Detection Of Corrosion In Aluminum Using Vibro-acoustic Modulation Technique

With excellent performance (strength, hardness, toughness, fatigue resistance,plasticity), the aluminum alloy is widely used in many types of aircraft structures.However, due to the long service time, the micro-defects generated inevitably, underthe action of some external factors (loads, temperature and corrosive media, etc.). Thecorrosion is the most common type of micro-defects in aluminum alloy. Corrosionresult in a high frequency of aircraft accidents, therefore, to ensure the safe operationof the aircraft and improving project value, early detection and assessment oncorrosion is conducive This paper researched on detection of aluminum corrosionusing vibro-acoustic modulation technique, the main contents includes:(1) Design of vibro-acoustic modulation detection software. Vibro-acousticmodulation detection software system was developed based on the Vibro-acousticmodulation hardware systems in the laboratory, automatic test of the structurefrequency response was presented, and vibro-acoustic modulation signals could beexcited and received successfully. Then the frequency response of aluminum wastestes using vibro-acoustic modulation software.(2) Research on Influencing parameters vibro-acoustic modulation detection ofaluminum corrosion. Aluminum corrosion was detected using vibro-acousticmodulation with different excitation parameters. Some parameters including thefrequency and amplitude of low-frequency signal and the amplitude of high-frequencysignal were researched, which affect the performance of modulation parametersincluding the amplitude of side-band and modulation index of received signals,. Thenthe optimal detection parameters were presented.(3) Research on the method of vibro-acoustic modulation characterization basedon time-frequency analysis. Vibro-acoustic modulation signals were processed byWavelet Packet Demodulation and Continuous Wavelet Transform wavelet. The typeof signal modulation was identified using time-frequency analysis, the degree ofsignal modulation was characterized by average modulation degree and averagemodulation index. This method was applied in the detection of aluminum corrosionbased on the processing about simulated signals. Finally, the results show thatvibro-acoustic modulation of aluminum corrosion belong to amplitude modulationand the two modulation parameters presented in this paper can be applied in the characterization of corrosion degree.