Aimed at the partial slip problem of contact interface between assemblies at different temperatures, a semi-analytical model for 3D steady-state thermoelastic partial slip contact was established. Based on the thermoelastic theory and the heat conduction equation, the frequency response functions of the half space under heat flux and force load were given, and the corresponding influence coefficients were established. With the discrete convolution and fast Fourier transform (DC-FFT), the partial contact between the rigid high-temperature indenter and the thermoelastic half space was efficiently solved. The heat conduction behavior was assumed to follow Fourier’s law, and the stick/slip state on the contact interface was determined under Coulomb’s law. Based on this semi-analytical model, the effects of external loads and temperature differences on the surface pressure distribution, the friction distribution, the rigid body displacement, and the stick/slip evolution behaviors, were analyzed in detail. The numerical results show that, the increase of the temperature difference will lead to a decrease of the contact area, result in an increase of the peak values of the normal pressure and the friction, and significantly influence the regions of the stick zone and the slip zone.

A numerical method based on the panel method was developed to calculate the added fluid mass coefficients of the rigid section group with arbitrarily complex shapes, and was successfully applied to the PWR fuel assemblies. The variation law of added mass coefficients with position deviations was analyzed in the seismic test of 1×5 fuel assemblies. The results show that, this method is suitable for the calculation of the added mass coefficients of rigid section groups with complex continuous boundaries. Compared with the gap between assemblies, the gap between baffles and assemblies has a dominant influence on the added mass coefficient. Regardless of the position deviation, the sum of the added mass coefficients of all assemblies and baffles in the assumed motion direction is approximately equal to –1, and that in the perpendicular direction is approximately equal to 0.

The top ends of marine risers are usually hinged under the floating platform, and the vortex-induced vibration due to ocean currents often leads to the potential fatigue damage. The non-intrusive optical measurement (high-speed camera) was employed to monitor the displacements of top-hinged-and-bottom-fixed flexible risers arranged in a circulating water flume. The experimental results indicate that, both the mode order of the riser excited in 3 directions and the dominant frequency increase gradually with the reduced velocity. The maximum out-of-plane root-mean-square vibration amplitude has a first downward and then upward trend in the mode transition cases. The spatial distribution of energy transfer between the fluid and the riser varies with the direction, resulting in the asynchronous mode transition. One of the in-plane vibration frequency coincides with the out-of-plane dominant one, which, if dominating the in-plane response, will make a strong coupling mode, or else a weak coupling mode.

The adsorption behavior of impurity gases on the surface of alloy ZrCo has an important influence on its hydrogen storage performance. The adsorption behavior of O₂ on the ZrCo(110) surface was investigated with the first principles based on the pseudopotential plane wave method. The results of adsorption energy and charge analysis show that, the most stable geometry configuration was B3 (the Zr—Co bridge site) where the adsorption energy was –8.124 eV. The analysis of the density of states and the differential charge density show that, the adsorption behavior of O₂ on the ZrCo(110) surface is a strong chemical adsorption, where the oxygen-oxygen bond breaks. The essence of bonding between atom O and the ZrCo(110) surface atom is that the electron orbit of atom O overlaps with the electron orbit of the surface atom, i.e. the 2s and 2p orbital electrons of atom O overlapped with the 4p and 4d orbital electrons of atom Zr and the 3d orbital electrons of atom Co on the surface. The research results make senses in revealing the poisoning mechanism of alloy ZrCo in impurity gases.

A linear buckling model for double-layered microplate systems filled with elastic media between layers was developed under the modified couple stress theory and the 2-variable higher-order shear deformation theory. The governing differential equations for system buckling were derived based on the Euler-Lagrange equation. With the Navier method, the synchronous and asynchronous buckling solutions were analytically obtained in the case of both upper and lower plates being simply supported on 4 edges. The influence of each parameter on the buckling characteristics of the system was discussed by numerical examples. Numerical results show that, the asynchronous buckling characteristics of the system depend on the material length scale parameter, the aspect ratio and the elastic medium modulus, while the synchronous buckling characteristics depend on the 1st 2 only; the asynchronous critical buckling load is noticeably greater than that of the synchronous buckling case; the Pasternak modulus has a more significant effect on the buckling characteristics of the system than the Winkler modulus.

Double-curved-beam (DCB) systems are usually seen in many engineering fields. Compared to straight double-beam systems, DCB systems are more efficient in noise and vibration control problems. To obtain closed-form solutions of steady-state forced vibrations of DCB systems, the classical Euler-Bernoulli curved beam (ECB) model was employed to model vibration equations for the DCB systems. Green’s functions and the Laplace transform methods were used to get the closed-form solutions to the vibration equations for the DCB systems. These solutions apply to arbitrary boundary conditions. Numerical tests were conducted to verify the present solutions with related results from previous literatures. Effects of some important geometric and physical parameters on vibration responses and the interaction between the elastic layer stiffness and the DCB system, were discussed. The results show that, the DCB system will degenerate to a straight double-beam system when the 2 radii approach infinity, moreover, the DCB system can be simplified as one comprising a straight beam and a curved beam.

The flutter responses of the Nanjing No.4 bridge flat box girder under different wind attack angles were tested in detail through sectional model tests. The evolution of unsteady and steady critical amplitudes at different wind speeds was discussed. Based on the amplitude envelope of the flutter response and the Hilbert transform, the amplitude-dependent modal damping of the system was identified, and the mechanism of the flutter mode change with the wind angle of attack was initially explained. Secondly, the modal parameters of the system under different wind attack angles were extracted. With the bimodal coupled flutter analysis method, the nonlinear flutter derivatives of the section under different wind attack angles were identified, and the change law for the amplitude dependence of the key flutter derivatives on the wind attack angle and the potential influence on the section flutter morphology and characteristics, were studied. Finally, the effects of the wind attack angle on the uncoupled and coupled aerodynamic damping were analyzed through analyses of the modal damping subterms one by one, and the dynamic mechanism of the differential flutter performance caused by fractional damping was illustrated.

Based on the homotopy analysis method, the nonlinear vibration of porous functionally graded material (FGM) conveying pipes under generalized boundary conditions was studied. Based on the power-law distribution of the FGM and the Voigt model, the physical properties of the porous pipe material were described. Under the Euler-Bernoulli beam theory and the von Kármán nonlinear theory, and by means of Hamilton’s variational principle, the dynamic control equations and generalized boundary conditions for porous FGM conveying pipes were established. The homotopy analysis method was used to solve the nonlinear vibration characteristics of the porous FGM conveying pipe under generalized boundary conditions. The numerical results show that, the translation spring has little effect on the critical velocity of instability, while the rotation spring increases the critical velocity of instability, making the system more stable; in the nonlinear system, the viscoelastic coefficient does not change the critical velocity; the pipe length, the power-law exponent and the porosity all influence the nonlinear free vibration of the porous FGM conveying pipe.

As more and more structural parts of military aircraft are formed with the additive manufacturing (AM) technology, it is very urgent to study the fatigue characteristics of the additive manufactured materials and structures. To investigate the fatigue life characteristics of the aluminum alloy and the titanium alloy manufactured with the selective laser melting (SLM) technology, a series of specimens with various structural details were designed and tested under the constant amplitude spectrum and the random spectrum. The basic reliable life of each test specimen was statistically analyzed and the reliable safety life curve was obtained. The fractography analysis shows that, more defects and mixed failure characteristics exist in the aluminum alloy specimens, while the fatigue scatter of the titanium alloy specimens is larger than that of forge pieces.

To study the effects of bamboo fiber and steel wire mesh on the flexural ductility of basalt fiber reinforced polymer（BFRP）bar concrete beams, 7 BFRP bar concrete beams with bamboo fiber and steel wire mesh were tested with different bamboo fiber lengths (0 mm, 30 mm and 45 mm) and different steel wire mesh layout ranges (0, 1/2 maximum bending moment point layout and full beam length layout). The flexural failure tests of the 7 beams were carried out, and the initial crack loads, the crack developments, the ultimate loads and the deformations were detected. The effects of the fiber length and the wire mesh layout range on the crack resistance and the deformation resistance of the specimens were analyzed based on the test data. With the function model, the equivalent yield points of the 7 test beams were obtained, and their ductility coefficients were calculated. The results show that, the addition of bamboo fiber and steel wire mesh increases the cracking loads of BFRP bar concrete beams by 12%~68%, decreases the crack spacings and the crack length development speed, reduces the test beam deformation under the same load, and increases the ductility coefficient by 1.58%~31.75%.

The uneven riverbed, and the impact and scour actions by water flow, make the underwater buried pipeline vulnerable to exposure and suspension, and endanger the pipeline operation safety. To investigate the mechanical properties and failure behaviors of the suspended pipeline section under water impact, according to the failure mechanism of the pipeline, the statics and dynamics analyses of the pipeline were carried out, and the graded safety evaluation technique for the buried pipeline with suspended sections was presented. First, a “static strength safety evaluation under static loads” (level 1) was conducted according to the mechanical features and stress states of the pipeline’s suspended section. Second, a “resonance safety evaluation under dynamic loads” (level 2) was conducted based on the correlation between the natural vibration frequencies of the suspended pipeline and the vortex emission frequencies of water flow. Finally, the periodical change process of the pipeline’s alternating stress was studied to solve the fatigue damage and fatigue life of the pipeline, and the “fatigue strength safety evaluation under dynamic loads” (level 3) was performed. Thus, a 3-level safety assessment procedure for pipelines with suspended sections was proposed. The stabilizing measures for pipelines of poor safety were suggested, and through an example, a specific calculation process was provided. The work serves as a theoretical guide for the safety evaluation of the suspended sections of underwater buried pipelines.