The mechanical response of geotechnical granular materials exhibits multi-scale characteristics. The multi-scale simulations coupling the Finite Element Method (FEM) and Discrete Element Method (DEM) can effectively capture the multi-scale responses while maintaining high computational efficiency. A GPU-parallel FEM-DEM coupling code was developed based on the high-performance DEM software MatDEM, with computational parameters and results analyzed in conjunction with granular pore fractal characteristics. Firstly, multi-fractal theory was employed to investigate the spatial distribution characteristics of pores, identifying key fractal indices. Subsequently, the reliability of the FEM-DEM coupling code was verified through single element tests and biaxial compression tests. Finally, the meso-scopic responses of Representative Volume Elements (RVEs) at different locations were investigated based on biaxial compression tests. Results demonstrate that the pore spatial distribution within RVE exhibits multi-fractal characteristics. When the particle quantity exceeds 400, the self-similarity of pore spatial distribution ensures the stability of stress-strain responses output after homogenization of granular assemblies within RVE. The capacity dimension D₀ and singularity index α₀, which characterize the average information of pore distribution, show linear correlations with RVE volumetric strain. These indices can serve as internal variables reflecting the complexity of granular material spatial characteristics. This study provides an exploration for analyzing the macro-meso mechanical relationships in engineering-scale granular deposits.

Interface consistency and error convergence are central issues in concurrent multiscale computational methods, particularly critical for atomistic-to-continuum coupling models. However, existing theoretical studies remain limited and are mostly confined to one-dimensional settings. This work focuses on the multiresolution molecular mechanics (MMM) approach and systematically investigates the impact of various energy sampling schemes on interface consistency and error convergence. Two-dimensional square and triangular lattice models containing both atomistic and coarse-grained regions are constructed under bilinear element interpolation. The results show that interface secondary sampling schemes can significantly improve consistency in the interfacial region, with the scheme incorporating all neighboring layers achieving the best performance. Error analysis reveals that discretization error dominates the total error, and increasing the number of secondary sampling points effectively reduces the sampling error, particularly under tensile loading conditions. Moreover, both lattice types exhibit consistent error convergence behavior, demonstrating high generality of the method to different structures. This study highlights the advantages of energy sampling strategies in improving interface treatment and convergence behavior in MMM, providing theoretical support for the development of high-accuracy multiscale computational mechanics methods.

A study is conducted on the nonlinear dynamics of inclined flow pipes reinforced with graphene composite materials conveying fluid under two-phase flow conditions. Based on the von Karman nonlinear strain-displacement relationship and Hamilton's principle, the dynamic equations for inclined two-phase flow pipelines are established. The nonlinear dynamic model was solved using Galerkin method and fourth-order Runge-Kutta method to analyze the influence of the distribution pattern, weight fraction, and gas volume fraction of graphene platelets on the natural frequency and nonlinear dynamics of pipes conveying fluid. The experimental results show that the vibration amplitude of graphene reinforced pipes with V-shaped distribution is the smallest, followed by X-shaped distribution and A-shaped distribution. In addition, increasing the gas volume fraction can help alleviate fluid-induced vibration phenomena in pipelines. The above conclusion provides a theoretical basis for the application of graphene-reinforced inclined two-phase flow pipelines in practical engineering.

As a critical step in flexible electronics packaging, the ultra-thin chip peeling process plays a vital role in ensuring high-yield manufacturing. This study focused on mechanical behavior differences between two peeling methods: roller-stretching and needle-ejecting. A theoretical model of the "chip-adhesive-substrate" laminated structure was established and validated by finite element simulation. A dual-criteria safety criterion was proposed to quantify process safety based on the competing relationship between interfacial fracture energy of the adhesive layer and surface cracking stress of the chip layer, which overcame the limitations of traditional methods for quantitatively evaluating the safety of the peeling process. Results demonstrated that the needle-ejecting procedure outperforms roller-stretching in terms of the safety of ultra-thin chip peeling. The roller-stretching process only has high engineering application prospect for peeling large-sized and thick chips from soft and thick substrates. Furthermore, an innovative stretching-ejecting combination technology is proposed, introducing the concept of synergistic matching to achieve chip stress neutralization and fracture mode optimization. This research provides theoretical insights into non-destructive ultra-thin chip peeling technology, and delivers practical guidance for advancing high-yield flexible microelectronics packaging.

In the precursor impregnation pyrolysis (PIP) process of ceramic matrix composites, the viscosity of the precursor liquid significantly affects the effectiveness and efficiency of its infiltration into the fiber preform. The solute mass fraction influences the viscosity itself in the impregnation solution. To provide a theoretical basis for optimizing the impregnation process, this study establishes an apparent viscosity model for precursor liquids with different solute contents. Firstly, an order parameter describing the solid and liquid phase content is introduced, establishing the interrelationship between shear stress, shear rate, and the order parameter of the precursor liquid. Then, based on Landau phase transition theory and the variational principle of the Lagrangian energy functional, a differential equation for the order parameter is constructed and solved, yielding an approximate analytical expression for apparent viscosity, mass fraction, and shear rate in a subdomain. Furthermore, a first-order approximation of the Bernstein polynomial is employed to extend the model to the entire computational domain, resulting in a viscosity model applicable to precursor liquids with different solute mass fractions. Finally, precursor liquids incorporating two types of additives, powders and binders, are examined. By calculating the effect of different mass fractions of additives on precursor viscosity, the validity of the model is verified, and the influence of solute mass fraction and shear rate on the apparent viscosity of the precursor liquid is analyzed based on the viscosity model.

This study systematically investigates the influence of the wall slip length (L_s) on the statistical properties and flow structures of turbulent channel flow. The Navier slip boundary condition is applied at the boundary of turbulent channel flow, and direct numerical simulation (DNS) is employed to numerically explore the evolution of turbulence for L_s ranging from 0 (no-slip) to 0.1. The results reveal that as L_s increases, the viscous damping effect at the wall is substantially reduced, resulting in an overall elevation of the mean velocity profile. Within the viscous sublayer, the mean velocity increment exhibits a linear relationship with L_s, satisfying the relation . In the near-wall region, the turbulence fluctuation intensity demonstrates an enhanced dependence on L_s, with the intensification of Q2 (ejection) events leading to an elevated Reynolds stress peak that shifts closer to the wall. Analysis of wall-attached low-speed streaks indicates that, for a dimensionless wall-normal structure scale , both their number and volume increase significantly with rising L_s. Furthermore, it is found that the effects of the wall slip condition are confined to the near-wall region, while the outer inertia-dominated region continues to follow the scaling laws of no-slip wall turbulence.

This study focuses on the integrated manufacturing process of sensors in unbonded flexible pipes for deep-sea mining engineering, investigating the sensor integration process with compensation reinforcement layers and their mechanical performance. A simulation model for the winding process of the compensation reinforcement layer in flexible pipes was established, systematically analyzing the influence patterns of winding tension and winding angles on sensor integration processes. Additionally, the effects of sensor quantity and winding angles on the tensile performance of integrated compensation reinforcement layers were explored. The results demonstrate that winding tension significantly affects sensor elongation rates, while winding angles predominantly influence stress distribution in the lining layer. The tensile performance of integrated compensation reinforcement layers shows minimal sensitivity to sensor quantity, and variations in winding angles within a specific range exhibit limited impact on anti-tensile properties. These findings reveal the correlation between sensor integration parameters and structural performance of flexible pipes, providing theoretical guidance for optimizing sensor integration processes in deep-sea flexible pipes.

Deoxyribonucleic acid (DNA), as the fundamental genetic material of life, possesses diverse mechanical characteristics endowed from its unique chemical and physical properties. These properties play a pivotal role in regulating gene expression, viral infection mechanisms, disease diagnostics, and intelligent nanodevices. A profound understanding of the mechanical properties and behaviors of DNA-like material—spanning from the molecular scale to the macroscopic device level—provides a foundation for unveiling the physical mechanisms underlying biological activities, advancing biomedical detection technologies, and enabling the precise design of dynamic nanodevices. This paper systematically reviewed recent research progress on the mechanical properties of DNA-like material and their applications in biomedicine and nanotechnology. First, some significant experimental advances across different-scale DNA systems were introduced, emphasizing how experiments revealed the influence of microstructure and environmental conditions on the mechanical properties and responses of DNA-like material. Second, the developments of theoretical models for the mechanical behavior of DNA-like material were explored, elucidating the mechanisms underlying relevant experimental findings. Finally, the paper identified the challenges in the current DNA-like material mechanics research and its practical implementation, and looked forward to the prospect of achieving breakthroughs through research paradigms such as "digital and intelligent mechanics".

The free vibration analysis of membranes is of significant importance in engineering structures, especially in the design and optimization of membrane structures. This paper presents a new type of triangular element, aiming to improve the computational accuracy in free vibration analysis of membranes. Traditional 3-node triangular elements in membrane vibration analysis typically rely on polynomial shape functions, but this method often suffers from insufficient accuracy in complex vibration modes and high-order frequencies. To address this issue, this paper constructs a 10-node triangular element with the shape function incorporating trigonometric functions. The proposed 10-node triangular element consists of three corner nodes, two points of trisection for every edge, and the centroid node with its shape functions derived using the area coordinate method. The stiffness matrix and mass matrix are derived, and the frequencies and modes for free vibration of the membrane are computed, thereby the dynamic characteristics can be studied. To evaluate the effectiveness of this element, several typical examples are chosen, including the free vibration analysis of rectangular membrane and triangular membrane. By comparing with theoretical solutions and the 3-node element calculations in Ansys, the obtained results show that the 10-node triangular element can approximate the theoretical solutions with few computational elements. And the precision of the presented 10-node element is similar with that of the standard 10-node triangular element. The high precision of the proposed element is demonstrated in analysis of free vibration of membrane, which has the potential of further research and promotion.

For the dynamic process of harvesting energy from water droplet impact by using piezoelectric beams, a water droplet impact force model was developed. Based on the Euler Bernoulli beam theory, an electromechanical coupling prediction model of piezoelectric cantilever beam was established. Droplet impact tests were conducted, the voltage output characteristics and dynamic response characteristics of the piezoelectric beams were analyzed. By comparing the experimental results and model prediction results under different impact conditions (droplet diameter D_d=2.4~4.4 mm and impact velocity V_d=1.0~3.4 m/s), the accuracy of the force electromechanical coupling model was verified. Results showed that there is a linear relationship between the maximum deformation of cantilever end and the peak voltage under the impact excitation of water droplets. Water droplets exhibit "rebound" and "splashing" characteristics under low and high Weber number conditions, respectively, and the experimental results are highly consistent with the predicted results of the model, verifying the applicability and accuracy of the model. As the cantilever length increases, the natural frequency and the bending stiffness of the system gradually decreases, the output voltage and the total energy harvested gradually increase; however, the electric energy density shows a trend of first increasing and then decreasing, reaching a maximum of d_E=4.27 mJ/m² when the cantilever beam length L=35 mm.