关键词: 高频谐振载荷, 疲劳裂纹尖端, 动态有限元, 位移, 应变场, 应力强度因子

Abstract:

This paper explored the variation law of mechanics parameters at fatigue crack tip of compact tension(CT) specimen with type Ⅰ pre-notch based on dynamic FEM in the high frequency resonant fatigue crack propagation tests. The displacement fields, the strain fields and the SIFs at CT specimen fatigue crack tip in one stress cycle and at different crack lengths under constant amplitude high frequency sinusoidal alternating loading condition were calculated and the related variation laws of mechanics parameters were analyzed. In order to calculate the dynamic SIF at fatigue crack tip, the static SIF was calculated first, the comparing results of the static finite element analysis with the theoretical calculation show that finite element modeling and calculated method and results are accurate. Secondly, the variation law of SIF at crack tip during the process of fatigue crack propagation tests was studied by dynamic FEM. Finally, the high frequency resonant fatigue crack propagation tests were performed, and the dynamic strain gauge was used to measure the strain at crack tip during one stress cycle. The research results show that during crack stable propagation stage, the displacement, strain and SIF at type Ⅰ fatigue crack tip are the same form with the high frequency resonant load, and the displacement, strain and SIF amplitude increase with the crack growth. The error of static SIF between the calculated result by FEM and the theoretical result is as 2.51%. The maximum error of the strain at crack tip between the calculated result by FEM and the experimental result is as 2.93%.

Key words: high frequency resonant load, fatigue crack tip, finite element method(FEM), displacement； strain field, stress intensity factor(SIF)