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  • Research Progress on Mechanical Properties of DNA-like Material
    ZHANG Nenghui, ZHANG Chengyin, TAN Zouqing, LIU Hanlin
    2025, 46(3): 541-569. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.001
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    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".
  • Mechanical Analysis and Comparative Study of Ultra-Thin Chip Stretching-Ejecting Peeling Process
    SHI Kewen, KONG Ziwen, LYU Wenhan, CHEN Siyu
    2025, 46(3): 570-585. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.002
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    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.
  • Impact of Slip Length on the Statistical Properties and Structure of Turbulent Channel Flow
    LIU Yahao, ZHOU Quan
    2025, 46(3): 586-598. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.003
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    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 ∆〈U〉^+=Re_τ L_s. In the near-wall region, the turbulence fluctuation intensity demonstrates an enhanced dependence on , 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 l_y^+ < 50, 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.
  • Structural Analysis and Design of Grid-Stiffened Sandwich Cylindrical Shells Using DQM
    LI Changxu, LIU Yongqi, WANG Jianwei, DU Dong, NIE Guohua
    2025, 46(3): 599-613. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.004
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    For the lightweight design problem of composite grid-stiffened sandwich cylindrical shells, this paper proposes an optimization strategy that couples the differential quadrature method (DQM) with intelligent algorithms. First, the buckling governing equations are established based on the smeared stiffener method and energy principle, which are efficiently solved using DQM and validated through finite element analysis. Subsequently, an artificial neural network (ANN) surrogate model and genetic algorithm (GA) are employed to achieve structural optimization. The results demonstrate that the critical buckling loads obtained via DQM agree well with finite element results, confirming the accuracy of DQM in analyzing the buckling of sandwich cylindrical shells. The ANN-based surrogate model exhibits high reliability in predicting the critical buckling loads of grid-stiffened sandwich shells. Moreover, the genetic algorithm, combined with theoretical results, efficiently yields lightweight design parameters. Case studies show that the optimized structure not only achieves significant weight reduction but also exhibits a substantial increase in critical buckling load.
  • Fracture Mechanism Evaluation of UHPC-NC Interface Based on Multiscale Interface Bond Characterization and Numerical Simulation
    WANG Yangchen, WANG Jiuyi, WANG Yanzhi, QIAO Pizhong, NIE Kefu, JIA Lei
    2025, 46(3): 614-630. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.005
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    To elucidate the complex bonding and fracture mechanisms at the interface between Ultra-High Performance Concrete (UHPC) and Normal Concrete (NC), this study systematically investigates how interfacial roughness and mesoscale structural characteristics influence interface mechanical performance. Four interface treatments (i.e., smooth surface, high-pressure water jetting, sandblasting, and chiseling) were comparatively analyzed through direct tension and shear tests, complemented by quantitative surface roughness characterization using laser scanning. Furthermore, X-ray Computed Tomography (X-CT) facilitated the three-dimensional reconstruction of UHPC-NC mesoscale structures, enabling advanced segmentation of pores, fibers, and other structural phases via deep learning algorithms. Multi-scale finite element modeling based on X-CT data simulated the damage evolution and crack propagation at the interface. Results indicate that chiseling significantly increased interfacial roughness, yielding substantial improvements in direct tensile and shear bond strengths by 123% and 126%, respectively, relative to the smooth surface. X-CT analysis revealed a distinct hydration transition zone at the interface, significantly influencing chemical bonding and exhibiting notably lower porosity compared to the NC matrix. Steel fibers from UHPC penetrated into the NC substrate, creating enhanced mechanical interlocking effects. Numerical simulations demonstrated that interface failure mechanisms are jointly governed by tensile failure within the NC substrate and crack propagation through the interfacial transition zone (ITZ), consistent with experimental observations of mixed-mode fractures. Overall, enhanced interfacial roughness improved bonding strength through both mechanical interlocking and chemical adhesion, while mesoscale structural defects critically influenced crack development pathways. The proposed multi-scale analytical approach provides comprehensive methodological support for optimizing the design and rehabilitation of concrete interfaces in engineering practice.
  • Interfacial Consistency and Convergence Analysis of Multiscale Coupling Method Based on Bilinear Interpolation
    LI Zi, YANG Qingcheng
    2025, 46(3): 631-648. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.006
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    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.
  • Modelling of Multi-Scale Mechanical Behaviours and Pore Fractal Characterization of Granular Materials
    WU Zhongyang, FU Longlong, ZHOU Shunhua
    2025, 46(3): 649-661. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.007
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    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.
  • Research on Sensor Integration Process in Unbonded Flexible Pipes for Deep-Sea Mining
    CUI Xinyu, XU Wanhai, WANG Yingying, SHEN Fei, KE Liaoliang
    2025, 46(3): 662-673. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.008
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    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.
  • Characterization Model of Precursor Viscosity in PIP Process of Ceramic Matrix Composite Materials
    HE Yunlu, WANG Ling, CHEN Xi, DAI Ying, HE Pengfei, QIU Haipeng
    2025, 46(3): 674-683. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.009
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    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.
  • A New Triangular Element and Its Application in Vibration Analysis of Membranes
    BAO Siyuan, REN Yixuan, SHEN Feng
    2025, 46(3): 684-694. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.010
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    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.
  • Nonlinear Vibration Isolation Study of a Simply Supported Beam Bridge Based on the IHBM
    ZHAO Xiang, TANG Guozhang, CHANG Chuang, LI Yinghui
    2025, 46(3): 695-703. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.011
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    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.
  • Design and Implementation of a Feeding Robot Based on Obstacle Avoidance Path Planning and Compliance Control
    YUAN Qing, LÜ Haoyang, LI Wei, ZHU Rui, BAI Wenxia, ZHANG Kai
    2025, 46(3): 704-714. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.012
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    With the rapid acceleration of population aging in China, the demand for feeding assistance among individuals with disabilities is becoming increasingly urgent. However, current feeding robots face several limitations such as poor adaptability to complex environments and safety concerns due to rigid structures. In this paper, a new six-degree-of-freedom feeding robot was developed that integrates obstacle avoidance path planning and compliance control. The robotic arm was designed employing a Bi-directional Rapidly-exploring Random Tree (Bi-RRT) algorithm to generate collision-avoidance trajectories, while inverse kinematics was solved using the Denavit-Hartenberg (D-H) parameter. At the control level, an impedance model-based compliance control strategy was introduced, and its compliant behavior under sudden external forces was verified through dynamic simulations. Prototype experiments demonstrated that the robot could effectively avoid obstacles and respond compliantly to external interference. While the robot achieved a 100% feeding success rate with solid and semi-liquid foods, it occasionally experienced spillage when feeding liquids due to structural limitations of the end-effector. This paper provides both a theoretical framework and practical guidance for enhancing the safety and environmental adaptability of feeding robots. Future work will focus on optimizing the end-effector design to further improve performance with liquid foods.
  • Smoothed Finite Element Method for Natural Frequency Optimization of Functionally Graded Plates
    CHEN Shenshen, ZENG Ergui, WEI Xing
    2025, 46(3): 715-723. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.013
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    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.
  • Nonlinear Dynamics of Graphene-Reinforced Inclined Two-Phase Flow Pipeline
    XU Yongsheng, WANG Aiwen, ZHONG Xinhua, LI Hezhang
    2025, 46(3): 724-734. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.014
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    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.
  • Sensitivity Analysis of Process Parameters in Split-Sleeve Cold Expansion of Holes
    XIE Zhou, YUAN Guoqing
    2025, 46(3): 735-748. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.015
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    Split-sleeve cold expansion technology is a critical process for improving the fatigue life of aerospace structural components. However, the influence of its parameter variations on fatigue performance remains insufficiently studied. This paper systematically investigates the sensitivity of initial hole diameter, thickness of split-sleeve, and diameter of the extrusion zone of the mandrel on the fatigue life of 7050-T7451 aluminum alloy through integrated fatigue testing, finite element simulation, and machine learning methods. Based on the S-N curve model of 7050-T7451 aluminum alloy and the critical distance line method, a fatigue life prediction model for cold-expanded holes was established. The model was then used to generate datasets for training an intelligent fatigue life prediction model. Leveraging 400 000 data points obtained from the intelligent model, Sobol global sensitivity analysis was conducted to quantify the independent and interactive contributions of these parameters to fatigue life.Results　indicate that the initial hole diameter has the most significant impact on fatigue life, dominating both independent effects and synergistic interactions, while the influence of Thickness of split-sleeve and mandrel diameter primarily manifests through interactive mechanisms. The study proposes prioritizing tolerance optimization for initial hole diameter while adopting collaborative design strategies for sleeve thickness and diameter of the extrusion zone of the mandrel. This methodology provides an efficient and economical approach for identifying critical process parameters and optimizing designs, demonstrating significant advantages over traditional physical experimentation and finite element analysis.
  • Analysis of Particle Stress and Settlement Patterns in the Ceramsite Layer of Molten Salt Tank Foundations
    HUANG Yao, LIU Yuanjiong, LI Yuanbing, HU Liang
    2025, 46(3): 749-760. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.016
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    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.
  • Electromechanical Coupling Modelling and Experimental Study of Piezoelectric Cantilever Beam Under Water Droplet Impact
    LI Zhinan, HAO Guannan, YU Ran, ZHANG Shuai, LU Lixin
    2025, 46(3): 761-774. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.017
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    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 Dd = 2.4~4.4 mm and impact velocity Vd = 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 dE = 4.27 mJ/m2 when the cantilever beam length L = 35 mm.
  • Optimization of Continuous Casting Mold Pull Velocity Based on Numerical Simulation
    XIA Haitao, LI Qiliang, CHEN Shuo, XIE Yu, YANG Jun
    2025, 46(3): 775-785. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.018
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    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.
  • Study on the Failure Mechanism of Combined Multi-Cracked Red Sandstone Based on Energy Evolution and Damage Constitutive Theory
    ZHANG Xueqiang, GUO Hongyan, GUO Huajun, WANG Chendi
    2025, 46(3): 786-801. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.019
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    To reveal the instability failure mechanism and energy evolution law of the rock mass with multiple cracks, a numerical model of red sandstone was established by using PFC2D. The mesoscopic parameters of the numerical model were calibrated based on the results of uniaxial compression tests and Brazilian splitting tests of intact red sandstone specimens. On this basis, the particle flow simulation tests of red sandstone with multiple cracks were carried out. The results show that with the increase of λ, the peak strength of the multiple-cracked red sandstone gradually decreases when the inclination angle remains unchanged; with the gradual increase of the inclination angle α, the peak strength of the multiple-cracked red sandstone gradually increases when the short-long axis ratio λ remains unchanged; the failure mode shows a diagonal tensile-shear failure, with tensile as the main and shear as the auxiliary, and the failure and instability mode of the specimens are all along the extension direction of the prefabricated cracks; the failure mode of the multiple-cracked red sandstone is jointly affected by the short-long axis ratio and the inclination angle; before the peak strength, the rock mainly shows the energy accumulation characteristics; at the peak strength, the total energy of the red sandstone is mainly elastic energy and supplemented by dissipated energy; at the instability failure, the total energy of the red sandstone is mainly dissipated energy and supplemented by elastic energy; the energy storage capacity and failure difficulty of the red sandstone change with the variation of the multiple-crack inclination angle α and the working conditions, which can be used as a reference for rock breaking operations; and a high-precision damage constitutive model of red sandstone based on different height-diameter ratios λ and different joint inclination angles α was established.
  • A Modified Test Method and Formula for Tensile Fracture Toughness of Putty
    ZHU Lin, LIU Ziyuan, WANG Teng
    2025, 46(3): 802-810. https://doi.org/10.15959/j.cnki.0254-0053.2025.03.020
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    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/m3/2. 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.