描述低周疲劳裂纹扩展速率的循环J积分新参量

探讨了低周疲劳加载条件下的应力增量．应变增量关系，提出了模拟裂纹疲劳扩展的二维模型以建立新的循环．积分参量，详细阐述了该积分参量的定义、主要特点、物理意义以及数值计算方法，并通过紧凑拉伸试样的疲劳试验检验该积分参量的有效性．结果表明：该积分参量能够较好描述恒幅低周疲劳裂纹的扩展速率．此外，基于积分参量体系，从能量的角度解释了疲劳迟滞现象．     

A NEW CYCLIC J-INTEGRAL FOR LOW-CYCLE FATIGUE CRACK GROWTH

The constitutive equation under the low-cycle fatigue (LCF) was discussed, and a two-dimensional (2-D) model for simulating fatigue crack extension was put forward in order to propose a new cyclic J-integral. The definition, primary characteristics, physical interpretations and numerical evaluation of the new parameter were investigated in detail. Moreover, the new cyclic J-integral for LCF behaviors was validated by the compact tension (CT) specimens. Results show that the calculated values of the new parameter can correlate well with LCF crack growth rate, during constant-amplitude loading. In addition, the phenomenon of fatigue retardation was explained through the viewpoint of energy based on the concept of the new parameter.     

砂土地基锚板基础抗拔承载力PFC数值分析

在模型试验的基础上,采用PFC离散单元法对条形锚板基础在中密砂土地基中的抗拔性能进行了数值分析。数值模拟采用簇颗粒单元来模拟砂粒的不规则形状,颗粒级配根据模型试验福建标准砂的级配按照相似级配法生成,细观参数根据数值双轴试验确定。水平锚板数值模拟结果与模型试验结果基本一致。与模型试验结果相比,颗粒流数值模拟能得到颗粒间接触力链的分布及其演化规律,能从细观角度来探明宏观抗拔承载力特性的演化机理。在此基础上对倾斜锚板上拔过程进行了模拟,分析了锚板前后砂粒的运动趋势以及接触力链的演化规律,并与已有承载力结果进行了对比分析。     

三分子反应在—维介质上的动力学行为

提出了一种简明的理论分析方法，求出了三分子反应Ａ＋２Ｘ　３Ｘ在一维介质上的动力学行为的解析解，并成功地解决了该反应动力学行为对初始条件的依赖性问题。还通过数值模拟证实了提出的理论方法的正确性。     

丁基罗丹明B-硫氰酸盐-吐温-20体系高灵敏分光光度法测定微量硒的研究

本文叙述了在吐温-20存在下用硫氰酸盐和丁基罗丹明B形成缔合型三元配合物测定微量硒(Ⅳ)。配合物的最大吸收波长为600nm,硒含量在0—5μg/25ml服从朗伯比尔定律,其ε_(600)=6.4×10~5,重现性好,选择性高,是目前测定微量硒的一种高灵敏度的新的分光光度法,已用于水样中微量硒的测定。     

聚氯乙烯接近玻璃化转变温度时的蠕变行为研究

利用动态力学分析仪,详细研究了小应力作用下聚氯乙烯（PVC）接近玻璃化转变温度（63℃）时的短期蠕变性能．根据Struik-Kohlrausch (SK)方程及Struik移位方法,分析了物理老化对PVC瞬时蠕变柔量的影响,并提出了基于多松弛机制的新模型定量描述初始蠕变柔量、松弛时间和形状因子．结果表明:SK方程虽可表征不同老化时间下PVC的蠕变性能,但通过Struik移位方法却无法获得理想的主曲线,且初始蠕变柔量、松弛时间、形状因子和蠕变率均受物理老化显著影响,并在双对数坐标下随老化时间呈明显的非线性变化;新模型不仅揭示了物理老化控制参量的演化规律,而且极好地预测了PVC在物理老化进程中的高温蠕变行为．     

Creep performance of PVC aged at temperature relatively close to glass transition temperature

In order to predict the mechanical performance of the polyvinyl chloride(PVC) at a high operating temperature,a series of short-term tensile creep tests(onetenth of the physical aging time) of the PVC are carried out at 63 C with a small constant stress by a dynamic mechanical analyzer(DMA).The Struik-Kohlrausch(SK) formula and Struik shifting methods are used to describe these creep data for various physical aging time.A new phenomenological model based on the multiple relaxation mechanisms of an amorphous polymer is developed to quantitatively characterize the SK parameters(the initial creep compliance,the characteristic retardation time,and the shape factor) determined by the aging time.It is shown that the momentary creep compliance curve of the PVC at 63 C can be very well fitted by the SK formula for each aging time.However,the SK parameters for the creep curves are not constant during the aging process at the elevated temperatures,and the evolution of these parameters and the creep rate versus aging time curves at the double logarithmic coordinates have shown a nonlinear phenomenon.Moreover,the creep master curves obtained by the superposition with the Struik shifting methods are unsatisfactory in such a case.Finally,the predicted results calculated from the present model incorporating with the SK formula are in excellent agreement with the creep experimental data for the PVC isothermally aged at the temperature relatively close to the glass transition temperature.     

便携式拉曼光谱仪快速测定磷酸浓度

用便携式激光拉曼光谱仪测定磷酸浓度,利用P—O键对称伸缩振动峰(893—911cm-1)的峰值,以硝酸根特征峰为内标,建立了激光拉曼光谱法测定磷酸含量的模型,并对拉曼位移与磷酸浓度的关系进行了拟合。两种方法用于实际样品检测的结果准确度和精密度良好,均能够满足水体中磷酸含量测定的要求。     

三分子反应在一维介质上的动力学行为

提出了一种简明的理论分析方法，求出了三分子反应Ａ＋２Ｘ←→３Ｘ在一维介质上的动力学行为的解析解，并成功地解决了该反应动力学行为对初始条件的依赖性问题。还通过数值模拟证实了提出了理论方法的正确性。