聚氧乙烯氧丙烯无规聚醚／水体系的流变性能研究

本文研究了无规聚醚／水体系的粘温粘浓特性，并对其流变性及粘弹性质进行了讨论。     

单向土工格栅加筋土的流变模型

在研究HDPE单向土工格栅的蠕变和应力松弛特性的基础上，建立了单向土工格栅的流变模型。将加筋土视为由筋、土组成的宏观均匀材料，建立单向土工格栅加筋土体的流变模型。分析表明，在承受长期荷载作用的加筋土的本构关系中，必须考虑由聚合物为原料制作的筋材所具有的明显时间相关的力学行为。     

Numerical simulation of damage and failure in aircraft windshield structure against bird strike

Based on the updated Lagrangian approach, the incremented form of a damage-modified nonlinear visco-elastic constitutive model and its failure criterion were deduced using the updated Kirchhoff stress tensors and strain tensors. The finite element model of a windshield structure including windshield, framework, arc-frame, gasket and rivets was established, in which the adaptive contact relation and boundary condition was defined. A contact–impact coupling algorithm and the explicit dynamic finite element program LS-DYNA were applied to simulate the damage and failure process of windshield structure under three kinds of bird strike velocities. The damage-modified nonlinear visco-elastic constitutive model and its failure criterion were implemented into the user material program. The results showed that the damage and failure of windshield under bird strike can be effectively simulated.     

人工边界及地震动输入在有限元软件中的实现

粘弹性人工边界不仅在时间上是局部的,而且在空间上也是局部的,这种边界物理意义清晰、简单有效,且易于在有限元法中得以实现,与之相对于的地震动输入则是通过在边界上施加等效节点力实现的,等效节点力的大小与入射地震波波速成正比.本文利用通用有限元软件提供的弹簧阻尼单元模拟粘弹性边界,介绍了土-地下结构开放系统人工边界及地震动输...     

Morphological Study of Cavity and Worthington Jet Formations for Newtonian and Non-Newtonian Liquids

In this article a morphological study of the cavity formation and the liquid column formation of the Worthington jet with lapse of time for the Newtonian liquids of water and glycerine wt 70% solution and for non-Newtonian liquids of acrylic copolymer solution of ACA-wt1%, ACA-wt2%, and ACA-wt3% by a droplet falling to the free surface of the target liquid in the cylindrical container from a height of H = 100, 200, 300, 400, and 500 mm is described. The calculated results by the energy equation for the maximum cavity radius Rmax/d and for the morphological size D · h/d² of the Worthington jet are in agreement with the experimental results. In order to take photographs of the cavity formation and the Worthington jet formation with lapse of time, a CCD camera was used. The falling droplet and the target liquid are the same material. Here d is the mean diameter of the droplet and D and h are the mean diameter and maximum height of the liquid column of the Worthington jet.     

隧道洞口段结构地震响应分析

隧道的进出口大多是风化的松散堆积体,是抗震设防的薄弱环节。运用Newmark隐式时间积分有限元法,采用粘-弹性人工边界,对在地震荷载作用下围岩材料的渐变对隧道洞口段抗震性能进行分析。得到了3种工况下沿隧道轴线方向衬砌最大应力、位移以及加速度变化曲线,及不同工况下洞口段隧道结构的抗震设防长度。洞口段设防长度与洞口段围岩性质有关,洞口段围岩由软弱向坚硬渐变长度越长,洞口段衬砌应力就越大,洞口段设防长度就越长。     

Superposition model for analyzing the dynamic ground subsidence in mining area of thick loose layer

The dynamic ground subsidence due to underground mining is a complicated time-dependent and ratedependent process. Based on the theory of rock rheology and probability integral method, this study developed the superposition model for the prediction and analysis of the ground dynamic subsidence in mining area of thick loose layer. The model consists of two parts(the prediction of overlying bedrock and the prediction of thick loose layer). The overlying bedrock is regarded as visco-elastic beam, of which the dynamic subsidence is predicted by the Kelvin visco-elastic rheological model. The thick loose layer is regarded as random medium and the ground dynamic subsidence is predicted by the probability integral model. At last, the two prediction models are vertically stacked in the same coordinate system, and the bedrock dynamic subsidence is regarded as a variable mining thickness input into the prediction model of ground dynamic subsidence. The prediction results obtained were compared with actual movement and deformation data from Zhao I and Zhao II mine, central China. The agreement of the prediction results with the field measurements show that the superposition model(SM) is more satisfactory and the formulae obtained are more effective than the classical single probability integral model(SPIM), and thus can be effectively used for predicting the ground dynamic subsidence in mining area of thick loose layer.     

One-dimensional consolidation of visco-elastic aquitard due to withdrawal of deep-groundwater

One-dimensional consolidation of visco-elastic aquitard due to withdrawal of deep-groundwater was studied. Merchant model was used to simulate visco-elastic characteristic of aquitard. General solutions of the governing equation were obtained by applying Laplace transform with respect to time, and then the pore-pressure, strain and deformation of the aquitard could be calculated by Laplace inversion. A case was analyzed to validate the correctness of the present method. Finally, some consolidation properties of the problem were analyzed. Comparison of the average degree of consolidation defined by pore pressure with that defined by settlement shows that they are different and the maximum difference is 22.8%. The influences of parameters of Merchant model and the rate of the water level on the consolidation are great. The smaller the viscosity coefficient is, the later the rate of consolidation decreases. The rate of consolidation is decreased with the decrease of the rate of the water level fall. Therefore, the lagged effect of land subsidence should be considered in the actual project.     

泥岩黏弹性剪切蠕变模型及参数辨识

基于泥岩黏弹性剪切蠕变试验结果,采用Burgers模型辨识获得了不同时间尺度下的泥岩黏弹性剪切蠕变参数,分析了时间尺度对泥岩黏弹性剪切蠕变模型参数的影响.结果表明,Burgers黏弹性剪切蠕变模型参数具有显著的时间尺度效应,以短期内的蠕变试验数据辨识获得的蠕变模型在预测岩石长期的黏弹性蠕变特征时显著高于试验结果.基于稳态蠕变阶段的试验数据拟合获得黏滞系数η2后再确定的蠕变模型能较好地预测长期的黏弹性蠕变特征,但在时间尺度较低时与试验结果吻合得不理想,然而建立的非线性黏弹性剪切蠕变经验模型,拟合得到的误差平方和Q(0.56×10-8～1.49×10-8)显著低于Burgers黏弹性剪切蠕变模型拟合得到的Q(0.16×10-8～8.15×10-8),能够更加准确地描述岩石的黏弹性蠕变特征.     

STUDY ON THE CREASE RESISTANCE TREATMENT OF THE NATURAL SILK WITH RESIN FINISHING (The first part)

In this paper we systematically inspect the crease resistance effect of several typicalkinds of resin,and try to probe into amore resonable method of the natural silks resinfinish.By inspecting the variation of the static visco-elastic constant and the degree ofcrosslinking caused by the different dinds of resin,the difference of degree of drafting andthe diffetence of precuring and curing,we may expound the crease resistance effect of theresin finish in mechanism.