Accurate detection of missing or misplaced rivets is critical for ensuring structural integrity in aircraft assembly and component manufacturing. Conventional manual inspection methods exhibit low efficiency and high error rates. Hence, this paper proposes an intelligent rivet-defect detection method based on feature template matching, which comprises three core modules: rivet assembly information extraction, modified iterative thin-plate spline (I-TPS) interpolation matching, and defect localization and visualization. First, rivet assembly information is formally defined, and a feature-detection model is constructed to locate rivet positions and types in both the template and target images, followed by the generation of scatter plots for spatial-distribution analysis. Second, for point-to-point matching, an enhanced I-TPS algorithm that incorporates a similarity-metric matrix deforms the feature set of the target image by aligning its spatial distribution with the template through a nonlinear transformation. A robust feature correspondence is established by computing the similarity-metric matrix between the template and target sets, thus enabling the precise identification of missing or misplaced rivets by cross-referencing positional and categorical data. The detected defects are visualized using an upper computer interface. Experiment results show that the proposed method achieves high accuracy in detecting rivet defects under varying angles and rivet distribution patterns, with a processing time of less than 800 ms per frame. This approach significantly enhances operational efficiency and reliability in quality-inspection workflows.
Laser-electrochemical hybrid machining (LECM) with a tubular electrode displays potential for use in the high-efficiency machining of deep small holes in difficult-to-machine superalloy materials. The tool electrode serves as the key component in coupling and transmitting the laser energy, electrical power, and electrolyte into the machining gap, thereby facilitating the hybrid machining process under the interaction of multi-energy fields. This study proposes a ring-shaped laser-guiding tubular electrode with a sidewall-insulating function for application in LECM. The novel electrode consists of an inner metal tube for electrical conduction and electrolyte transportation and an outer quartz tube functioning as a laser waveguide for efficient laser transmission while ensuring reliable sidewall insulation. The retraction distance of the sidewall-insulating laser waveguide is optimized via multiphysics simulations, and the optical modulation structure of the electrode tip is analyzed to regulate the spatial distribution of the laser within the machining gap. A tool electrode and machining head were fabricated and assembled. Performance tests show that the newly designed electrode achieves a numerical aperture above 0.24, a laser transmittance exceeding 80
In laser powder bed fusion (LPBF), circular internal flow channels in small aerospace satellite integration plates must be fabricated without supporting structures, particularly for horizontal channels. This can cause melt-pool collapse defects during the LPBF process, leading to reduced relative density, increased surface roughness, and thermal stress-induced deformation. To address these challenges, we developed a multi-objective collaborative optimization forming method for fabricating φ1-mm TC4 horizontal circular internal flow channels via LPBF. Optimal heat treatment parameters were obtained to enhance the corrosion resistance of the internal flow channels. The results revealed that the forming quality of the horizontal circular internal flow channels was comprehensively improved. The channel achieved a relative density of 99.64
Reaction bonded SiC (RB-SiC) possesses advantages such as high hardness, temperature resistance, and corrosion resistance; however, these advantages also result in significant challenges in the machining of RB-SiC. Considering its high efficiency and low cost in the processing of difficult-to-cut materials, blasting erosion arc machining (BEAM) demonstrates considerable potential for the efficient machining of RB-SiC. However, research on BEAM has primarily focused on highly conductive materials, and application to low-conductivity, hard, and brittle ceramic materials has received limited attention. Thus, this study proposed the application of BEAM to RB-SiC and investigated its machining characteristics. Firstly, as the heat source in BEAM, the arc plasma behavior during RB-SiC machining was investigated via single-discharge experiments and compared with that observed for AISI 304 stainless steel. The results showed that the arc plasma generated during RB-SiC machining exhibited a higher development speed, stability, and maintaining voltage. Therefore, to ensure timely extinction of the arc plasma and protect the workpiece surface from thermal damage, a shorter pulse duration is more suitable for machining RB-SiC as it forcibly terminates energy input. Then, to analyze the machining effect of BEAM, the behavior of the molten pool and morphology of craters were investigated. The results indicate that RB-SiC is difficult to melt and expel efficiently, owing to its high thermal conductivity, high melting temperature, and large specific heat capacity. Therefore, high-speed flushing is essential to ensure effective material removal. Based on the research of arc discharge characteristics of RB-SiC, the machining performance was evaluated through machining experiments. The material removal rate (MRR) in RB-SiC machining reached 539.6 mm3/min, which was five times higher than that achieved using electrical discharge machining (EDM). The surface roughness was 25.31 µm, which was only 67.39
Carbon fiber-reinforced silicon carbide (C/SiC) composites are extensively employed in aerospace applications owing to their high-temperature strength, low density, and thermal stability. However, conventional machining of these hard and brittle materials is hindered by severe tool wear, low processing efficiency, and high operational costs. As a non-contact and tool-wear-free technique, abrasive waterjet (AWJ) machining enables efficient bulk material removal and can function as a roughing process that complements conventional finishing operations to ensure dimensional accuracy. In this study, AWJ milling was systematically investigated to elucidate how fiber orientation and jet parameters influenced material-removal behavior and surface integrity. Experiments were conducted on a five-axis AWJ system at traverse speeds ranging from 2 000 mm/min to 4 000 mm/min and standoff distances between 6 mm and 18 mm. Scanning electron microscopy (SEM), white-light interferometry, and depth-profilometry identified three orientation-dependent fiber-damage modes—splitting and pull-out in warp yarns, circumferential fracture in weft yarns, and protrusion-bending in needled fibers—originating from crack deflection and fiber-matrix interfacial debonding under localized jet loading. An increase in standoff distance broadened the kerf width while reducing the maximum removal depth by approximately 50
