Shuailin Liu

Bio: Shuailin Liu is an academic researcher from Dalian University of Technology. The author has contributed to research in topics: Phased array ultrasonics & Signal. The author has an hindex of 2, co-authored 3 publications receiving 7 citations.

Defect two-dimensional morphology imaging detection method based on multi-mode acoustic beam synthetic aperture focusing

Abstract: The invention discloses a defect two-dimensional morphology imaging detection method based on multi-mode acoustic beam synthetic aperture focusing, belonging to the technical field of nondestructive testing. According to the method, a phased array ultrasonic detector, a phased array ultrasonic probe and a phased array ultrasonic detection system of an oblique wedge block are adopted; and signal acquisition of a detected test block is performed by the electronic scanning function of the phased array ultrasonic detector to obtain A-scanning signal of each aperture of the phased array ultrasonic probe. According to different mode conversion types of excitation acoustic beam of each aperture on the interface between the wedge block and test block, at the bottom of the test block and on the defect surface, proper multi-mode acoustic beam is selected from 8 acoustic beam transmission modes. Based on SAFT imaging principle and Fermat's theorem, the transmission delay of the multi-mode acoustic beam of each aperture is calculated, and amplitudes are overlapped to obtain a reconstructed SAFT image, thus realizing complete representation of defect two-dimensional morphology features. The invention can realize correct recognition of volume type and area type defects so as to realize accurate quantification of defect length, depth and orientation, and has relatively high engineering application value.

Simulation on qualitative detection of defects with multi-mode total focusing method

Abstract: Multi-mode total focusing method (TFM) is applied to overcome the limitation that defect type is difficult to be accurately determined with conventional ultrasonic testing. The phased array transducer connected with wedge is employed to implement electronic scan and receive the multiple reflected waves generated from defect surface. The signals are post-processed with delay-and-sum (DAS) beamforming algorithm to reconstruct images for the TTT case and obtain defect morphology for qualitative detection. The carbon steel models with 5.0 mm vertical crack and ĭ0.5 mm side-drilled holes (SDHs) having center-to-center spacing of 5.0 mm were detected with multi-mode TFM by simulation in this paper. The defect types were distinguished effectively from imaging results compared with conventional TFM, and the positioning and quantitative errors were no more than 8.4%. The multi-mode TFM is appropriate for the qualitative recognition of defects, especially for the cracks with gap.

Research on TFM Imaging of Main Pipe Weld of Compound Steel Based on FMC/SMC

Abstract: Main pipe weld of compound steel with welding layer of coarse-grained austenitic stainless steel leads to the reduction of image resolution and signal-to-noise ratio (SNR) using phased array ultrasonic testing (PAUT). Total focusing method (TFM) can be employed to improve imaging quality, but computational efficiency is influenced significantly by element number. It is very important to balance quality and efficiency of TFM imaging by reasonably choosing array element. Focusing on 75 mm thickness main pipe weld of compound steel having a ϕ2 mm side-drilled hole in 65 mm, the TFM imaging were compared with data acquisition modes of full matrix capture (FMC) and sparse matrix capture (SMC). The results showed that, with the increasement of element number, the quality of TFM images were both improved. When the element number was 8, compared with FMC-TFM image, the array performance indicator (API) of SMC-TFM image decreased 20% and SNR differed by 0.75dB, while API and SNR were almost the same with 48 elements. The detection result was up to element number and location, so SMC could be utilized to ensure imaging quality and improve computational efficiency in practical inspection.

Metallic molten pool internal contour online measurement device and method

Abstract: The invention discloses a metallic molten pool internal contour online measurement device and method. The device comprises an excitation assembly, a receiving assembly and a computer for data analysisand control; the excitation assembly comprises a laser, a beam splitter for dividing a beam emitted by the laser into a plurality of beams, and a plurality of sets of array optical fibers for receiving the plurality of beams respectively; and the computer is provided with a dynamic modulation module for dynamically modulating the beam. With the metallic molten pool internal contour online measurement device and method of the invention adopted, metallic molten pool internal contour online measurement can be realized based on a laser ultrasonic phased array detection technology; and a printingprocess can be adjusted according to a detection result, so that high manufacturing quality of parts can be realized.

Profile reconstruction and quantitative detection of planar defects with composite-mode total focusing method (CTFM)

Abstract: The profile reconstruction of planar defects by ultrasonic imaging is helpful for obtaining the flaw type, size, orientation and other characteristics. In this paper, composite-mode total focusing method (CTFM) is proposed by selecting the strongest response from 21 views at every reconstructed point, realizing the profile reconstruction and quantitative detection of priori unknown planar defects except for the near-horizontal defects with a set of phased array (PA) probe and wedge. Subsequently, eight effective views corresponding to 45° longitudinal-wave wedge are determined considering Snell's law and beam directivity. The 64-element linear array probe with 5 MHz central frequency and 45° wedge were used to reconstruct a series of 5 mm length cracks with different orientations (0°, ±15°, ±30°, ±45°, ±60° and ±75°) by CTFM in simulation. The measurement errors of crack lengths, orientation angles and central depths with the 6 dB drop rule were within 0.42 mm, 1.87° and 0.58 mm, respectively. The experimental results showed that the characteristics of 5 mm length slots were presented with high accuracy, verifying the feasibility of CTFM. Meanwhile, the planar and volumetric defects can be distinguished qualitatively by CTFM. Finally, the reconstructed image by naive sum is compared with the CTFM image, and the effects of wedge angle and number of elements on profile reconstruction are discussed.

Ultrasonic defect detection qualitative system and qualitative method

Abstract: The invention provides an ultrasonic defect detection qualitative system and qualitative method that are implemented based on an ultrasonic phased array P-scan imaging device. With the ultrasonic phased array P-scan imaging device, the traditional ultrasonic detection equivalent method can be implemented and the structural defect like an object solder joint defect can be evaluated qualitatively byusing the P scanning imaging technique. For example, for an object solder joint defect, the defect property can be determined by using the P-scan imaging technique based on the morphology features ofthe defect as well as the weld joint groove structure, welding method, and defect position; and thus the morphology of the object defect is reconstructed to achieve a corresponding ultrasonic qualitative detection objective.

Comparison of Morphology Characterization for Regular Cracks with Multi-mode Total Focusing Method

Abstract: The multi-mode total focusing method (MTFM) is used for characterization of crack morphology, whose imaging quality is closely related to crack orientation. In this paper, the signal acquisition was performed using the 39° wedge and 16-element linear array probe with center frequency of 10 MHz. The morphology of regular cracks was characterized and compared by MTFM imaging in direct, half-skip and full-skip modes, respectively. The established simulation model was a 9.0 mm thickness aluminum plate containing a series of regular bottom cracks, whose lengths were all 2.0 mm and orientation angles were 0°, ±15°, ±35° and ±60°, respectively. The simulated results showed that direct, half-skip and full-skip modes were suitable for morphology characterization of regular cracks with orientation angles of 35°, 0° and -35°, respectively. The quantitative errors of crack lengths and orientation angles were no more than 0.22 mm and 0.8°, respectively. The measurement errors in experiment were within 0.28 mm and 0.9° for crack lengths and orientation angles, being in good agreement with simulated results. On the basis, the increment of element pitch is helpful for enlarging receiving area of ultrasonic beam and characterization range for crack morphology.

Honeycomb sandwich structure detection method based on position-ultrasound signals

Abstract: The invention belongs to the technical field of aviation and aerospace, transportation, construction, non-destructive detection and the like, and relates to a honeycomb sandwich structure detection method based on position-ultrasound signals. According to the honeycomb sandwich structure detection method proposed by the invention, inspectors can simultaneously observe the ultrasonic signals corresponding to each detection position point in each scanning row or column and the changes of the ultrasonic signals on an instrument screen, and then the discrimination of defects and the ultrasonic detection of the honeycomb structure can be carried out more intuitively according to the change of P(x,y)-A(t) signals displayed on the instrument screen. Since the inspectors can simultaneously observethe ultrasonic signals corresponding to each detection position point in each scanning row or column and the changes of the ultrasonic signals on the instrument screen, and then the discrimination ofthe defects and the ultrasonic detection of the honeycomb structure can be carried out more intuitively according to the change of the P(x,y)-A(t) signals displayed on the instrument screen, the difficulty of discriminating the defects is simplified, and thus the accuracy of defect discrimination is improved, the detection rate of the defects is improved, and the misjudgment rate of the defects is reduced.