Search Results (1,863)

Targeting the rock burst hazard induced by the hard roof key stratum during deep mining at the Mengcun Coal Mine in the Binchang mining area, this study takes the No. 403109 working face as the engineering background and systematically investigates the rockburst prevention mechanism and effectiveness of ground hydraulic fracturing through theoretical analysis, UDEC numerical simulation, and surface microseismic monitoring. The results indicate that fracturing pre-weakens the overlying key stratum, transforming its load-bearing mode from a long-beam rigid support to a segmented flexible support. This significantly reduces the cantilever length, lowers the accumulation of elastic strain energy, and enables flexible load transfer and stress redistribution in the overburden. Numerical simulations reveal that after fracturing, the breakage timing of the key stratum advances, the fragmentation size decreases, and the over-burden movement shifts from stepwise fracturing to sequential caving, with the stress concentration zone substantially narrowed. In the field, a total of 44 fracturing stages were implemented in wells MC-05L and MC-06L, creating a fracture network with an average fracture length of 317 m and an average fracture height of 55 m, achieving an effective stimulated volume ratio of 86.7%. During the mining period, microseismic events exhibited a median energy of only 868.14 J, characterized by high frequency and low energy. The average weighting interval was 13.69 m, the peak coal stress was controlled within 5.0–6.7 MPa, and the loads on roadway bolts and cables remained within safe limits. This study validates the source-control effect of ground hydraulic fracturing on working faces with strong rock burst risks in deep mining, providing a theoretical basis and engineering reference for mines with analogous conditions. Full article

Hybrid cross-laminated timber combining plantation Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) with oriented strand board (OSB) is resource-efficient, but its bond line may govern delamination. Double cantilever beam (DCB) specimens bonded with one-component polyurethane were tested at four initial crack lengths (a₀ = 40–100 mm), comparing untreated bond lines with bond lines pretreated by sandblasting followed by hydroxymethylated resorcinol (HMR). The arms differed in bending stiffness by a factor of about 3.7, so the specimen was an asymmetric bi-material DCB, and the reported values were apparent, predominantly Mode I quantities. Pretreatment raised the critical load by 17%–24% and the apparent initiation toughness by 18%–35%. A bilinear cohesive-zone model with one parameter set per surface condition reproduced all eight calibration groups to within 5% in critical load and load-point displacement; the calibrated cohesive energies (402 and 594 N/m) differed from the apparent toughness at a₀ = 100 mm by −9.6% and +12.9%. Apparent toughness fell with crack length, but the measured compliances do not follow the cubic scaling expected of a DCB, so this trend is unexplained. The calibrated parameters describe the responses measured here; their transfer to other geometries remains to be verified. Full article

Vibration-based piezoelectric energy harvesting provides a potential power source for low-consumption devices; however, its prediction requires a consistent representation of localized structural properties and experimentally identified modal behavior. This study presents the structural and modal qualification of an analytical electromechanical model for a 6061-T6 aluminum cantilever beam carrying a finite one-sided PZT-5J piezoelectric patch, with unequal beam and patch widths, under base excitation. The specific contribution is the traceable integration of local neutral-axis relocation, spatially varying mass and flexural rigidity, a finite-patch indicator function, $d_{31}$ electromechanical coupling, multimodal projection, and mode-specific reduced-order equations. Two beam lengths, $275$ and $250 \mathrm{m}\mathrm{m}$, were investigated using broadband shaker excitation, accelerometry, and scanning laser vibrometry. The measured first and second bending frequencies were $16.56$ and $110.31 \mathrm{H}\mathrm{z}$ for the $275 \mathrm{m}\mathrm{m}$ beam and $19.14$ and $125.00 \mathrm{H}\mathrm{z}$ for the $250 \mathrm{m}\mathrm{m}$ beam. Experimental damping ratios obtained from the frequency-response functions ranged from $6.54\times {10}^{-3}$ to $1.55\times {10}^{-2}$. The analytical formulation reproduced the increase in modal frequencies produced by reducing the beam length and captured the measured transverse mode-shape trends. Experimentally identified frequencies, base accelerations, and damping ratios were subsequently introduced into the reduced model to obtain experimentally parameterized model outputs. The largest calculated peak voltage and estimated average electrical power were $155.99 \mathrm{m}\mathrm{V}$ and $1.22 \mathsf{\mu }\mathrm{W}$, respectively, for the first mode of the $275 \mathrm{m}\mathrm{m}$ beam across a reference $10 \mathrm{k}\mathsf{\Omega }$ resistive load. The reported qualification is restricted to the structural and modal response of the two tested configurations; the electrical quantities are calculated outputs rather than independent electrical measurements. Full article

The pattern recognition of structural safety states is of great significance for the performance evaluation and maintenance of existing structures and post-disaster damaged buildings. Under the general framework of machine learning, this study adopts the BP neural network as the implementation of the structural safety classification model and proposes a method of safety state pattern recognition for reinforced concrete flexural members. Based on the MATLAB platform, the method takes crack characteristic parameters extracted from the surface of concrete members as inputs and the safety state classifications defined in the FEMA-356 code as outputs, thereby establishing a mapping relationship between crack features and the corresponding safety states of the members. The experimental results show that the constructed neural network model achieved a recognition accuracy of 90.9% for safety state classification, demonstrating good pattern recognition capability. In addition, this study established a damage database for cantilevered reinforced concrete flexural members and further validated the generality and applicability of the neural network method for safety state recognition across different structural members. The results indicate a recognition accuracy of 91.7%, enabling the safety state recognition of members with different sizes, strengths, and reinforcement configurations. The proposed method enriches the technical means of structural health monitoring. Full article

Whether arch-specific anatomical configuration affects early peri-implant bone behavior in monolithic zirconia full-arch prostheses is unclear. This prospective cohort study evaluated 40 edentulous patients with 49 monolithic zirconia full-arch prostheses (25 maxillary, 24 mandibular; 308 implants). MBR and patient-reported outcomes were recorded at baseline and 12 months; mandibular morphology (U- vs. V-shaped) was classified on CBCT, and inter-implant distance and cantilever length were measured on CAD designs. Because 9 of 40 patients contributed both arches, the primary MBR comparison used a linear mixed-effects model; morphology and geometry associations were exploratory (ANOVA; Pearson correlation). Implant and prosthetic survival were 99.4% and 97.9%. Mean MBR was higher in the mandibular (0.86 ± 0.06 mm) than the maxillary arches (0.73 ± 0.02 mm); the mixed-effects model estimated this difference as β = 0.13 mm (95% CI: 0.10–0.16; p < 0.001). V-shaped mandibles (0.91 ± 0.04 mm) showed higher MBR than U-shaped mandibles (0.81 ± 0.04 mm; mean difference 0.10 mm; p < 0.001), and inter-implant distance correlated negatively with MBR in the mandible (r = −0.70, p < 0.001) but not in the maxilla (r = 0.01, p = 0.97). Patient-reported outcomes improved markedly in both arches; two minor chipping events occurred, both in V-shaped mandibles. Monolithic zirconia full-arch prostheses showed favorable short-term outcomes in both arches. Arch- and mandibular-morphology-related differences in early MBR were statistically robust and highly consistent in standardized effect size, although the absolute differences were numerically modest; these findings suggest an association between anatomical configuration and early bone remodeling under rigid, full-arch monolithic zirconia frameworks that warrants further confirmation. Full article

This research introduces an analytical model based on a semi-rigid nodal bar system. In this model, carbon–carbon covalent bonds are represented as beam elements, while carbon atoms are treated as semi-rigid nodes connecting these elements. A spring coefficient is incorporated to quantify nodal stiffness. Building upon this construct, spatial stiffness equations for the semi-rigid beam elements are derived, enabling a systematic exploration of how boundary conditions and dimensional factors influence the Young’s modulus and buckling stress in both pristine and defect-laden graphene. The findings reveal that defect-free graphene exhibits remarkable dimensional stability, with its Young’s modulus consistently approximating 1.0 TPa and fluctuating within ±2%. Upon the introduction of defects, the material’s stiffness diminishes significantly, with a maximum reduction of 19% observed when the density of defective elements surpasses a critical threshold. Moreover, the relationship between boundary conditions and buckling stress aligns closely with classical thin plate theory. Under identical dimensional constraints, the buckling stress ratios for fully fixed, fixed-simple, simply supported, and cantilevered boundaries conform to the theoretical ratio of 16:8:4:1. Full article

To simulate the fracture behavior of members during structural collapse, this paper proposes a member fracture simulation algorithm that integrates the plastic hinge model with a ductile fracture damage model within the member discrete element method (MDEM) framework. The coupling is achieved by computing stresses at the four most unfavorable edge points of the contact section and using the minimum fracture strain as the section-level failure criterion. The algorithm is validated against a cantilever beam fracture example, yielding results in good agreement with reference data under two yield stress conditions. The fracture algorithm is then embedded as a self-contained module into an adaptively coupled DEM/FEM algorithm and applied to simulate the shaking table collapse test of a single-layer spherical reticulated shell. The simulation predicts structural collapse at a peak ground acceleration (PGA) of 2268 gal—consistent with the experimental value—with 126 members fractured at collapse onset, and reproduces the observed fracture sequence in which first-ring diagonal members near the supports fail progressively from the bottom upward. The proposed framework provides a computationally robust and practically deployable tool for collapse analysis of large-span reticulated structures, with direct implications for progressive-collapse prevention in seismic design and post-event structural forensic investigation of collapse mechanisms. Full article

The rapid evolution of Urban Air Mobility (UAM) necessitates high-performance morphing structures capable of seamless transitions between flight and ground modes. This research presents a rigorous structural optimization framework for a wing deployment mechanism, addressing the critical challenge of minimizing stress concentrations in cantilevered revolute joints. To overcome the computational prohibitive cost of traditional multibody dynamics, a Generalized Spectral Surrogate Model (GSSM) is introduced. This novel approach maps the mechanism’s geometric parameters to its kinetic response using polynomial-modulated Fourier series, reducing the evaluation time of ${10}^5$ design configurations from 4.2 h to merely 0.8 s while maintaining a determination coefficient $R^2>0.995$. Comparative analysis demonstrates that the GSSM outperforms Artificial Neural Networks and Kriging models in capturing periodic kinematic boundaries without spurious local minima. Through a weighted topological analysis, the study identifies a global optimum ($L_2=0.5$ m, ${\theta }_2={64.2}^{\circ }$) that effectively shunts 70.3% of the aerodynamic load to the robust vehicle chassis. The proposed solution deviates from the theoretical unconstrained minimum by only 0.24%, providing a validated mathematical basis for the rapid synthesis of reliable aerospace mechanisms. Full article

Cantilever roadheaders are widely used in medium-soft rock tunneling. However, conventional pick cutters suffer from high rock-breaking load, excessive energy consumption, and severe abrasion, which restrict the performance of roadheader vehicle-end intelligent control systems. Existing ultrasonic rock-breaking studies mainly focus on drilling and polycrystalline diamond compact (PDC) cutters, while calibrated EDEM simulation and experimental studies of synchronous ultrasonic-vibration-assisted pick cutter cutting remain limited. This study investigates the rock-breaking behavior of synchronous ultrasonic vibration coupled with pick cutter cutting using 21 MPa artificial rock-like specimens. A calibrated EDEM simulation model was developed based on the Hertz–Mindlin with Bonding contact model and validated by uniaxial compression and Brazilian splitting tests. Meta-particle technology was applied to analyze fragmentation characteristics. The effects of ultrasonic frequency, cutting angle, and cone angle on rock-breaking load, debris production, and specific energy consumption were investigated through simulations and experiments. An ultrasonic-assisted cutting test system equipped with force sensors was established for validation. Results show that 30 kHz ultrasonic vibration effectively reduces rock-breaking load under the investigated operating conditions. A relatively favorable parameter combination obtained from the numerical simulations consists of an ultrasonic frequency of 30 kHz, a cutting angle of 40°, and a cone angle of 60°. Compared with conventional cutting, the optimized scheme reduces average cutting load by 74.69%, increases debris yield by 54.71%, and decreases mass-specific mechanical cutting energy consumption by 83.63%. This study provides quantitative data support for roadheader vehicle-end intelligent control systems. Full article

Hybrid structural materials (HSMs), such as nanoparticle-treated fabrics, have been shown to enhance acoustic and ballistic performance in multifunctional protective structures. They offer a promising means for low-frequency (<~1000 Hz) noise mitigation, which remains a critical challenge in aerospace and defense applications. The measurement and modeling of their sound transmission loss (TL) behavior using a coupled acoustic–poroelastic approach is explored in this study. A colloid-based soaking and drying process is used to impregnate nanoparticles into the fabric. Previous studies using SEM imaging have established that at low (<~20 wt.%) treatment levels, the nanoparticles agglomerate in the interstitial spaces between yarn crossover points, whereas at higher levels, they begin to coat the yarn bundle tops. TL was measured experimentally using normal-incidence impedance tube tests. Further, parameters such as static flow resistivity, porosity, flexural modulus, and density required to model the neat and treat samples as fluid-filled porous solids using the Biot–Allard model were obtained from experiments for a limited set of neat and treated cases. Static flow resistivity was measured using an air permeability tester as per ISO 9237, and a modified version of the Peirce’s cantilever beam test was used to obtain the flexural modulus for neat and treated samples. Porosity was estimated using digital image analytics. The poroelastic fabric model was implemented in finite element simulations, and the predicted TL was compared with experiments including those for uncalibrated treated cases. The model shows close alignment with measured TL at low frequencies (<~600 Hz) for all cases but deviates closer towards the theoretical mass law at higher frequencies, where flanking effects and the influence of the hierarchy of pores are expected to be dominant in experiments. Further studies are underway to incorporate such higher-order effects to improve predictions at higher frequencies. The development of this model provides a means to capture the influence of nanoparticle addition on the acoustic performance of Kevlar, enabling fast and efficient virtual design iterations. The approach helps optimize HSMs for noise mitigation in multifunctional applications for the aerospace, defense, and infrastructural sectors. Full article

Residual stresses generated during laser powder bed fusion (LPBF) can cause substantial distortion in slender structures, compromising dimensional accuracy and structural reliability. This study tests the hypothesis that, under identical nominal processing conditions, geometry-dependent stiffness and constraint govern how the evolving thermally induced stress field is redistributed and manifested as warpage after support removal. Bridge-type TA15 titanium alloy cantilever specimens with different spans, thicknesses, and support densities were fabricated by LPBF, and their post-cut warpage was quantified by three-dimensional scanning. A coupled thermo-mechanical finite element model was validated against the measured deformation profiles and subsequently used to examine simulated stress evolution during deposition and redistribution after support removal. Cantilevers with different spans approached similarly high simulated surface tensile-stress plateaus in the constrained as-built state but exhibited markedly different measured warpage after cutting, showing that the as-built stress magnitude alone does not reliably rank post-release deformation. Increasing span reduced global flexural resistance and enlarged the effective bending arm, whereas increasing thickness enhanced flexural rigidity and suppressed curvature even when relatively high localized stress was retained. With the total support volume held constant, changing support density altered the system-level constraint through the combined effects of support-leg stiffness, support spacing, local thermal and mechanical response, and deformation compatibility. Together, these results provide an experimentally supported process-structure interpretation of LPBF cantilever distortion across controlled variations in span, thickness, and support distribution. Full article

Long-span cable-stayed bridges undergo substantial changes in mass distribution, boundary conditions, cable forces, and load paths during erection, yet their stage-dependent free-vibration characteristics are less documented than those of completed bridges. This study establishes a refined finite element (FE) model of the Liulu Yongjiang Extra-large Bridge and evaluates the frequency evolution over 26 construction stages. Detailed modal interpretations are provided for the maximum double-cantilever, maximum single-cantilever, and completed-bridge configurations. The subspace iteration eigensolver is used for modal extraction, and ambient-vibration measurements at the three representative stages provide an independent frequency check. The calculated fundamental frequencies are 0.399, 0.417, and 0.436 Hz for the three configurations, respectively. The governing mode changes from antisymmetric vertical girder bending at the maximum double-cantilever stage to lateral girder bending at the maximum single-cantilever and completed-bridge stages. Across CS1-CS26, cantilever extension generally reduces the governing frequency, cable installation produces a diminishing vertical-stiffening effect, and the modeled 390 t form-traveler mass lowers both lateral and vertical frequencies. Field tests indicate that the measured frequencies at three stages deviate less than 9.6% from the FE values, confirming the reliability of the model. The revealed evolution laws and influencing mechanisms of dynamic characteristics during construction provide theoretical support for vibration control and safety assurance of similar bridges. Full article

Slender cantilever precision positioning actuators are highly susceptible to ambient low-frequency micro-vibrations, which severely deteriorate dynamic positioning accuracy and operational stability. To address this challenge, this paper proposes a passive vibration attenuation method utilizing a customized partitioned particle damper. A micro-vibration-adapted discrete element method (DEM) coupled dynamic model is established to quantitatively characterize the underlying multi-mechanism energy dissipation driven by micro-slip friction and weak inelastic collisions. Through systematic numerical parametric analysis and physical experimentation, the optimal damper configuration is identified. Experimental results rigorously demonstrate that the optimized particle damper effectively suppresses broadband micro-vibrations (10–100 Hz), achieving a maximum steady-state vibration damping efficiency of 63.24% and a transient peak acceleration attenuation of 67.5% at the cantilever tip. This work provides a highly compact, energy-free, and robust structural vibration suppression strategy, demonstrating significant potential for application in high-precision actuation systems. Full article

Crops cultivated on trellis systems, such as kiwifruit, grapes, et al., create a partially structured workspace; this environment is highly suitable for Cartesian robotic harvesting. However, limited extension range of current Cartesian manipulators necessitates a large vertical space, which directly conflicts with the height constraints of trellis canopies. This paper presented a hollow telescopic Cartesian manipulator with a belt-driven cascaded differential transmission for single-degree-of-freedom kiwifruit operations. The two-stage nested carbon fiber structure offers an extension ratio of 1.83:1 and a 549 mm retracted length, requiring 45.36% less vertical space than its single-stage architecture. The hybrid model–vision error compensation (HMVEC) strategy is proposed to address nonlinear positioning errors inherent in the cantilever telescopic configuration. It combines a polynomial–Fourier kinematic model for feedforward correction with YOLO11n AprilTag detection. The results showed the HMVEC strategy reduced the positioning root mean square error (RMSE) by 42.28% (from 7.90 mm to 4.56 mm). The designed manipulator achieved a 95% kiwifruit-transfer success rate at a mean cycle time of 4.8 s per fruit. These results demonstrate the feasibility of the proposed structural design and HMVEC strategy for precise manipulator positioning and post-detachment fruit transfer. Full article

Implicit flexible multibody dynamics using three-dimensional continuum finite elements remains computationally demanding due to repeated nonlinear iterations in large-scale simulations. The component-level co-rotational (CR) continuum finite element approach alleviates this cost by assigning a shared rotating reference frame to all elements within a flexible component. However, this shared-frame assumption introduces a kinematic approximation when significant rotation differences exist among elements, and reliable criteria for reference-frame construction and approximation assessments are still lacking. This paper presents a systematic framework to control the approximation in component-level CR formulations. A deterministic quality-controlled algorithm is first developed to automatically select three reference nodes from arbitrary three-dimensional component meshes, considering component membership, geometric non-degeneracy, and mesh quality. Furthermore, a mass-weighted rotation-dispersion metric based on the geodesic difference between the relative component and element rotations is proposed to quantitatively evaluate the validity of the shared-frame assumption. The proposed framework is integrated into component-level CR flexible multibody analysis and validated through several numerical examples, including a three-dimensional pendulum, spinning top, flexible cantilever system, and slider-crank mechanism. Results demonstrate that the proposed reference-frame construction and rotation-dispersion assessment effectively characterize and control the kinematic approximation while retaining the computational advantages of component-level CR formulations. This work provides a practical criterion for the reliable application of component-level CR continuum finite elements in large-scale flexible multibody dynamics. Full article