检索结果-内蒙古大学图书馆

11th International Conference on Fracture 2005, ICF11

作者： Bammann, D.J. Sofronis, P. Center for Materials and Engineering Science Sandia National Laboratories Livermore CA 94550 United States Department of Theoretical and Applied Mechanics University of Illinois Urbana IL 61801 United States

ISBN: (纸本)9781617820632

An inelastic model is developed within the thermodynamic framework of Gurtin to describe the hydrogen effect on material deformation. Internal state variables associated with statistically stored dislocations, the concentration of hydrogen, and associated gradients are introduced into the Helmholtz free energy, in addition to the standard variables of elastic strain and temperature. The power expended by microforces related to the hydrogen solutes and concentration gradients is included in the thermodynamics, and these forces are required to satisfy equilibrium conditions at the micro level. The theory is developed for small strains, whereby the total strain is decomposed into the sum of contributions form elasticity, plasticity (dislocation) and hydrogen effects. Thermodynamic restrictions from the dissipation inequality result in the restriction that the stress and microforces are defined as derivatives of the free energy with respect to elastic strain, and hydrogen concentration and its gradient, respectively. Furthermore, a general form for the chemical potential is constructed based upon thermodynamic restrictions. It is a function of the hydrogen concentration and its gradient, and includes the effects of hydrogen on lattice dilatation and dislocation density. Mass balance for the hydrogen results in Fick's law (hydrogen rate is proportional to the flux of hydrogen). The flux is then expressed as the divergence of a function proportional to the gradient of the chemical potential. The energy balance yields a heat conduction equation that includes plastic working as a source term (dissipation) and also the effects of dislocation storage and hydrogen. The plastic flow rule is based upon the thermally activated motion of dislocations over local barriers, and therefore depends upon the von Mises stress. The strength of the activation barrier depends upon the internal strength of the material through the statistically stored dislocations. These dislocations are stor

关键词： Free energy

来源：评论

学校读者我要写书评

暂无评论

Characterization of thin films and intermetallic compounds in solder joint

Characterization of thin films and intermetallic compounds i...

引用

6th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Micro-Electronics and Micro-Systems - EuroSimE 2005

作者： Tsai, Iting Tai, Li Jung Yen, S.F. Chuang, T.H. Lo, Robert Ku, Terry Wu, Enboa Institute of Applied Mechanics National Taiwan University Department of Materials Science and Engineering National Taiwan University Electronics Research and Service Organization Industrial Technology Research Institute VIA Technologies Inc. Taiwan Taiwan

ISBN: (纸本)0780390628

Numerical simulation such as finite element methods have been widespread in structure designs and analyses in IC industry and researches. Only if the inputs of material properties are correct, can the outcome be referable to its applications. Thin-film materials have been widely used in many applications. The mechanical properties of thin films may be markedly distinct with different processes and processing conditions. To study the mechanical behvoir of thin films, thin films on substrates are adopted most often [1]. The most commonly used material for substrate is silicon, which has low coefficient of thermal expansion (CTE) and is a prevalent semiconductor material. The theoretical values of Young's moduli of silicon were usually applied. However, the values might be different in practice. Before further study of thin-films, the actual mechanical properties of silicon substrates should be cautiously investigated first. Intermetallic compounds (IMC) are formed when interconnections in IC packages are jointed with solder. Though IMC just comes into a small amount, it usually dominates the reliability of the interconnections because of its characteristic material properties. Individual mechanical properties of a solder/IMC/UBM layered structure are required for simulation and analyses of the interconnection reliability, but always difficult to obtain because the thickness of each layer is on micrometer order. Further, it is impossible to separate each thin layer and apply commercially available testing machines to test it. In this extended abstract, we present results and methods for obtaining mechanical properties of silicon substrates and IMC formed at the interface between lead-free solders and the copper substrate. To determine the mechanical properties of the silicon substrate, 255 um (100) and 306 um (110) thick silicon wafers with double side ground were adopted. In the original crystallographic orientation, there are three independent elastic constants for s

关键词： Thin films

来源：评论

学校读者我要写书评

暂无评论

Identification of mechanical properties of intermetallic compounds on lead-free solder

Identification of mechanical properties of intermetallic com...

引用

55th Electronic Components and Technology Conference, ECTC

作者： Tsai, Iting Tai, Li Jung Yen, S.F. Chuang, T.H. Lo, Robert Ku, Terry Wu, Enboa Institute of Applied Mechanics National Taiwan University Taiwan Department of Materials Science and Engineering National Taiwan University Taiwan Electronics Research and Service Organization Industrial Technology Research Institute Taiwan VIA Technologies Inc. Taiwan

In this paper, we present methods for obtaining mechanical properties of silicon substrates and two intermetallic compounds (IMC) formed at the interfaces between lead-free solders and the copper and between lead-free solders and nickel substrates. To determine the mechanical properties of the silicon substrate, 255 um (100) and 306 um (110) thick silicon wafers were adopted. With proper sensor locations of strain gages and ANSYS finite element models, the in-plane Young's moduli were optimally determined to be E〈100〉= 101.6 GPa, E〈110〉=140.7 GPa, E〈-110〉= 140.5 GPa, which agreed with the trend of theoretical values in each orientation. Some defects made the Young's moduli smaller than the theoretical values. Further, the in-plane Young's moduli of the anisotropic (110) wafer were inversely determined to be E〈-111〉= 170.1 GPa, E〈1-12〉=157. 9 GPa, which were also smaller but closer to the theoretical values because of its thicker thickness. For IMC material properties, two types of lead free solder were used, namely, SnZn and Sn. For the IMC mechanical property determination using SnZn solder, specimens were prepared by dipping to overcome the poor wetting problem. A uniform layer of Cu33.5Zn66.5 IMC was then formed. For out-of-plane Young's modulus measurement, the specimen was pressed by a nanoindentor. An average value for the Young's modulus was recorded to be 158 GPa. With the whole field slope measurement method, the reflection moiré, the CTE of Cu33.4Zn66.5 was found to be approximate to that of copper. As for the Cu-Sn intermetallic compounds, electroplating was used to have an even tin layer on copper substrates. After soldering reaction and annealing, there existed two phases of Cu-Sn IMC, Cu6Sn5 and Cu3Sn. With the nanoindentor, average values for the Young's moduli were determined to be 124 GPa for Cu6Sn5 and 143 GPa for Cu3Sn. The warpage change of Cu3Sn/copper foil structure under thermal load is adopted for the CTE of Cu3Sn, which is determined to be 1

关键词： Intermetallics

来源：评论

学校读者我要写书评

暂无评论

Fatigue of self-healing polymers: Multiscale analysis and experiments

Fatigue of self-healing polymers: Multiscale analysis and ex...

引用

11th International Conference on Fracture 2005, ICF11

作者： White, S.R. Maiti, S. Jones, A.S. Brown, E.N. Sottos, N.R. Geubelle, P.H. Department of Aerospace Engineering University of Illinois Urbana IL 61801 United States Department of Theoretical and Applied Mechanics University of Illinois Urbana IL 61801 United States Materials Science and Technology Division Los Alamos National Laboratory Los Alamos NM 87545 United States

ISBN: (纸本)9781617820632

Self-healing polymers were recently developed at the University of Illinois by incorporating a microencapsulated healing agent and chemical catalyst in a polymer matrix. Whenever damage occurs, the repair process is triggered and after sufficient healing time the inherent strength and toughness of the material is recovered. Self-healing polymers are designed to heal the microcracks that occur naturally during fatigue, thereby preventing large-scale cracks from forming. In this paper we report on the fatigue response of self-healing epoxy and show that under certain conditions fatigue cracks can be permanently arrested when the chemical kinetics of healing are much faster than the mechanical kinetics of crack growth. To understand the complex role that various kinetic processes have on the ultimate fatigue behavior of self-healing polymers we have developed a multiscale analytical model of fatigue crack growth from molecular dynamic (MD) simulations of the curing reaction of the healing agent to a cohesive volumetric finite element (CVFE) description of the self-healing polymer system. We show that good agreement with experiments can be obtained by properly calibrating the cohesive law that is used in the CVFE simulations. Our cohesive law describes the natural competition between progressive degradation of the cohesive properties associated with the fatigue process and their restoration through self-healing. Ultimately, the cohesive law and its kinetic description will be directly linked to MD level simulations of the healing process.

关键词： Reaction kinetics

来源：评论

学校读者我要写书评

暂无评论

Renormalization-group and numerical analysis of a noisy Kuramoto-Sivashinsky equation in 1+1 dimensions

引用

Physical Review E 2005年第4期71卷 046138-046138页

作者： K. Ueno H. Sakaguchi M. Okamura Research Institute for Applied Mechanics Kyushu University Kasuga Fukuoka 816-8580 Japan Department of Applied Science for Electronics and Materials Interdisciplinary Graduate School of Engineering Sciences Kyushu University Kasuga Fukuoka 816-8580 Japan

The long-wavelength properties of a noisy Kuramoto-Sivashinsky (KS) equation in 1+1 dimensions are investigated by use of the dynamic renormalization group (RG) and direct numerical simulations. It is shown that the noisy KS equation is in the same universality class as the Kardar-Parisi-Zhang (KPZ) equation in the sense that they have scale invariant solutions with the same scaling exponents in the long-wavelength limit. The RG analysis reveals that the RG flow for the parameters of the noisy KS equation rapidly approach the KPZ fixed point with increasing strength of the noise. This is supplemented by numerical simulations of the KS equation with a stochastic noise, in which scaling behavior close to the KPZ scaling can be observed even in a moderate system size and time.

关键词： LONG-WAVELENGTH PROPERTIES LARGE-SCALE PROPERTIES GROWING INTERFACES STOCHASTIC-MODEL TIME

来源：评论

学校读者我要写书评

暂无评论

Collagen content and organization relate to bone nanomechanical properties

Collagen content and organization relate to bone nanomechani...

引用

2005 Materilas Research Society Spring Meeting

作者： Donnelly, Eve Williams, Rebecca M. Baker, Shefford P. Van der Meulen, Marjolein C. H. Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca NY United States Department of Applied and Engineering Physics Cornell University Ithaca NY United States Department of Materials Science and Engineering Cornell University Ithaca NY United States Musculoskeletal Integrity Program Hospital for Special Surgery New York NY United States

Cancellous bone plays an important load-bearing role in the skeleton, yet relatively little is known about the microstructure-mechanical property relationships of the tissue at the sub-10 μm level. Cancellous tissue is characterized by a layered microstructure with variable proportions of collagen and mineral. The lamellar material is substantially stiffer than the interlamellar material at the nanomechanical level. However, the microstructural origin of the observed differences in mechanical properties of these structures has not been investigated. In this study, second harmonic generation microscopy was used to examine collagen in human vertebral cancellous bone. At the same location in the tissue, nanoindentation was used to assess the indentation modulus of lamellar and interlamellar bone. The stiff lamellae corresponded to areas of highly ordered, collagen-rich material, while the compliant interlamellar regions corresponded to areas of unoriented or collagen-poor material. The lamellar bone was approximately 30% stiffer and contained approximately 50% more oriented collagen than the interlamellar bone. These observed differences in the mechanical properties and collagen content and organization of lamellar and interlamellar tissue are consistent with previous scanning electron microscopy studies showing greater mineral and collagen content and organization in lamellar bone. Given the well-known coupling between collagen and mineral in bone tissue, the mineral distribution may mirror that of the aligned collagen. However, similar measurements of local variations in mineral content are needed to confirm this hypothesis and may provide additional insights into the tissue nanomechanical behavior. © 2005 materials Research Society.

关键词： Bone

来源：评论

学校读者我要写书评

暂无评论

Elastic Self-Healing during Shear Accommodation in Crystalline Nanotube Ropes

引用

Physical Review Letters 2005年第6期94卷 065502-065502页

作者： Haiyi Liang Moneesh Upmanyu Department of Modern Mechanics University of Science and Technology of China Hefei People's Republic of China Group for Simulation and Theory of Atomic-Scale Material Phenomena (stAMP) Materials Science Program Division of Engineering Colorado School of Mines Golden Colorado 80401 USA

Rigid-tube computations of simple (transverse) shear in crystalline nanotube ropes (CNTRs) reveal that shear modulus and strength increase and decrease with the tube radius, respectively. High modulus to strength ratios suggest that dislocations play a minor role during their plasticity. The computed shear moduli are in agreement with previous studies, although shape change and rolling-based shear may modify low strain and temperature behavior. The instability past the shear strength is due to shear localization via interlayer sliding, wherein stress relief results in significant elastic energy dissipation. Large-tube radius CNTRs accommodate large strains at minimal energetic cost during sliding, due to the increasingly cohesive and short range nature of the intertube potential. Fascinatingly, the crystal aids its recovery, implying that CNTRs may be promising materials for energy absorption and tribology.

关键词： .shape change PRL energetic cost shear strength shear modulus shear localization transverse shear tube radius intertube Elastic Self-Healing Shear Accommodation Crystalline Nanotube Ropes Rigid-tube CNTRs Large-tube

来源：评论

学校读者我要写书评

暂无评论

Femtosecond laser ablation of silicon (100) with thermal oxide thin films of varying thickness

Femtosecond laser ablation of silicon (100) with thermal oxi...

引用

Conference on Lasers and Electro-Optics, CLEO 2005

作者： McDonald, Joel P. Ray, Katherine E. Mistry, Vanita R. Mourou, Gérard Yalisove, Steven M. Center for Ultrafast Optical Science Department of Electrical Engineering University of Michigan Ann Arbor MI 48109-2099 United States Applied Physics Program 2477 Randall Laboratory University of Michigan Ann Arbor MI 48109-1120 United States College of Engineering University of Michigan Ann Arbor MI 48109 United States Department of Materials Science and Engineering 2200 Hayward Street Ann Arbor MI 48109-2136 United States

Femtosecond laser ablation of Silicon (100) with thermal oxide thin films was studied in order to further understand the ablative properties of thin films and to evaluate their influence on the ablation of the substra... 详细信息

ISBN: (纸本)1557527709

关键词： Laser ablation

来源：评论

学校读者我要写书评

暂无评论

Recovery of hardness, impact properties and microstructure of neutron-irradiated weld joint of a fusion candidate vanadium alloy

Recovery of hardness, impact properties and microstructure o...

引用

作者： Nagasaka, Takuya Muroga, Takeo Watanabe, Hideo Yamasaki, Kazuhiro Heo, Nam-Jin Shinozaki, Kenji Narui, Minoru National Institute for Fusion Science Toki 509-5292 Japan Research Institute for Applied Mechanics Kyushu University Kasuga 816-8580 Japan Interdisciplinary Graduate School of Engineering Sciences Kyushu University Kasuga 816-8580 Japan Center for Advanced Research of Energy Conversion Materials Hokkaido University Sapporo 060-8628 Japan Department of Mechanical System Engineering Graduate School of Engineering Hiroshima University Higashi Hiroshima 739-8527 Japan International Research Center for Nuclear Materials Science Institute for Materials Research Tohoku University Oarai 311-1313 Japan

Weld samples of fusion reactor vanadium alloy (NIFS-HEAT-2) were neutron-irradiated at 563 K up to 4.5 × 1023 neutrons/m 2 (0.08 dpa). The recovery of irradiation hardening, degradation of impact properties, and damage structures in the weld metal were investigated after post-irradiation isothermal annealing at temperatures between 673 and 1073 K. Irradiation hardening and the decrease in impact absorbed energy at 77 K were larger for the weld metal than for the base metal. Recovery of the hardening by post-irradiation annealing was coincident with recovery of the impact absorbed energy in both the weld metal and the base metal. Recovery of the mechanical properties required post-irradiation annealing at 1073 K for 1 h for the weld metal, which was 100 to 200 K higher than that for the base metal. The dislocation loops introduced by the neutron irradiation are likely to account for the hardening. The dislocation loops were observed even after annealing at 973 K in the weld metal, whereas they disappeared in the base metal. The characteristics of the radiation defects in the weld metal and the mechanisms for irradiation hardening and embrittlement are discussed. © 2005 The Japan Institute of Metals.

关键词： Welds

来源：评论

学校读者我要写书评

暂无评论

Physical origin of directional beaming emitted from a subwavelength slit

引用

Physical Review B 2005年第4期71卷 041405(R)-041405(R)页

作者： Liang-Bin Yu Ding-Zheng Lin Yi-Chun Chen You-Chia Chang Kuo-Tung Huang Jiunn-Woei Liaw Jyi-Tyan Yeh Jonq-Min Liu Chau-Shioung Yeh Chih-Kung Lee Institute of Applied Mechanics National Taiwan University Taipei Taiwan Materials Research Laboratory Industrial Technology Research Institute Hsinchu Taiwan Institute of Engineering Science and Ocean Engineering National Taiwan University Taipei Taiwan Department of Engineering and Applied Sciences National Science Council Taiwan

We propose the physical origin for a directional beam of light emitting from a single subwavelength slit in metallic film that is characterized by a corrugation feature at the exiting side of the film. We theorize that the beaming phenomenon can be explained simply as surface plasmon diffraction along the corrugation as long as the multiple scattering effects are taken into account to restate the dispersion relationship of the surface plasmon. In order to prove our theory, both an experimental setup and numerical simulations were undertaken. Results obtained match well with our theory of an explanation based on a surface plasmon diffraction scheme.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：