Search Results (1,503)

The present study extends the previous work which was concerned with the identification of damage in GFRP composite plates by damage detection algorithms such as the Normalized Curvature Damage Factor (NCDF), Strain Energy Difference (SED), and Damage Index (DI), using a novel damage (crack) modeling technique called the ‘Node-Releasing Technique’ (NRT) in Finite Element Analysis (FEA) for modeling and detecting perpendicular and slant partial-depth cracks in GFRP composite beams. This study explores the sensitivity of the damage modeling technique NRT in damage detection for composite beams using the NCDF algorithm, since it was concluded in the previous work that the NCDF performs better compared to the other methods when detecting both perpendicular and slant partial-depth cracks. This study also examines the variations in the Frequency Response Function (FRF) as another novel tool for identifying even small-scale damage. Most prior research in this domain has focused on variations in natural frequency, displacement mode shape, and damping as indicators for detecting and localizing structural damage through various experimental, theoretical, and computational approaches. However, these conventional parameters often lack the sensitivity required to detect small-scale damage and, still, there exists a gap in the use of the node-releasing technique in FEA to model the partial-depth perpendicular and slant crack damage in laminated composite structures, such as beam-like structures. To fill this gap, the present study attempts to use Curvature Mode Shapes (CMS)-based NCDF, obtained from numerical modal analysis, and variations in the Frequency Response Function (FRF), obtained through harmonic analysis, as more sensitive indicators for damage detection in laminated composite beams. FEA simulations are performed using the commercial FEA software package ANSYS 2021 R1 to obtain the first five flexural natural frequencies and the corresponding displacement mode shapes of both the intact and damaged composite beams. The curvature mode shapes are obtained from the displacement mode shapes data using the central difference approximation method to compute the NCDF. Simultaneously, GFRP composite beams were fabricated by the hand lay-up method, and Experimental Modal Analysis (EMA) was employed to substantiate the FE model and the validity of the numerical results. By combining both numerical and experimental methods, we proved that NCDF and FRF are reliable tools to determine and locate structural damage, even at a comparatively small scale. In general, the results indicate that NCDF is a stable and practically applicable parameter to locate cracks in laminated composite beams and provide meaningful information to be used as guidelines in applications of vibration-based structural health monitoring. Full article

Geogrids significantly enhance the soil matrix stability and foundation bearing capacity. Despite the development of numerous geogrid configurations, their geometric design has not yet been systematically optimized. The design of geogrid aperture geometry aims to maximize geogrid performance while maintaining material efficiency. Nevertheless, topology optimized geogrid designs remain underexplored, particularly regarding the influence of aperture shape on interface shear behavior. To address this gap, this study developed SIMP-based variable density topology optimization models for three types of tensile geogrid structures: uniaxial, biaxial, and triaxial geogrid. The effects of key model parameters on the optimization results are examined, resulting in new geogrid geometries optimized primarily to minimize compliance, achieving weight reductions of 7%, 10%, and 12%, respectively. Subsequently, FLAC3D was used for tensile performance analysis, while coupled PFC3D–FLAC3D was employed for interfacial friction performance analysis. In FLAC3D, numerical simulations demonstrated that the topologically optimized geogrid outperformed conventional ones in both tensile resistance and strain distribution. Consequently, conventional biaxial and triaxial geogrids, along with their topologically optimized versions, were chosen for further analysis. Pull-out interface simulations of these geogrids were conducted using the coupled discrete element–finite difference method (PFC3D–FLAC3D) to investigate the influence of geogrid aperture shape and aperture ratio on the soil–geogrid interface. The results indicate that the reinforcement efficiency of the topologically optimized biaxial and triaxial geogrids was 10% and 8% higher, respectively, than that of the conventional geogrids. Taking the biaxial geogrid as an example, a comprehensive comparison of performance parameters between the conventional and topology-optimized versions revealed that the optimized design achieved a 10% reduction in weight. Simultaneously, it reduced stress concentration at critical locations by approximately 60% and increased the interface pull-out resistance by 20%. These findings demonstrate that the new topologically optimized geogrid exhibits significant potential for further promotion and application in practical engineering. Full article

The mechanical behavior of assembled culverts under high rocky backfill presents significant challenges due to the complex interaction between the rigid structure and coarse-grained fill. This study investigates the full-process mechanical performance of an assembled culvert through comprehensive in situ monitoring and three-dimensional finite element numerical analysis. Key parameters, including earth pressure distribution, structural deformation, and joint strain, were continuously monitored throughout the backfilling process. A high-fidelity numerical model considering the soil-structure interaction was established and strictly validated against field data. The results indicate that the earth pressure growth rate gradually decreases with fill height, confirming the development of a soil arching effect within the rocky backfill. The numerical predictions show strong consistency with experimental measurements, verifying the model’s accuracy. Crucially, the culvert exhibited minimal deformation, with cumulative settlement less than 25 mm, fully meeting safety requirements. Furthermore, a distinct alternating tension-compression strain pattern was observed at the joints during early backfilling, highlighting the critical necessity of symmetrical layered compaction. These findings validate the safety of the proposed construction methodology and provide a theoretical basis for optimizing the design and quality control of high-fill infrastructure in mountainous terrain. Full article

Existing structural stress is an important parameter for evaluating the current state of a structure. In order to improve the accuracy of in situ stress measurement in the field, this paper proposes an in situ stress measurement method for existing structures, which combines Digital Image Correlation (DIC) technology with the drilling stress relief method. The method utilizes DIC technology to monitor the local displacement or strain caused by stress release from the drilled hole in real time, and further inverts the in situ stress state of the structure based on this data. First, the principle and specific implementation process of the method are introduced. Then, finite element simulations are used to analyze the influence of factors such as size effects, drill hole diameter, drill hole depth, and initial stress magnitude on the measurement results. Finally, experimental validation of the method’s effectiveness is conducted. The results show that the in situ stress measurement method based on the combination of DIC and stress relief has good application effects and prospects in the stress analysis of existing structures. The accuracy and effectiveness of the method are influenced by factors such as specimen size, drill hole diameter, drill hole depth, and stress magnitude. In practical engineering, a comprehensive evaluation should be made, considering the precision of DIC testing and the magnitude of in situ stress, to select appropriate drilling parameters and measurement ranges. During the subsequent stress inversion process, a size calibration factors is applied to adjust the theoretical results, significantly improving the method’s applicability under finite size conditions, and achieving good results. This research provides important references for the stress testing and evaluation of existing structures with finite sizes. Full article

This paper proposes a novel mortise-and-tenon grouted masonry (MTGM) structure to enhance the mechanical performance and engineering applicability of masonry. The axial and eccentric compressive behavior of the system was systematically investigated through experimental testing and numerical simulation. A refined three-dimensional finite element model, developed in DIANA, effectively accounted for material nonlinearity and interfacial contact, with its high accuracy confirmed by experimental results. The parametric analysis of 52 numerical models elucidated the influence of block strength, core material type, wall thickness, steel fiber content, and geometric ratios on the compressive strength, deformation capacity, and failure modes. The results demonstrate that using steel fiber-reinforced concrete (SFRC) as the core filling material significantly enhances ductility and toughness; an SFRC content of 1.6% increased the ultimate strain by approximately 37%. Furthermore, increasing the eccentricity from 0.1 to 0.3 led to an average 40% reduction in load-bearing capacity. Theoretical analysis led to the derivation of calculation formulae relating to key axial compression parameters. Furthermore, a stress–strain constitutive relationship suitable for MTGM was established, featuring a parabolic ascending branch and a linear descending branch (R² = 0.992). For eccentric compression, a practical design method was developed based on the plane section assumption, which demonstrated superior predictive accuracy compared to existing code provisions. This study provides a reliable theoretical foundation and practical computational tools for the structural design and application of MTGM. Full article

Acrylonitrile Styrene Acrylate (ASA) is widely used in outdoor structural applications due to its favorable mechanical stability and weather resistance; however, its temperature-dependent plastic behavior remains insufficiently characterized for accurate numerical simulation. This study presents a non-standard method of calibrating the temperature-dependent Johnson–Cook (J-C) plasticity model for ASA in the practical operating temperature range below the glass transition temperature. Uniaxial tensile tests at constant strain rate 0.01 s⁻¹ were performed at −10 °C, +23 °C, and +65 °C to characterize the effect of temperature on the material’s plastic response. The J-C parameters $A$, $B$, and $n$ were identified for each temperature separately and globally using least-squares optimization implemented in MATLAB R2024b, showing good agreement with the experimental stress–strain curves. The calibrated parameters were subsequently implemented in Abaqus 2024 and validated through finite element simulations of the tensile tests. Numerical predictions demonstrated a very high correlation with the experimental data across all temperatures, confirming that the J-C model accurately captures the hardening behavior of ASA. The presented parameter set and calibration methodology provide a reliable basis for future simulation-driven design, forming analysis, and structural assessment of ASA components subjected to variable thermal conditions. Full article

Steel bridge deck pavements (SBDPs) are susceptible to complex mechanical and service environmental conditions, yet current design methods often struggle to simultaneously capture global bridge system behavior and local pavement responses. To address this issue, this study develops a multi-scale finite element modeling framework that integrates a full-bridge model, a refined girder-segment model, and a detailed pavement submodel. The framework is applied to an extra-long suspension bridge to evaluate the mechanical responses of five typical pavement structural configurations—including double-layer SMA, double-layer Epoxy Asphalt (EA), EA-SMA combinations, and a composite scheme with a thin epoxy resin aggregate overlay. By coupling global deformations from a full-bridge model to the local pavement submodel, the proposed method enables a consistent assessment of both bridge-level effects and pavement-level stress concentrations. The analysis reveals that pavement structures significantly alter the stress and strain distributions within the deck system. The results indicate that while the composite configuration with a thin overlay effectively reduces shear stress at the pavement–deck interface, it results in excessive tensile strain, posing a high risk of fatigue cracking. Conversely, the double-layer EA configuration exhibits the lowest fatigue-related strain, demonstrating superior deformation coordination, while the optimized EA-SMA combination offers a robust balance between fatigue control and interfacial stress distribution. These findings validate the effectiveness of the multi-scale approach for SBDP analysis and highlight that rational structural configuration selection—specifically balancing layer stiffness and thickness—is critical for enhancing the durability and long-term performance of steel bridge deck pavements. Full article

This review provides a comparative analysis of the structure and physical properties of low-dimensional aperiodic crystalline solids, aiming to elucidate the origin and nature of aperiodicity in reduced-dimensional lattices. The breakdown of periodicity in low-dimensional systems arises from several mechanisms, including the suppression of specific force constants, thermodynamic instabilities, and topological constraints associated with imperfect space filling. At the nanoscale, certain cubic crystalline materials can form finite, zero-dimensional multiply twinned particles (MTPs) with decahedral or icosahedral symmetry. These clusters lack translational invariance and experience intrinsic structural strain due to solid-angle mismatch at twin junctions, which limits their characteristic size and renders them finite aperiodic solids. Particular attention is devoted to the electronic and spin properties of pentagonally symmetric MTPs: icosahedral particles exhibit symmetry-protected spin degeneracy consistent with centrosymmetric lattices, whereas non-centrosymmetric decahedral particles may display spin polarization and emergent low-dimensional magnetism. Collectively, these systems illustrate the diverse physical origins, manifestations, and consequences of aperiodicity in low-dimensional crystalline matter. Full article

Fibrin clots with strain-hardening characteristics exhibit pronounced material nonlinearity and acoustic dispersion under ultrasound, leading to waveform distortion and shock formation during finite-amplitude wave propagation. However, peak-shock stress is limited by viscoelastic dissipation and dispersion, constraining the efficiency of ultrasound in applications such as thrombus ablation. To overcome this limitation, a shock wave amplification method using designed multi-wave-packet sequences is proposed. Based on a power-law model from quasi-static compression tests, shock generation under a single sinusoidal pulse was first simulated. The dual-wave-packet chasing strategy was then developed, in which the amplitude, frequency, and time delay of the second packet were tuned to achieve effective superposition with the precursor. The waveform superposition factor (WSF) was introduced for quantitative evaluation. Numerical results demonstrate that this strategy can significantly increase the peak-shock-wave stress, with a maximum gain of 22.7%. Parametric analysis further identified amplitude as the dominant factor influencing wavefront steepness and amplification effectiveness. This study provides a novel method and theoretical support for developing efficient and controllable ultrasonic sequences for thrombolysis. Full article

This study aimed to evaluate the biomechanical behavior of different implant macrogeometries under immediate and delayed implantation protocols in a single maxillary anterior tooth model using three-dimensional finite element analysis. Six implant models from three different implant systems were analyzed, each including one aggressive and one passive macrogeometric design. In the immediate implantation models, implants were placed within the extraction socket, with the buccal gap filled using a xenograft material, whereas in the delayed implantation models, a fully remodeled healed bone condition was simulated. Stress and strain distributions were evaluated under a 120 N static oblique load representing functional occlusal forces in the anterior maxilla. Under immediate implantation conditions, aggressive designs demonstrated a more homogeneous stress distribution and reduced cervical stress concentration compared with passive designs, while maintaining comparable apical stress levels. Similarly, in delayed implantation models, aggressive macrogeometries exhibited lower stress concentrations in the cervical cortical bone relative to cylindrical designs. Overall, these findings suggest that aggressive implant macrogeometry may favorably balance cervical stress reduction and apical load transfer, supporting peri-implant bone preservation while maintaining primary mechanical anchorage. Full article

Mechanical stimulation critically regulates mesenchymal stem cell (MSC) differentiation, yet its effects in three-dimensional (3D) environments remain poorly defined. Here, we developed a custom dynamic stretcher integrating poly(dimethylsiloxane) (PDMS) chambers to apply cyclic strain to human MSCs encapsulated in Fmoc-diphenylalanine (Fmoc-FF) peptide hydrogels—a fully synthetic, tunable extracellular matrix mimic. Finite element modeling verified uniform strain transmission across the hydrogel. Dynamic stretching at 0.5 Hz and 10% strain induced pronounced cytoskeletal alignment, enhanced actin stress fiber formation (coherency index $\approx 0.85$), and significantly increased proliferation compared to static or high-frequency (2.5 Hz, 1%) conditions (coherency index $\approx 0.6$). Quantitative image analysis confirmed strain-dependent increases in coherency index and F-actin intensity, indicating enhanced mechanotransductive remodeling. Biochemical assays and qRT–PCR revealed 2–3-fold upregulation of osteogenic markers—RUNX2, ALP, COL1A1, OSX, BMP, ON, and IBSP—under optimal strain. These results demonstrate that low-frequency, high-strain mechanical loading in 3D peptide hydrogels activates RhoA/ROCK and YAP/TAZ pathways, driving osteogenic differentiation. The integrated experimental–computational approach provides a robust platform for studying mechanobiological regulation and advancing mechanically tunable biomaterials for bone tissue engineering. Full article

Accurately assessing collapse risks of high-elevation, concealed rock mass blocks within the steep cliffs of Bijiashan, Three Gorges Reservoir Area, is challenging. This study employed a multidimensional approach—integrating airborne Light Detection and Ranging (LiDAR), the transient electromagnetic method (TEM), close-range photogrammetry, horizontal drilling, and borehole optical imaging—to characterize the rock mass structure of the WD1 cliff belt and delineate 52 individual blocks. Stability analysis incorporated stereographic projection for macro-scale assessment and employed mechanical models specific to three primary failure modes (toppling, sliding, falling). Finite element strength reduction quantified the stress–strain response of a representative block under natural and rainstorm conditions. Particle Flow Code (PFC) simulated dynamic instability of the exceptionally large block W1-37. Results indicate the WD1 rock mass is highly fractured, with base sections prone to weakness. Toppling failure dominates (90.4%). Under rainstorm conditions, the average Factor of Safety (FOS) decreased by 14.7%, and 73.1% of the blocks that were stable under natural conditions were destabilized—specifically transitioning to marginally stable or substable states—often triggering chain-reaction instability characterized by “crack propagation—base buckling”. W1-37 exhibited staged failure under rainstorm: “strain localization at fissure tips—penetration of basal cracks—overturning of the upper rock mass”. Its frontal rock reached a peak sliding velocity of 15.17 m/s, indicative of base-breaking toppling. The integrated “multi-technology survey—multi-method evaluation—multi-scale simulation” framework provides a quantitative basis for risk assessment of rock mass disasters in the Three Gorges Reservoir Area and offers a technical paradigm for similar high-steep canyon regions. Full article

Numerical simulations of the forming limit diagram (FLD) for SUS430/Al1050/TA1 laminated metal composites (LMCs) are conducted through the crystal plasticity finite element (CPFE) model integrated with the Marciniak–Kuczyński (M–K) theory. Representative volume elements (RVEs) that reconstruct the measured crystallographic texture, as characterized by electron backscatter diffraction (EBSD), are developed. The optimal grain number and mesh density for the RVE are calibrated through convergence analysis by curve-fitting simulated stress–strain responses to the uniaxial tensile data. The established multi-scale model successfully predicts the FLDs of the SUS430/Al1050/TA1 laminated sheet under two stacking sequences, namely, the SUS layer or the TA1 layer in contact with the die. The Nakazima test results validate the effectiveness of the proposed model as an efficient and accurate predictive tool. This study extends the CPFE–MK framework to multi-layer LMCs, overcoming the limitations of conventional single-layer models, which incorporate FCC, BCC, and HCP crystalline structures. Furthermore, the deformation-induced texture evolution under different loading paths is analyzed, establishing the relationship between micro-scale deformation mechanisms and the macro-scale forming behavior. Full article

This study explores the viability of ultra-high-performance concrete (UHPC) as a structural material for compressed air storage (CAES) systems, combining comprehensive experimental testing and numerical simulations. Scaled (1:20) CAES tanks were designed and tested experimentally under controlled pressure conditions up to 4 MPa (580 psi), employing strain gauges to measure strains in steel cylinders both with and without UHPC confinement. Finite element models (FEMs) developed using ANSYS Workbench 2024 simulated experimental conditions, enabling detailed analysis of strain distribution and structural behavior. Experimental and numerical results agreed closely, with hoop strain relative errors between 0.9% (UHPC-confined) and 1.9% (unconfined), confirming the numerical model’s accuracy. Additionally, the study investigated the role of a rubber interface layer integrated between the steel and UHPC, revealing its effectiveness in mitigating localized stress concentrations and enhancing strain distribution. Failure analyses conducted using the von Mises criterion for steel and the Drucker–Prager criterion for UHPC confirmed adequate safety factors, validating the structural integrity under anticipated operational pressures. Principal stresses from numerical analyses were scaled to real-world operational pressures. These thorough results highlight that incorporating rubber enhances the system’s structural performance. Full article

Assessing the stress–strain state around interacting mining excavations using the finite element method (FEM) is computationally expensive for parametric studies. This study evaluates tabular machine-learning surrogate models for the rapid prediction of full stress–strain fields in fractured rock masses treated as an equivalent continuum. A dataset of 1000 parametric FEM simulations using the elastoplastic generalized Hoek–Brown constitutive model was generated to train Random Forest, LightGBM, CatBoost, and Multilayer Perceptron (MLP) models based on geometric features. The results show that the best models achieve R² scores of 0.96–0.97 for stress components and 0.99 for total displacements. LightGBM and CatBoost provide the optimal balance between accuracy and computational cost, offering speed-ups of 15 to 70 times compared to FEM. While Random Forest yields slightly higher accuracy, it is resource-intensive. Conversely, MLP is the fastest but less accurate. These findings demonstrate that data-driven surrogates can effectively replace repeated FEM simulations, enabling efficient parametric analysis and intelligent design optimization for mine workings. Full article