• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.13-22
• /
• 1999

Both the resonance and ultrasonic techniques are standard methods far characterizing the physical properties of piezoelectric materials. However, we found that each technique can only offer a few reliable measurements while the rest often have errors or impossible to implement because of the sample requirements. This paper show that one can use the combination of both techniques to achieve much better accuracy and be able to get the complete set of elastic, dielectric and piezoelectric coefficients using fewer samples. Using an ultrasonic spectroscopy we have also measure the dispersion of the ultrasonic velocity and the attenuation up to 65 MHz. Pb(Zr,Ti)O$_3$[PZT] ceramics were used as examples fur both studies.

• Journal of Sensor Science and Technology
• /
• v.22 no.5
• /
• pp.374-378
• /
• 2013

In this paper, a new structure of probe unit is designed and fabricated with PDMS, which is well-known elastic material, as a buffer layer for increasing overdrive force and mechanical strength. In general, PDMS is widely used as actuation material due to its elasticity and compatibility of fabrication process. In this work, PDMS layer is chosen for mechanical elasticity of the proposed probe unit. We achieved the high overdrive force by placing PDMS buffer layer under the silicon based cantilever due to its elasticity. Moreover, the relation between prove length and overdrive force was measured by experiment in this work. Therefore, the various specifications of the micro prove unit can be designed by using the results of this work.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.359-360
• /
• 2007

In this paper, the elastic modulus and hardness of poly 3C-SiC thin films growed by APCVD were measured using nanoindentation test. The resulting values of elastic modulus E and hardness H of the poly 3C-SiC film are 305 GPa and 26 GPa, respectively. The mechanical properties of the poly 3C-SiC film are better than bulk Si wafers. Therefore, the poly 3C-SiC thin film is suitable for abrasion resistance, high frequency, and bio MEMS applications.

• Advances in nano research
• /
• v.13 no.2
• /
• pp.147-164
• /
• 2022

This article investigates the longitudinal vibration of a nanorod embedded in viscoelastic medium according to the nonlocal strain gradient theory. Viscoelastic medium is considered based on Kelvin-Voigt model. Governing partial differential equation is derived based on longitudinal equilibrium and analytical solution is obtained by adopting harmonic motion solution for the nanorod. Modal frequencies and corresponding damping ratios are presented to demonstrate the influences of nonlocal parameter, material length scale, elastic and damping parameters of the viscoelastic medium. It is observed that material length scale parameter is very influential on modal frequencies especially at lower values of nonlocal parameter whereas increase in length scale parameter has less effect at higher values of nonlocal parameter when the medium is purely elastic. Elastic stiffness and damping coefficient of the medium have considerable impacts on modal frequencies and damping ratios, and the highest impact of these parameters on frequency and damping ratio is seen in the first mode. Results calculated based on strain gradient theory are quite different from those calculated based on classical elasticity theory. Hence, nonlocal strain gradient theory including length scale parameter can be used to get more accurate estimations of frequency response of nanorods embedded in viscoelastic medium.

• Computers and Concrete
• /
• v.25 no.6
• /
• pp.537-549
• /
• 2020

Geometrically nonlinear axisymmetric bending analysis of shear deformable circular plates on a nonlinear three-parameter elastic foundation was made. Plates ranging from "thin" to "moderately thick" were investigated for three types of material: isotropic, transversely isotropic, and orthotropic. The differential equations were discretized by means of the finite difference method (FDM) and the differential quadrature method (DQM). The Newton-Raphson method was applied to find the solution. A parametric investigation using seven unknowns per node was presented. The novelty of the paper is that detailed numerical simulations were made to highlight the combined effects of the material properties and the boundary conditions on (i) the deflection, (ii) the stress resultants, and (iii) the external load. The formulation was verified through comparison studies. It was observed that the results are highly influenced from the boundary conditions, and from the material properties.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.1009-1014
• /
• 1997

The small material removal rate of elastic emission machinong (EEM) becomes a serious problem due to using fine powder particles for obtaining finished of high quality. If a cylindrical polyurethane-wheel is used as a tool for accelerating powder particles, the efficiency of machining may be increased through enlarging the machining regionand increasing the surface velocity of the wheel. If these analyicl results are compared with experimental ones, characteristics of EEM using polyurethan-wheel can be clarified. In this study, effects of EEM using cylindrical polyurethane-wheel on the surface roughness and the material removal rate were verified through polishing of the brittle material under various conditions. The high-efficient polishing of silicon wafer has been also carried out using this method.

• Steel and Composite Structures
• /
• v.35 no.1
• /
• pp.147-157
• /
• 2020

In the present research, thermo-elastic buckling of small scale functionally graded material (FGM) nano-size plates with clamped edge conditions rested on an elastic substrate exposed to uniformly, linearly and non-linearly temperature distributions has been investigated employing a secant function based refined theory. Material properties of the FGM nano-size plate have exponential gradation across the plate thickness. Using Hamilton's rule and non-local elasticity of Eringen, the non-local governing equations have been stablished in the context of refined four-unknown plate theory and then solved via an analytical method which captures clamped boundary conditions. Buckling results are provided to show the effects of different thermal loadings, non-locality, gradient index, shear deformation, aspect and length-to-thickness ratios on critical buckling temperature of clamped exponential graded nano-size plates.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1-6
• /
• 2008

Due to the self-similarity of Berkovich and conical indenters, different materials may show the same loaddepth curve for single indentation. In this study, we first compare the load-depth characteristics of conical and Berkovich indenters via finite element method. We also analyze the variation of load-depth curves with angle of Berkovich indenter, indentation parameters, and material properties. With numerical regressions of obtained data, we then propose dual-Berkovich indentation formulae for material property evaluation. The proposed approach provides the values of elastic modulus, yield strength and strain-hardening exponent and corresponding stress-strain curve with an average error of less than 3%. The method is valid for any elastic indenters made of tungsten carbide and diamond for instance.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.6 no.3
• /
• pp.204-210
• /
• 1982

The mechanical behaviors of an elastic body containing another materials are studied with the statistical method since they are generally distributed at random in size, orientation, and position. As the basis of this research, the size, the shape, and the ratio of volume for another material assumed to be constant, and only the positions of another material are changed randomly. The stress intensity factor, the compliance, and the modulus of elasticity are investigated in two-dimensional state by using the Monte Carlo Method and the Finite Element Method. The methodology of the simulation analysis for the mechanical behavior of such material is also proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.812-815
• /
• 2002

The shape of K-R curve for an ideally brittle material is flat because the surface energy is an unvaried material property. However, the K-R curve can take on a variety of shapes when nonlinear material behavior accompanies fracture. By the way, a general metallic material is nonlinear, structural steel is such. Therefore, the J-R curve form J-integral value instead of K parameters can be used to evaluate elastic-plastic materials with flaws in terms of ductile fracture that can be significant to design. In this paper, R-curve behaviors form K and J parameter is considered for the precise assessment of fracture analysis, in case of JS-SS400 steels.