Experimental and stochastic investigations of the influence of the inclusions on the fatigue life (C04)

在第三个供资期内，该子项目的目标是-在第二个供资期内继续-确定现有的最大的，即重新启动的，未过滤的非金属夹杂物，并确定在长使用寿命范围内疲劳载荷情况下疲劳寿命分布对夹杂物分布的依赖性。为了能够更具体地研究VHCF范围内内部夹杂物的失效，对具有改性表面性能（残余压应力）和拉伸平均应力下的试样进行了测试。夹杂物在铸件以及在失败的状态下的微观结构特征，以阐明夹杂物团聚体的形成和破坏机制。开发一个可以预测疲劳过程中热生成的三维热机械模拟模型，可以得出关于样品内部热源空间分布的结论，从而可以从耗散能量中得出关于VHCF范围内裂纹萌生和扩展行为的进一步结论。

The objectives of the subproject during the third funding period are – in continuation for the second funding period - the determination of the largest existing, i.e. fracture-initiating, non-metallic inclusion that has not been filtered, and the determination of the dependence of the fatigue life distribution in the case of fatigue loading in the range of long service lives on the inclusion distribution. In order to be able to investigate the failure of internal inclusions in the VHCF range more specifically, specimens with modified surface properties (residual compressive stresses) and under tensile mean stresses are tested. Microstructural characterizations of the inclusions in the cast as well as in the failed state serve to elucidate the formation and damage mechanisms of inclusion agglomerates. The development of a three-dimensional thermo-mechanical simulation model that can predict the heat generation during fatigue allows to conclude about the spatial distribution of the heat source(s) inside the samples, so that further conclusions about the crack initiation and growth behavior in the VHCF range can be expected from the dissipated energy.