This paper studied factors influencing AU detection results on different damage specimens, including simulation frequency, transducer modes and transducer location. Correlation between acousto-ultrasonic parameters (AUP1, AUP2) and impact damage severity in composite was investigated. The results showed that as damage severity increased, AUP1 and AUP2 of three different transducers decreased. Applying low frequency transducer, the variation of AUP1 may indicate a more rapid detection prospect. In addition, applying S1-transducer and WD-transducer, AUP2 was more effective for the early damage detection. Varying transducer’s location, S1-transducer applying 500khz simulation frequency presented a valuable results.
Between aircraft bearings lugs, plates fracture appeared. The failure mode and cause were analyzed by macro and micro observation, EDS analysis, metallographic examination and hardness testing. The results showed that two bearings’ failure were stress corrosion cracking. Bearings’ failure were related with abnormal force state, material cast loose exceeding the allowed limited values played a catalytic role to crack propagation. It is suggested that bearings material surface protection should be strengthened to improve corrosion resistance, bearings design should be optimized to avoid abnormal tensile stress, and material casting process should be improved to reduce cast loose.
In this study, carbon fiber reinforced polymer (CFRP) laminates that were under three-point bending load within and without initial impact damage, were detected and monitored by ultrasonic C-scan method. The defect morphology at various load levels was recorded. The dynamic monitoring for the growth of delaminations in CFRP laminates was acquired, and it provided an experimental evidence for the health monitoring on CFRP in service.
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