Microcracks in MDF Cement

The relationspip between the microcracks and the mechanical behaviors and the characteristics of fracture of MDF cement have been studied. The results show that most of the microcracks lie and propagate in the matrix or along the boundary of the clinkers. The microcracks improve the toughness of MDF cement. The Griffith's equation is invalid to describe the fracture of MDF cement.     

平面微裂纹扩展过程的计算机模拟

运用二维Voronoi网络划分技术模拟了金属材料的多晶体结构,在此基础上,对二维微裂纹在多晶体结构中的扩展过程进行了计算机可视化模拟,并开发出相应的计算机模拟软件.模拟结果再现了微裂纹在各个扩展阶段的形状变化特征及扩展路径,为预测在一定载荷条件下、特定材料中微裂纹的扩展行为提供了一个有效的可视化的手段,同时还为三维微裂纹扩展过程及其行为的模拟奠定了基础.     

陶瓷断裂非平衡统计理论

研究了陶瓷断裂非平衡统计理论.文中从微裂纹随机长大导致断裂的思路出发,给出了随机长大方程,导出了微裂纹分布函数、断裂几率、可靠性、强度和寿命的统计分布函数及其统计平均值。     

激光散斑法对冻土微裂纹形貌和发展过程的研究

将激光散斑法用于冻土材料,得出了裂纹尖端存在一个微裂纹损伤区（或称为断裂过程区）的结论．通过对裂纹尖端一系列散斑图的逐点分析,绘出了微裂纹区随载荷增加而发展的形貌及其全过程,测定了裂纹嘴张开位移的临界值δＣ,从而为冻土材料的宏微观力学行为研究及弹塑性断裂韧度测试分析提供了有效的途径．     

Caving performance through the integration of microseismic activity and numerical modeling at DOZ-PT Freeport, Indonesia

This article describes an undergoing research at PT Freeport, Indonesia, in which the main goal is to use the microseismic information recorded as a result of mining to analyze cave propagation and stress performance on the actual production and fixed infrastructure. At the moment, several numerical experiments have been conducted to correlate the mining activity with the microseismic events using the data collected during year 2005 and 2006. As a result of the preliminary analysis a micro- and a macrocracking envelop were proposed on the basis of computation of stress behavior at the location of the events. Stresses have been computed using standard elastic continuous boundary element models. The correlation between the average source radius and the stress performance has provided a method to propose a macrocracking criterion. Several techniques have been tested to nucleate the microseismic activity around different geological features. This last attempt was aimed to look at potential overstresses induced over the undercut and extraction level drifts. A method was devised to integrate the microseismicity into a 3-dimensional ride distribution model. This model has shown to be very effective to quantify the overstress induced as a result of computing volumetric microseismicity density. The volumetric microseismic model showed to induce overstress up to 10 MPa over a period of two months. The future work will concentrate on the calibration of the integrated model with actual damage observations made at the current mining infrastructure.     

ZrO_2 CeO_2涂层显微组织和抗热震性能

为了改善等离子喷涂ZrO2 涂层的抗热震性能 ,利用热震试验、SEM和EPMA等技术 ,研究了CeO2 添加剂对其显微组织和抗热震性能的影响 .研究结果表明 :当CeO2 添加剂的质量分数小于 9.0 %时 ,涂层的抗热震性能随CeO2添加剂质量分数的增加而提高 ,当CeO2 质量分数大于 9.0 %时 ,涂层的抗热震性能随其质量分数的增加而降低 ;ZrO2 涂层的抗热震次数为 46次 ,而ZrO2 9.0 ?O2 涂层的抗热震次数为 10 5次 ;ZrO2 9.0 ?O2 涂层在热循环中形成网状微裂纹 ,不仅可以降低涂层中的应力 ,而且可以提高涂层开裂的临界温差 ,从而改善其抗热震性能 .     

PZT在机电疲劳作用下的微裂纹和畸变

通过对PZT铁电陶瓷试样在交变力四点弯、交变电场及机电耦合疲劳作用前后的微裂纹和电畴的观察研究发现：电畴畴壁垂直于硬度痕边界排列;裂纹附近畴壁趋于转向与裂纹平行的方向;极化试样中的微裂纹萌生和扩展显示出强烈的各向异性。另外,还试图解释实验实验观察到的在外加极化电场方向平行的初始试样表面内存在大量微观畴带的现象。     

脆性断裂非平衡统计理论(Ⅰ)

本文和下文试图用非平衡统计的概念和方法建立微观机理和宏观特性相结合的脆性断裂理论。 本文给出了微裂纹的演化方程,讨论了微裂纹长大的位错机理,求得了长大的动力学方程和长大速率,探索了断裂韧性的微观物理基础和表达式,解得了微裂纹分布函数。     

混凝土抗渗性能研究

阐述了混凝土抗渗性能的重要性,分析了影响混凝土抗渗性能的各个方面和主要因素,并且针对这些影响因素,介绍了国内外研究现状及目前获得的一些重要结论,对今后混凝土抗渗性能研究的发展方向也进行了探讨。     

哈弗斯皮质骨径向直裂纹研究

哈弗斯皮质骨的断裂微观力学已被提出,在骨中由于疲劳负荷和循环载荷形成微裂纹,有研究者利用二维力学纤维陶瓷基复合材料模型,针对间骨板中出现任一径向直线裂纹的问题,研究了骨单位与裂纹间的相互作用;为更真实模拟骨裂纹的情形,研究了骨单位和间骨板中同时出现一条直线裂纹的情况,通过将裂纹看作一系列连续韧性位错的塞积群,运用格林函数转化为一系列奇异积分方程,然后通过Erdogon和Gupta方法求解方程,并用高斯-切比雪夫数值离散求得相应的应力强度因子,分析对骨微结构形态的影响。