Creep characterization of a fiber reinforced plastic material

Creep behavior of [±45°]_s composite material is characterized by using uniaxial creep and recovery tests. The well-known Schapery nonlinear viscoelastic consti tutive relation was modified to make it suitable for characterizing the creep behavior of this material. Then, using this modified Schapery constitutive equation, by which the vis coplastic and creep damage can be taken into consideration, the creep behavior of [±45°]. glass fiber reinforced epoxy laminate was studied. The constitutive parameters of the material were determined experimentally, and the procedure and method of determination of the material parameters are proved to be valid.

Quantum and variational monte-carlo interaction potentials for li2 (x1-sigma-g+)

Optimized trial functions are used in quantum Monte Carlo and variational Monte Carlo calculations of the Li₂(X ¹Σ⁺_g) potential curve. The trial functions used are a product of a Slater determinant of molecular orbitals multiplied by correlation functions of electron—nuclear and electron—electron separation. The parameters of the determinant and correlation functions are optimized simultaneously by reducing the deviations of the local energy E_L (E_L  Ψ⁻¹_THΨ_T, where Ψ_T denotes a trial function) over a fixed sample. At the equilibrium separation, the variational Monte Carlo and quantum Monte Carlo methods recover 68% and 98% of the correlation energy, respectively. At other points on the curves, these methods yield similar accuracies.

Fatigue crack-growth rate in ferrite martensite dual-phase steel

An empirical study is made on the fatigue crack growth rate in ferrite-martensite dual-phase (FMDP) steel. Particular attention is given to the effect of ferrite content in the range of 24.2% to 41.5% where good fatigue resistance was found at 33.8%. Variations in ferrite content did not affect the crack growth rate when plotted against the effective stress intensity factor range  which was assumed to follow a linear relation with the crack tip stress intensity factor range ΔK. A high  corresponds to uniformly distributed small size ferrite and martensite. No other appreciable correlation could be ralated to the microstructure morphology of the FMDP steel. The closure stress intensity factor , however, is affected by the ferrite content with  reaching a maximum value of 0.7. In general, crack growth followed the interphase between the martensite and ferrite.

Dividing the fatigue crack growth process into Stage I and II where the former would be highly sensitive to changes in ΔK and the latter would increase with ΔK depending on the  ratio. The same data when correlated with the strain energy density factor range ΔS showed negligible dependence on mean stress or R ratio for Stage I crack growth. A parameter α involving the ratio of ultimate stress to yield stress, percent reduction of area and R is introduced for Stage II crack growth so that the  data for different R would collapse onto a single curve with a narrow scatter band when plotted against αΔS.

Crack deflection at an interface between dissimilar elastic-materials

A crack intersecting an interface between two dissimilar materials may advance by either penetrating through the interface or deflecting into the interface. The competition between deflection and penetration can be assessed by comparison of two ratios: (i) the ratio of the energy release rates for interface cracking and crack penetration; and (ii) the ratio of interface to material fracture energies. Residual stresses caused by thermal expansion misfit can influence the energy release rates of both the deflected and penetrating crack. This paper analyses the role of residual stresses. The results reveal that expansion misfit can be profoundly important in systems with planar interfaces (such as layered materials, thin film structures, etc.), but generally can be expected to be of little significance in fiber composites. This paper corrects an earlier result for the ratio of the energy release rate for the doubly deflected crack to that for the penetrating crack in the absence of residual stress.

Mixed-mode fracture mechanisms near the fatigue threshold of aisi-316 stainless-steel

Near threshold, mixed mode (I and II), fatigue crack growth occurs mainly by two mechanisms, coplanar (or shear) mode and branch (or tensile) mode. For a constant ratio of ΔK_I/ΔK_II the shear mode growth shows a self-arrest character and it would only start again when ΔK_I and ΔK_II are increased. Both shear crack growth and the early stages of tensile crack growth, are of a crystallographic nature; the fatigue crack proceeds along slip planes or grain boundaries. The appearance of the fracture surfaces suggest that the mechanism of crack extension is by developing slip band microcracks which join up to form a macrocrack. This process is thought to be assisted by the nature of the plastic deformation within the reversed plastic zone where high back stresses are set up by dislocation pile-ups against grain boundaries. The interaction of the crack tip stress field with that of the dislocation pile-ups leads to the formation of slip band microcracks and subsequent crack extension. The change from shear mode to tensile mode growth probably occurs when the maximum tensile stress and the microcrack density in the maximum tensile plane direction attain critical values.

复合材料及其结构的力学进展（第三册）

复合材料及其结构的力学进展（第一册）

理性力学基础

《理性力学基础》为《中国科学院研究生教学丛书》之一。
    《理性力学基础》系统地介绍了理性力学的主要科学体系和基本理论。《理性力学基础》由四部分，共十五章组成。第一部分综合介绍了理性力学的科学意义、方法和特点，从理性力学角度概括论述变形几何学与运动学、力学基本定律与场方程以及本构方程的一般原理。着重阐明张量和场方程的时空无差异原理，以及本构方程所应遵循的客观性原理。第二部分着重介绍简单物质的理论体系。作为典型范例进一步阐明弹性物质和简单流体的本构方程以及弹性体有限变形边值问题的分析方法。第三部分详细介绍黏弹性物质、弹塑性物质及晶体塑性的基本理论。第四部分主要介绍含缺陷物质的本构理论。
    《理性力学基础》可作为力学、应用数学、理论物理等专业的研究生教材，也可供力学工作者及高等院校力学专业教师参考。

目录 

第一章 绪论
1·1 理性力学目的和意义
1·2 理性力学的特点与体系
1·3 理性力学的方法
1·4 符号
第二章 变形几何学和运动学
2·1 直角坐标系的张量
2·2 物体的构形与运动
2·3 变形梯度
2·4 应变度量和面元、体元变形
2·5 应变率
第三章 基本定律与场方程
3·1 质量守恒定律
3·2 应力原理与动量守恒定律
3·3 能量守恒定律和熵定律
3·4 功共轭与应力度量
3·5 场方程
3·6 随体坐标系
第四章 本构方程的一般原理
4·1 时空系的变换
4·2 基本定律的客观性
4·3 本构方程的一般原理
第五章 简单物质
5·1 张量函数
5·2 张量函数表示定理
5·3 简单物质的本构方程
5·4 本构方程的简化形式
5·5 各向同性物质
5·6 简单固体
5·7 简单流体和流晶
5·8 内部约束
5·9 特殊类型物质
5·10 衰退记忆
第六章 弹性物质
6·1 弹性物质的本构方程
6·2 物质对称性
6·3 各向同性弹性固体
6·4 超弹性物质
6·5 各向同性超弹性物质
6·6 主轴表示
6·7 储能函数表示式
6·8 二次弹性
6·9 均匀变形场
6·10 储能函数的实验确定
第七章 弹性体有限变形边值问题
7·1 边值问题的提法
7·2 若干典型问题
7·3 平面应变问题
7·4 不可压缩各向同性弹性体
第八章 简单流体
8·1 直线流动
8·2 曲线流动
8·3 伸长历史恒定运动
8·4 定常测黏流动
8·5 Poiseuille流动
8·6 Couette流动
8·7 圆锥-平板流动
8·8 端部正应力效应
8·9 Stokes流体测黏流动
8·10 定常拉伸流动
第九章 黏弹性物质
9·1 线性黏弹性理论
9·2 非线性黏弹性固体
9·3 本构泛函展开
9·4 非线性黏弹性流体
第十章 弹塑性物质
10·1 微小变形塑性理论
10·2 张量的时间导数
10·3 有限塑性变形的本构方程
10·4 塑性大变形基本方程
10·5 Drucker公设与有限塑性变形
第十一章 晶体塑性理论
11·1 晶体塑性变形运动学
11·2 硬化规律
11·3 硬化系数表示式
11·4 晶体塑性本构关系
11·5 滑移剪切率γ(α)的存在性与惟一性
11·6 率相关流动规律
第十二章 缺陷连续统的线性理论
12·1 张量场的微分运算
12·2 协调条件
12·3 缺陷的几何意义
12·4 位错弹性理论
12·5 位错塑性理论
12·6 一般缺陷塑性理论
12·7 晶体塑性位错理论
12·8 Nye张量及缺陷塑性理论小结
12·9 位错塑性理论二维公式及算例
第十三章 非黎曼几何及流形简介
13·1 Euler空间张量场的绝对微分
13·2 曲率张量
13·3 线性空间
13·4 仿射联络空间
13·5 非完整变换
13·6 拓扑空间
13·7 微分流形
第十四章 缺陷连续统的非线性理论
14·1 非Niemann物质流形的构造
14·2 缺陷的几何意义
14·3 缺陷连续统的弹性理论
14·4 缺陷连续统的塑性理论
14·5 晶体塑性位错理论
第十五章 理性力学若干应用
15·1 有限变形的精确描述
15·2 曲线坐标的相应公式
15·3 本构方程的客观性原理
15·4 物质对称性
15·5 主轴法
15·6 客观应力率
附录 曲线坐标
1 基向量与度量张量
2 逆变导数
3 应力张
4 运动方程

 

固体力学进展及应用: 庆贺李敏华院士90华诞文集

《固体力学进展及应用：庆贺李敏华院士90华诞文集》收录了近代固体力学基础理论及其应用领域的重要科技成果和最新进展。作者是在同体力学领域工作多年的资深研究员，他们来自各行各业，有丰富的科研与丁作经验。他们提供的论文在相当程度上反映当前同体力学的发展现状与成就，并能看出发展趋势，对未来研究的课题选择有参考价值。《固体力学进展及应用：庆贺李敏华院士90华诞文集》还收集了李敏华院士的珍贵照片和纪念李敏华院士90华诞的庆贺和回忆文章，具有重要的史料价值。

南海两种特殊地质沉积物中结构物的稳定性研究

Influences of phase shift on superresolution performances of annular filters

This paper investigates the influences of phase shift on superresolution performances of annular filters. Firstly, it investigates the influence of phase shift on axial superresolution. It proves theoretically that axial superresolution can not be obtained by two-zone phase filter with phase shift pi, and it gets the phase shift with which axial superresolution can be brought by two-zone phase filter. Secondly, it studies the influence of phase shift on transverse superresolution. It finds that the three-zone phase filter with arbitrary phase shift has an almost equal optimal transverse gain to that of commonly used three-zone phase filter, but can produce a much higher axial superresolution gain. Thirdly, it investigates the influence of phase shift on three-dimensional superresolution. Three-dimensional superresolution capability and design margin of three-zone complex filter with arbitrary phase shift are obtained, which presents the theoretical basis for three-dimensional superresolution design. Finally, it investigates the influence of phase shift on focal shift. To obtain desired focal shifts, it designs a series of three-zone phase filters with different phase shifts. A spatial light modulator (SLM) is used to implement the designed filters. By regulating the voltage imposed on the SLM, an accurate focal shift control is obtained.

Design and application of three-zone annular filters

We design three-zone annular filters to be applied to optical storage system. The designed filters extend the depth of focus and realize transverse superresolution simultaneously, which will improve the performance of optical storage system greatly. And we propose two feasible schemes to improve imaging resolution of three-dimensional imaging system. One scheme depends on a complex filter formed by cascading of a three-zone phase filter and a three-zone amplitude filter. The complex filter converge the optimized transverse superresolution and the optimized axial superresolution of two different filters onto a single filter. It can improve the three-dimensional imaging performances greatly. Another scheme depends on a single three-zone complex filter. We propose a three-zone complex filter with phase shift 0.8 pi, which presents bigger design margin, better imaging quality and stronger three-dimensional superresolution capability. (c) 2006 Elsevier GmbH. All rights reserved.

利用晶体串接实现高效宽带三倍频

从耦合波方程出发,分别在小信号、高功率(1.5 GW/cm2)条件下研究KDP晶体串接三次谐波转换。当两块混频晶体的长度选择为8 mm和6 mm,晶体分别偏离原混频匹配角0.35 mrad和-0.25 mrad时可以有0.3 nm的谐波转换带宽,同时系统的三次谐波转换效率与两块混频晶体之间的距离有密切关系,当两块晶体之间的距离使从第一块混频晶体出射的光波之间的相位差改变π时,会使第一块混频晶体产生的三次谐波大部分回流到基频和倍频光,从而使转换效率大幅度下降,最合适的距离应当使光波之间的相位差改变为2π。

山东山旺中新世气候定量重建的综合研究

新生代以来，全球气候经历了一系列的冷暖交替，呈现总体变冷的趋势。对该时期不同区域气候变化过程的深入研究有助于我们更好地理解现今全球气候变化规律。中新世是新生代古气候与古环境演变的一个重要转折时期，定量重建山东山旺中新世气候是认识和理解中国东部与东亚新近纪气候演变的一个关键环节。 将化石植物作为气候代用指标，用于研究过去全球气候变化，已经广为国际科学界接纳。国际上，定量研究第三纪气候的植物学方法按照不同原理可以划分为两大类，其各自代表分别为基于化石的现存最近亲缘类群生态适应度推演古气候参数值的共存分析法（Coexistence Approch, CA ）和基于叶片形态特征与气候相关关系的叶缘分析（Leaf Margin Analysis, LMA ）与气候叶片多变量程序（Climate Leaf Analysis Multivariate Program, CLAMP）。两大主流方法各有优势，也各有局限性。前人运用两大主流方法对山旺中新世植物群相同地层，同套数据的分析结果表明：LMA 和CLAMP 所估测年均温数值要显著低于CA 所估测的数值。其差异的原因既可能是LMA 和CLAMP 由于埋藏因素的影响造成估测值偏低，也可能由于CA 数据库数据主要来自于欧洲和北美而缺乏东亚的资料所致。 本论文提出了一种新的方法——分布区叠加分析（Overlapping Distribution Analysis, ODA ）对山旺中新世古气候进行定量重建。ODA 采用最近亲缘类群在叠加区间的气候参数来重建化石植物所生活的当时当地的气候。其详细步骤如下：1. 鉴定化石植物和认定它们的最近亲缘类群（尽量到种级水平）。2. 调查这些最近亲缘类群的分布数据（包括经度、纬度和海拔数据）。某些类群可能会有不止一个最近亲缘类群，须将这些最近亲缘类群的分布数据合并。3. 对分布数据分析，得出包含最多类群的最大叠加区间。4. 调查在最大叠加区间中气象站点的气候数据。5. 按照公式（1）和（2）来转换年均温数据TU=T0 - (HU -H0)×Γ (1); TL=T0 - (HL -H0)×Γ (2) 其中HU (m) 是海拔叠加区间的上界; HL (m) 是海拔叠加区间的下界; H0 (m) 气象站的实测海拔; T0 (ºC) 气象站的实测年均温; TU (ºC) 在海拔叠加区间气温的下界; TL (ºC) 在海拔叠加区间气温的上界; 系数Γ 为大气垂直直减率，年均温为0.5ºC/100m，最冷月均温为 0.45ºC/100m，最热月均温为 0.6ºC/100m。同样的方法，在海拔叠加范围内最冷月均温与最热月均温范围也可以确定，而降水量则采用气象台站的原始数据。6. 在这些转换数据的基础上，得出年均温，最冷月均温，最热月均温，年较差和年平均降水量波动范围。 ODA 分析结果表明：山旺中新世时期年均温为10.9-14.5oC，年较差为21.1-22.7oC，最冷月均温为-0.5-3.3oC，最热月均温为21.9-25.0oC，年平均降水量为1107.3-1880.0mm 。同时本论文还定量恢复了山旺硅藻土矿各层的古气候参数，其所估测的古气候参数数值与CLAMP 和LMA 的结果一致，而与CA 不同。对山旺气候参数的恢复表明，虽然其中新世年均温与现在相似，但最冷月均温要高于现在。 本项研究的创新之处是选择同一个研究地点（山东山旺），依据同一套数据（化石植物的类群资料），采用国际上以不同原理为基础的主流方法，同时加入我们自己提出的新方法，进行的古气候重建，对所获得气候参数值进行对比和验证，并对其存在的差异进行分析和探讨。

A new species of the genus Tor from Yunnan, China (Teleostei : Cyprinidae)

A new species of the subfamily Barbinae, Tor yingjiangensis, is recognized from Yunnan province, China. It can be distinguished from other Tor species by the following combination of characters: last simple dorsal-fin ray osseous and non-serrated; no forward directed predorsal procumbent spine; head length considerably longer than body depth; no tubercles on the snout or sides of the face; 18-20 gill rakers on the outside of first gill arch; 24-26 lateral line scales; median lobe of lower lip short, its posterior margin truncate, not extending to the vertical across the inner corners of the mouth; and the condition of the lower lip consistent in individuals of different sizes. The new species has been misidentified previously as Tor putitora (Hamilton, F. 1822. An account of the fishes found in the River Ganges and its Branches. Edinburgh & London. 405 pp), which occurs in the Ganges and Indus River basins. The new species can easily be distinguished from T. putitora by having 3-3.5 (vs. 2.5) scales from lateral line to pelvic-fin origin, shorter caudal peduncle length (13.0% vs. 17.2% of standard length), lesser body depth (26.4% vs. 24.0% of standard length) and longer caudal peduncle depth (12.0% vs. 10.9% of standard length), no longitudinal stripe present along side of body, and eyes visible in ventral view of head.