Influence of the particle packing on the fracture-mechanical behavior of carbon-free coarse-grained refractories

耐火陶瓷在其他分类类型中分为无碳和碳结合材料。无碳材料的好处是，随着闭环回收的建立，它们更具可持续性。此外，无碳材料由于没有致癌树脂或沥青成分，对工人的风险更低，安全性更高。然而，从技术的角度来看，碳结合材料具有更好的抗热震性，这在使用过程中往往是一个至关重要的要求。热冲击强度随热冲击而下降。如果更多的能量从扩展的裂缝中消散，它会得到改善。在我的博士论文中，我研究了粗粒耐火材料的粒度分布对热冲击强度行为以及其他性能的影响。根据颗粒充填的不同，强度下降在0 ~ 70%之间。百分之零意味着保持了初始强度，这是一个意想不到的非凡结果。这些显著的差异来自于调整后的材料结构。提出了能量耗散机制在结构中导致这些不同行为的假设。这些假设包括断裂力学现象，如裂纹在粗晶上的偏转，以及由于粗晶结构的锯齿状而导致的裂纹面之间的摩擦。这些假设的调查是提交的提案的核心主题。澄清了结构对断裂力学行为的影响，表明这种机制可以通过颗粒充填来调节。因此，对工人具有较低风险和较高安全性以及优异的抗热震性能的无碳可回收耐火材料可能在未来被制造出来。为了确定作用机制并将其与颗粒堆积的具体调整联系起来，将首先对样品进行结构分析，然后通过楔形劈裂试验对断裂力学进行研究。根据劈裂试验的力-位移曲线，可以计算出完全消耗能量的断裂能。此外，从曲线可以计算出抗裂纹扩展的阻力是否随着裂纹的扩展而增加，这通常与裂纹加工区域的扩大有关。通过数字图像相关，在楔形劈裂试验中也可以观察到裂纹偏转，从而使加工区域扩大。此外，还将进行微型楔形劈裂试验，以便在试验过程中观察结构的微观变化。因此，力-位移曲线的变化可能与上述断裂力学机制有关。此外，对楔形劈裂试验样品进行了微观研究，以支持微型楔形劈裂试验的结果。

Refractory ceramics are classified into carbon free and carbon bonded materials amongst other classification types. Carbon free materials have the benefits that they are more sustainable as a closed-loop recycling is established. Furthermore, carbon free materials have a lower risk and higher safety for the workers due to the missing carcinogenic resin or pitch components. From a technological point of view, however, carbon bonded-materials have a better thermal shock resistance which is during service often a crucial requirement. The thermal shock resistance is characterized by the strength drop with thermal shocking. It improves if more energy is dissipated from a propagating crack.In my PhD thesis, I investigated the influence of the particle size distribution of coarse-grained refractories on the strength behavior with thermal shocks amongst other properties. In dependence on the particle packing, strength drops between 0 and 70% occurred. Zero percent means that the initial strength was kept which was an unexpected extraordinary result. The significant differences had to result from the adjusted material structures. Hypotheses were presented which proposed energy dissipating mechanisms acting in the structures to lead to these different behaviors. The hypotheses comprise fracture-mechanical phenomena such as crack deflection on coarse grains as well as friction between the crack faces due to a serration of the coarse-grained structure.The investigation of these hypotheses is the core topic of the submitted proposal. The clarification of the structural influences on the fracture-mechanical behavior promises that the mechanisms can be adjusted by the particle packing. Consequently, carbon-free recyclable refractories with a lower risk and higher safety for the workers and an excellent thermal shock resistance might be manufacturable in the future.To identify the acting mechanisms and to link them to specific adjustments of the particle packing, samples will be firstly analyzed structurally and then investigated fracture-mechanically by aid of wedge-splitting tests. From the force-displacement curves of the wedge splitting tests, the fracture energy can be calculated which characterizes the completely consumed energy. Furthermore, from the curves can be calculated if the resistance against crack propagation increases with the propagating crack, often related to an enlarged crack process zone. The process zone can become enlarged e.g. by crack deflection which will be also observed during the wedge splitting tests by Digital Image Correlation. Moreover, Mini-wedge splitting tests will be conducted which allow to observe microscopically changes in the structure during the test. Therefore, changes in the force-displacement curves might be linkable to the aforementioned fracture-mechanical mechanisms. Additionally, the wedge splitting test samples are investigated microscopically to support the results from the mini-wedge splitting tests.