(1. 哈爾濱理工大學 材料科學與工程學院，哈爾濱 150040；
2. 哈爾濱理工大學 測控技術(shù)與通信學院，哈爾濱 150040)
摘 要: 基于非線性超聲調(diào)制頻譜法，對航空鋁合金板材中的疲勞裂紋識別進行研究；以兩個不同頻率的超聲蘭姆波為激勵信號，依靠超聲換能器、波形發(fā)生器和激光測振儀等，對含有疲勞裂紋和無損傷的2024-T351鋁合金薄板試樣進行對比實驗；分別采用時域、頻域和時頻域聯(lián)合法分析非線性超聲波在鋁合金薄板試樣中傳播的響應信號。結(jié)果表明：非線性聲學特征即調(diào)制頻譜及三階諧波可作為識別2024-T351鋁合金板材介質(zhì)中疲勞裂紋的判據(jù)，通過對試樣表面進行掃描，建立調(diào)制頻譜的峰值幅度與位移的關系，據(jù)此可確定樣板中疲勞裂紋的位置和輪廓，這為航空鋁合金板材疲勞裂紋的識別提供更多技術(shù)支撐。
關鍵字: 2024鋁合金；薄板；非線性聲學特征；調(diào)制頻譜；疲勞裂紋
（1. School of Material Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China;
2. School of Measurement-Control Technology and Communications Engineering,
Harbin University of Science and Technology, Harbin 150040, China）
Abstract:The identification of fatigue cracks in the aviation aluminum alloy plates based on nonlinear ultrasonic modulation spectrum method was studied. Taking two different frequencies nonlinear Lamb wave as actuators, comparative experiments on two types of 2024-T351 aluminum alloy plate samples, with and without fatigue crack, were performed by using ultrasonic transducer, waveform generator and non-contact laser vibration meter and so on. The ultrasonic response signals during propagation were analyzed by the time domain, frequency domain and time-frequency domain methods, respectively. The results show that the acoustic characteristic of the modulation frequency components and the third harmonics can be used to indicate the presence of fatigue cracks in 2024-T351 aluminum alloy plates. By scanning the cracked plate, a relationship between the modulation frequency peak magnitude and scanning displacement was established, and according to this relationship the fatigue cracks can be located approximately, the crack contour can be obtained, which will provide more technical support for identification fatigue cracks in aviation aluminum alloy plate.
Key words: 2024 aluminum alloy; plates; nonlinear acoustic characteristic; modulation spectrum; fatigue cracks
