Phase Shifting Full-Field Interferometric Methods for Determination of In-Plane Tensorial Stress

A new method that combines phase shifting photoelasticity and transmission Coherent Gradient Sensing (CGS) is developed to determine the tensorial stress field in thin plates of photoelastic materials. A six step phase shifting photoelasticity method determines principal stress directions and the difference of principal stresses. The transmission CGS method utilizes a standard four step phase shifting method to measure the x and y first derivatives of the sum of principal stresses. These stress derivatives are numerically integrated using a weighted preconditioned conjugate gradient (PCG) algorithm, which is also used for the phase unwrapping of the photoelastic and CGS phases. With full-field measurement of the sum and difference of principal stresses, the principal stresses may be separated, followed by the Cartesian and polar coordinate stresses using the principal stress directions. The method is demonstrated for a compressed polycarbonate plate with a side V-shaped notch. The experimental stress fields compare well with theoretical stress fields derived from Williams solution for a thin plate with an angular corner.     

Wavelet-based Numerical Methods

This paper will give an overview of wavelet methods applied to computational fluid dynamics, including scale resolution, grid and order selection throughout a domain. In addition, Spline-based wavelet methods will be placed in the context of finite elements where the element size is adjusted throughout the domain.     

超高速发射实验及其数值分析

采用多介质流体高精度欧拉并行计算程序HVL-MFPPM,对Sandia实验室和中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室进行的两个超高速发射实验装置进行数值模拟,前者给出的二级飞片前界面速度历史与VISAR实验测试和HVL-CTH程序计算结果一致,后者给出二级飞片稳定时的速度和飞行姿态与实验测试结果吻合,同时还给出了128个和216个CPU计算的界面形状.为进一步获得更高二级飞片速度的实验装置设计提供了理论和数值分析基础.     

加筋材料的格形模型和统计数值方法

本文采用格形化方法和统计技术建立加筋复合材料有限元力学模型,使用自动选取载荷步长方法和非平衡迭代技术,对加筋复合材料的宏观等效模量和破坏全过程进行了数值模拟,分析了材料分布的非均匀程度,相对体积比和横截面加筋分布方式对加筋复合材料整体宏观等效模量和承载力的影响。     

云纹干涉仪中偏振相移的实验方法研究

本文根据偏振相移原理,将其成功地应用于云纹干涉系统中,给出具体实施方案,利用该装置进行实验,得到一组相移条纹图,给出相移结果和条纹倍增结果.     

Numerical and Experimental Evaluation of Dispersion Coefficient for Resin Transfer Modeling

Resin transfer molding (RTM) is a composite manufacturing process. A preformed fiber is placed in a closed mold and a viscous resin is injected into the mold. In this article, a model is developed to predict the flow pattern, extent of reaction, and temperature change during the filling and curing in a thin rectangular mold. A numerical simulation is presented to predict the free surface and its interactions with heat transfer and cure for flow of a shear-thinning resin through the preformed fiber.To simulate this process, using local thermal equilibrium assumption, it is essential to include the thermal dispersion term in energy equation. The best method to achieve this result is experimental simulation and preparing proportionate system at simple conditions without curing. By comparison of recorded temperature values (using installed instruments at various locations), and the corresponding results from numerical solution for different estimated values of dispersion coefficient, this coefficient has been evaluated based on the best matching estimate. The results show that, to simulate composite manufacturing process by RTM method, the effect of dispersion term in energy equation shall not be neglected.     

Numerical and Experimental Models of the Mandible

This study aimed to validate a numerical model of an intact mandible for further development of a new TMJ implant. Numerical and experimental models of the biomechanics of the mandible were elaborated to characterize the human temporomandibular joint and to approach the development of a condyle implant. The model of the mandible was obtained through the use of a polymeric replica of a human cadaveric mandible and through 3D geometry acquisition. The three-dimensional finite element model was generated as a tetrahedral finite element mesh. The level of mesh refinement was established via a convergence test and a model with more than 50,000 degrees of freedom was required to obtain analysis accuracy. The functional loading cases included muscle loading in four different load boundary conditions. The same boundary conditions were applied to the experimental model. The strains were measured with an experimental procedure using electric resistance strain gauges applied on the external surface of the mandible. The mechanical response is shown and discussed in terms of strains, principal numerical and measured strains. This study proved that FE models of the mandible can reproduce experimental strains within an overall agreement of 10%. The FE models correctly reproduced bone strains under different load configurations and therefore can be used for the design of a novel TMJ implant considering other load configurations and bone mechanical properties.     

理想塑性结构极限与安定分析的数值方法

极限分析和安全分析的近代发展方向是寻找通用性强，计算效率高的数值方法。本文介绍将有限单元法和数学规划法相结合的、同时适用于极限分析和安全分析的统一数值方法，包括下限格式和上限格式。     

Optical Methods in Experimental Mechanics

Experimental Techniques -     

Penalty Methods for Numerical Approximations of Optimal Boundary Flow Control Problems

Abstract

This article is concerned with penalty methods for solving optimal Dirichlet control problems governed by the steady-state and time-dependent Navier-Stokes equations. We present, in two different versions, the penalized methods for solving the steady-slate Dirichlet control problems. These approaches are implemented and compared numerically. We also generalize the penalty methods to the time-dependent case. Scmidiscrete and fully discrete approximations of time-dependent Dirichlet control problems are discussed and implemented. Numerical results for solving both the steady-state and the time dependent Dirichlet control problems are reported.