Formation of three dimensional crack patterns

三维裂纹图案的形成

• 批准号: 213158658
• 负责人: Dr.-Ing. Martin Hofmann
• 金额: --
• 依托单位: Lehrstuhl für Werkstofftechnologie (LWT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/213158658?language=en
• 关键词: Formation; three; dimensional; crack; patterns

The aim of the project is a detailed understanding for the mechanisms of the formation of three dimensional (3D) crack patterns as a result of inhomogeneous shrinkage processes. During the 1st phase the method of fracture mechanical 3D bifurcation analysis based on a series expansion of the crack contour itself was developed successfully. This method now shall also be applied to cases with transient thermal shock loads at ceramics. Thereby both, the penetration depth of the cracks at overload cases and the residual strength can be predicted computationally. In addition, the impact on the crack propagation by internal stresses that develop during the thermal sputtering of insulation layers shall be examined. The drying procedure of ceramic precursor material in small tubes leads to star-shaped crack patterns. The mentioned bifurcation analysis shall be applied to investigate this phenomenon as well.For the first time, 3D crack patterns with curved crack surfaces were computed in the last period of the project. This calculation verified successfully that hexagonal cross sections in the columnar structures of basalt are energetically preferred during the process of development. In this simulation it is assumed that the crack front propagates in a direction at which the released energy is at a maximum. Now, the unexplained phenomenon of the oscillating crack surfaces of basalt columns shall be investigated using the same approach.In the experimental part of the project imaging techniques with significantly higher resolution shall be developed in order to improve the imaging of thermal shock cracks in ceramics. That way, cracks with small openings will become detectable. This methodical improvement aims at a quality of the measurement of crack spacings and crack depths that suffices for a verification of the expected results of the simulation. In order to map the cracks more clearly the techniques of computer laminography, serial sectioning technique with dye penetrant testing and tomographic microscopy are compared. Furthermore, instead of the formerly used ceramics with their tiny crack openings, now more suitable ceramics like for example porcelain or pottery shall be subjected to thermal shocks.Moreover, the software that processes the 3D images obtained by X-ray analyses techniques will be enhanced to detect the cracks more robust. For this purpose, the evaluation of each tomographic slice will incorporate the information in the adjacent tomographic slices. A software solution that tracks the column transitions occurring during the development of crack patterns is planned by which the transitions between several column arrangements are identified and their frequencies are quantified . In so doing, the analyses of experimentally obtained 3D images of crack patterns in ceramic systems and in dried starch-water-suspensions will contribute to the general understanding of the development of 3D crack patterns.

该项目的目的是对由于不均匀收缩过程而导致的三维（3D）裂纹模式形成机制的详细理解。在第一阶段，基于裂纹轮廓本身的串联膨胀的断裂机械3D分叉分析的方法已成功开发出来。现在，该方法还应应用于陶瓷瞬时热休克载荷的病例。因此，两者都可以通过计算预测过载案例的裂缝的穿透深度和残留强度。另外，应检查在绝缘层热溅射过程中产生的内部应力对裂纹传播的影响。小管中陶瓷前体材料的干燥程序导致星形裂纹图案。提到的分叉分析也适用于研究这种现象。首次在项目的最后一个时期计算出具有弯曲裂纹表面的3D裂纹模式。该计算成功验证了玄武岩柱结构中的六边形横截面在发育过程中是能量优先的。在此模拟中，假定裂纹前部沿最大释放能量的方向传播。现在，应使用相同的方法研究玄武岩柱的振荡裂纹表面的无法解释的现象。在项目成像技术的实验部分中，应开发出明显更高的分辨率，以改善陶瓷中陶瓷热冲击裂纹的成像。这样，可以检测到小小的开口的裂缝。这种有条不紊的改进旨在旨在测量裂纹间距和裂纹深度，这足以验证模拟的预期结果。为了更清楚地绘制计算机层压术的技术，比较了具有染料渗透剂测试和断层扫描显微镜的串行切片技术。此外，现在更合适的陶瓷（例如瓷器或陶器）应受到热震动。更重要的是，通过X射线分析技术获得的3D图像的软件将得到增强，以增强裂纹的功能。为此，对每个断层扫描切片的评估将将信息纳入相邻的断层片切片中。计划在开发裂纹模式期间跟踪列过渡的软件解决方案，并计划通过确定几个列布置之间的过渡并量化其频率。这样，在陶瓷系统和干燥的淀粉 - 水 - 悬浮物中，实验获得的裂纹模式的3D图像的分析将有助于对3D裂纹模式的发展的一般理解。