Mechanics of Solids最新文献

This study investigates penetration mechanisms of non-circular long-rod projectiles (triangular/cruciform cross-sections) under a low-strength projectile (A3 steel) and high-strength target (45 steel) configuration. Simulations at 1000–1600 m/s reveal velocity-dependent penetration gains: triangular sections achieved gains of 1.11% at 1000 m/s and 1.45% at 1300 m/s, while cruciform sections gained 2.83 and 3.52% at 1600 m/s. Material parameters exert distinct effects: yield strength predominantly governs circular-section performance, whereas shear modulus significantly influences non-circular sections. Optimizing these parameters amplifies shape effects—e.g., higher yield strength with lower shear modulus enhances triangular-section efficiency. Mechanistically, triangular sections benefit from structural self-sharpening and non-uniform debris flow at edges, favoring lower velocities. Cruciform sections form internal debris pathways, reducing friction to improve high-velocity penetration. A novel star-shaped cross-section, synergizing both mechanisms, outperformed conventional shapes across all velocities (e.g., 37.62 mm vs. 35.83 mm/37.47 mm at 1600 m/s). This work advances penetrator design through velocity- and material-optimized cross-sections.

This comprehensive study explores the reflection phenomenon at the surface of triple-porosity medium. It investigates the incidence of two primary waves and identifies five reflected waves within the medium. The study derives expressions for the reflection coefficients as a non-singular system of linear equations and calculates the energy distribution of the reflected waves in the form of an energy matrix. A numerical example is provided to analyze how the incident energy is partitioned for both fully closed and perfectly open pores. Additionally, the impact of incident direction on the partitioning of incident energy is examined, considering variations in homogeneity parameter, gas saturation, porosity, critical porosity, depth, and wave-induced fluid flow. The numerical interpretation confirms that during the reflection process, the conservation of incident energy is maintained at each angle of incidence, even in the presence of interaction energy.

This paper systematically reviews the current research status and development trends of perforated cold-formed thin-walled steel (CFTS) members, including both compression and flexural members. Since the late 19th century, researchers have used experimental testing, theoretical analysis, and finite element simulation to explore the effects of perforations on the load-carrying capacity, buckling stress, and mode of buckling of members, providing theoretical support and practical guidance for engineering design. It has been found that most existing studies have focused on columns and web perforations, while research on beams and flange perforations is relatively limited, indicating potential directions for future research. Although theoretical analysis has its value, experimental testing and finite element analysis have gradually become dominant due to their efficiency in handling complex conditions. Future research should focus on new buckling modes and performance changes caused by perforations in composite sections, as well as the mechanical behavior of complex section forms after perforation. The direct strength method (DSM) is not sufficiently accurate in predicting the load-carrying capacity of perforated members and exhibits significant variability. The application of machine learning algorithms is expected to offer new perspectives and methods for mechanical performance analysis. The research findings of this paper can lay a solid foundation and provide direction for future research on perforated CFTS members.

Utilizing the theories of nearly saturated porous media and mixture continuum mechanics, this study formulates a mathematical model to describe P-wave oblique incidence on a seawater–nearly saturated ocean sediment layer–bedrock system. Theoretical analysis and numerical simulations are conducted to examine how incident frequency, sediment layer thickness, saturation, and porosity influence the seismic response of ocean foundation sites. The results indicate that P-wave incidence angle and frequency have a pronounced effect on seismic response, with horizontal displacement peaking near 65° and increasing significantly with frequency. At 50 Hz, the horizontal displacement amplitude is approximately 56 times greater than that at 1 Hz. Changes in saturation lead to significant quantitative differences: under fully saturated conditions, the maximum vertical displacement can be about 20 times larger than under nearly saturated conditions. Sediment thickness also plays a critical role: an increase in thickness can result in up to a 43% rise in maximum horizontal displacement and more than a hundredfold increase in maximum vertical displacement. Additionally, porosity exhibits a nonlinear effect on seismic response, wherein increased porosity amplifies horizontal movement, whereas reduced porosity exacerbates vertical vibrations. These findings provide both theoretical and quantitative insights for the seismic evaluation and design of oceanic foundations, highlighting the importance of accounting for the dynamic properties of nearly saturated sediment layers.

This study, utilizing analytical methods, presents for the first time the static bending response of a two-curvature micro shell composed of three material layers: two outer layers made of ceramic and micro-porous metal, and a middle layer featuring an auxetic structure. The stiffness of the shell can achieve its maximum when optimal geometric parameters of the auxetic core are identified. Calculation formulas are derived from classical shell theory and coupled stress theory to ascertain the impact of size effect on the static bending response of micro shells. The length scale parameter determined in this study varies with thickness. Furthermore, this research presents an explicit expression for the displacement of the micro shell under bending and demonstrates the reliability of the analytical formula by comparing it with previously published results. This study demonstrates the dependence of micro shell displacement on various geometrical and material parameters of the shell and each individual material layer. This is a compilation of reference data for designers to select suitable parameters to maximize the bending load capacity of the micro shell, hence minimizing the bending displacement of the micro shell.

The article is devoted to elastic-plastic torsion of a multilayered rod under torque. It is assumed that the rod consists of several layers. Each layer has its own elastic properties, but the plastic properties of both layers are the same. For simplicity, a three-layer rod is considered. The contact boundaries of the layers are located along the x-axis. The lateral boundary of the rod is free of stresses, the displacements and stresses are continuous at the interlayer boundaries. The stress tensor components at a point are calculated, using the contour integrals obtained from the conservation laws calculated on the edge of the cross section. Then, the second invariant of the stress tensor is compared with the yield strength. At the points where the yield strength is reached, the plastic state occurs, and the remaining parts are elastic. This lets us construct a boundary between the plastic and elastic regions. This method provides a way to calculate the elastic-plastic boundaries for the standard rolled profiles of rods. This issue will be considered in future studies. It should be noted that previously, using the conservation laws, the main boundary value problems were solved for the plastic two-dimensional medium, elastic-plastic torsion of isotropic rods and elastic media for finite-sized bodies.

The Johnson-Cook constitutive model is extensively utilized in numerical simulations of high-velocity impact and penetration scenarios, with its primary material parameters (A, B, n, C, and m) directly governing the material’s flow stress. However, material parameters obtained exclusively through dynamic and static experiments generally prove inadequate for direct application in penetration analysis, necessitating further calibration for penetration studies. To investigate the influence of penetrator core material parameters on computational outcomes—particularly maximum penetration depth—during high-velocity penetration of semi-infinite metallic targets by long-rod projectiles, numerical simulations employing an experimentally validated ANSYS/LS-DYNA model were conducted. These simulations examined 93W alloy penetrator cores with varied material parameters impacting Rolled Homogeneous Armor steel at identical velocities. Results demonstrate that the initial yield strength (parameter A) constitutes the predominant factor influencing penetration depth; within the investigated range (500–2500 MPa), increasing A enhances penetration performance by 15.23%, while penetration depth sensitivity to the remaining parameters (B, n, C, m) remains below 5% across ranges typically covered by most materials.

Auxetic materials, characterized by their negative Poisson’s ratio (NPR), exhibit unique mechanical properties that make them highly desirable for lightweight structural applications. This study introduces a novel 3D double arc star-shaped (3D DASS) auxetic structure and systematically investigates the influence of cross-sectional shape (square vs. circular) and thickness variation on its mechanical behavior. We derive expressions for Poisson’s ratio and Young’s modulus using analytical modeling and numerical simulations and validate them across different geometric configurations. The results reveal that while Poisson’s ratio remains nearly constant for both cross-sections, Young’s modulus is significantly influenced by cross-sectional thickness, particularly in circular configurations. These findings provide valuable insights into the design optimization of lightweight auxetic structures and their potential applications in engineering.

The study examines the effects of point source on SH wave propagation in a functionally graded piezoelectric material layer over a functionally graded piezoelectric substrate. The formulation of dispersion equation for SH wave propagation on a given formation is produced by taking appropriate boundary conditions into account and utilizing the governing equations. Using Mathematica 7, numerical calculations are performed to visually represent the significant influence of the piezoelectric constant, dielectric constant, and functional gradient factors on phase velocity of the SH wave.

The present article indicates a pioneering investigation into the photo-thermal transport processes within semiconductor materials influenced by a mobile heat source. This study addresses critical research gaps by employing an advanced heat transfer theory grounded in fractional derivatives, as formulated by Atangana-Baleanu. This innovative approach incorporates non-singular kernel functions, enabling the derivation of accurate solutions for complex thermal mechanisms. The research makes a significant contribution to the field by providing analytical solutions in the frequency domain through the application of the Laplace transform algorithm and the eigenvalue methodology. Key findings reveal intricate relationships between various field quantities, including temperature, displacement, carrier density, and thermal stress, which are illustrated through the graphical results. These results are analyzed across diverse parameters such as material depth, fractional parameters, the lifetime of photo-generated carriers, as well as the velocity and intensity of the moving heat source. Notably, the inclusion of fractional quantities elucidates the precise and finite nature of photo-thermal waves, distinguishing this work from traditional hyperbolic thermoelasticity theories. The implications of these findings extend to a deeper understanding and optimization of semiconductor materials in practical applications, while also suggesting new avenues for future research in the field of thermal transport.