THE USE OF VISCO-ELASTOPLASTIC DAMAGE CONSTITUTIVE MODEL TO SIMULATE NONLINEAR BEHAVIOR OF CONCRETE

A visco-elastoplastic damage constitutive model is proposed for simulating nonlinear behavior of concrete. Based on traditional plastic theory, the irreversible deformation is simulated in effective stress space. In order to reflect different stiffness degradation mechanism of concrete under tensile and compressive loading conditions, both tensile and compressive damage variables are introduced, and then on the basis of energy release rate, the model is firmly derived within the concept of irreversible thermodynamics. The rate-dependent model is considered by introducing viscous regularization into the inelastic strain and damage variable, and combined with an additional elastic condition. Fully implicit backward-Euler algorithm is used to perform constitutive integration. Results of numerical examples using the proposed model agree well with test results for specimens under uniaxial tension and compression, biaxial loading and triaxial loading. Failure processes of single-edge-notched (SEN) beam and double-edge-notched (DEN) specimen are also simulated to further validate the proposed model.     

激光陀螺单轴旋转式惯导系统的转动方案分析

目前国际上的激光陀螺单轴旋转式惯导系统中,普遍采用一种四位置转停的惯性测量组合转动方案.通过对这种四位置转停方案的误差分析,指出它并不能够完全抵消掉转轴垂直平面内的所有陀螺常值漂移误差,并且载体航向变化会降低误差抵消的程度,基于此,在这种四位置转停方案基础上,首先提出了一种改进的四位置转停方案,可以抵消掉转轴垂直平面内的所有陀螺常值漂移误差,然后进一步提出了一种动态调整停止时间的四位置转停方案,使转轴垂直平面内的常值漂移误差的抵消程度不受载体航向变化的影响.分析表明,文中提出的这些改进措施和方法能够提高系统精度,而不会降低系统的可靠性,并且使用简单易行,可以应用于实际的单轴旋转式惯导系统中.     

泊松比对拉伸法测材料杨氏模量的影响

用拉伸法测杨氏模量较小的圆形材料杨氏模量实验时,伴随材料的拉长,其直径将明显减小.此时,实验必须考虑材料直径的变化.以拉伸法测圆形硅胶的杨氏模量为例,将材料直径的变化通过泊松比转为材料伸长量,实验结果表明引入泊松比所测杨氏模量精确度提高,不确定度减小.     

聚变堆用结构材料CLF-1研究进展

本文报道了我院近半年来低活性铁素体／马氏体钢CLF-1的研究进展。通过微观组织观察和室温拉伸性能测试，证明该钢已具有优于Eurofer97的室温拉伸性能，而且得到了全马氏体的微观组织。     

双调制步进扫描红外光谱技术用于聚氨酯薄膜动态拉伸实验

将步进扫描多调制傅里叶红外光谱技术用于聚氨酯薄膜动态拉伸的流变光谱性质研究。讨论了步进扫描干涉仪的工作原理、包括相调制在内的多调制频率与数字采集实验设置及数字信号处理方法。得到聚氨酯薄膜在100Hz频率、1.0λ振幅的相调制作用下，相对于5Hz拉伸频率的同相位（In-phase)和正交相位（Quadrature)的红外吸收光谱。     

分子链大尺度高取向而小尺度接近无规取向态的非晶态聚对苯二甲酸…

对非晶态聚对苯二甲酸乙二酯膜片经在Ｔｇ以上单轴拉伸然后淬冷至室温的试样，其物理性质的各向同性或各向异性进行了研究。实验结果说明这种分子链大尺度高度取向而小尺度接近无规取向的非晶态（ＧＯＬＲ态）其折光指数和小形变的拉伸模量是接近各向同性的，而热导率和微波介电常数很可能是各向异性的。     

凸泛函型的区域压缩与拉伸不动点定理

利用赋范线性空间中的收缩核,给出了凸泛函型的区域压缩与拉伸不动点定理,推广了郭大钧定理.     

交联1，4－顺式聚丁二烯的取向结晶

用ＷＡＸＤ和ＳＡＸＳ研究交联１，４－顺式聚丁二烯的取向结晶．结果表明：该试样在拉伸状态时，形成折叠链片晶，而不是伸直链纤维晶．片晶之间不断产生新的片晶，使长周期减小，并且片晶的横向尺寸不断增大，由此导致结晶度增大．     

Pressure effect study on the I－V property of the GaAs-based resonant tunnelling structure by photoluminescence measurement

This paper discusses the I-V property of the GaAs-based resonant tunnelling structure （RTS） under external uniaxial pressure by photoluminescence studies. Compressive pressure parallel to the [110] direction, whose value is determined by Hooke＇s law, is imposed on the sample by a helix micrometer. With the increase of the applied external uniaxial compressive pressure, the blue shift and splitting of the luminescence peaks were observed, which have some influence on the I-V curve of RTS from the point of view of the energy gap, and the splitting became more apparent with applied pressure. Full width at half maximum broadening could also be observed.     

Liquid Film on Unsteady Stretching Sheet with General Surface Temperature and Viscous Dissipation

We study the effects of viscous dissipation on flow and heat transfer in a thin liquid film on an unsteady stretching sheet. A general surface temperature is taken into consideration. The velocity and temperature fields are solved using the homotopy analysis method. The results show that the increasing values of the Eckert number can increase temperature distribution and the heat transfer rate.