Surface texture design is an effective way to achieve small leakage, long life and highly reliable operation of mechanical end seals. To investigate the characteristics of the interface film of guide groove texture, through the design and preparation of semi-circular, herringbone and E-shaped guide groove textures, experiments and theoretical research under high-speed operation conditions were carried out, the influence of different guide groove textures on the tribological properties of end face seals was explored. The results show that the existence of the guide groove can effectively improve the bearing capacity of the interface film and improve the tribological performance. In numerical calculations, the results show that the frictional performances of face seals varied with the configuration of guide groove. The herringbone textures and E-type ones show an obvious guide-aggregation effect. When the lubricant in E-type texture after being guide-aggregation through the groove, the pressure accumulates at the textured tail barrier, and fluid in the face seal clearance cannot escape from the guide groove boundary. As a result，the low energy loss in system, and an optimal liquid film bearing capacity achieves. Under different depths, the existence of guide groove promotes the hydrodynamic pressure. With the increase in depth, the bearing capacity of the liquid film increases first and then decreases. For the E-shape texture, the optimum bearing capacity of liquid film P_av=0.527 5 MPa is obtained at h₁=10 μm. The bearing capacity of fluid film of E-shape texture has a 51.2% increase in comparison to the common grooved texture, the value of frictional torque has a 53.5% decrease. The analysis show that, the configuration of guide groove results in an accumulation of lubricant on the top of texture, which enhances the pressure convergence, thereby improving the bearing capacity of the lubricating fluid film and reducing friction（‘guide⁃aggregation effect’）. The geometric parameters of the guide groove have a significant impact on the fluid dynamic pressure in the end face sealing pair，which will influence the tribological performances of face seal. The research result provides theoretical support for the design of non-contact end face seal material surface texture in future.

To improve the accuracy and efficiency of load identification and structural response reconstruction, an improved Tikhonov regularization method that simultaneously considers transfer matrix error and measurement error was proposed. Firstly, the state space equation and transfer matrix were constructed through the structural dynamics model to obtain the reconstruction equation of the structural load and response. Secondly, the truncated randomized singular value decomposition method was used to calculate the approximate transfer matrix at the locations of the measurement points, while the total least squares method (TLSM) and the traditional Tikhonov regularization method were combined to identify the load,and then the unknown response was reconstructed by the transfer matrix at the locations. Finally, a numerical simulation and an experimental analysis were carried out for two-dimensional truss and simply supported beam to verify the proposed method. The results show that compared with the traditional Tikhonov regularization method, the proposed method can improve the reconstruction efficiency while guaranteeing the reconstruction accuracy.

In order to improve the carrying capacity of double curved beams negative stiffness structure composed of two curved beams arranged in parallel, the curved sandwich beam negative stiffness structure was proposed. The design idea was to array the sandwich straight beam between the upper and lower curved beams of the double curved beam negative stiffness structure, and the bearing capacity and energy absorption characteristics were studied systematically. Firstly, the negative stiffness structure model was fabricated using 3D printing technology and silicone emolding process, the compressive mechanical response of the curved sandwich beam and double curved beam negative stiffness structure was compared and analyzed by quasi-static compression experiment, and the reliability of the finite element simulation model was verified. Then,the influence of structural parameters (width, spacing, height and angle) of the sandwich straight beam on the bearing capacity and energy absorption characteristics of the negative stiffness structure was studied by simulation. The results indicate that the introduction of the sandwich significantly enhances the load-bearing capacity of the double curved beam negative stiffness structure. Compared with the spacing and angle of the sandwich straight beam, increasing the width and height of the sandwich straight beams can notably enhance the load-bearing capacity and energy absorption capacity of the structure.

To explore the penetration resistance of aluminum alloy tubes under spherical steel projectile impact, focusing on the effects of varying tube radii and wall thicknesses on ballistic limit velocity, providing a foundation for tube protection design. A finite element model of spherical steel projectile penetration into 2024-T42 aluminum alloy targets was established using Ansys/Workbench software and the Johnson-Cook material model, which was then verified. Simulations of the response characteristics of aluminum alloy tubes with different radii and wall thicknesses under normal impact of spherical steel projectiles were conducted, along with an analysis of tube deformation and damage. The study found that the penetration resistance of the upper and lower walls of aluminum alloy tubes differs, with the upper convex structure outperforming the lower concave structure. A smaller tube radius enhances the penetration resistance of the upper wall, while for tubes of the same radius,increasing the wall thickness leads to a roughly linear increase in the ballistic limit velocity of both upper and lower walls.

Elbows are an important component of oil and gas pipelines. The force state and the medium flow state are more complex than that of the straight pipe. Once the defect occurs at the elbow, the elbow pipe is more prone to fail. The high steel grade pipeline is the development trend of the long distance oil and gas pipeline construction, and it is urgent to evaluate the residual strength of the high steel grade bending pipe. Through the establishment of the finite element model, the defect size, relative position, bending radius, pipe parameters and pipe performance influence were studied on the ultimate internal pressure of the elbow, and finally the prediction formula of the bending was established. The results show that with the increase of defect length and defect depth, the ultimate internal pressure of the elbow is significantly reduced. The trench defect affects the ultimate internal pressure when the trench defect is located in the inner arch of the elbow. The bending radius, the wall thickness and the pipe material will affect the ultimate internal pressure. The error analysis shows that the prediction formula is more accurate, which can provide the basis for the residual strength evaluation of high steel grade elbows with trench defects.

In order to study the mechanical properties of high volume fraction ratio metal particle reinforced resin matrix composites, the elastic modulus of the composites was predicted based on the micromechanics theory and the meso-finite element method. Firstly, standard specimens of the composites were prepared, and their macroscopic elastic moduli were tested by uniaxial tensile experiments, and the microscopic properties were observed. Secondly, the elastic modulus of the composites was predicted by using Voigt, Reuss, Mori-Tanaka and Generalized means based on the micromechanics theory.Then, based on the microscopic particle size statistics of the specimens, the gradation of the metal particle size and its quantity were determined by using the Gaussian distribution law, and the random particle placement program was written by Python language to construct a two-dimensional representative volume element (RVE) finite element model consisting of the particles,the resin matrix, and the interface. Finally, the elastic modulus of resin matrix composites reinforced with high volume fraction metal particles was predicted by theoretical and finite element simulations. The analysis results show that the generalized means and finite element models predict the elastic modulus with less error from the experimental test results, and the elastic modulus of the composites increases with the increase of the volume fraction of the metal particles.

The main purpose was to study the local cyclic plastic behavior of 3D printed titanium alloy notched parts. Firstly, the local stress and strain field near the 3D printed titanium alloy notch was analyzed in detail by finite element method，and the evolution of stress and strain field was deeply investigated. Then, the experimental study was carried out and the influence of the forming direction on the results was analyzed. The results show that ratcheting deformation occurs at the notch root, with the maximum ratcheting strain rate in the L₃ direction and the minimum ratcheting strain rate in the L₁ direction. The influence of the forming direction on the stress triaxiality is not too obvious. The elastic strain energy of different forming directions is almost no difference. However, the forming direction has a great influence on the plastic strain energy. With the increase of the number of cycles, the difference of plastic strain energy results for different notch radii also becomes larger.

In order to improve the mechanical properties of three-dimensional negative Poisson ratio materials, and expand the application of negative Poisson ratio materials. A new unit cell of negative Poisson ratio structural material was proposed by introducing internal concave angles into the edges of tetrahedral porous structures, and 7 kinds of orthogonal isotropic and orthogonal anisotropic enhancement designs were carried out on it. The influence of cell geometry parameters on the dimension one equivalent elastic modulus and Poisson ratio of new and enhanced cells was studied by using the homogenized finite element method and periodic boundary conditions，and the 3D printed resin sample was used for experimental verification. Compared with the existing negative Poisson ratio unit cells, the novel unit cell can save 50% of materials while maintaining the negative Poisson ratio characteristics. The three reinforcement schemes in x-direction, y-direction and xy-direction can significantly improve the bearing-load capacity while improving the negative Poisson ratio characteristics.

Under the medium and high speed of spherical hybrid sliding bearings, the dynamic pressure effect causes the fluid in the wedge space to whirl, and the vibration characteristics of the rotor may be affected by the oil whirl, so the rotation accuracy of the main shaft is reduced. The spherical hybrid sliding bearings with the orifice throttle was divided into cylindrical and conical whirl. The lubrication mathematical model and rotor dynamic model were established and solved simultaneously, the journal center trajectory and vibration amplitude were obtained. The influence of the centroid offset distance and initial deflection angle on the vibration characteristics of the rotor system were studied.The results show that,compared with the pure cylindrical whirl, the stability of the journal center trajectory decreases and the vibration amplitude increases after considering the conical whirl.With the increase of the centroid offset distance, the stability and vibration amplitude of the journal center trajectory decrease greatly.With the increase of the initial deflection angle, the stability and vibration amplitude of the journal center trajectory decrease only slightly.It can be concluded that changing the distance of the centroid offset has more influence on the stability of the journal center trajectory and the vibration characteristics of the rotor system than changing the initial deflection angle.

Aiming at the problem of nonlinear vertical vibration control during the dynamic rolling of strip mills, a nonlinear vibration absorber with the disc spring was designed. Firstly, considering the constraints of dynamic rolling force of the rolling mill in the vertical direction, the mathematical model of the rolling mill under the control of the nonlinear vibration absorber was established, the amplitude-frequency characteristic curve equation of the system was solved by the multi-scale method, and the influence of damping, excitation amplitude and nonlinear stiffness on the vibration suppression effect of nonlinear dynamic vibration absorber was discussed. Secondly, by analyzing the spectrum curve and time domain curve, the vibration absorber device could increase the distance between the resonance frequency and the main resonance frequency, and shorten the time of the rolling mill system from the unstable state to the stable cycle was concluded. The results show that the addition of nonlinear vibration absorber can effectively increase the anti-vibration ability of the system and suppress the vertical vibration of the system.