• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.550-554
• /
• 2014

Regarding thin films in MEMS/NEMS structures, the exact evaluation of mechanical properties is very essential to enhance the reliability of their design and manufacturing. However, such methods as a tensile test and a resonance test, general methods to measure elastic moduli, cannot be applied to thin films since its thickness is so small. This work concerns guided wave based elastic modulus measurement method. To this end, guided wave excitation and detection system using a pulsed laser and a laser interferometry has been established. Also an elastic modulus extraction algorithm from the measured guided wave signal was developed. Finally, it was applied to actual thin film structures such as Ni-Si and Al-Si multilayers. From experimental results, we confirm that the proposed method has considerable feasibility to measure elastic properties of thin films.

• Computers and Concrete
• /
• v.23 no.3
• /
• pp.161-170
• /
• 2019

This paper aims at presenting a numerical method for estimating the elastic modulus of recycled concrete with crushed aggregates. In the method, polygonal aggregates following a given sieve curve are generated, and placed into a square simulation element with the aid of the periodic boundary condition and the overlap criterion of two polygonal aggregates. The mesostructure of recycled concrete is reconstructed by embedding an old interfacial transition zone (ITZ) layer inside each recycled aggregate and by coating all the aggregates with a new ITZ layer. The square simulation element is discretized into a regular grid and a representative point is selected from each sub-element. The iterative method is combined with the fast Fourier transform to evaluate the elastic modulus of recycled concrete. After the validity of the numerical method is verified with experimental results, a sensitivity analysis is conducted to evaluate the effects of key factors on the elastic modulus of recycled concrete. Numerical results show that the elastic modulus of recycled concrete increases with the increase of the total aggregate content and the elastic moduli of old and new ITZ but decreases with increasing the replacement ratio of recycled aggregate and the thicknesses of old and new ITZ. It is also shown that, for a replacement ratio of recycled aggregate smaller than 0.3, the elastic modulus of recycled concrete is reduced by no more than 10%.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.21 no.6
• /
• pp.437-443
• /
• 2009

Impact echo method estimating the soundness of concrete measures the dynamic elastic modulus of specimens which are different with static elastic modulus tested by uni-axial compression test. Thus, this paper investigates the relationships between dynamic and static elastic modulus based on in-situ concrete cores. Also, dynamic elastic modulus was compared with compressive strength. Concrete cores were obtained from about 20 to 70 years concrete structures at three different harbors which were Incheon, Wando, and Masan in Korea. In order to investigate the influence of exposure condition on the relationship, air zone, splash zone, and tidal zone were selected. Different harbors showed the different relationships between dynamic and static elastic modulus, but exposure conditions have no influence on the relationship between dynamic and static elastic modulus. Also, the relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus. The relationship equations were proposed to estimate the relationships properly.

• The Journal of Engineering Geology
• /
• v.29 no.3
• /
• pp.339-349
• /
• 2019

The relationship between the P wave velocity, static elastic modulus, and dynamic elastic modulus of different rock types was investigated to identify the distributive characteristics of the dynamic elastic modulus. Laboratory and in situ test results from 1,646 rock specimens, which are obtained for design and construction of structure, were analyzed, and grouped into three key rock types: gneiss, granite, and sandstone. These relationships were verified by comparing them with the results from previous studies. The gneiss samples exhibit a linear P wave velocity-static elastic modulus relationship, whereas the granite and sandstone samples exhibit exponential relationships. Their coefficient of determination ($R^2$) values are all in the 0.491-0.642 range, and are similar to those obtained in previous studies. The relationship between the static and dynamic elastic modulus exhibits a linear relationship for all rock types, yielding a coefficient of determination in the 0.543-0.676 range. The relationship between the P wave velocity and static elastic modulus follows an exponential regression for all rock types, with a high coefficient of determination that is in the 0.875-0.940 range.

• Computers and Concrete
• /
• v.9 no.5
• /
• pp.389-402
• /
• 2012

In this study, the modulus of elasticity of low, normal and high strength steel fiber reinforced concrete has been predicted by developing a fuzzy logic model. The fuzzy models were formed as simple rules using only linguistic variables. A fuzzy logic algorithm was devised for estimating the elastic modulus of SFRC from compressive strength. Fibers used in all of the mixes were made of steel, and they were in different volume fractions and aspect ratios. Fiber volume fractions of the concrete mixtures have changed between 0.25%-6%. The results of the proposed approach in this study were compared with the results of equations in standards and codes for elastic modulus of SFRC. Error estimation was also carried out for each approach. In the study, the lowest error deviation was obtained in proposed fuzzy logic approach. The fuzzy logic approach was rather useful to quickly and easily predict the elastic modulus of SFRC.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.66 no.1
• /
• pp.15-24
• /
• 2024

Unlike artificially created homogeneous materials, the process of calculating the elastic modulus of natural soil involves the possibility of errors. Because the stress-strain behavior of soil is nonlinear, the secant modulus of elasticity is often used based on 1/2 of the stress at failure. Since soil has the property of changing its elastic modulus depending on the confining pressure, numerical analysis models that analyze its behavior inevitably include complex elements. The hyperbolic model, which relatively accurately simulates the behavior immediately after loading in soft ground, assumes that the stress-strain curve of the consolidated undrained triaxial test is hyperbolic and requires the slope of the tangent line at the starting point. However, the slope of the initial tangent in the stress-strain curve obtained from an actual triaxial test is difficult to have regularity according to changes in confining pressure. Additionally, due to the characteristics of a hyperbola, even small changes in related factors cause large changes in the hyperbola. Therefore, there is a lot of randomness in the process of calculating model parameters from the triaxial test results, which causes large differences in the results. Therefore, the method of calculating the initial elastic modulus by the consolidation test presented in this study is also used to verify the method by the triaxial test. It can be applied. However, since this study was applied to only one sample showing typical consolidation characteristics, it is necessary to check samples with various physical properties in the future.

• Journal of the Korean Ceramic Society
• /
• v.35 no.8
• /
• pp.813-818
• /
• 1998

A simple method to measure the elastic modulus E and Poisson's ratio v of diamod-like carbon (DLC) films deposited on Si wafer was suggested. Using the anisotropic etching technique of Si we could make the edge of DLC overhang free from constraint of Si substrate. DLC film is chemically so inert that we could not on-serve any surface damage after the etching process. The edge of DLC overhang free from constraint of Si substrate exhibited periodic sinusoidal shape. By measuring the amplitude and the wavelength of the sinu-soidal edge we could determine the stain of the film required to adhere to the substrate. Since the residual stress of film can be determine independently by measurement of the curvature of film-substrate com-posite we could calculated the biaxial elastic modulus E/(1-v) using stress-strain relation of thin films. By comparing the biaxial elastic modulus with the plane-strain modulus E/(1-{{{{ { v}^{2 } }}) measured by nano-in-dentation we could further determine the elastic modulus and Poisson's ratio independently. This method was employed to measure the mechanical properties of DLC films deposited by {{{{ { {C }_{6 }H }_{6 } }} rf glow discharge. The was elastic modulus E increased from 94 to 169 GPa as the {{{{ { V}_{ b} / SQRT { P} }} increased from 127 to 221 V/{{{{ {mTorr }^{1/2 } }} Poisson's ratio was estimated to be abou 0.16∼0.22 in this {{{{ { V}_{ b} / SQRT { P} }} range. For the {{{{ { V}_{ b} / SQRT { P} }} less than 127V/{{{{ {mTorr }^{1/2 } }} where the plastic deformation can occur by the substrate etching process however the present method could not be applied.

• International Journal of Highway Engineering
• /
• v.13 no.1
• /
• pp.33-40
• /
• 2011

The resilient modulus which is presented mechanical properties of compacted subbase material is the design parameter on the Mechanistic - Empirical pavement design guide. The compaction control method on the Mechanistic - Empirical pavement design guide will be the way to confirm whether the in-situ elastic modulus measured after the compaction meets the resilient modulus which is applied the design. The resilient modulus in this study is calculated by the neural network suggested by Korea Pavement Research Program, and degree of compaction as the existing compaction control test and plate bearing capacity test(PBT) was performed to confirm whether the in-situ elastic modulus is measured. The Light Falling Weight Deflectometer(LFWD) is additionally tested for correlation analysis between each in-situ elastic modulus and resilient modulus, and is proposed correlation equation and test interval which can reduced overall testing cost. Also, the subbase compaction control procedure based on the in-situ elastic modulus is proposed using the in-situ PBT and LFWD test result.

• Journal of the Korean Vacuum Society
• /
• v.19 no.5
• /
• pp.360-364
• /
• 2010

Most research groups used two analysis methods (spectroscopy and nanotribology) to measure the mechanical properties of nano-materials: NMR (Nuclear Magnetic Resonance), IR (Infrared Spectroscopy), Raman Spectroscopy as the spectroscopy method and AFM (Atomic Force MicroScope), EFM (Electrostatic Force Microscope), KFM (Kelvin Force Microscope), Nanoindenter as the nanotribological one. Among these, the nano-indentation technique particularly has been recognized as a powerful method to measure the elastic modulus and the hardness. However, this technique are prone to considerable measurement errors with pressure conditions during measurement. In this paper, we measured the change of elastic modulus and hardness of an Al single crystal with the change of load, hold, and unload time, respectively. We found that elastic modulus and hardness significantly depend on load, hold, and unload time, etc. As the indent time was shortened, the elastic modulus value decreased while the hardness value increased. In addition, we found that elastic modulus value was more sensitive to indent load, hold, and unload time than the hardness value. We speculate that measurement errors of the elastic modulus and the hardness originate from the residual stress during indenting test. From our results, the elastic modulus was more susceptible to the residual stress than the hardness. Thus, we find that the residual stress should be controlled for the minimum measurement errors during the indenting test.

• Journal of the Korean Vacuum Society
• /
• v.18 no.5
• /
• pp.372-376
• /
• 2009

In the modern semiconductor industry, lithography process is used to construct specific patterns. However, due to the decreasing of line width, these days, more and more researchers are interested in PMMA(Poly Methyl Methacrylate) lithography by using e-beam instead of the prior method, PR(Photoresist) lithography by using UV(Ultra-Violet). Additionally, the patterns constructed by lithography are collapsed during the process of cleansing remnants and the resistance against the breakdown of the patterns is known to be proportional to the elastic modulus of pattern-constructing materials. In this research, we measured the change of hardness and elastic modulus of PMMA film surface according to the change of time spent to soft-bake the PMMA film. During the measurement, we controlled the tip pressure from $25{\mu}N$ to $8,500{\mu}N$ having intervals that are $134.52{\mu}N$. For these measurements, we used the Triboindenter from Hysitron to gauge the hardness and elastic modulus and the tip we used was Berkovich diamond Tip.