一种相容决策表的属性值与属性约简方法

针对相容决策表,另辟一种数据约简思路,与传统数据约简方法不同的是,本文方法考虑属性值约简与属性约简之间的关联,该方法首先进行属性值约简,然后再进行属性约简,本文并给予了充分的证明,而普通的方法并没有考虑它们之间的联系,并有许多冗余的比较操作。     

基于递推技术的算法设计方法的应用研究

算法是计算机科学的核心,算法设计对于开发正确、高效的程序至关重要。基于递推技术的算法设计方法通过形式化推导保证算法的可靠性,同时能较好地提高算法程序的效率。本文通过两个实例,详细介绍基于递推技术的算法设计方法形式化推导算法程序的过程。     

应用人工神经网络理论建立热粘塑性材料的本构关系

本文将人工神经网络（ＡＮＮ）用于建立热粘塑性材料的本构关系，意在探索出一种描述材料变形力学行为的新方法。文中给出了应用人工神经网络建立热粘塑性材料本构关系的ＢＰ模型和学习算法过程，并应用于４５号钢在高温和高速变形条件下的流动应力计算。计算结果与实测结果比较表明，二者吻合良好。因此，应用人工神经网络建立热粘塑性材料的本构关系具有重要的工程应用价值。     

小型预制桩基础承载特性数值模拟研究

本文建立硬化土本构模型,针对江苏省软土地区的土质条件选取数值计算参数,通过PLAXIS 2D软件对小型预制桩在的单桩水平受荷及竖向受荷进行数值模拟,得到桩身弯矩沿桩长的分布以及荷载-位移曲线,分析小型预制桩基础桩身弯矩的分布特点,并探求其在水平及竖向荷载作用下的承载特性,进而能够为小型预制桩基础工程设计以及计算方面提供一定的参考依据。     

On certain aspects of strain rate sensitivity of sheet metals

The formability of a material depends upon the strain hardening and strain rate hardening of the material. In this study, constitutive parameters using the power law constitutive equation are determined for six different strength steels and two aluminum alloys over different strain ranges, including approximations of the postuniform elongation range. Constitutive parameters are found to be different at different strain ranges. The strain hardening of steels increases with strain at low strain levels (less than 5%) and decreases at high strain levels (greater than 10%). Strain rate hardening decreases with strain for all steels and aluminum alloys. Uniform elongation depends only on strain hardening, and postuniform elongation depends only on strain rate hardening. However, the total elongation depends on both strain hardening and strain rate hardening.     

TA15合金的热变形行为及加工图

研究了TA15合金的热模拟压缩实验。结果表明：变形温度的升高和应变速率的减小使峰值应力和稳态应力显著降低，变形温度会影响进入稳态流动所需变形量。以热模拟压缩实验为基础，建立的加工图表明：TA15合金高温变形时存在2个非稳定区域，一个是变形温度1300K以上和应变速率10．0s^-1以上的区域，另一个是变形温度1200K以下和应变速率0．006s^-1～1．995s^-1之间的区域。同时，建立的TA15合金高温变形时的流动应力模型表征了变形温度、应变速率和变形程度对流动应力的影响，模型的计算精度较高。     

云关系模式及其应用*

在云变换的基础上,结合非经典关系数据库理论提出了云关系模式,给出了云关系模式的定义,探讨了云关系模式的意义,并将它应用于学生成绩数据库中,改进了目前学生定性评定方法,克服了其中的主观因素,实例证明该方法具有可行性.     

A STUDY OF B-P UNIFIED VISCOPLASTIC CONSTITUTIVE MODEL

By combining the Bodner-Partom constitutive model and equivalent stress function, finite element methods and program on analyzing non-elastic deformation and stress for thermal viscoplastic material are studied in this paper, and it's the first time that this material model is used in a kind of engineering software-MARC. Thermal viscoplastic behavior of high temperature alloy GH536 specimen with gap is analyzed by this program. The research results show it is feasible to analyze thermal viscoplastic behavior of specimen or structure by applying B-P model.     

New inverse method for identification of constitutive parameters

A new inverse method by coupling iSIGHT and ABAQUS was proposed to determine the constitutive parameters of Al2O3sf/LY12 composite deforming at elevated temperature. It combined the merits of the f＇mite element simulation and optimization technique. The direct model was simulated with finite element code ABAQUS. The inverse problem associated with the identification of the constitutive parameters was expressed as a least square optimization problem. The direct simulation and the parameters optimization were implemented in iSIGHT integrated environment. The aim was to match the output of the direct simulation with the experiment data. The capability of the proposed inverse method was demonstrated through the identification of constitutive parameters of Al2O3sf/LY12 composite. The proposed new inverse method is also applicable to other parameters identification which is hardly determined through experiments or direct analytical method.     

连续铸轧流变行为的物理模拟及其应力-应变关系的演变

在Gleeble-1500热/力机上用专制的夹具系统对铝合金铸轧过程流变行为及其影响因素进行了系列的模拟实验研究,得到了不同变形条件下铝合金瞬态凝固连续固态流变成形过程中的形变规律.实验表明铝合金的[液-糊状-固]流变过程存在4个不同特征阶段,通过对实验数据进行多元线性回归分析,建立了适用于连续铸轧这一特定工况条件下铝合金流变本构方程.