Minimal surfaces are characterized by spatially continuous smoothness, which can effectively avoid the problem of the stress concentration, and have become a significant focus in the research of mechanical metamaterials. A Scherk single-periodic minimal surface (SPMS) was studied, and the spatially continuous smooth geometrical model was generated using a voxel reconstruction technique with multi-software association method. The mechanical behavior and energy absorption characteristics of the single-period Scherk surface structure were investigated using finite element simulation. The impact of the mathematical parameters of the minimal surface on the geometric configuration was examined.Five minimal surfaces with different parameters were established, and the deformation patterns and stress distributions of the five structures were explored under positive and lateral compression conditions. The Scherk surface structures were fabricated by metal printing technology, and quasi-static compression tests were conducted. The results show that the Scherk single-period surface has an obvious negative Poisson ratio effect, and the SPMS structure exhibits X-and V-shaped deformation modes, which can well withstand the external loading effects. The compression tests show the hump phenomenon of the reaction force and displacement curves of the SPMS structure, indicating that the structure has a negative Poisson ratio and negative stiffness property. This property provides a wide space for its application research in large deformation damage and structural energy absorption.

The telescopic arm, a pivotal component in the pipeline grabbing vehicle, links the lifting platform and the mechanical claw, shouldering the majority of the load. Conducting a reliability analysis is imperative. Traditional methods for reliability face challenges like high computational costs and low accuracy dealing with multidimensional uncertainties. To overcome these, our study proposed an engineering mechanical reliability analysis method, leveraging Adams dynamic simulation, semi-supervised learning, deep neural networks, and Monte Carlo method. In this study, a virtual prototype model of the pipeline grabbing vehicle was established, identifying hazardous operating conditions. Combining the telescopic arm model’s geometric parameters and overall structure, uncertain factors influencing the maximum von Mises stress were determined, conducting a sensitivity analysis was conducted. Utilizing optimal Latin hypercube sampling based on uncertain parameter distributions, Ansys Workbench was employed to build a finite element model, obtain output results for the sample size. Semi-supervised learning processed the finite element simulation data, enhanced deep neural network training accuracy.Finally, based on the fourth strength theory, a failure criteria for the telescopic arm component was determined. Combining deep neural networks and Monte Carlo method, the reliability and failure probability were predicted. Results show that this method surpasses actual engineering precision requirements，provides a certain guiding significance.

The harsh operational environment of helicopters renders their structures highly susceptible to the initiation and propagation of hole-edge cracks around bolt holes, thereby compromising structural integrity and load-bearing capacity. To monitor hole-edge cracks in helicopter attachment lug structures, piezoelectric guided wave-based structural health monitoring(SHM) techniques are commonly employed. However, due to the difficulty in detecting small cracks at the early stages of propagation and the presence of large through-hole configurations in attachment lug structures, the accuracy of guided wave monitoring remains suboptimal. Therefore, addressing the accuracy issues in crack monitoring of attachment lug structures,this study proposes a piezoelectric guided wave array-based method for hole-edge crack detection. Firstly, damage feature information was extracted from acquired piezoelectric guided wave array signals encompassing the entire sensor network.Subsequently, a damage alarm threshold was established using a mean-value method to facilitate damage detection.Furthermore, an improved delay-and-sum imaging algorithm was developed based on the specific configuration of the attachment lug structure to optimize probability distribution and achieve precise crack localization. Finally, validation was conducted through test monitoring of crack propagation in attachment lug structures. Test outcomes demonstrate that the proposed method enables accurate alarm triggering and localization of hole-edge cracks around bolt holes, with localization errors confined within 2.01 mm, thereby confirming the efficacy and precision of the proposed approach.

Aiming at the problems of traditional impact load identification methods, such as the requirement for a large number of sensors, high sampling frequency, and low identification accuracy, a new impact load identification method based on empirical mode decomposition (EMD) technology was proposed.The EMD technology was used to decompose the complete impact response to obtain the modal acceleration response. The impact location was quickly realized by measuring the collinearity between the uncorrected mode shape vector and the column vector of the mode shape matrix in the modal acceleration response. According to the positioning results, an optimization objective function was constructed. The time history of the impact load was fitted by using the Gaussian basis function, and the optimal fitting parameters were quickly solved by using the two-dimensional gradient descent method.Tests conducted on a cantilever plate with dimensions of 600 mm×200 mm×3 mm show that with only one accelerometer, the success rate of 36 impact positioning tests is 91.67%. The peak relative error and relative error index of the reconstruction results are less than 10% and 40%, respectively.

To address the issue of accuracy degradation caused by aerodynamic damping when measuring the moment of inertia of irregular specimens with large airfoil surfaces using the torsional pendulum method, a compensation approach based on drag simulation results was proposed. Initially, the mechanism of aerodynamic damping in torsional oscillations was analyzed, and a measurement model incorporating compensation through calculation of aerodynamic damping torque was established. Subsequently, the reduced frequency parameter was introduced to characterize the unsteady aerodynamic nature of the aerodynamic damping torque. By employing a quasi-steady assumption combined with equivalent linearization techniques,the unsteady time-varying aerodynamic damping torque was equivalently represented as viscous damping. Furthermore,computational fluid dynamics (CFD) simulations were conducted to obtain drag coefficients during specimen motion, from which a compensation formula based on drag coefficients was derived. Finally, validation test were designed and performed to verify the proposed method. The findings indicate that under low reduced frequency conditions (reduced frequency less than 0.01), the relative error between the equivalent aerodynamic damping ratio calculated via quasi-steady assumption and test separation values is approximately 7%. After compensating using the proposed equivalent aerodynamic damping ratio, the error between measured and theoretical moments of inertia is approximately 0.2%, demonstrating that the proposed method effectively enhances measurement accuracy for moments of inertia of irregular specimens with large airfoil surfaces.

To accurately simulate the complicated load transfer pattern of the launch device under cold launch mode, the rigid-flexible coupling dynamic simulation method was adopted to analyze the dynamic response of a launch vehicle, the structural strength was also verified. The finite element flexible body was introduced and a multi-rigid-flexible-body dynamic simulation model of a launch vehicle was constructed. Accuracy of the model was verified by the actual launch test. The influence law between the vibration response and stress state of the launch vehicle and the launch angle was further analyzed. The results show that amplitudes of the transmitted load and stress inside the launcher will reduce when the launch angle is close to 90°. The modeling and analysis approaches proposed in this study can effectively support the optimal design of the launch device.

Shot peening process is widely used in the manufacturing process of gears and other basic components, and its own limitations limit the enhancement of the surface integrity of the workpiece. In order to further improve the surface integrity of the workplece, A combination of numerical simulation and experimental methods was utilized to study the effect of two surface composite strengthening processes, such as double shot peening and shot peening-ultrasonic rolling, on the surface integrity of 18CrNiMo7-6 carburization gear steel samples, and mainly analyzed the effect of the two composite strengthening processes on the improvement of surface integrity of the shot peened samples. The results show that the maximum value of the residual compressive stress of the double shot peening sample was 1 359.56 MPa, locates at the depth of 0.08 mm, and the maximum value of the residual compressive stress of the shot peening-ultrasonic rolling peening sample was 1 329.05 MPa,locates at the depth of 0.25 mm. Compare with the single shot peening sample, the surface roughness of the double shot peening sample and the shot peening-ultrasonic rolling sample was 29.42% and 29.42% lower than that of the single shot peening sample. Compare with the single shot peening samples，the surface roughness of the double shot peening samples and shot peening-ultrasonic tumbling peening samples decreased by 29.42% and 62.76%，respectively, the surface microhardness increased by 8.70% and 17.60%, and the standard deviation of the surface node compressive residual stress value decreased by 23.36% and 89.50%. The shot peening-ultrasonic rolling process is more effective in enhancing the surface hardness,thickness of the residual stress layer and uniformity of the residual compressive stress, as well as reducing the surface roughness of the specimens，and can effectively improve the surface integrity of the shot peened samples.

In pressurized-water reactor nuclear power plants, the vessel nozzles of large carbon steel equipment such as reactor pressure vessel (RPV), steam generator (SG), and main pumps are connected to austenitic steel pipes through dissimilar metal welds (DMWs). The thick-walled DMW has material inhomogeneity and complex weld residual stress (WRS), which easily leads to the generation of fatigue or stress corrosion cracks.Firstly, the WRS of DMW in nuclear power plants obtained through international measurements and numerical analyses was investigated. Then, based on a rapid WRS simulation method for volume uniform heating of unit cells, the WRS of DMW in the hot leg of the primary loop (the connecting pipe section from RPV outlet to SG inlet, which is the pipe section with the highest operating parameters in the primary loop pressure boundary) was obtained.The numerical simulation results are consistent with the trend of the fitting envelope curve recommended by the United States, and the overall results can be enveloped by the fitting curve recommended by the United States, indicating that the described rapid WRS simulation method is feasible. The WRS of thick-walled DMW is relatively high, and the stress values at the inner and outer surfaces of the pipe are more conservative than the recommended values of the United States, suggesting that more safety margins can be obtained in actual structural analyses.

Due to the needs of transportation, installation, grid connection, and maintenance, the construction of offshore wind farms in inshore areas often cannot be far from busy surrounding waterways, which significantly increases the probability of offshore wind turbines being impacted by ships. To analyze the performance and damage of different hollow ratios of protective devices when offshore wind turbines are hit by ships，the collision process of a 5000-ton bow-downward ship with an offshore wind turbine at a speed of 2.0 m/s was simulated using Ansys/Ls-Dyna. The influence of the hollow ratio on the anti-collision performance of Ogden rubber，Mooney-Rivlin rubber and Aluminum foam aluminum constitutive protective devices was studied and compared. The results show that with the increase of hollow ratio, the impact duration of aluminum foam protective devices increases, and the contact force decreases accordingly, while rubber materials show the opposite trend. As the hollow ratio decreases, the protective device is more similar to a solid tube, with a relatively smaller maximum indentation depth. Under the influence of hyperelastic properties, the indentation depth of rubber materials is smaller than that of aluminum foam after the collision is completed, and the material damage of the protective device is smaller. However, the proportion of internal energy in the support area gradually increases, so the influence of hollow ratio on the leg support needs to be considered in the design and research of protective devices.

Aiming at the problem that loop-end braided stents are prone to loop-end fracture during crimping, the key design parameters affecting the structural stability of loop-end braided stents were explored, and an improvement scheme was proposed.Numerical simulation of crimping for magnesium alloy loop-end braided stents was conducted using Abaqus analysis software. The results showed that increasing the braiding angle can effectively reduce the risk of loop-end fracture.Based on this finding, a variable pitch stent was designed, which features increasing the braiding angle at both ends to form sparse segments while maintaining the braiding angle in the middle of the stent. The influence of adjusting the length and braiding angle of the sparse segments on the mechanical response of the stent was evaluated.The research results showed that increasing the braiding angle and length of the sparse segments can effectively reduce the axial elongation and loop-end stress of the stent, but it will shorten the length of the middle dense segment, thereby reducing the radial force of the stent. Different from the flared expansion of the constant pitch open-end stent, the variable pitch stent presents a shape with large middle expansion and small end expansion after expansion.This study reveals the potential of variable pitch design in controlling loop-end fracture and provides a reference for the structural optimization of magnesium alloy braided stents.