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991.
J. Fornell A. Concustell S. Suriñach W.H. Li N. Cuadrado A. Gebert M.D. Baró J. Sort 《International Journal of Plasticity》2009
Bulk metallic glass with composition Ti40Zr25Ni8Cu9Be18 exhibits considerably high compressive yield stress, significant plasticity (with a concomitant vein-like fracture morphology) and relatively low density. Yielding and intrinsic plasticity of this alloy are discussed in terms of its thermal and elastic properties. An influence of normal stresses acting on the shear plane is evidenced by: (i) the fracture angle (<45°) and (ii) finite-element simulations of nanoindentation curves, which require the use of a specific yield criterion, sensitive to local normal stresses acting on the shear plane, to properly match the experimental data. The ratio between hardness and compressive yield strength (constraint factor) is analyzed in terms of several models and is best adjusted using a modified expanding cavity model incorporating a pressure-sensitivity index defined by the Drucker–Prager yield criterion. Furthermore, comparative results from compression tests and nanoindentation reveal that deformation also causes strain softening, a phenomenon which is accompanied with the occurrence of serrated plastic flow and results in a so-called indentation size effect (ISE). A new approach to model the ISE of this metallic glass using the free volume concept is presented. 相似文献
992.
Classical constitutive models exhibit strong mesh dependency during softening and the numerical responses tend towards perfectly brittle behavior upon mesh refinements. Such sensitivity can be avoided by adopting the gradient-enhanced formulation. The implicit approach incorporates the gradient contributions indirectly via an additional Helmholtz equation and requires only C0 continuity. The explicit approach computes the gradient terms directly from the local field variables. Assuming a weak satisfaction of the yield function, C1 continuity or C0 continuity with additional degrees of freedoms in the penalty approach is required. This makes the explicit method less attractive computationally. However, the explicit approach is able to fully regularize some material models where the standard implicit method fails to perform. Drawing analogy to the over-nonlocal integral formulation, the over-implicit-gradient framework is proposed. In addition, an alternative framework for the explicit gradient method requiring only C0 continuity is proposed. The regularizing effects of the abovementioned two gradient frameworks show promising applications to strain-softening materials. 相似文献
993.
随着上海地铁隧道建设大规模的展开,建设中面临的工程地质问题日趋凸现。本文结合上海市特有的地质条件,分析了与地铁隧道建设相关的工程地质条件,包括工程地质结构特征及浅部含水层地下水位特征。在此基础上,对地铁车站基坑开挖以及区间隧道施工可能面临的工程地质问题进行了分析研究,绘制了市中心地区工程地质问题严重性程度分区图,可为工程设计、施工提供从参考依据。 相似文献
994.
This paper presents a new smooth memristor oscillator,
which is derived from Chua's oscillator by replacing Chua's diode
with a flux-controlled memristor and a negative conductance. Novel
parameters and initial conditions are dependent upon dynamical behaviours
such as transient chaos and stable chaos with an intermittence
period and are found in the smooth memristor oscillator. By using
dynamical analysis approaches including time series, phase portraits
and bifurcation diagrams, the dynamical behaviours of the proposed
memristor oscillator are effectively investigated in this paper. 相似文献
995.
计算机代数系统在力学教学中应用非常普遍. 摘录Maple在理论力学、材料力学、弹性
力学和有限元中的应用, 以简便地完成模型求解和结果处理. 并扩展到备课、讲课和
课后作业演练等环节, 提供最大限度地计算支持.
将其引入力学教学, 引导和培养学生利用数学工具的习惯和能力, 强化算
法设计和程序的通用性和灵活性, 为处理复杂问题提供帮助. 相似文献
996.
集值优化问题的Benson次梯度及其应用 总被引:1,自引:0,他引:1
引进集值映射的Benson次梯度,证明Benson次梯度的存在性定理,给出了它的等价刻画。作为应用,给出了带约束集值优化问题取得Benson真有效元的充分条件和必要条件,得到了集值优化问题在Benson真有效意义下的若干新刻画。 相似文献
997.
In this paper the theoretical and experimental results of sum-frequency mixing of a Ti∶sapphire laser and a 1.064 μm Nd∶YAG laser are presented. By using two KTP crystals cut at θ=76° and 85° (φ=90° in both crystals), respectively, the sum-frequency mixing tuning range from 459.3 to 509.6 nm in one Ti∶sapphire laser setup is experimentally achieved. The maximum output energy was 14.6 mJ and the energy conversion efficiency was up to 15.2%. 相似文献
998.
Adrian Doicu Thomas Wriedt 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):663-673
We describe a T-matrix program for light scattering calculations from particles with complex structure. The code treats the cases of homogeneous, layered and composite scatterers. These results are combined with basic results concerning the scattering by inhomogeneous scatterers and aggregates to apply to more general types of scatterers. Some numerical simulations are presented. 相似文献
999.
ABSTRACT. Variability influences ecological processes at various scales and is incorporated in different ways in forest models. The forest model Dis CFor M scales an individual based, stochastic forest patch model up to a height structured tree population model. To describe the variability arising from stochastic processes in the patch model, Dis CFor M uses theoretical random dispersions of trees in each height class over all patches. This yields a spatial distribution of light and consequently of light dependent process rates. Three major influences of variability on simulations are examined: site condition, patch to patch, and temporal environmental variability. Simulation studies and comparison with forest compositions from the Swiss National Forest Inventory reveal that these influences affect simulated forest dynamics, species composition, and biodiversity, depending on climatic boundary conditions and hence have to be taken into account in modeling. 相似文献
1000.