Interaction of microcracks with a macrocrack yielded in a narrow strip

Plastic zone growth of collinear cracks has had a longstanding interest in ductile fracture. This work further considers yield zone growth in an isotropic, homogeneous elastic–perfectly plastic infinite plate containing a macrocrack with several neighboring microcracks. Normal loading is considered at distances far away from the cracks. The strip yield is adopted where the plastic zone is assumed to be confined to two narrow strips extending from the ends of a finite length crack while the microcracks are assumed to be elastic. The plastic zone length and crack opening displacement are found from asymptotic solution and compared with finite element solution.     

含微裂纹弹性体的应力应变关系

本义建立了考虑裂纹闭合和裂纹表面摩擦影响的含微裂纹弹性体的应力应变关系，给出了柔度张量增量的显式表达式。对于二维平面应力和平面应变状态，给出了等效工程弹性系数。数值计算结果表明，裂纹闭合和裂纹面摩擦对裂纹体的应力应变关系和等效工程弹性系数有重要影响。     

含微裂纹弹性体的应力应变关系

本义建立了考虑裂纹闭合和裂纹表面摩擦影响的含微裂纹弹性体的应力应变关系，给出了柔度张量增量的显式表达式。对于二维平面应力和平面应变状态，给出了等效工程弹性系数。数值计算结果表明，裂纹闭合和裂纹面摩擦对裂纹体的应力应变关系和等效工程弹性系数有重要影响。     

Mesoscopic characterization and modeling of microcracking in cementitious materials by the extended finite element method

This study develops a mesoscopic framework and methodology for the modeling of microcracks in concrete. A new algorithm is first proposed for the generation of random concrete meso-structure including microcracks and then coupled with the extended finite element method to simulate the heterogeneities and discontinuities present in the meso-structure of concrete. The proposed procedure is verified and exemplified by a series of numerical simulations. The simulation results show that microcracks can exert considerable impact on the fracture performance of concrete. More broadly, this work provides valuable insight into the initiation and propagation mechanism of microcracks in concrete and helps to foster a better understanding of the micro-mechanical behavior of cementitious materials.     

The Potential of Microencapsulated Self-healing Materials for Microcracks Recovery in Self-healing Composite Systems: A Review

The autonomic self-healing materials based on microcapsules have made major advancements for the repairing of microcracks in polymers and polymer composite systems. Self-healing encapsulated materials have the inborn ability to heal polymeric composites after being damaged by chemical and mechanical progressions. These intelligent micro-encapsulated self-healing materials possess great capabilities for recovering the mechanical as well aesthetic properties and barrier properties of the polymeric structures. Based on real world observations and experimental data, it is believed that microcracks and microcracking in polymeric materials can result because of many chemical and physical routes and is one of the foremost critical issues for polymeric materials. Especially in polymeric coatings, these microcracks can lead towards disastrous failure, and conventional healing systems like patching and welding cannot be used to repair microcracks at such a micro-level. Self-healing materials, especially, capsule based self-healing materials is a new field sought as an alternative to the conventional repairing techniques, requiring no manual intrusion and uncovering. This review covers the basic and major aspects of the microencapsulated self-healing approach like the effect of synthesis parameters on the size of microcapsules, healing efficiency determination, and the potential of the existing developed microencapsulated agents.     

随机分布共线微裂纹的强相互作用

微裂纹串接为宏观灾难性裂纹的过程取决于相邻微裂纹的强相互作用。微裂纹的分布规律影响材料的强度和韧性。本文研究简单的共线微裂纹构型，确定由于微裂纹长度和韧度尺寸的统计分布所产生的影响。研究结果预计了脆性材料的尺度效应，即对于相同密度的微裂纹分布，大尺寸构件的强度比小尺寸构件要低。计算还表明脆性体的强度随微裂纹分布函数标准方差的增加而减小。     

内压对电场下晶内微裂纹演化的影响

基于表面扩散的经典理论及其弱解描述,建立曲率、内压和电场共同作用下的有限单元法,分析了金属材料内部晶内微裂纹的演化过程。对于形态比为β的微裂纹,存在一临界电场值χc,当χ<χc时,微裂纹逐渐圆柱化;当χ>χc时,微裂纹分节为上下或左右两个较小的微裂纹。内压加速有助于微裂纹分节。对于β>1的微裂纹,当β和χ一定时存在一临界内压值qc,当q>qc时,随着电场和内压的增大会率先在裂纹的右端发生裂纹扩展。     

A decoration technique for defect analysis in ceramics

A decoration technique for the visualization of microcracks based on chemical impregnation and transmitted light optical investigation is described.