考虑粉末盘服役特性的FGH95合金疲劳寿命与失效机制研究

Fatigue Life and Failure Mechanism of FGH95 Superalloy Considering Service Characteristics of Powder-Discs

摘要:

针对挤压锻造态FGH95合金在模拟航空发动机粉末盘组件服役工况下的使用性能评价缺失关键问题，本研究首先基于粉末盘组件止动槽上的最大主应变梯度，按照一定的设计准则设计出模拟件，并对其设计方法进行验证，然后采用基于临界距离（theory of critical distances, TCD）的疲劳寿命方法进行寿命预测，最后对疲劳寿命方法及失效机理进行验证。结果表明：本研究提出的1种三维空间域全自动搜索方法能够获得止动槽上的最大主应变梯度；与工程中常用Morrow修正的总应变寿命方法相比，采用考虑应变梯度的TCD寿命方法能够更准确地预测止动槽的疲劳寿命；合理解释了缺口标准圆棒试样不能准确模拟止动槽疲劳寿命的重要原因；运用断口分析技术验证了缺口标准圆棒试样、止动槽及其模拟件疲劳失效机理的差异。

Abstract:

To address the lack of service performance evaluation of the extruded and forged FGH95 alloy under the service conditions of the aero-engine powder-disc components, a feature-base specimen based on the maximum principal strain gradient on the retaining groove of the powder-disc component were designed according to certain design criteria, and the design method was verified. Then, the fatigue life method based on the theory of critical distance (TCD) was employed to predict the service life. Finally, the fatigue life method and failure mechanisms were validated. The results show that the three-dimensional spatial domain automatic search method proposed in the present study can obtain the maximum principal strain gradient on the retaining groove. Compared with the Morrow-modified total strain life method commonly used in engineering, the TCD-life method incorporating the strain gradient can more accurately predict the fatigue life of the retaining groove. The important reason why the standard notched round bar specimen cannot accurately predict the fatigue life of the retaining groove is reasonably explained. The differences in the fatigue failure mechanisms of the standard notched round bar specimen, retaining groove, and its feature-base specimen are verified by fracture analysis techniques.