超声振动载荷下合金的疲劳裂纹扩展性能研究

FCG BEHAVIOR OF ALLOYS UNDER ULTRASONIC FATIGUE LOADING

本文应用超声共振试验技术研究了４种工程常用合金（Ａｓｔｒｏｌｏｙ，１７－４ＰＨ，Ｔｉ－６Ａｌ－４Ｖ，Ａｌ－Ｌｉ８０９０）在超声振动载荷（ｆ＝２０ｋＨｚ，Ｒ＝－１）下的疲劳裂纹扩展性能，并与常规疲劳载荷（ｆ≤５０Ｈｚ，Ｒ＝０．７）下材料的有关性能做了对比分析。对超声疲劳载荷下材料损伤及裂纹扩展机理的特点做了研究，给出了这种特定载荷形式下应力强度因子的计算方法。研究结果表明，超声疲劳载荷下各种合金的裂纹扩展性能与常规疲劳试验中确定的有效应力强度因子△Ｋｅｆｆ类同。

Fatigue crack growth (FCG) and threshold behavior of four widely used engineering alloys have been investigated at high frequency Z(f =20kHz) by means of an ultrasonic fatigue device.Specimen design has been given.Crack propagating rate da/dN was obtained between 10 -9 and 10 -5 mm/cycle in function of stress intensity factor △K ,which was determined by a modified analytic experimental method.For comparison,conventional FCG data ( f =2 to 50Hz) were carried out with a high stress ratio (R=0 7) applied.High frequency effect on the fracture behavior of different materials was discussed and the failure mechanism was obtained in the two different regimcs.