ZHENG Huan bin1, GAO Hong li1, LIU Hui1, LIU Huan1, QI Zi cheng1,2

 

(1. Key Laboratory of E&M, Ministry of Education & Zhejiang Province, Zhejiang University of Technology,

 

Hangzhou 310014,China; 2. Ningbo Branch of China Academy of Ordnance Science, Ningbo 315103, China)

 

 

Abstract: Aiming at keeping the testing load stability when the fatigue crack growing, an amplitude control system of the resonance fatigue crack propagation test based on the crack on line measuring was established, and its applied methods which are crack length on line measuring nature frequency tracking method with the changing tracking steps and the amplitude fuzzy PID control method were proposed. Firstly, the system nature frequency data related with different crack length was obtained applying the designed measuring system. In the fatigue crack propagation test the nature frequency was followed applying the proposed method according to the measured crack length, on the same time, the amplitude fuzzy PID control was used to keep the amplitude to be stable during the frequency tracking. The experiment results indicate that the proposed methods have greatly improved the amplitude control accuracy which is less then 2% during the fatigue crack growing process and have shortened the tuning time, can meet the resonance fatigue crack propagation test requirement.

 

Key words:  resonance fatigue crack propagation test; nature frequency tracking; fuzzy PID control; fatigue crack; on line measuring