In order to achieve simulation prediction of the isolation performance of rubber isolators, simulation and testing comparative research on the vibration transmissibility of standard specimens were conducted. Firstly, a compression test was conducted on the standard specimen to obtain pressure deformation data. Based on the theory of the large deformation, the data was processed to obtain the true stress-strain curve. The Mooney-Rivlin model was chosen to define the material properties. Secondly, a vibration transmissibility testing system was established, an exciter to excite the standard sample was used, and the measured vibration transmissibility curve was obtained. Then, a simulation model based on the testing system was built, and the simulation transmissibility curve based on the transient dynamic analysis was obtained.Finally, the test results were compared with the simulation results to achieve the simulation prediction of the rubber isolation performance. The results show that the simulated isolation rate curve is highly consistent with the test results, with a peak frequency error of only 4.8%, which can achieve the simulation prediction and provide a simulation guidance for the optimization design and performance improvement of isolators.

Considering the time-varying stiffness characteristics of mechanical systems, a single-degree-of-freedom time-varying impact vibration system model with clearance stiffness was studied. The dynamic model and Poincaré map were established, and numerical calculation methods were given. The influence of the ratio of time-varying stiffness amplitudes on the dynamic response and characteristics of the system was analyzed using numerical simulation and the maximum Lyapunov exponent. By combining multiple initial value bifurcation diagrams, attraction domains, phase diagrams, and Poincaré mapping diagrams, the evolution and bifurcation of coexisting attractors in the system were studied by applying the continuation shooting method. When the bifurcation parameter changes and the system exhibits the coexistence phenomenon,the reasons for the appearance and disappearance of local attractors and the distribution mechanism of unstable attractors in the attraction domain before and after bifurcation are revealed. The stability change rule of coexisting attractors is obtained.

The influence of different multi-delamination forms on the tensile strength of blade spar cap laminates was studied. Static tensile tests were conducted on laminates with single and multiple delaminations. The continuous damage model(CDM) and cohesive zone model (CZM) were used to analyze the damage process and failure mode. The numerical results showed good agreement with test values, with an overall error rate below 7%. A numerical model of 1.5 MW-40.3 m blade spar cap equivalent laminates was established to predict the effect of different types of multi-delamination on the tensile strength. The results show that the arrangement, maximum area, and step difference of delaminations all have an impact on tensile strength. The tensile strength of triangular multi-delamination is higher than that of inverted triangular multi-delamination laminates, and the maximum delamination near the surface greatly affects the tensile failure load.

The six-component forces at the wheel-road interaction represent the sole coupling between the vehicle and the road surface, and obtaining these forces is critical for conducting reliability and durability assessments of the entire vehicle. In response to the high cost, long cycle, and low efficiency associated with traditional methods for obtaining wheel six-component forces, a data-driven approach for rapidly predicting wheel loads was proposed. Firstly, for the non-stationary random signals on real vehicle roads, a joint method of the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), permutation entropy (PE), and wavelet threshold denoising (WTD) was applied for the data denoising.Secondly, the easily obtainable and low-cost data, such as wheel center acceleration, damper displacement, and center of mass acceleration, were used as inputs. Various neural network architectures with nonlinear transfer relationships were designed for multi-surface wheel six-component force prediction. A multi-dimensional load prediction evaluation system was established in the time domain, frequency domain, and damage domain. Finally, in order to overcome the challenges of a large and costly training dataset, an input channel compression method based on the correlation and coherence analysis of neural network inputs and outputs was proposed. Minimum load signal segment division criteria were introduced, and the minimum segment duration for each road surface was determined to compress the training dataset. Through continuous model iterations, the predicted values of the wheel six-component forces closely match the measured values, and the load characteristics are preserved. This demonstrates that the minimal dataset model can achieve a high level of prediction accuracy with fewer input channels and shorter load segment durations, resulting in a 28.85% improvement in computational efficiency.

The aircraft’s inlet structure is connected to the engine sleeve using countersunk rivets. During maintenance,fatigue fractures were discovered in some rivets. It suggests that the inadequate perpendicularity of rivet holes during manufacturing causes the rivet misalignment, reducing the load-bearing capacity, and leading to fatigue fractures under aircraft vibrations. The finite element simulation was used to study the effect of inclined rivet holes on the load-bearing capacity,simulation results show that inclined holes cause uneven stress distribution across the rivet section. The higher the tilt angle,the higher the maximum stress and the more uneven stress distribution on the rivet head section. Fatigue tests under axial loads at different tilt angles demonstrated a reduction in the rivet’s fatigue life due to the hole inclination. The study concludes that non-compliance with perpendicularity standards during hole fabrication results in uneven stress distribution, decreasing load-bearing capacity. Therefore, the strict control over rivet hole perpendicularity during the aircraft manufacturing is crucial to ensure structural reliability.

Abnormal yaw positioning during yaw operations induces progressive deviation in yaw alignment accuracy,thereby compromising wind-tracking precision and risking excessive cable twisting that threatens operational safety.Concurrently, frequent position oscillations or repetitive short-duration position holding generate transient control errors,destabilizing the yaw control system. These coupled mechanisms collectively escalate yaw system failure frequency and operational maintenance costs. To proactively mitigate these risks, a data-driven fault diagnosis methodology is proposed for early detection of anomalous yaw positioning in wind turbines. Firstly, a large amount of data in a supervisory control and data acquisition (SCADA) system was processed using a standardized interaction gain and Relief-F (SIG-Relief-F) feature selection algorithm to identify multiple feature parameters with the strongest correlation with the target variable (which in this case may be yaw system failure). The advantage of this method lied in its ability to consider effectively the correlation between features,thus maximizing the retention of relevant features related to yaw system failures and interaction features. Secondly, a back propagation neural network (BPNN) yaw position prediction model was established, and the distribution of residuals was statistically analyzed using a sliding window method to determine the fault threshold. Finally, through empirical verification,the effectiveness and accuracy of the proposed method were demonstrated, and compared with multivariate state estimation technique (MSET) and support vector machine (SVM) algorithms, it was shown to have superior abnormal warning performance. The conclusions drawn can serve as a reference for the fault diagnosis of a practical yaw system.

In view of the problem that the formulary design load based on the design standard can't truly reflect the actual service conditions of the welded frames of subway vehicles, and a large number of online measured data information has not been fully explored in the structural design of the frame, an anti-fatigue design spectrum compilation method based on the stress-time history sample information measured at the weak position of the subway vehicle frame was proposed.The small stress threshold value was determined by clustering ordered samples using the rain-flow counting method to compile measured stress spectrum reflecting structural damage, determining the stress-frequency-damage relation based on the fatigue damage theory, and using the methods of Bayesian parameter estimation and kernel density estimation to obtain stress extrapolation results. Considering the stress concentration caused by structural geometry changes in the cross-section of the welding site, the hot spot stress method and stress linearization method were used to obtain the stress concentration coefficient, and the measured stress spectrum was corrected to achieve the compilation of the design load spectrum. The research results show that the small stress threshold value is 3.18 MPa determined by extrapolation of stress extremes and the relation analysis between normalized stress-frequency-damage, which is 8.19% higher than the stress threshold value determined by traditional methods, the effect of discarding the number of small stress cycles is significant. Considering the load dispersion and stress concentration factor at the weld seam, while ensuring that the structure meets the current service conditions, the relation between the design mileage and equivalent stress is determined, the necessity of compiling the design spectrum is emphasized further. The above research builds the construction method of load spectrum compilation and the equal strength design of structures.

To enhance the energy absorption efficiency of conventional sandwich panels, a biomimetic tree-like fractal core (BTLFC) inspired by the dendritic fractal structure of the royal lotus leaf vein was designed. Firstly, quasi-static compression tests revealed that the 2-order BTLFC exhibited a specific energy absorption 5.69% higher and an average load 4.46% greater than traditional honeycomb cores. Secondly, a finite element numerical model of the BTLFC was established;combined with quasi-static compression test data, the finite element model error was within 2.2%, demonstrating high accuracy of the model. Finally, Latin hypercube test design, Kriging surrogate model, and the non-dominated sorting genetic algorithm-II (NSGA-II) were employed to perform multi-objective optimization on the structural parameter combinations of the BTLFC (size ratio r, bifurcation angle θ, fractal order D). The optimized BTLFC structure exhibited superior comprehensive performance, with specific energy absorption increased by 10.19%, peak crushing force reduced by 12.27%,and mass decreased by 11.79% compared to traditional honeycomb cores. The findings provide novel biomimetic design insights for developing high-performance energy absorption structures.

To enhance the computational efficiency of structural lightweight design for complex structures, a structural lightweight design method based on the Kriging surrogate model is proposed. The proposed method incorporates a hybrid addition strategy and a sample deletion strategy considering a distance threshold，aiming to rapidly improve the fitting accuracy of the Kriging surrogate model. This model was then applied to a multi-objective lightweight design model of the truck frame, with the optimization objectives of minimizing frame mass and maximum stress. Subsequently, the multi-objective lightweight model was solved using the non-dominated sorting genetic algorithm-II (NSGA-II). The results demonstrate that the proposed hybrid addition strategy and sample deletion strategy considering the distance threshold effectively enhance the update process of the Kriging surrogate model. The structural lightweight design method based on the Kriging surrogate model exhibits significant advantages in both computational efficiency and lightweight performance.

To evaluate the performance of various equivalent stress intensity factor models in predicting mixed-mode fatigue crack growth and to address the challenge of parameter estimation under limited sample conditions. A crack growth parameter estimation method based on the Bootstrap method resampling technique was proposed firstly. Mode Ⅰ fatigue crack growth tests were conducted on CT specimens to obtain the material parameters, and the proposed method was employed to expand the sample set and mitigate the issue of data scarcity. Then, using the statistically augmented material parameters,mixed-mode Ⅰ+Ⅱ fatigue crack growth experiments were performed on 6005A-T6 aluminum alloy CTS specimens under loading angles of 0°, 30°, 45° and 60°, employing a Richard-type loading fixture, to validate the accuracy of various equivalent stress intensity factor models. The results indicate that the Irwin model achieved the highest goodness-of-fit, with a value of 0.942 1, demonstrating the best crack growth prediction performance. Increasing the loading angle was found to reduce the initial crack growth rate, highlighting the need for angle-specific experiments to obtain appropriate Paris law parameters. This study confirms the applicability of multiple ΔK_eq models and provides theoretical support for fatigue life prediction in mixed-mode crack growth scenarios.