Dichloromethane solution was introduced as the corrosion medium by the liquid drop method.Based on the regular quadrilateral, regular hexagon and concave structures with different porosities，the effects of different corrosion cycles and areas on the porous structural mechanical properties of polylactic acid (PLA) were analyzed by comparing with the finite element simulation results.The results show that concave porous structure plate is the least affected by the corrosion cycle,while the other two structures are affected by it depending on the size of the porosity.The hexagonal structure with a porosity of 72% has the weakest corrosion defect bearing capacity, while the concave structure has the strongest bearing capacity.The regular quadrilateral structure with a porosity of 54% is most affected by the single cell corrosion.The corrosion bearing capacity of the expanded area of a single cell in a regular hexagonal structure is weaker than that of a single cell, while the corrosion bearing capacity of the expanded area of a single cell in a regular quadrilateral structure is stronger than that of a single cell.

Body centered cubic (BCC) structure has excellent mechanical properties, but the stress concentration phenomenon at the nodes limits its further development in mechanical properties. At present, the method of adding spherical nodes or variable cross-section pillars is commonly used to alleviate stress concentration at nodes and achieve strengthening design of lattice structures, but there is a lack of research on the influence of the volume ratio of nodes to pillars on the strengthening effect. A new type of variable cross-section pillar based on trigonometric function reduction is designed, and a variable cross-section body centered cubic lattice (VC-BCC) lattice is designed. Dynamic node design is achieved by directly connecting the pillars to explore the optimal node to pillar volume ratio. Theoretical formula estimation of the volume of VC-BCC lattice is carried out, and based on the Timoshenko beam model, the equivalent elastic modulus of VC-BCC lattice is theoretically analyzed. A simplified model is established using the method of equivalent cross-section. Finite element simulation analysis was conducted on VC-BCC lattice with different proportions of node pillars, and lattice specimens were manufactured using selective laser melting technology for quasi-static compression testing. The experimental results show that there is little difference between theoretical calculations and simulation analysis. The maximum stress of the VC-BCC lattice structure is significantly reduced, and the equivalent yield strength is significantly improved. In all analyses, the VC-BCC lattice structure with a variable cross-sectional parameter of 0.6 exhibited excellent performance and had the best overall mechanical properties.

Considering cracks of various length and depth (various constraints) on the nuclear power main pipeline as the research object, through the mass acceleration application method, applying vertical load of 5 earthquake intensities and 3 real earthquakes to the nuclear power main pipeline under varying constraints respectively, and based on a method to determine the constraint related to fracture toughness of the actual structure, the calculation of constraint related fracture toughness was performed, the various constraint under various vertical earthquake loads related crack toughness was systematically studied.The results show that under the same constraint, the crack opening force curve shifts to the left with the increase of earthquake intensity, and the constraint related fracture toughness decreases gradually.With an increased crack length, the effect of earthquake intensity on constraint related fracture toughness becomes more obvious.With an increased crack depth, the effect of earthquake load on constraint related fracture toughness firstly becomes obvious, and then becomes insignificant.Under different constraints, the influence trend of the real earthquake load on constraint related fracture toughness is the same as that of the earthquake intensity, and has a certain relation with the magnitude and earthquake acceleration time history curve.

The research on multiaxial fatigue life prediction of materials is one of the critical elements in ensuring the structural integrity of components. In recent years, machine learning, especially neural networks, has been widely applied in fatigue life prediction. However, the scarcity of fatigue data has limited the further application of neural networks in fatigue prediction. To address this issue, physics-informed neural networks that consider prior physical knowledge of fatigue have gradually gained attention. Firstly, provided an overview of the classification of machine learning algorithms and the application of neural-network models in multiaxial fatigue life prediction. Then, it focused on a deep exploration of the research on material fatigue life prediction based on physics-informed neural networks. Finally, the development of physics-informed neural networks was introduced from three aspects: physics-informed input features, the construction of physics-informed loss functions, and physics-informed network frameworks. Relevant studies show that physics-informed neural networks can exhibit better physical consistency and prediction performance in the process of multiaxial fatigue life prediction of materials.

Reinforced shell structure is widely used in aerospace load-bearing structures because its high specific stiffness and specific strength.By considering the uncertainty and risk factors in the structural parameters, the reliability-based design optimization (RBDO) can avoid the overly conservative design of the structure and ensure its reliability and safety.An efficient RBDO method based on adaptive surrogate model was proposed to solve the problem of lightweight design of reinforced shell structure under buckling reliability constraints.The adaptive addition of sample points was implemented through the expected feasibility function criterion, and the discrete variables was continued by constructing piecewise functions.This increases optimization efficiency while ensuring the reliability of design results.Finally, the effectiveness of the proposed method is verified by comparing the RBDO results with the deterministic optimization results.

For the contact fatigue failure problem of vehicles’ hypoid gears under complex conditions, the rain-flow counting method and Goodman’s average stress equation were used to establish a contact statics model.The load-time history of the contact gear surface was extracted. And the load spectrum of hypoid gears was produced.The research focused on predicting the high-cycling fatigue life of hypoid gears based on the load spectrum.The study also utilized the finite element method to simulate gear teeth’s meshing or contact behaviour under loading conditions. Moreover, the influence mechanism of fatigue damage criterion on the gear fatigue life prediction was revealed.The proposed method is highly significant in assessing and predicting the high-cycling fatigue life of vehicles’ hypoid gears.

Considering the uncertainty associated with structural boundary conditions, a method for modifying the boundary constraint static model of beam structures was proposed based on the homotopy stochastic finite element method.The overall modification of both the beam body elements and boundary elements was achieved using uncertain static measurement data. By employing the static condensation method, computational degrees of freedom were ensured to match measured degrees of freedom. Regularization methods were applied to mitigate ill-conditioned solutions in modification equations for stochastic models. The probabilistic residual minimization method enables optimal selection of homotopy coefficients, ensured accurate identification of boundary constraints and precise overall modification. Finally, simulations on variable-section concrete beams and static loading tests on aluminum alloy beams were conducted to verify the effectiveness of this approach.

During the operation of the BV500 type controlled seismic source vibrator in Sichuan and Chongqing areas,due to the improper plate design, the vibration energy down-transfer rate is low and the excitation signal distortion is serious.Therefore, the continuum topology optimization method was introduced, and a variable density method of the solid isotropic material with penalization (SIMP) model was used to optimize the design of BV500 controlled seismic source vibrator plate from two aspects — reducing mass and increasing stiffness, and an “octagonal I-steel-20a” plate was innovatively developed.After optimization, the mass of the plate was reduced by 45.29%, and the stiffness of the plate was increased by 79.92%, the vibration performance of the plate before and after optimization is studied.The simulation results show that compared with the original aluminum alloy plate, the energy down-transfer rate of the “octagonal I-steel-20a” plate increases by 15.11%, the displacement amplitude of the ground surface contact center point increases by 43.74%, and the amplitude of the interaction force increases by 40.56%.The field experiment shows that when the “octagonal I-beam-20a” plate is excited, the effective value of the average vibration velocity of the near-field signal of the detector is increased by 22.23%, and the effective value of the average vibration velocity of the far-field signal of the detector is increased by 39%, the law is consistent with the numerical simulation conclusion of controlled seismic source road excitation.The excitation performance of the “octagonal I-beam-20a” plate is better than that of the original aluminum alloy integral plate, which effectively improves the road excitation effect of BV500 type controlled seismic source in Sichuan and Chongqing areas.

Carbon fiber is increasingly used to replace conventional glass fiber in layup designs of large wind turbine blades to improve their structural strength, but the high cost of carbon fibers makes it difficult to cover the entire area of the blade.Therefore, the research of the influence of mixing ratio and relative position of carbon fibers and glass fibers on the structural performance of the blade can help to obtain higher performance and lower cost wind turbine blades.The proportion of carbon fibers and glass fibers in the corresponding position of the main beam of the blade and the relative position of layup were adjusted by Ansys software.And the structural statics, modal and buckling analyses were conducted by using a combination of computational fluid dynamic method and finite element method.The results show that the performance of the blade main beam using carbon fibers and glass fibers mixed layer can be similar to that of carbon fiber blades.When the carbon fibers near the tip of the blade can improve the blade first-order modal and buckling factors. When it is close to the root of the blade has less impact on the blade maximum stress and strain.Under the premise of ensuring the blade stability and anti-resonance performance, when the carbon fibers and glass fibers layup ratio is 3∶1 and the carbon fibers are close to the root of the blade, the overall performance of the blade is better.

Vertical axis wind turbines have gradually become a research hotspot due to their ease of scalability, but the research involving structural aspects is relatively limited.Therefore, a blade and strut composite layup design solution was proposed to meet the structural performance requirements.The computational fluid dynamics method was used to obtain the aerodynamic loads under extreme environments and loaded them onto the wind turbine surface.The finite element method was used to perform the statics and modal analysis.The results show that the proposed wind turbine blade, strut, and tower have sufficient safety under extreme loads.The maximum displacement is located at the top of the blade trailing edge, the maximum stress is located at the connection between the tower and the strut, and the maximum strain is located at the blade web in contact with the strut; the vertical axis wind turbine wind wheel still has strong torsional load characteristics under the windward condition; the wind turbine operating frequency is less than the wind turbine first-order natural frequency, and its relative difference exceeds 10%.The wind turbine will not resonate under rated conditions.