无滑动滚动时的摩擦力

通过一个演示实验 ,分析论证了纯滚动刚体所受摩擦力为静摩擦力 ,静摩擦力与物体的运动状态有关 ,与接触面性质无关 .     

pH-Dependent Slipping and Exfoliation of Layered Covalent Organic Framework

Layered/two-dimensional covalent organic frameworks (2D COF) are crystalline porous materials composed of light elements linked by strong covalent bonds. Interlayer force is one of the main factors directing the formation of a stacked layer structure, which plays a vital role in the stability, crystallinity, and porosity of layered COFs. The as-developed new way to modulate the interlayer force of imine-linked 2D TAPB-PDA-COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene, PDA = terephthaldehyde) by only adjusting the pH of the solution. At alkaline and neutral pH, the pore size of the COF decreases from 34 Å due to the turbostratic effect. Under highly acidic conditions (pH 1), TAPB-PDA-COF shows a faster and stronger turbostratic effect, thus causing the 2D structure to exfoliate. This yields bulk quantities of an exfoliated few/single-layer 2D COF, which was well dispersed and displayed a clear Tyndall effect (TE). Furthermore, nanopipette-based electrochemical testing also confirms the slipping of layers with increase towards acidic pH. A model of pH-dependent layer slipping of TAPB-PDA-COF was proposed. This controllable pH-dependent change in the layer structure may open a new door for potential applications in controlled gas adsorption/desorption and drug loading/releasing.     

一种间接测量圆柱形管内样品冲击波压力的方法

 描述了一种联合使用锰铜计和康铜计间接测量柱对称滑移爆轰条件下，金属管内样品中冲击波压力的方法。给出了冲击压缩方法合成纤锌矿型氮化硼（wBN）时的测量结果。结果表明：管内样品中压力范围大致在11.5~22 GPa范围内，满足冲击波合成wBN所需的压力条件；管内样品压力的发展变化具有不连续性。证明了这种间接测量管内压力的方法是可行的。     

Phase structure change and ER effect in liquid crystalline polymer/dimethylsiloxane blends

The mechanism of the electrorheological (ER) effect in two types of liquid crystalline polymer (LCP)/dimethylsiloxane (DMS) blends was investigated by rheological measurements and by structure observation under electric field and shear flow. The results show that the phase structures of these immiscible blends can be categorized into slipping (low viscosity) and non-slipping (high viscosity) states. In the non-slipping state, higher viscosity LCP domains connect the electrodes. In the slipping state, on the other hand, LCP domains do not connect the electrodes and the shear is mainly confined in the lower viscosity DMS domains. The ER effect (electrically induced viscosity increase) originates from the electrically induced slipping to non-slipping transition. In one of the blends, the ER effect occurs only at high shear rate, since this blend is in non-slipping state even under no field if the shear rate is low. Received: 29 April 1997 Accepted: 3 November 1997     

多思路巧妙测量阻尼常数及计时仪器的开发

本文从物理实验测量和计时仪器开发两个方面同时入手,从运动学角度出发,分别选用U形和条形遮光片,且灵活利用通用计数器的各个功能,综合提炼出7种实验方案测量阻尼常数,其测量值在1.31～1.53之间,实验结果重复性和一致性较好.同时开发新的计时仪器,直接应用于本实验,使测量过程变得简单易行.     

应用杆束系统研究水泥砂浆节理面的压剪动特性

基于分离式Hopkinson压杆系统提出一套Hopkinson束杆装置,研究水泥砂浆节理面在压剪复合加载下的动态界面滑移特性。应用三根小杆作为接收杆,分别采用单杆和三杆两种入射方式,对含有节理面的水泥砂浆试件进行冲击加载。在节理面发生滑动时,由三根接收杆测试得到水泥砂浆试件不同位置滑移状态,进而得出节理面的整体滑移速度。此研究初步揭示了节理面在发生滑移时的局部滑移状态以及整体滑移状态,为节理面的动摩擦特性研究提供了较可靠的实验技术。     

Green's functions for anisotropic piezoelectric bimaterials with a slipping interface

An explicit full-field expression of the Green's functions for anisotropic piezoelectric bimaterials with a slipping interface is derived. When the electro-elastic singularity reduces to a pure dislocation in displacement and electric potential, interaction energy between the dislocation and the bimaterials is obtained explicitly while the generalized force on the dislocation is given in a real form which is also valid for degenerate materials. The investigation demonstrates that the boundary conditions at the slipping interface between two piezoelectric materials will exert a prominent influence on the mobility of the dislocation. Project supported by the National Natural Science Foundation of China (No. 59635140).     

Electrophoresis of large colloidal particles with surface charge layers. Position of the slipping plane and surface layer thickness

A theory is proposed for the electrophoresis of a large colloidal particle with a surface charge layer. The slipping plane is assumed to be located within the surface layer but may not be located at the boundary between the surface layer and the particle core. In previous studies, the depth of the slipping plane is assumed to coincide with the surface layer thickness. The present theory makes it possible to examine the separate dependence of the electrophoretic mobility on the position of the slipping plane and on the surface layer thickness. It is shown that, at constant amount of particle-fixed charges in the surface layer, the mobility increases as the depth of the slipping plane (d _s ) increases, while it decreases as the surface layer thickness (d _c ) increases, causing a mobility maximum in some cases ifd _s =d _c . Several approximate analytic expressions for the mobility are presented.     

Damping of Magnetorheological Elastomers

The damping property of magnetorheological (MR) elastomers is characterized by a modified dynamic mechanical-magnetic coupled analyzer. The influences of the external magnetic flux density, damping of the matrix, content of iron particles, dynamic strain, and driving frequency on the damping properties of MR elastomers were investigated experimentally. The experimental results indicate that the damping properties of MR elastomers greatly depend on the interfacial slipping between the inner particles and the matrix. Different from general composite materials, the interfacial slipping in MR elastomers is affected bythe external applied magnetic field.