Imperfections due to the manufacturing process can significantly affect the local fatigue strength of the bulk material in cast aluminium alloys. Most components possess several sections of varying microstructure, whereat each of them may inherit a different highly-stressed volume (HSV). Even in cases of homogeneous local casting conditions, the statistical distribution parameters of failure causing defect sizes change significantly, since for a larger highly-stressed volume the probability for enlarged critical defects gets elevated. This impact of differing highly-stressed volume is commonly referred as statistical size effect. In this paper, the study of the statistical size effect on cast material considering partial highly-stressed volumes is based on the comparison of a reference volume $V_0$ and an arbitrary enlarged, but disconnected volume $V_{\alpha }$ utilizing another specimen geometry. Thus, the behaviour of disconnected highly-stressed volumes within one component in terms of fatigue strength and resulting defect distributions can be assessed. The experimental results show that doubling of the highly-stressed volume leads to a decrease in fatigue strength of 5% and shifts the defect distribution towards larger defect sizes. The highly-stressed volume is numerically determined whereat the applicable element size is gained by a parametric study. Finally, the validation with a prior developed fatigue strength assessment model by R. Aigner et.al. leads to a conservative fatigue design with a deviation of only about 0.3% for cast aluminium alloy.

中文翻译：

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铸铝统计尺寸效应的验证研究

由于制造工艺造成的缺陷会严重影响铸铝合金中散装材料的局部疲劳强度。大多数组件都具有几个具有不同微观结构的部分，每个部分都可能继承不同的高应力体积（HSV）。即使在均匀的局部铸造条件下，引起缺陷尺寸的失效统计分布参数也会显着变化，因为对于较大的高应力体积，扩大的严重缺陷的可能性会增加。不同的高应力体积的这种影响通常称为统计尺寸效应。在本文中，基于参考体积的比较，研究考虑部分高应力体积的铸造材料的统计尺寸效应 $V_0$ 和任意放大但不连续的音量 $V_{\alpha }$ 利用另一个标本几何。因此，就疲劳强度和所产生的缺陷分布而言，可以评估一个组件内断开的高应力体积的行为。实验结果表明，高应力体积的两倍会使疲劳强度降低5％，并使缺陷分布向较大的缺陷尺寸转移。通过数值确定高应力体积，然后通过参数研究获得适用的单元尺寸。最后，使用R. Aigner等人先前开发的疲劳强度评估模型进行验证。导致保守的疲劳设计，铸造铝合金的偏差仅为0.3％。