固体炸药损伤破坏实验研究

利用显微观察和数字图像相关处理,对一种固体炸药材料的损伤破坏行为进行了研究,获得了带预制裂纹试件在裂纹尖端附近区域的位移分布,以及微裂纹的诱发和发展历程.断裂过程的结果表明,裂尖的位移分布与裂纹的受载形式有关,而最终断裂的裂纹破坏路径总是趋向于加载方向.通过扫描电镜下的实验观察,发现造型粉颗粒的界面脱落是炸药损伤的主要因素,它的发展会导致微裂纹的产生和发展.     

Inter-contact force analysis of impacted disk assembly by dynamic caustics

The caustic method was utilized to study the contact force transmission in disk assemblies under impact load. The mapping equations were obtained based on the first invariant of the stress components in the disk subject to a normal concentrated force, and a characteristic dimension of the maximum size in the caustic curve was proposed to evaluate the contact force between the disks. Transient patterns of the caustic shadows were recorded by means of a high-speed camera of off-focus imaging, then the histories of the inter-contact forces among the disks were obtained with respect to the conditions of different masses and heights of the falling hammers. The influence of the impact loading and impulsive velocity was analyzed with respect to the force responses of the disk assembly, the double-peak phenomenon with comparison to the initial masses, and the energy dissipation of the systems under impact of different momentums. The project supported by the National Natural Science Foundation of China (10125211)     

Damage and fracture evaluation of granular composite materials by digital image correlation method

This paper presents the applications of digital image correlation technique to the mesoscopic damage and fracture study of some granular based composite materials including steelfiber reinforced concrete, sandstone and crystal-polymer composite. The deformation fields of the composite materials resulted from stress localization were obtained by the correlation computation of the surface images with loading steps and thus the related damage prediction and fracture parameters were evaluated. The correlation searching could be performed either directly based on the gray levels of the digital images or from the wavelet transform (WT) coefficients of the transform spectrum. The latter was developed by the authors and showed higher resolution and sensitivity to the singularity detection. Because the displacement components came from the rough surfaces of the composite materials without any coats of gratings or fringes of optical interferometry, both surface profiles and the deformation fields of the composites were visualized which was helpful to compare each other to analyze the damage of those heterogeneous materials. The project supported by the National Natural Science Foundation of China (10125211 and 10072002), the Scientific Committee of Yunnan Province for the Program of Steel Fiber Reinforced Concrete, and the Institute of Chemical Materials, CAEP at Mianyang     

石英晶体微天平传感器的膜厚敏感性

近几年,石英晶体微天平(QCM)作为一种简易、灵敏的实时监测手段,广泛地应用于研究生物活性分子之间的相互作用,其中包括蛋白质吸附动力学、抗原/抗体相互作用、DNA杂交、适配体-蛋白相互作用等领域.但是QCM作为商业化的生物传感器一直发展不顺利.主要因为QCM在液态环境中的非理想行为导致了对QCM数据分析困难.我们利用阻抗分析法对QCM的数据进行分析,分离出质量和粘弹性两种因素引起的频率改变,解决粘弹性的困扰问题.同时,我们提出了"固化水层"模型,合理地处理了溶剂的影响.在该模型的基础上发展了一种基于QCM的分子尺技术,该技术能够简便、有效地测量出固定在固-液界面的生物大分子的纳米尺寸.我们的主要工作是将"固化水层"模型拓展到三维结构的高分子基质中.我们联合QCM和表面等离子共振(SPR)技术研究基于高分子基质的蛋白质的固定,抗原/抗体识别的过程,进一步采用"固化水层"模型解释高分子的溶胀行为、羧基活化、抗体固定、抗原、抗体识别等过程.理论分析表明,结合生物分子势必排出相同体积的溶剂,由于溶剂的密度接近于蛋白质溶液的密度.从而导致"固化水层"质量增加不明显.实验上也证实了石英晶体微天平的响应主要取决于"固化水层"的厚度变化(T2-T1),而并非固定的生物分子的质量.我们利用QCM实时监测在高分子基质中IgG的固定以及IgG与anti-IgG识别的过程,并将石英晶体微天平监测的频率变化与相应的厚度变化直接关联.这一方法的建立在一定的应用范围内简化了QCM的定量分析模型,有望实现QCM作为传感器在界面物理与化学等相关领域研究中的应用.     

Characterization of Wave Dispersion in Viscoelastic Cellular Assemblies by Doublet Mechanics

Using the Voigt model, we analyze wave propagation in viscoelastic granular media with a monatomic lattice, planar simple cubic package and cubical-tetrahedral assembly within the context of doublet mechanics. Microstrains of elongation between the doublet particles are considered in the models. Wave dispersive relations are derived from dynamic equations of the particles involved in the media, and phase velocities and attenuations of the dispersive waves are obtained for the different assemblies. Variations in these dispersion characteristics are analyzed with the changes of cell interval, modulus, and wave frequency. The relations between micro-constants and macro-parameters are presented under the condition of non-scale continuity of the media.     

钢纤维增强混凝土的断裂破坏研究

在钢纤维增强混凝土的断裂力学性能的实验研究中,利用数字图像相关技术对素水泥砂浆试件和钢纤维增强水泥砂浆试件进行裂纹尖端的位移场测量,求解不同纤维分布情况下的应力强度因子从而进行增强性能的分析比较.对于单纤维桥联增强的情况,实验结果与Carpinteri的模型计算结果进行了分析比较,证明这种图像和数据处理方法对裂纹尖端的纤维位增强特性分析是有效可行的.     

Electro-mechanical coupling analysis of MEMS structures by boundary element method

In this paper, we present the applications of Boundary Element Method (BEM) to simulate the electro-mechanical coupling responses of Micro-Electro-Mechanical systems (MEMS). The algorithm is programmed in our research group based on BEM modeling for electrostatics and elastostatics. Good agreement is shown while the simulation results of the pull-in voltages are compared with the theoretical/experimental ones for some examples. The project supported by the 973 Program (G199033108) and the national Natural Science Foundation of China (10125211)     

细胞牵引力显微镜反演方法研究进展

细胞与胞外基质微环境的物理力学相互作用涉及许多复杂的生物信号转导通路,对于细胞的增殖、分化、收缩、迁移和凋亡等都起着重要的调控作用。在单细胞水平上,运用细胞牵引力显微镜方法定量研究细胞活动规律及特点具有重要的生理病理学意义。牵引力显微镜方法的核心在于如何通过基底变形信息反演得到细胞牵引力场。本文首先介绍细胞牵引力反演方法的基本原理,然后针对细胞牵引力求解过程中所涉及到的反问题的病态本性,重点介绍近十几年来细胞牵引力反演算法的研究进展(包括边界元反演算法、基于集中力假设的反演算法、基于积分Boussinesq解的反演算法、基于傅立叶变换的反演算法、基于最优滤波的反演算法等)。     

细胞牵引力显微镜反演方法研究进展

细胞与胞外基质微环境的物理力学相互作用涉及许多复杂的生物信号转导通路,对于细胞的增殖、分化、收缩、迁移和凋亡等都起着重要的调控作用。在单细胞水平上,运用细胞牵引力显微镜方法定量研究细胞活动规律及特点具有重要的生理病理学意义。牵引力显微镜方法的核心在于如何通过基底变形信息反演得到细胞牵引力场。本文首先介绍细胞牵引力反演方法的基本原理,然后针对细胞牵引力求解过程中所涉及到的反问题的病态本性,重点介绍近十几年来细胞牵引力反演算法的研究进展(包括边界元反演算法、基于集中力假设的反演算法、基于积分Boussinesq解的反演算法、基于傅立叶变换的反演算法、基于最优滤波的反演算法等)。     

冲击载荷作用下韧－脆复合板结构中脆性材料破碎的实验和数值模拟

本文以冲击实验和有限元分析研究了韧－脆复合材料结构中脆性材料的破碎问题。材料的破碎图具有一定的分形特征，其分形维数随冲击载荷的增大而增加。基于实验结果的非线性动力有限元分析对这类破碎图样的演化给出了动态过程模拟