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 paper investigates the nonlinear vibration isolation problem of simply supported beam bridge structures under displacement excitation, employing the Incremental Harmonic Balance Method (IHBM) to derive an approximate analytical solution for the nonlinear vibration response of the beam. The research focuses on a coupled system consisting of a quasi-zero stiffness (QZS) isolator, constructed using a three-spring system, and a simply supported beam bridge. Based on the classical Euler-Bernoulli beam theory, the governing equations of motion under displacement excitation are established and systematically solved using the IHBM, with the entire analytical process thoroughly derived. The study transforms the final solution into a linear matrix equation using generalized coordinates, achieving a procedural and standardized computational process. To validate the reliability of the IHBM approximate analytical results, the study compares the IHBM computational results with numerical solutions obtained using the fourth-order Runge-Kutta method (ODE45). The results demonstrate that the IHBM method exhibits significant advantages in computational stability and result completeness. Additionally, through parametric analysis, the study explores the influence of key isolator parameters on system amplitude, further confirming the effectiveness and engineering practicality of the IHBM in nonlinear vibration isolation research. The research outcomes provide new theoretical foundations and methodological references for the nonlinear vibration isolation analysis of simply supported beam structures, offering important guidance for engineering practice.

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.

Optimization of the natural frequencies of exponential functionally graded plates is a critical issue in the engineering field, playing a vital role in enhancing the dynamic performance of plate structures. In response to this challenge, this paper presents an innovative optimization approach that synergistically integrates the smoothed finite element method (SFEM) with surrogate models, aiming to address the problem with both high efficiency and precision. Based on the first order shear deformation theory, a SFEM is established for free vibration analyses of functionally graded plates. During the computation of the system stiffness matrix, gradient smoothing operations are applied to bending strains within smoothed domains, effectively improving computational accuracy. To overcome the shear locking phenomenon, different interpolation forms are adopted to treat bending strains and shear strains separately. For natural frequency optimization, a series of sample points are selected, and their corresponding natural frequencies are calculated using the SFEM. Subsequently, a surrogate model is established to map the relationship between the gradient index and the natural frequencies. The golden section method is employed to determine the optimal gradient index that achieves preset natural frequency targets. Numerical examples demonstrate that the surrogate model based on piecewise cubic Hermite interpolation exhibits high computational accuracy. Moreover, the surrogate model-based optimization significantly reduces the number of SFEM frequency calculations required, substantially enhancing optimization efficiency. This approach provides an efficient and practical method for optimizing natural frequencies of exponential functionally graded plates.

In the process of energy storage and power generation in molten salt tanks, the ceramic particle layer at the bottom of the tank plays a critical role in load-bearing and thermal insulation. Under cyclic loading, analyzing the effects of particle compression, flow, and contact stress on the overall settlement of the ceramic particle layer provides an important basis for design. In this study, the Hertz-Mindlin contact model in EDEM software was employed to establish a discrete element particle simulation model for the ceramic particle layer at the bottom of the molten salt tank. Simulations were conducted for the compaction backfill process and full-tank working conditions, and a comparative analysis was performed to investigate the effects of pre-compaction processes and particle size distribution on the compression settlement and maximum equivalent stress of the ceramic particles, as well as the influence of randomness in discrete element analysis results. The results indicate that for a ceramic particle layer height of 1.6 m and a particle size range of 5~20 mm, adopting a segmented compaction backfill process under a 50 000-ton tank load results in a maximum internal particle stress of 18.1~21.8 MPa and an overall settlement of 20.44~29.6 mm. As the particle size increases, the maximum stress decreases, with a maximum stress of 12 MPa observed for particle sizes of 15~20 mm. However, the settlement increases significantly, reaching 184 mm. Therefore, a wide particle size distribution range is beneficial for reducing settlement. Considering these factors comprehensively, the optimal configuration is a particle size range of 5~20 mm with a segmented and repeated pre-compaction process. Accounting for the influence of particle randomness, the maximum stress of the ceramic particle layer is 23.16 MPa, and the maximum settlement is 23.5 mm, meeting the design requirements.

Due to the low strength of putty, it is impossible to directly measure its fracture toughness using the standard tensile fracture test. In order to accurately measure the tensile fracture toughness of low-strength materials such as putty, this study presents an improved compact tension test method and derives a tensile fracture toughness formula through numerical analysis. The formula is further refined by accounting for boundary effects, and its accuracy is validated through systematic testing with varying initial crack lengths. The results demonstrate that, the modified formula enables direct calculation of material fracture toughness. The stress intensity factor depends on relative boundary conditions rather than absolute boundary effects, with boundary effects becoming more pronounced with increasing initial crack length. The specimens exhibit pure Mode I fracture, with the modified formula yielding a stable fracture toughness of approximately 42 kN/m^3/2. Experimental validation confirms the accuracy of both the improved test method and the modified formula, establishing their applicability for measuring fracture toughness in low-strength materials like putty and contributing to putty material development.

Currently, over 90% of crude steel production is achieved through continuous casting. Increasing the casting speed during continuous casting can significantly enhance production efficiency, but it also impacts the flow field, exacerbating slag entrapment and argon bubble entrainment, which lead to a series of quality defects. These issues have become critical constraints on the development of high-speed continuous casting molds. This paper establishes a multiphase numerical model of the continuous casting mold by coupling Large Eddy Simulation (LES) with the Volume of Fluid (VOF) method and a two-way coupled Discrete Phase Model (DPM). By analyzing flow field variations, steel-slag interface velocity, interface fluctuations, and slag entrapment ration under three different casting speeds, the internal correlation mechanisms are revealed. The study finds that appropriately increasing casting speed can improve production quality, providing a reference for optimizing casting speed in continuous casting processes.

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".

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.