Young's Modulus and Hardness Characteristics of In-Situ-Doped Polycrystalline 3C-SiC Thin Films Measured by Using a Nanoindenter

정귀상,김강산,한기봉 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

3C-SiC thin films are widely used in extreme environments, radio frequency (RF) environments and bio-materials for micro/nano electronic mechanical systems (M/NEMS). The mechanical properties of 3C-SiC thin films need to be considered when designing M/NEMS, so Young's Modulus and the hardness need to be accurately measured. Young's Modulus and the hardness are in fluenced by N-doping. In this paper, we show that the mechanical properties of poly (polycrystalline) 3C-SiC thin films are in uenced by the N-doping concentration. Furthermore, we measure the mechanical properties of 3C-SiC thin lms for N-doping concentrations of 1 %, 3 % and 5 %, by using nanoindentation. For films deposited using a 1 % N-doping concentration, Young's Modulus and the hardness were measured as 270 GPa and 30 GPa, respectively. When the surface roughness of the thin films was investigated by using atomic force microscopy (AFM), the roughness of the 5 % N-doped 3C-SiC thin film was the lowest of all the films, at 15 nm. 3C-SiC thin films are widely used in extreme environments, radio frequency (RF) environments and bio-materials for micro/nano electronic mechanical systems (M/NEMS). The mechanical properties of 3C-SiC thin films need to be considered when designing M/NEMS, so Young's Modulus and the hardness need to be accurately measured. Young's Modulus and the hardness are in fluenced by N-doping. In this paper, we show that the mechanical properties of poly (polycrystalline) 3C-SiC thin films are in uenced by the N-doping concentration. Furthermore, we measure the mechanical properties of 3C-SiC thin lms for N-doping concentrations of 1 %, 3 % and 5 %, by using nanoindentation. For films deposited using a 1 % N-doping concentration, Young's Modulus and the hardness were measured as 270 GPa and 30 GPa, respectively. When the surface roughness of the thin films was investigated by using atomic force microscopy (AFM), the roughness of the 5 % N-doped 3C-SiC thin film was the lowest of all the films, at 15 nm.

A Study on the Effect of Young’s Modulus Modeling on the Energy Conservation in Elastic–Plastic Material Computation

Eun-Ho Lee 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.10

Young’s modulus has a strong effect on the mechanical behavior of elastic–plastic materials, such as elastic stiff ness, elastic recovery, and potential energy. Since springback prediction is important in the sheet metal forming process, many of Young’s modulus studies have been focused on capturing the amount of springback. This work investigated the effect of Young’s modulus modeling focusing on energy conservation point. For this study, three representative concepts of Young’s modulus modeling (fixed modulus, chord modulus, and nonlinear modulus models) were employed. The three modulus models were coupled with the Chaboche kinematic hardening, and implemented into the ABAQUS User-defined material subroutine. The models were used to simulate cyclic loading, monotonic loading conditions, and 2D-draw bending process including the springback prediction. The models showed good agreement with the measured data in the numerical studies. However, in the chord modulus model, a negative potential energy phenomenon was detected during the elastic recovery path, which is unrealistic, while the fixed and nonlinear modulus models keep the energy conservation law. This work discusses the reason for the negative potential energy computation based on the energy dissipation, and presents a numerical method to compensate the negative potential energy.

NR과 SBR 가황물의 경도와 강성도에 대한 온도의 영향

진현호 ( Hyun Ho Jin ),홍창국 ( Chang Kook Hong ),조동련 ( Dong Lyun Cho ),강신영 ( Shin Young Kaang ) 한국고무학회 2007 엘라스토머 및 콤포지트 Vol.42 No.3

본 연구에서는 고무제품의 수치 안정성과 성능유지에 직접적으로 영향을 미치는 중요한 특성 중 하나인 온도변화에 따른 고무재료의 경도변화를 고찰하였다. 새롭게 제작된 International Rubber Hardness Degree(IRHD, Normal type) 경도측정 시험기를 사용하여 미충전된 NR과 SBR시편의 여러 온도에서 경도변화를 측정하였으며 Young`s modulus 값과 비교하였다. NR과 SBR 모두 유리전이온도 근처에서 경도와 Young`s modulus의 급격한 변화를 보였다. 온도가 증가함에 따라 경도와 Young`s modulus 값이 증가하는 경향을 보였으며 이는 분자의 운동성과 엔트로피 영향으로 해석할 수 있다. 카본블랙과 실리카가 충전된 NR과 SBR의 경우 충전제의 함량이 증가함에 따라 경도에 미치는 온도의 영향이 감소함을 관찰하였다. Hardness of rubbery materials, which is important for dimensional stability and product performance, was investigated upon temperature change in this study. A newly developed IRHD (International Rubber Hardness Degree) tester was used to measure the hardness changes of NR and SBR specimens at various temperatures and the hardness values were compared with the Young`s modulus. The hardness and Young`s modulus of NR and SBR showed an abrupt change near the glass transition temperatures. The hardness and Young`s modulus were increased by increasing temperature due to the increased random chain conformation of molecules. The effect of temperature on hardness and Young`s modulus of NR and SBR specimens filled with carbon black and silica was decreased by increasing filler content.

Stability of a slender beam-column with locally varying Young's modulus

Kutis, Vladimir,Murin, Justin Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.23 No.1

A locally varying temperature field or a mixture of two or more different materials can cause local variation of elasticity properties of a beam. In this paper, a new Euler-Bernoulli beam element with varying Young's modulus along its longitudinal axis is presented. The influence of axial forces according to the linearized 2nd order beam theory is considered, as well. The stiffness matrix of this element contains the transfer constants which depend on Young's modulus variation and on axial forces. Occurrence of the polynomial variation of Young's modulus has been assumed. Such approach can be also used for smooth local variation of Young's modulus. The critical loads of the straight slender columns were studied using the new beam element. The influence of position of the local Young's modulus variation and its type (such as linear, quadratic, etc.) on the critical load value and rate of convergence was investigated. The obtained results based on the new beam element were compared with ANSYS solutions, where the number of elements gradually increased. Our results show significant influence of the locally varying Young's modulus on the critical load value and the convergence rate.

Proposal of Post-Processing Method for Ring Tensile Test Results for Relative Comparison of Young’s Modulus of Materials

JaeYong Kim,YongSik Yang,JuYeop Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Ring Tensile Test (RTT) is mainly performed for comparing tensile strength and total strain between nuclear fuel cladding specimens under various initial conditions. Through RTT, the loaddisplacement (F-D) curve obtained from the uniaxial tensile test can also be obtained. However, the Young’s modulus estimated from the gradient of the straight portion is much lower than general value of materials. The reasons include tensile machine compliance, slack in the fixtures, or elastic deformation of the fixtures and the tooling. Another reason is that the bending of the test part in the ring is stretched with two pieces of tools. Although the absolute value of the Young’s modulus is smaller than the actual value, it is applicable to calculate the ratio of the Young’s moduli of different materials, that is, the relative value. The Young’s modulus, or slope of the linear section, varies slightly depending on which location data is used and how much data is included. In order to obtain a more accurate ratio of Young’s moduli between materials using the RTT results, a post-processing method for the ring tensile test results that can prevent such human errors is proposed as follows. First, the slope of the linear section is obtained using the displacement and load when the load increase is the largest and the displacement and load of the position that is 95% of the maximum load increase. To replace the section where the ring-shaped specimen is stretched at the beginning of the F-D curve, a straight line equal to the slope of the linear section is drawn to the displacement axis from the position of maximum load increase and moved to the origin to obtain the final F-D curve for a RTT. Lastly, the yield stress uses the stress at the point where the 0.2% offset straight line and the F-D curve meet as suggested in the ASTM E8/E8M-11 “Standard test methods for tensile testing of metallic materials”. RTT results post-processing method was coded using FORTRAN language so that it could be performed automatically. In addition, sensitivity analysis of the included data range on the Young’s modulus was performed by using the included data range as 90%, 85%, and 80% of the maximum load increase.

전기 도금 법으로 제조된 Cu 박막 구조물의 탄성계수와 미세조직과의 연관성 연구

김영무(Youngmoo Kim),한준희(Jun-Hee Hahn),이창승(Chang Seung Lee),박준협(Jun-Hyub Park),홍순형(Soon Hyung Hong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

This paper reports on the manufacturing, surface morphology and Young's modulus of Cu thin films used as MEMS (micro-electro-mechanical systems) devices. Nanoindentation test and microcantilever bending test were performed to evaluate the mechanical properties, especially Young's modulus of these thin films. Cu thin film specimens were produced by MEMS fabrication techniques such as sputtering, electrochemical deposition, lithography and silicon bulk micromachining. Surface morphologies of specimens were measured by atomic force microscopy (AFM). Young's moduli of Cu electrodeposited films were decreased with increasing the thickness of specimens. From these results, it was shown that Young's modulus of Cu thin films had anisotropy with crystal orientations. Elastic moduli were varied with the thickness of thin film due to the texture of Cu thin films. Young's modulus of Cu thin films can be predicted by using two methods. One is to use the elastic modulus of single crystal and the information of distribution of crystal orientation, Voigt model. The other is to calculate it from load-deflection curves computed with ABAQUS. The theoretical estimation of elastic modulus using texture analysis showed good agreement with the results of nanoindentation test. But in computational modeling, Young's moduli were different from the results of bending test with isotropic and anisotropic Cu beams having (001) texture.

가속도계를 이용한 재료의 영계수 측정방법

손창호(Sohn, Chang-Ho),박진호(Park, Jin-Ho),윤두병(Yoon, Doo-Byung),정의필(Chong, Ui-Pil),최영철(Choi, Young-Chul) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.11

For the description of the elastic properties of linear objects a convenient parameter is the ratio of the stress to the strain, a parameter called the Young's modulus of the material. Young's modulus can be used to predict the elongation or compression of an object as long as the stress is less than the yield strength of the material. Conventional method for estimating Young's modulus measured the ratio of stress to corresponding strain below the proportional limit of a material using a tensile testing machine. But the method needs precision specimens and expensive equipment. In this paper, we proposed method for estimating Young's modulus using accelerometer. The basic idea comes from that the wave velocity is different as the Young's modulus. To obtain Young's modulus, a group velocity is obtained. It is difficult to measure group velocity. This is because plate medium has a dispersive characteristics which has different wave speed as frequency. In this paper, we used Wigner-Ville distribution to measure group velocity. To verify the proposed method, steel and acryl plate experiments have been performed. Experimental results show that the proposed method is powerful for estimating Young's modulus.

Characterization of Young’s modulus of silicon versus temperature using a ‘‘beam deflection” method with a four-point bending fixture

Chun-Hyung Cho 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Young’s modulus (E) and Poisson’s ratio (m) are dependent upon the direction on the silicon surface. In this work, E and m of silicon have been calculated analytically for any crystallographic direction of silicon by using compliance coefficients (s11, s12, and s44), and the values of E are confirmed experimentally by using a ‘‘beam deflection” method with a four-point bending fixture. Experimental results for E as a function of temperature from -150 ℃ to +150 ℃ are presented for (001) and (111) silicon wafers. Young’s modulus (E) and Poisson’s ratio (m) are dependent upon the direction on the silicon surface. In this work, E and m of silicon have been calculated analytically for any crystallographic direction of silicon by using compliance coefficients (s11, s12, and s44), and the values of E are confirmed experimentally by using a ‘‘beam deflection” method with a four-point bending fixture. Experimental results for E as a function of temperature from -150 ℃ to +150 ℃ are presented for (001) and (111) silicon wafers.

AN IN-SITU YOUNG'S MODULUS MEASUREMENT TECHNIQUE FOR NUCLEAR POWER PLANTS USING TIME-FREQUENCY ANALYSIS

Choi, Young-Chul,Yoon, Doo-Byung,Park, Jin-Ho,Kwon, Hyun-Sang Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.3

Elastic wave is one of the most useful tools for non-destructive tests in nuclear power plants. Since the elastic properties are indispensable for analyzing the behaviors of elastic waves, they should be predetermined within an acceptable accuracy. Nuclear power plants are exposed to harsh environmental conditions and hence the structures are degraded. It means that the Young's modulus becomes unreliable and in-situ measurement of Young's modulus is required from an engineering point of view. Young's modulus is estimated from the group velocity of propagating waves. Because the flexural wave of a plate is inherently dispersive, the group velocity is not clearly evaluated in temporal signal analysis. In order to overcome such ambiguity in estimation of group velocity, Wigner-Ville distribution as the time-frequency analysis technique was proposed and utilized. To verify the proposed method, experiments for steel and acryl plates were performed with accelerometers. The results show good estimation of the Young's modulus of two plates.

Effect of swaging on Young@?s modulus of β Ti-33.6Nb-4Sn alloy

Hanada, S.,Masahashi, N.,Jung, T.K.,Miyake, M.,Sato, Y.S.,Kokawa, H. Elsevier 2014 Journal of the mechanical behavior of biomedical m Vol.32 No.-

The effect of swaging on the Young's modulus of β Ti-33.6Nb-4Sn rods was investigated by X-ray diffraction, thermography, microstructural observations, deformation simulator analysis and cyclic tensile deformation. Stress-induced α'' martensite was stabilized by swaging, dependent on the diameter reduction rate during swaging. Thermography and deformation simulator analysis revealed that swaged rods were adiabatically heated, and consequently, stress-induced α'' underwent reverse transformation. Young's modulus, which was measured by the slope of the initial portion of the stress-strain curve, decreased from 56GPa in the hot-forged/quenched rod to 44GPa in the rapidly swaged rod with a high reduction rate and to 45GPa in the gradually swaged rod with a low reduction rate. The tangent modulus, which was measured by the slope of the tangent to any point on the stress-strain curve, decreased with strain even in the linear range of the stress-strain curve of the hot-forged/quenched rod and the rapidly swaged rod, while the tangent modulus remained unchanged for the gradually swaged rod. It was found that Young's moduli in swaged β Ti-33.6Nb-4Sn rods were affected by stabilized α'' martensite. Low Young's modulus of 45GPa and high strength over 800MPa were obtained when the reverse transformation by adiabatic heating was suppressed and the stress-induced α'' was sufficiently stabilized by gradual swaging to a 75% reduction in cross section area.