Lattice sandwich structures have drawn considerable attention in engineering applications owing to their exceptional specific strength, specific stiffness, and outstanding impact resistance. Regarding structural dynamic performance, current research predominantly concentrates on global vibration responses while overlooking the influence of local vibration characteristics of lattice trusses on dynamic behavior as fundamental aspects for nondestructive evaluation techniques. This investigation systematically examined the local vibration properties and damage detection methods for lattice sandwich structures. Firstly, combined numerical simulations and experimental measurements were conducted to analyze the effects of lattice trusses on guided wave propagation characteristics. Signal processing through Fourier analysis and wavelet transform revealed distinct energy concentrations at specific frequency peaks. Furthermore, by correlating the guided wave signals with local resonance modes of lattice unit cells, we demonstrated that these characteristic frequency peaks were intrinsically determined by the vibrational modal frequencies of lattice trusses, particularly their axial compression-tension vibration modes. Based on these findings, an innovative damage identification methodology is developed that utilizes the frequency peak shifts in wave signals for structural integrity assessment. The proposed approach is numerically validated, with results confirming its effectiveness in both damage detection and localization for lattice truss structures.

The test platform, composed of components such as a superconducting magnet, Dewar, and cryogenic system can realize the force-thermal-electrical-magnetic multi-field testing of superconductors, in which the superconducting magnet functions to provide a background magnetic field. The split low-temperature superconducting magnet can generate a uniform transverse magnetic field at the center, and its semi-open structure provides convenience and large space for testing. The split low-temperature superconducting magnets operate in low-temperature, strong magnetic fields, and high-current environments, verifying the structure and performance of split low-temperature superconducting magnets is necessary because these conditions can cause the complex electromagnetic forces, thermal stresses, and assembly forces they carry to deteriorate the magnets’ electromagnetic performance and stability. The dynamic winding process of superconducting coils, as well as the excitation and cooling processes of the coil assembly, were experimentally studied in the research applying wireless strain testing method and using techniques like cryogenic strain gauges, cryogenic thermal sensors, and Hall plates. The findings demonstrate that the strain accumulated in the coils during dynamic winding is approximately linear with the number of winding layers and falls back slightly with time, and the strain of the coil assembly and the surrounding magnetic field in energized conditions have a high synchronization with the excitation current, the properties of the superconducting magnet testing and processing procedures can be efficiently revealed by the strain evolution law inside the coil.

Identification of microcracks in time is important for the safety control of concrete structures. In this study, four-point bending experiments were conducted on basalt fiber concrete specimens. The strain fields information on the specimen surface were acquired by digital image correlation technique during the loading process. In the horizontal strain field, 300 points with large strains were selected as points of interest (POI), the aggregation factor was calculated based on the standard deviation of the coordinates of the POI in the strain field, and a method for identifying microcracks associated with a single strain field only was proposed by using the distribution evolution of the aggregation factor during the loading process. This method can exclude the error generated by human judgment of microcracks, but it is not sufficient to identify multiple microcracks. The accuracy of the method exceeds 95% and is suitable for engineering applications.

A new dynamic performance degradation testing platform of advanced composite structures under high temperature-scouring-vibration environments has been self-designed and developed to achieve corresponding tests under such coupled environments. Firstly, the functional design and implementation principles of various parts of this system were introduced in detail, and the construction of the testing platform was completed. Additionally, the degradation curves of natural frequency and resonant response of quartz fiber ceramic matrix composite thin plates under various temperatures, degradation time, and flushing time were obtained based on the above testing platform. The results indicate that the effects of high temperature, scouring, and vibration lead to the degradation of the dynamic performance of ceramic matrix composites, characterized by a reduction in the first two natural frequencies and a significant amplification of the resonant response.

Poly(p-phenylene benzobisoxazole) (PBO) fibers have garnered significant attention due to their exceptional mechanical properties, high thermal stability, and flame resistance, demonstrating broad application prospects in aerospace, transportation, and new energy sectors. However, the aging behavior of PBO fibers in humid environments severely compromises their long-term service performance, limiting their development and application in high-tech fields. Therefore, enhancing the anti-aging properties of PBO fibers under humid conditions remains a critical challenge. In this study, the protective effect of graphene coatings on PBO fibers in humid environments was investigated using single-fiber micro-tensile testing. The results indicate that PBO fibers undergo hydrolysis in humid environments, leading to a reduction in Young’s modulus and tensile strength. While coating PBO fibers with covalently cross-linked graphene oxide significantly enhances their mechanical properties, it fails to improve their moisture resistance. Further, the reduction of covalently cross-linked graphene oxide through high-temperature pyrolysis yields reduced graphene oxide with a dense layered stacking structure and excellent hydrophobicity, effectively improving the anti-aging performance of PBO fibers. The reduced graphene oxide-coated PBO fibers exhibit a strength retention rate of nearly 98.2% at 50% relative humidity and up to 96.4% at 80% relative humidity.

Rock physico-mechanical parameters, such as porosity, permeability, and elastic modulus of fractured-vuggy carbonate reservoirs, are key factors affecting oil and gas extraction efficiency. Consequently, this paper examined the Ordovician fractured-vuggy type carbonate reservoir in the Fuman area of the Tarim Basin, and systematically studied the mechanical parameters of the reservoir rock through uniaxial and triaxial compression experiments, acoustic emission experiments, and stress sensitivity experiments to elucidate the stress state of the reservoir under in-situ conditions. The results indicate that: 1) as the confining pressure increases, the compressive strength and elastic modulus of the rock progressively increase, transitioning the rock from brittle to plastic and exhibiting strain hardening characteristics. 2) the permeability of the carbonate reservoir gradually decreases with increasing confining pressure, with significant changes observed below 30 MPa. 3) the maximum horizontal principal stress in the study area is 186.14 MPa, the minimum horizontal principal stress is 150.82 MPa, and the vertical stress is 172.89 MPa, reflecting the stress characteristics of a strike-slip fault. The results of this study can provide technical support for the efficient exploration and development of fractured-vuggy carbonate reservoirs.

High-precision full-field morphology measurement of specular structures is an indispensable step in numerous high-end manufacturing fields. This paper proposes Translational Phase Measuring Deflectometry to achieve high-precision measurement of specular surfaces. Based on a monoscopic single-screen setup, the method establishes a complete model of the relationship between fringe phase, surface gradient, and height, and establishes basic constraints in the model through the assumption of surface continuity. A method for solving model parameters is proposed, addressing the ambiguity issue present in traditional phase measuring deflectometry. This method allows for the measurement of the morphology and pose of the structure under test through simple and arbitrary movements of the screen. A series of validation experiments are conducted to discuss the influence of surface gradient and height variation on the method’s ability to measure morphology and validate its comprehensive measurement capability. Experimental results demonstrate a significant improvement in measurement accuracy compared to traditional methods in the measurement of specular structures’ morphology.

Digital Image Correlation (DIC) is a non-contact optical measurement technique that uses speckle patterns as deformation carriers to measure surface displacement and deformation fields of objects. It has been widely applied in key industrial fields such as aerospace, mechanical engineering, and power engineering. In general, specialized software is required for Digital Image Correlation (DIC) measurement and analysis. In particular, in the measurement of fatigue and dynamic problems, it is essential to address challenges arising from big data processing, such as long computation times and low efficiency. With the development of artificial intelligence technology, deep learning provides new opportunities for DIC method. However, a huge dataset is required for the construction of DIC deep learning network, which not only increases the cost of data collection but also takes a long computation time. To solve the above problems, this paper proposes a DIC-2D displacement measurement method based on migration learning, which is based on U-Net network including a multi-level feature extractor, an attention mechanism and a depth-separable convolution. In the pre-training process of the network, simulated scattering images are used as the training dataset to form the pre-trained network；On this basis, multiple transfer learning fine-tuning strategies are used to optimize the network parameters using a small number of real speckle images with different mean intensity gradients to establish the migration network, and real speckle images are used for verification. The analysis results show that the network trained by the global fine-tuning strategy exhibits higher accuracy and better robustness in the training of different mean intensity gradient speckle images. The DIC migration learning method proposed in this paper can significantly reduce the training time and cost for data acquisition.

In order to investigate the dynamic process of calculi ablation by holmium(Ho) laser and its collateral damage to the surrounding tissues, various model experiments were conducted on artificial gelatin-gypsum samples, along with a homemade holmium laser device. The experimental parameters included the laser energy, the fiber diameter, and the distance between the fiber and the artificial calculi. High-speed shadow graphs showed that an hourglass-shaped bubble would occur in gelatin during the ablation, and a discussion was provided on the morphology evolution mechanism of hourglass-shaped bubbles under different loading conditions. Characterizations on the recovered samples were carried out via optical imaging and scanning electron microscope. The results revealed that gelatin tissue undergoes damage from erosion, cavitation, and fragments jetting of artificial calculi. The ablation crater shows two kinds of morphology on its side face and subface with different roughness due to different material failure mechanisms. Geometric parameters of the ablation crater were obtained using the white-light interferometry technique, along with discussions on the effects of loading conditions. Energy analysis was given on the ablation process, and a linear relation between crater volume and laser energy was evaluated.

To investigate the effect of different cooling methods on the uniaxial compressive properties of ultra-high performance concrete (UHPC) after high temperature, 45 specimens with the dimension of 100 mm×100 mm×300 mm were designed and fabricated. The cooling methods and heating temperature were chosen as test variable parameters. Observe the apparent characteristics, quality loss, and failure mode were observed after different high temperatures and cooling methods. The variation law of compressive strength was analyzed. The experimental results show that as the temperature increases, the surface cracks increase. The mass loss rate increases under different cooling methods. A higher mass loss rate occurs under natural cooling with the same temperature. Under natural cooling, the mass loss rate increases rapidly at first and then slowly. An approximately linear increase is presented under water cooling. The compressive strength shows a trend of first slightly increasing and then decreasing. Compared with the normal temperature, with the temperature increase, the maximum compressive strength increased by 18.3% and 13.4% respectively under natural cooling and water cooling. When the temperature reaches 800 ℃, the compressive strength under natural cooling and water cooling decreases to 20.8% and 18.8% of compressive strength at normal temperature, respectively. When the temperature exceeds 600 ℃, the axial deformation ability of blocks is significantly enhanced. Compared with natural cooling, the peak strain under water cooling develops rapidly, but tends to be consistent at 800 ℃. The peak strain under natural cooling and water cooling increases to 2.22 times and 2.24 times the peak strain under normal temperature conditions, respectively. Compared with natural cooling, the elastic modulus under water cooling is relatively small and undergoes three stages: slow decrease, fast decrease, and slow decrease. Based on the experiments, a formula for calculating the residual strength of UHPC after water cooling is proposed, which can provide a basis for evaluating the load-bearing capacity of a building after fire.