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In order to explore the adaptability and failure mechanism of landing gear materials for amphibious aircraft in the marine environment. By preparing a high-speed flame sprayed WC coating on the surface of hot-rolled 300M high-strength steel, the corrosion behavior of the coating in an artificial seawater environment was studied using electrochemical testing, salt spray testing, tensile testing, fatigue testing, and characterization by SEM, EDS, XRD, and CLSM. The research results indicate that the WC coating undergoes significant passivation and exhibits good corrosion resistance in an artificial seawater environment with pH value 8.2, which is related to the passivation of Co in the coating under alkaline conditions. The long-term electrochemical impedance results indicate that the corrosion resistance of the coating increases after soaking for 28 days, which is related to the oxide formed by the surface binder. Compared with the 300 M substrate, the tensile strength of the sprayed material slightly increases, which is related to the residual stress releasing inside the coating. Its cracking in artificial seawater is mainly controlled by the anodic dissolution process. As the pre corrosion time increases, the fatigue life of the material significantly decreases. The corrosive medium from the environment enters the interior of the coating during the pre corrosion process, which increases the number of defects, causes premature failure of the coating, and leads to an increase in material fracture sensitivity. WC coatings have good corrosion resistance, and the release of residual stress during the tensile process slightly increases the tensile strength of the material. The coating fails prematurely after pre corrosion, which results in a reduced fatigue life of the material.

Lining void is a common defect in tunnel construction, which might lead to the deterioration of tunnel structure and reduce tunnel safety. It is necessary to detect the tunnel lining in the stages of construction and operation. In this study, a three dimensional (3D) model of tunnel lining and surrounding rock is established based on finite difference time domain (FDTD) method, and the application of 3D GPR (ground penetrating radar) in lining detection is simulated forward to obtaine the 3D GPR data of void. The response characteristics of void in different measuring lines are analyzed, the influence of lining void on electromagnetic waveform and wave field distribution are discussed. Finally, the reliability of the forward modeling result is verified by a tunnel project. The results show that the electric intensity of void area increases as the measuring line is close to the center, and the three dimensions of void can be detected according to this change. In addition, the electromagnetic wave is reflected many times in the void, causing the concussion in the surrounding rock layer. Besides, the metal parts will cause strong interference to the signal of the void, and the extreme values of the electric field are metal-free parts, single-layer steel and double-layer steel in order from large to small. This study will provide valuable reference for promoting the application of 3D GPR in lining void detection and improving the accuracy of detection. [ABSTRACT FROM AUTHOR]