دانلود رایگان مقاله انگلیسی مهاجرت زمان معکوس امواج آکوستیک در تشخیص نواقص مبتنی بر تصویرسازی برای سازه بتنی - الزویر 2019

abstract

Ultrasonic non-destructive testing (NDT) technology has been widely used for defect inspection of concrete structures in civil engineering. However, most of the current data processing methods can only provide qualitative information regarding the existence of concrete inner defects. In this study, an ultrasonic inner defects inspection approach with a high-resolution imaging method which combines travel time tomography (TTT) and reverse time migration (RTM) is proposed for concrete and concrete-filled steel tube (CFST) columns. TTT estimates a reasonable distribution of ultrasonic velocity over the cross-section of the concrete and CFST columns from the first arrival time of the ultrasonic transmission signal. The velocity distribution is used as an input of the initial model for RTM to image the defects inside the concrete and CFST column cross-sections with a high resolution. Numerical experiments demonstrate that the air cavity inside the concrete and CFST columns, and the debonding between the concrete core and the steel tube of the CFST column can be identified clearly, and that the location, size and shape of both defects can be determined accurately. It is concluded that the proposed defect detection approach with a high-resolution imaging method is efficient for the non-destructive inspection of concrete and CFST structures using ultrasonic waves.

5. Concluding remarks and future work

In this study, an acoustic imaging method of RTM combined with TTT for the detection of void defects in concrete structure, void in concrete core and the interface debonding defect in CFST members is proposed and numerically validated. By the numerical experiments, the following conclusions can be made.

(1) TTT can only reveal a large defect as a low-velocity anomaly and can hardly determine its shape and size, especially when noise is added. But TTT can provide a reasonable velocity distribution as an initial model for RTM. Compared with the reconstructed image by RTM using a homogeneous velocity model established by experience with an error, that using the TTT-estimated velocity model possesses a higher quality.

(2) Combining TTT with RTM, the existence of a concrete defect embedded inside a concrete structure and a CFST member, and the interface debonding defect between concrete core and steel tube of a CFST member can be easily imaged with a high resolution, even when the air interface debonding in the CFST member is 10 mm in thickness.

(3) The location, shape and size of the air void in a concrete structure and the concrete core and the interface debonding of CFST member can also be accurately determined by the proposed imaging-based defect detection method.