Aigner Roman, Leitner Martin, Stoschka Michael, Hannesschläger Christian, Wabro Thomas, Ehart Robert
Christian Doppler Laboratory for Manufacturing Process based Component Design, Chair of Mechanical Engineering, Montanuniversität Leoben, 8700 Leoben, Austria.
University of Applied Sciences Upper Austria, 4600 Wels, Austria.
Materials (Basel). 2018 Dec 14;11(12):2546. doi: 10.3390/ma11122546.
Cast parts usually inherit internal defects such as micro shrinkage pores due to the manufacturing process. In order to assess the fatigue behaviour in both finite-life and long-life fatigue regions, this paper scientifically contributes towards a defect-based fatigue design model. Extensive fatigue and fracture mechanical tests were conducted whereby the crack initiating defect size population was fractographically evaluated. Complementary in situ X-ray computed tomography scans before and during fatigue testing enabled an experimental estimation of the lifetime until crack initiation, acting as a significant input for the fatigue model. A commonly applied fatigue assessment approach introduced by Tiryakioglu was modified by incorporating the long crack threshold value, which additionally enabled the assessment of the fatigue strength in the long-life fatigue regime. The presented design concept was validated utilising the fatigue test results, which revealed a sound agreement between the experiments and the model. Only a minor deviation of up to about five percent in case of long-life fatigue strength and up to about 9% in case of finite-lifetime were determined. Thus, the provided extension of Tiryakioglu's approach supports a unified fatigue strength assessment of cast aluminium alloys in both the finite- and long-life regimes.
由于制造工艺的原因，铸造部件通常会继承内部缺陷，如微缩孔。为了评估有限寿命和长寿命疲劳区域的疲劳行为，本文为基于缺陷的疲劳设计模型做出了科学贡献。进行了广泛的疲劳和断裂力学试验，通过断口金相分析对裂纹起始缺陷尺寸群体进行了评估。疲劳试验前和试验过程中的补充原位X射线计算机断层扫描能够对裂纹起始前的寿命进行实验估计，这是疲劳模型的重要输入。通过纳入长裂纹阈值，对Tiryakioglu提出的一种常用疲劳评估方法进行了修改，这还能够评估长寿命疲劳区域的疲劳强度。利用疲劳试验结果对所提出的设计概念进行了验证，结果表明实验与模型之间具有良好的一致性。在长寿命疲劳强度方面，仅确定了高达约5%的微小偏差，在有限寿命方面，偏差高达约9%。因此，对Tiryakioglu方法的扩展支持了对铸造铝合金在有限寿命和长寿命区域的统一疲劳强度评估。
