Si-Young Kwak
,
Jae-Wook Baek
,
Jeong-Ho Nam
,
Jeong-Kil Choi
材料科学技术（英）
It is important to analyse the casting product and the mold at the same time considering thermal contraction of the casting and thermal expansion of the mold. The analysis considering contact of the casting and the mold induces the precise prediction of stress distribution and the defect such as hot tearing. But it is difficult to generate FEM mesh for the interface of the casting and the mold. Moreover the mesh for the mold domain spends lots of computational time and memory for the analysis due to a number of meshes. Consequently we proposed the virtual mold technique which only uses mesh of the casting part for thermal stress analysis in casting process. The spring bar element in virtual mold technique is used to consider the contact of the casting and the mold. In general, a volume of the mold is much bigger than that of casting part, so the proposed technique decreases the number of mesh and saves the computational memory and time greatly. In this study, the proposed technique was verified by the comparison with the traditional contact technique on a specimen. And the proposed technique gave satisfactory results.
关键词:
Casting process
,
null
,
null
李朝升
,
王先平
,
方前锋
金属学报
利用振簧技术测量了不同退火状态下的nc-TiN／a-Si3N4超硬薄膜的Young's模量和内耗随温度的变化关系．在280--300℃附近观察到一个弛豫内耗峰．随着退火温度的升高，该内耗峰逐渐减弱，而Young's模量变化不大，750℃退火后，该内耗峰消失，而模量却从未退火时的430GPa激增至530GPa，初步认为该内耗峰来源于非稳定界面的弛豫过程.
关键词:
纳米TiN／非晶Si3N4薄膜
李朝升
,
王先平
,
方前锋
,
S.Veprek
,
李世直
金属学报
doi:10.3321/j.issn:0412-1961.2003.11.019
利用振簧技术测量了不同退火状态下的nc-TiN/a-Si3N4超硬薄膜的Young's模量和内耗随温度的变化关系.在280-300℃附近观察到一个弛豫内耗峰.随着退火温度的升高,该内耗峰逐渐减弱,而Young's模量变化不大.750℃退火后,该内耗峰消失,而模量却从未退火时的430 GPa激增至530 GPa.初步认为该内耗峰来源于非稳定界面的弛豫过程.
关键词:
纳米TiN/非晶Si3N4薄膜
,
内耗
,
Young's模量
,
非稳定界面
Zeitschrift Fur Metallkunde
Young's equation is discussed on a thermodynamic basis. The result shows that the equation is a thermodynamic equilibrium of the wetting system rather than a force balance. The equilibrium satisfies the general equilibrium condition, that is, Gibbs free energy should be minimum when the wetting equilibrium is reached. The validity of Young's equation is only limited to some special cases, namely if the droplet shape is an exact sphere sector. It implies that Young's equation can only be used in the case without the action of gravity. If the curve of the liquid surface changes, the term of cos theta in Young's equation should be replaced by another functional form of the contact angle theta. In the discussion, the author suggests that, in the case of a solid, the surface energy should be considered rather than the surface tension, and the concept of a solid surface tension should be reconsidered based on the difference between a liquid surface and a solid surface.
关键词:
Zhimin ZHOU
,
Yong ZHOU
,
Mingjun WANG
,
Chunsheng YANG
,
Ji'an CHEN
,
Wen DING
,
Xiaoyu GAO
,
Taihua ZHANG
材料科学技术（英）
Microbridge testing was used to measure the Young's modulus and residual stress of metallic films. Samples of freestanding NiFe film microbridge were fabricated by microelectromechanical systems. Special ceramic shaft structure was designed to solve the problem of getting the load-deflection curve of NiFe film microbridge by the Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of load-deflection curves of the microbridges was proposed to evaluate the Young's modulus and residual stress of the films simultaneously. The calculated results based on experimental measurements show that the average Young's modulus and residual stress for the electroplated NiFe films are 203.2 GPa and 333.0 MPa, respectively, while the Young's modulus measured by the Nano-hardness method is 209.6±11.8 GPa for the thick NiFe film with silicon substrate.
关键词:
Mechanical properties
,
金属薄膜
,
纳米压痕
Wuzhu YAN
金属学报(英文版)
doi:10.1016/S1006-7191(08)60125-8
The flat cylindrical indentation tests with different sizes of punch radius were investigated using finite element method (FEM) aimed to reveal the effect of punch size on the indentation behavior of the film/substrate system. Based on the FEM results analysis, two methods was proposed to separate film's reduced Young's modulus from a film/substrate system. The first method was based on a new weight function that quantifies film's and substrate's contributions to the overall mechanical properties of the film/substrate system in the flat cylindrical indentation test. The second method, a numerical approach, including fitting and extrapolation procedures was put forward. Both of the results from the two methods showed a reasonable agreement with the one input FE model. At last, the effect of maximum indentation depth and the surface micro-roughness of the thin film on the reduced Young's modulus of the film/substrate system were discussed. The methods proposed in the present study provide some new conceptions on evaluating other properties of thin films, e.g. creep, for which a flat-ended punch is also employed.
关键词:
Indentation test
,
表观杨氏模量
,
压痕测试；压头尺寸效应；权重方程
Y. Zhou
,
C.S. Yang
,
J.A. Chen
,
G.F. Ding
,
L. Wang
,
M.J. Wang
,
Y.M. Zhang
,
T.H. Zhang
金属学报(英文版)
Microbridge testing is used to measure the Young's modulus and residual stresses of
metallic films. Nickel film microbridges with widths of several hundred microns are
fabricated by Microelectromechanical Systems. In order to measure the mechanical
properties of nickel film microbridges, special shaft structure is designed to solve the
problem of getting the load-deflection curves of metal film microbridge by Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of the microbridge load-deflection curve is proposed to evaluate the Young's modulus and residual
stress of the films simultaneously. The calculated results based on the experimental
measurements show that the average Young's modulus and residual stress are around
190GPa and 175MPa respectively, while the Young's modulus measured by Nano-
hardness method on nickel film with silicon substrate is 186.8±7.34GPa.
关键词:
nickel film microbridge
,
null
,
null
,
null
郭振丹
,
王秀芳
,
杨晓萍
,
蒋冬梅
,
马学鸣
,
宋洪伟
金属学报
doi:10.3321/j.issn:0412-1961.2008.08.002
采用纳米压入(nanoindentation)和电子背散射衍射(EBSD)技术对多晶Cu样品多个晶粒进行了微观力学性能表征和晶体取向分析.结果表明,Young's模量随晶粒表面法向方向(hkl)与(111)和(001)最小夹角的变化有明显的规律:(hkl)越接近(111),其Young's模量越大;(hkl)越接近(001),其Young's模量越小;而Young's模量随(hkl)与(110)最小夹角的变化无明显规律.硬度随(hkl)与(111),(110)和(001)最小夹角的变化均无明显规律.通过理论计算讨论了上述规律性.
关键词:
多晶铜
,
晶体取向
,
纳米压入
,
电子背散射衍射
,
Young's模量
,
硬度
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Quaternary Ti-(20-26)Nb-(2-8)Zr-(3.5-11.5)Sn (.wt%) alloys were investigated to evaluate the effects of Zr and Sri on Young's modulus and superelasticity of Ti-Nb-based alloys. X-ray diffraction analysis showed that solution-treated alloys have beta + alpha", beta + omega, alpha" + omega, alpha", or beta microstructures. Zr and Sn increase the lattice parameters of the beta phase; for orthorhombic alpha" matensite, they increase the lattice parameter a but decrease both b and c. The martensitic start temperature of the alpha" is depressed by Zr and Sri additions, whereas the formation of athermal w is dependent on Zr and Sn contents. Differential scanning calorimetry (DSC) measurements show that 1 wt% of Nb, Zr or Sn addition decreases the martensitic start temperature by 17.6, 41.2 or 40.9 K, respectively, due to their negative effect on lattice parameter ratios of the martensite (c/a and b/a). Tensile tests were used to evaluate Young's modulus and superelasticity of the solution-treated alloys. Of the studied alloys Ti-24Nb-4Zr-7.5Sn with single P microstructure has the lowest Young's modulus of 52 GPa and recoverable elastic strain of about 2% at room temperature after cyclic strain. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
Young's modulus;superelasticity;biomedical titanium alloy;martensitic;transformation;alloying effect;shape-memory behavior;mechanical-properties;biomedical applications;plastic-deformation;induced martensite;titanium-alloy;mo alloys;ti-29nb-13ta-4.6zr;ta;ti-10v-2fe-3al
Applied Physics Letters
Based on a self-similar array model, we systematically investigated the axial Young's modulus (Y-axis) of single-walled carbon nanotube (SWNT) arrays with diameters from nanometer to meter scales by an analytical approach. The results show that the Y-axis of SWNT arrays decreases dramatically with the increases of their hierarchy number (s) and is not sensitive to the specific size and constitution when s is the same, and the specific Young's modulus Y-axis(s) is independent of the packing configuration of SWNTs. Our calculations also show that the Y-axis of SWNT arrays with diameters of several micrometers is close to that of commercial high performance carbon fibers (CFs), but the Y-axis(s) of SWNT arrays is much better than that of high performance CFs. (C) 2005 American Institute of Physics.
关键词:
mechanical-properties;ropes;fibers;bundles
