基于能量平衡原理的有限单元耦合方法

结构非线性数值计算分析应真实反映局部损伤破坏细节,以作为损伤演化全过程分析的依据。对同类构件,有限单元耦合方法可以解决破坏细节与整体模拟的空间尺度差异问题。基于能量平衡原理,建立了梁与实体单元、梁与壳单元以及壳与实体单元的耦合方程,适用于结构的损伤数值计算。对某RC框架结构原位推覆试验的损伤数值分析表明,有限单元耦合模型能正确反映整体结构的承载力和变形性能,并且能准确反映局部损伤破坏细节。     

高斯过程响应面法研究

新型的高斯过程响应面法具有灵活性好、精度高和能量化不确定性等优点,但某些关键技术细节还存在争议。本文简要介绍了高斯过程响应面法的基本理论,结合算例详细讨论了关键技术细节的处理方法;提出了先验期望函数选用低阶多项式、相关函数选用高斯形式、粗糙度参数用边缘后验众数法固定、模型有效性必须经过验算点检验等应用建议。     

Subcritical crack growth in weak interface under mixed mode in two dimension

Constitutive equations, which govern subcritical crack growth within a weak brittle interface, are derived assuming mixed-mode loading, i.e., both tensile and shear stresses acting at the crack tip. The subcritical crack growth is assumed to be caused by the classical activation mechanism of fluctuation fracture kinetics. To derive the constitutive equations, two approaches are developed. The first approach is process-zone-detail-independent (PZI), which ignores any details of the process zone, i.e., a near-crack-tip zone of significant damage resulting in fracture, and takes into account only the process zone length. The second approach is process-zone-detail-dependent (PZD), which takes into account some details of the process-zone structure. After some general considerations including 3D case, the detailed consideration is given for 2D case, particularly, for plane strain. Illustrative calculated examples of the obtained theoretical results are presented.     

Universal motions for a class of viscoelastic materials of differential type

Universal quasi-static motions for a class of incompressible, viscoelastic materials of differential type are examined. These time dependent motions are similar to corresponding static universal deformations well-known for incompressible, isotropic elastic materials. General details are illustrated for the pure torsion problem, and specific results and physical effects are provided for the viscoelastic Mooney-Rivlin model.     

Computational grid,subgrid, and pixels

Free-surface flows in rivers, estuaries, and coastal areas are strongly dominated by the geometrical details of the study area. Nowadays, accurate bathymetric data are easily available on raster-based digital elevation models with an impressive spatial resolution. These data are often accessible as large two-dimensional arrays containing several millions of pixel values. Recent numerical methods are very efficient and rather accurate but far from being able to solve the governing differential equations on a computational grid with such a fine spatial resolution. In the present investigation, the unaltered pixel values from a digital elevation model are clustered to form subgrids of a coarser computational grid. Artificial cross-flow between disconnected areas is inhibited by introducing cell clones and edge clones. Each clone consists of directly connected pixels. It is shown how the resulting computational grid is able to resolve geometrical details of complex study areas to pixel resolution and for any grid size. As an example, the performance of the proposed algorithm is tested to simulate a typical tidal flow in the San Francisco Bay and the Sacramento-San Joaquin Delta area by using an extreme subgrid resolution given by a digital elevation model containing 196 000 000 pixels with 10 m pixel size.     

A practical implementation of turbulence models for the computation of three-dimensional separated flows

An upwind MUSCL-type implicit scheme for the three-dimensional Navier-Stokes equations is presented and details on the implementation for three-dimensional flows of a ‘diagonal’ upwind implicit operator are developed. Turbulence models for separated flows are also described with an emphasis on the numerical specificities of the Johnson-King non-equilibrium model. Good predictions of separated two- and three-dimensional flows are demonstrated.     

Boltzmann transport equation-based thermal modeling approaches for hotspots in microelectronics

Fourier diffusion has been found to be inadequate for the prediction of heat conduction in modern microelectronics, where extreme miniaturization has led to feature sizes in the sub-micron range. Over the past decade, the phonon Boltzmann transport equation (BTE) in the relaxation time approximation has been employed to make thermal predictions in dielectrics and semiconductors at micro-scales and nano-scales. This paper presents a review of the BTE-based solution methods widely employed in the literature and recently developed by the authors. First, the solution approaches based on the gray formulation of the BTE are presented. The semi-gray approach, moments of the Boltzmann equation, the lattice Boltzmann approach, and the ballistic-diffusive approximation are also discussed. Models which incorporate greater details of phonon dispersion are also presented. Hotspot self-heating in sub-micron SOI transistors and transient electrostatic discharge in NMOS transistors are also examined. Results, which illustrate the differences between some of these models reveal the importance of developing models that incorporate substantial details of phonon physics. The impact of boundary conditions on thermal predictions is also investigated.     

A new hybrid method to obtain viscoelastic principal stress

The basic relations in linear isotropic photoviscoelasticity have been theoretically discusse in details. A new routine has been found to obtain the time-dependent principal stress without the measurement of isoclinics. As a test of our method, examples are given at the end of this paper.     

非线性周期波及破碎波对杆件的作用力

本文采用十五阶 Stokes 波的 Pade 逼近,获得了与实验较为一致的流场,并且利用已有的破碎波的速度、加速度场,计算了非线性波和破碎波对各种杆件作用力,比较了它们的主要特征,为海洋工程设计提供依据。     

Recording dynamic fringe patterns with a Cranz-Schardin camera

The requirements of a high-speed recording system in dynamic photoelastic studies are closely met with a Cranz-Schardin camera. This camera, which operates at framing rates between 32,000 and 815,000 frames/sec, is capable of resolving a dynamic fringe pattern with a fringe gradient of 20 fringes/in. traveling with a velocity of 75,000 ips. Design details of the Cranz-Schardin system are given, and typical results obtained are illustrated.     

Nonlocal approach to nonequilibrium thermodynamics and nonlocal heat diffusion processes

We study some aspects of nonequilibrium thermodynamics and heat diffusion processes based on Suykens’s nonlocal-in-time kinetic energy approach recently introduced in the literature. A number of properties and insights are obtained in particular the emergence of oscillating entropy and nonlocal diffusion equations which are relevant to a number of physical and engineering problems. Several features are obtained and discussed in details.     

工程地质与岩土工程

对于工程地质与岩土工程的两个概念进行了详细对比 ,指出他们的异同。指出工程地质是岩土工程的基础 ,岩土工程是工程地质的一个延伸     

有限变形问题过程最优控制算法

在非增量算法的基础上,提出了用最优控制变分原理形成过程最优控制迭代求解的基本思路,并给出求解的基本控制方程。这一工作为有限变形力学问题的数值求解提供了一个新的处理方法。     

Natural Frequency for Rectangular Orthotropic Corrugated-Core Sandwich Plates with All Edges Simply-Supported

ＩｎｔｒｏｄｕｃｔｉｏｎＳａｎｄｗｉｃｈｐｌａｔｅｓｈａｖｅｆｏｕｎｄｗｉｄｅａｐｐｌｉｃａｔｉｏｎｆｏｒａｉｒｃｒａｆｔ,ａｓｔｒｏｎａｕｔｉｃａｌａｎｄｏｔｈｅｒｂｒａｎｃｈｅｓｏｆｃｏｎｔｅｍｐｏｒａｒｙｓｔｒｕｃｔｕｒａｌｅｎｇｉｎｅｅｒｉｎｇ .Ｔｈｅａｎａｌｙｓｉｓｏｆｓａｎｄｗｉｃｈｓｔｒｕｃｔｕｒｅｓｈａｓｂｅｅｎｔｈｅｔｏｐｉｃｏｆｅｘｔｅｎｓｉｖｅｉｎｖｅｓｔｉｇａｔｉｏｎｉｎｔｈｅｌａｓｔｆｅｗｄｅｃａｄｅｓ,ａｎｄｓｅｖｅｒａｌｒｅｆｅｒｅｎｃｅｂｏｏｋｓｈａｖｅｂｅｅｎｗｒ…     

流体双折射方法及其应用

本文在1923—1989年的工作基础上,论述了流体双折射方法,对它的发展和原理进行了详细讨论,介绍了流体双折射方法的各种应用,尤其是在生物力学,二维三维场显示方面的应用.     

A photoelectric compensator with good zero stability

Summary A laboratory made apparatus for long-time recording of small voltages is described. Care is taken to reduce zero-drift. Some details concerning the construction and adjustment of the equipment are discussed.     

Correction to: Interlaboratory Reproducibility of Contour Method Data Analysis and Residual Stress Calculation

Experimental Mechanics - The original version of this article has been corrected to include authors middle initials in the author list. The details given in this correction are correct.     

An automatically recording densitometer

Summary An instrument for the recording of photographic density distributions is described. It is based on the principle of continuous comparison of the density of points along a line on the moving film and the density of a gray wedge, the position of which is continuously set to balance by means of a servo-system and recorded on a drum. Constructional details of the instrument are described, and the conditions of proper functioning are briefly discussed.     

海洋平台碰撞和损伤分析的进展

本文详细综述了平台结构的碰撞和损伤分析.十儿年来,在这一领域内提出了许多有用的概念和切实可行的分析方法.文中介绍了分析碰撞和损伤的各种方法,并介绍和比较了钢质平台的能量吸收模型.