Multi-Mode Ultrasonic Integrated Visual Inspection Technique for Composite Repairs in Different Scenarios
With the increasingly urgent repair demand brought by the extensive application of composites in industrial field,the advanced non-destructive testing and evaluation(NDT&E)methods and techniques for composite repairs have been highly concerned in the industry.At present,integrated visual NDT&E methods and techniques suitable for different repair scenarios are lacking.A integrated visual NDT&E method based on the principle of multi-mode ultrasound(MU)is proposed.The NDT&E requirements and features for composite repairs situ,off-location and manufacturing scenarios were analysed.A MU visual NDT&E method for multi-repair scenarios was constructed.Typical composite repair specimens were prepared.The regularity of ultrasonic signals and images from the composite repaired areas and the visualized detection effect of the developed integrated MU method were revealed experimentally.The results show that the geometrical topologies of the matrix,repaired zone and repaired edges in the composite body can be clearly identified and quantitatively characterized based on the change characteristics of ultrasonic signals from the repaired composites.Different ultrasonic modes have different visualized imaging effects and defect detection capabilities,among which mono-pulse ultrasonic mode(M3)and asymmetric-frequency ultrasonic mode(M2)have the best visual imaging quality and defect detection capabilities,while air-coupled ultrasonic mode(M1)is obviously inferior to M2 and M3.M3 has the most imaging details compared with M1 and M2;M2 and M3 have the highest accuracy and resolution in detected defects,the smallest surface detection dead-zone,and their sensitivities for detected out delamination and disbonding reach Φ3 mm.The surface resolution of M2 and M3 is smaller to a single ply thickness in composites(about 0.125 mm).The sensitivity of M1 for detecting delamination and disbonding is close to Φ6 mm.Thus,the integrated MU method and technique provide a powerful and visualized quantitative NDT&E approach for composite repairs in different repair scenarios,and have been applied well in practical inspection.
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