evaluate effects of stiffener configuration welded to the plate on the fatigue strength. Nominal stress and hot spot stress for the stiffened plate under pure bending condition were evaluated using FEA and experiment and fatigue test for each specimen was performed. For S and SD type, the fatigue strength increase with a decrease in the nominal stress and hot spot stress. D type with doubler plate was found to have the lowest value of nominal and hot spot stress for a given condition. However its fatigue strength was smaller than the others.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.792-798
• /
• 2012

This study shows the vibration characteristics of an actuator with six wire-suspensions, used in optical pickups of optical disc drives (ODDs). In this paper, the vibration characteristics of this beam structure is induced mathematically. To obtain vibration modes of focusing direction, the vibration analysis is achieved in lateral and longitudinal directions of the structure. The accuracy of induced vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode shapes can be modified by changing design parameters in mathematical expressions.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.11
• /
• pp.1128-1136
• /
• 2012

This paper analyzes the vibration characteristics of an optical pickup actuator, which has six wire-suspensions and is used in optical disc drives(ODDs). The vibration characteristics of the actuator is mathematically described by analyzing its beam configuration and motion condition confined to lateral and longitudinal directions of the beams. The accuracy of the vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode frequencies and shapes can be modified by changing design parameters in mathematical expressions.

• Journal of the Korean Ceramic Society
• /
• v.26 no.6
• /
• pp.763-770
• /
• 1989

A very fine and pure mullite powder of the stoichiometric composition was prepared from aluminium isopropoxide and tetraethylorthosilicate by an alkoxide hydrolysis method using NH4OH as a catalytic agent. The gel powder obtained from the hydrolysis was calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$. The average particle sizes of the powders calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$ were 0.19${\mu}{\textrm}{m}$ and 0.25${\mu}{\textrm}{m}$, respectively. The specific surface areas of the powders calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$ were 114.7$m^2$/g and 20.6$m^2$/g, respectively. The bending strength and fracture toughness of the mullite ceramics sintered at 1$650^{\circ}C$ were 263.1MPa and 2.30MPa.m1/2 respectively.

• Structural Engineering and Mechanics
• /
• v.37 no.6
• /
• pp.617-632
• /
• 2011

A concept of crash energy absorbing (CEA) lattice structure for an inflatable morphing vehicle body (Lee et al. 2008) has been investigated as a method of providing rigidity and energy absorption capability during a vehicular collision (Lee et al. 2007). A modified analytical model for the CEA lattice structure design is described in this paper. The modification of the analytic model was made with a stiffness approach for the elastic region and updated plastic limit analysis with a pure plastic bending deformation concept and amended elongation factors for the plastic region. The proposed CEA structure is composed of a morphing lattice structure with movable thin-walled members for morphing purposes, members that will be locked in designated positions either before or during the crash. What will be described here is how to model the CEA structure analytically based on the energy absorbed by the CEA structure.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1998.04a
• /
• pp.449-456
• /
• 1998

A consistent finite element formation and analytic solutions are presented for spatial stability of thin-walled circular arch. The total potential energy is derived by applying the principle of linearized virtual work and including second order terms of finite semitangential rotations. As a result the energy functional corresponding to the semitangential rotation is obtained, in which the elastic strain energy terms are considered restrained warping effects. We have obtained analytic solution for the lateral buckling of monosymmetric thin-walled curved beam subjected to pure bending or uniform compression and it's boundary conditions are simply supported. For finite element analysis, the two node cubic Hermitian polynomials are utilized as shape Auctions. In order to illustrate the accuracy of this study, parameter studies for lateral buckling problems of circular arch are presented and compared with available solutions and numerical results analyzed by the FEM using straight beam element.

• Advanced Composite Materials
• /
• v.16 no.2
• /
• pp.83-94
• /
• 2007

Woven sisal textile fiber reinforced composites were used to evaluate fracture toughness, tensile and three-point bending. The water absorption testing of all specimens was repeated five times in this study. All specimens were immersed in pure water during 9 days at room temperature, and dried in 1 day at $50^{\circ}C$. Two kinds of polymer matrices such as epoxy and vinyl-ester were used. Fractured surfaces were taken to study the failure mechanism and fiber/matrix interfacial adhesion. It is shown that it can be enhanced to improve their mechanical performance to reveal the relationship between fracture toughness and water absorption fatigue according to different polymer matrices. Water uptake of the epoxy composites was found to increase with cycle times. Mechanical properties are dramatically affected by the water absorption cycles. Water-absorbed samples showed poor mechanical properties, such as lower values of maximum strength and extreme elongation. The $K_{IC}$ values demonstrated a decrease in inclination with increasing cyclic times of wetting and drying for the epoxy and vinyl-ester.

• Journal of Industrial Technology
• /
• v.27 no.B
• /
• pp.137-144
• /
• 2007

Sintering condition and various chemical composition of bond materials for micro-blades were studied. The methods mixing of pure powders and using pre-alloyed powders for compaction and sintering were compared and optimized in terms of the evaluation of bending strength and fractographic study. The effect of the amount of graphite as a lubricant and diamond abrasive on the strength of sintered bond materials and fracture toughness was investigated. The strength decreased with increasing the amount of graphite and diamond abrasive.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.04a
• /
• pp.489-496
• /
• 2002

The lateral buckling of a laminated composite beam is studied. A general analytical model applicable to the lateral buckling of a composite beam subjected to various types of loadings is derived. This model is based on the classical lamination theory, and accounts for the material coupling for arbitrary laminate stacking sequence configuration and various boundary conditions. The effects of the location of applied loading on the buckling capacity are also included in the analysis. A displace-based one-dimensional finite element model is developed to predict critical loads and corresponding buckling modes for a thin-walled composite beam with arbitrary boundary conditions. Numerical results are obtained for thin-walled composites under central point load, uniformly distributed load, and pure bending with angle-ply and laminates. The effects of fiber orientation location of applied load, and types of loads on the critical buckling loads are parametrically studied.

• Steel and Composite Structures
• /
• v.3 no.3
• /
• pp.199-212
• /
• 2003

An experimental investigation of lightweight aggregate and foamed concrete contribution to the ultimate strength capacity of square and rectangular steel tube sections is presented in this study. Thirty-four simply supported beam specimens, 1000-mm long, filled with lightweight aggregate and foamed concretes were tested in pure flexural bending to calculate the ultimate moment capacity. Normal concrete-filled steel tubular and bare steel sections of identical dimensions were also tested and compared to the filled steel sections. Theoretical values of ultimate moment capacity of the beam specimens were also calculated in this study for comparison purposes. The test results showed that lightweight aggregate and foamed concrete significantly enhance the load carrying capacity of steel tubular sections. Furthermore, it can be concluded from this study that lightweight aggregate and foamed concretes can be used in composite construction to increase the flexural capacity of the steel tubular sections.