Browsing by Author "Qiu, Jinxing"

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    Inspection of delamination defect in first wall panel of Tokamak device by using laser infrared thermography technique
    (IEEE, 2018-04-16) Liu, Haochen; Pei, Cuixiang; Qiu, Jinxing; Chen, Zhenmao
    First wall panels (FWPs), which adjoin the inner wall of the blanket modules in the vacuum vessel (VV) of a Tokamak device, are in structures of multilayer bounded together with a solid welding technique in order to perform its heat exchange, VV protection, and neutron breeding functions. The quality of the welding joint between layers is the key factor for FWP integrity. In order to conduct online inspection of the delamination defect in the FWPs, a nondestructive testing (NDT) method capable to detect delamination defect without accessing into the VV is required. In this paper, the feasibility of the laser infrared thermography (LIRT) testing NDT method was investigated experimentally for this purpose. To clarify its detectability under practical VV environment, inspections of several inspection modes were conducted based on the practical structure of FWP and VV of the EAST Tokamak device, i.e., modes of different distances and angles of FWPs toward the LIRT transducers. In practice, an LIRT testing system was established and several double-layered plate specimens with different artificial delamination defects were inspected under the selected testing conditions. Through thermography signal reconstruction, an image processing algorithm was proposed and adopted to enhance the defect detectability. From the results of different inspection modes, it was found that the angle factor may worsen the inspection precision and reduce the detectability for delamination defects in case of big defect depth-to-width ratio, even though the LIRT method is still applicable for inspection of relative large defects in FWP. Finally, the detectability in different inspection modes was clarified, which proved the feasibility of LIRT for FWP online inspection.
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    Progress on the ultrasonic testing and laser thermography techniques for NDT of tokamak plasma-facing components
    (Elsevier, 2019-06-24) Pei, Cuixiang; Liu, Haochen; Qiu, Jinxing; Liu, Tianhao; Chen, Zhenmao
    During manufacturing and operation, different kinds of defects, e.g., delamination or surface cracks, may be generated in the plasma-facing components (PFCs) of a Tokamak device. To ensure the safety of the PFCs, various kinds of nondestructive testing (NDT) techniques are needed for different defect and failure mode. This paper gives a review of the recently developed ultrasonic testing (UT) and laser thermography methods for inspection of the delamination and surface cracks in PFCs. For monoblock W/Cu PFCs of divertor, the bonding quality at both W-Cu and Cu-CuCrZr interfaces was qualified by using UT with a focus probe during manufacturing. A noncontact, coupling-free and flexible ultrasonic scanning testing system with use of an electromagnetic acoustic transducer and a robotic inspection manipulator was introduced then for the in-vessel inspection of delamination defect in first wall (FW). A laser infrared thermography testing method is highlighted for the on-line inspection of delamination defect in FW through the vacuum vessel window of the Tokamak reactor. Finally, a new laser spot thermography method using laser spot array source was described for the online inspection of the surface cracks in FW.
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    Quantitative evaluation of surface crack depth with laser spot thermography
    (Elsevier, 2019-02-28) Qiu, Jinxing; Pei, Cuixiang; Liu, Haochen; Chen, Zhenmao
    In this study, a numerical method based on finite element method (FEM) is developed to simulate the heat flow generated by laser spot source and investigate the relationship between crack size and temperature distribution. The feasibility of the simulation method is validated by experiments both in time and spatial domains. The simulation and experiment results also show that the crack depth can be described by two characteristic parameters. Furthermore, a quantitative retrieval method based on neural network is developed for the crack depth evaluation by using the parameters. By using the proposed method, crack depth can be determined only by analyzing measured surface temperature values.
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    Remote measurement and shape reconstruction of surface-breaking fatigue cracks by laser-line thermography
    (Elsevier, 2020-09-15) Qiu, Jinxing; Pei, Cuixiang; Yang, Yang; Wang, Rongbang; Liu, Haochen; Chen, Zhenmao
    In this paper, a method for remote measurement and shape reconstruction of fatigue cracks by using laser-line thermography (LLT) technique is developed. A new feature parameter derived from the LLT signals is proposed to evaluate the length and estimate the general inner profile of a surface-breaking fatigue crack. An inversion analysis scheme based on conjugate gradient optimization algorithm is then applied to reconstruct the detailed inner profile and dimension of the crack. The reconstruction results with both numerically simulated LLT signals and experimental signals proved the feasibility of proposed inversion scheme and remote LLT method. Based on methods of this paper, not only the size of cracks can be quantitatively evaluated, but the inner profile is also reconstructed for cracks in different shapes from the LLT signals