Search Results (379)

This study presents the development, calibration, and validation of cohesive zone models (CZMs) for epoxy-based adhesive joints connecting stainless steel and CFRP composites. The objective of this study is to develop and rigorously validate cohesive zone models for epoxy-based adhesive joints between stainless steel and CFRP composites, ensuring their reliability for numerical simulations of structural failure under quasi-static and large-deformation conditions. The work focuses on accurately describing the quasi-static behaviour and failure mechanisms of hybrid adhesive interfaces, which are crucial for multimaterial structures in modern transportation systems. Experimental tests in Mode I (DCB) and Mode II (ENF) configurations were performed to determine the cohesive parameters of the structural adhesive SikaPower 1277. The obtained data were further analysed through analytical formulations and validated numerically using PAM-CRASH. Excellent agreement was achieved between experiments, analytical predictions, and simulations, confirming the reliability of the proposed material definitions under large deformations. The validated models were subsequently implemented in a large-scale numerical simulation of a bus rollover according to UN/ECE Regulation No. 66, demonstrating their applicability to real structural components. The results show that the developed cohesive zone models enable accurate prediction of failure initiation and propagation in adhesive joints between dissimilar materials. These findings provide a robust foundation for the design of lightweight, crashworthy structures in transportation and open new perspectives for integrating epoxy-based adhesives into additively manufactured hybrid metal–composite systems. Full article

Seasonal groundwater rise of 2.5–3.0 m leads to full saturation of the lakeside slope of the railway embankment, significantly reducing the strength of clayey–sandy loam layers. Laboratory shear tests showed that saturation decreases the internal friction angle from 24–26° to 16–19°, while effective cohesion drops from 12–18 kPa to 0–3 kPa, identifying the 3–6 m depth interval as the critical weak zone. These parameters were incorporated into PLAXIS 2D/3D hydro-mechanical models to assess the embankment behaviour under three scenarios: natural conditions, high water level, and reinforced configuration. Under elevated water levels, lateral displacement toward the lakeside increased to 0.16–0.21 m, and the plastic strain zone expanded by a factor of 2.4, reducing the safety factor from FS ≈ 1.32 to below 1.10. The proposed stabilization system—replacement of a 1.5 m weak layer, installation of geotextile reinforcement, and application of a bituminous waterproofing layer—substantially improved stability, reducing maximum lateral displacement to 0.12 m (≈43% reduction) and restoring the safety factor to FS = 1.25–1.40. The results demonstrate that low-cost geosynthetic barriers provide an effective and practical engineering solution for maintaining the long-term stability of railway embankments exposed to seasonal inundation. Full article

Freeze–thaw cycles (FTCs) are a prevalent weathering process that threatens the stability of canal slopes in seasonally frozen regions. This study combines direct shear tests under multiple F-T cycles with coupled thermo-hydro-mechanical numerical modeling to investigate the failure mechanisms of slopes with different moisture contents (18%, 22%, 26%). The test results quantify a marked strength degradation, where the cohesion decreases to approximately 50% of its initial value and the internal friction angle is weakened by about 10% after 10 freeze–thaw cycles. The simulation reveals that temperature gradient-driven moisture migration is the core process, leading to a dynamic stress–strain concentration zone that propagates from the upper slope to the toe. The safety factors of the three soil specimens with different moisture contents fell below the critical threshold of 1.3. They registered values of 1.02, 0.99, and 0.78 within 44, 44, and 46 days, which subsequently induced shallow failure. The failure mechanism elucidated in this study enhances the understanding of freeze–thaw-induced slope instability in seasonally frozen regions. Full article

This article examines the role of coworking and flexible workspaces in promoting sustainable spatial development in the non-metropolitan areas of Bulgaria. A mixed-method approach was applied, combining inventory enumeration, spatial classification, SDG-based sustainability assessment, and qualitative coding (open, axial, selective). A total of 74 coworking and flexible workspaces were identified across the six national planning regions, evaluated according to six analytical criteria (accessibility, seasonality, specialization, municipal administrative district, urban planning zone, building function) and assessed against five SDG-aligned dimensions (SDG 8, 9, 11, 12, 13). The results reveal uneven territorial distribution, strong concentration in major cities outside the capital, and emerging sustainable models in peripheral areas. Comparative SDG scoring and typological interpretation demonstrate three recurring models—Sustainable Reuse, Nature-Oriented, and Innovative/Experimental—each associated with distinct spatial and environmental characteristics. A metropolitan benchmarking exercise further contextualizes the strongest sustainability profiles. Based on these findings, a conceptual sustainable coworking model is developed for a nationally significant spa and climatic resort, illustrating how coworking can address regional disparities, support green transition policies, and reinforce territorial cohesion. The article concludes by outlining research directions related to digitalization, circular construction, environmental performance indicators, and feasibility assessments for non-metropolitan coworking development. Full article

Agricultural materials frequently undergo fragmentation due to high-stress conditions during processing, storage, and transportation. Throughout these processes, the spatial arrangement and morphology of particles continuously evolve, rendering the breakage behaviour of particle groups particularly complex. Thus, an in-depth understanding of the fracture processes and breakage mechanisms within particle beds holds significant research value. This study systematically investigates the breakage behaviour of rice particle groups under confined compression through an integrated methodology combining experimental testing, X-ray CT imaging, and finite element modelling (FEM) based on the cohesive zone model (CZM). Results demonstrate that, at the granular assembly scale, external loads are transmitted through force chains and progressively attenuate. As compression proceeds, stress disseminates toward peripheral particle regions. At the individual particle level, particle breakage results from the intricate interaction between coordination number (CN) and localized contact stress, with tensile stress playing a predominant role in the fracture process. An increase in coordination number promotes a more uniform stress distribution and inhibits breakage, thereby exhibiting a “protective effect”. These findings provide valuable insights for the design and optimization of grain processing equipment, contributing to a deeper comprehension of particle breakage characteristics. Full article

Rainfall infiltration is one of the main factors inducing slope instability, while the spatial heterogeneity and uncertainty of soil parameters have profound impacts on slope response characteristics and stability evolution. Traditional deterministic analysis methods struggle to reveal the dynamic risk evolution process of the system under heavy rainfall. Therefore, this paper proposes an uncertainty analysis framework combining Karhunen–Loève Expansion (KLE) random field theory, Polynomial Chaos Kriging (PCK) surrogate modeling, and Monte Carlo simulation to efficiently quantify the probabilistic characteristics and spatial risks of rainfall-induced slope instability. First, for key strength parameters such as cohesion and internal friction angle, a two-dimensional random field with spatial correlation is constructed to realistically depict the regional variability of soil mechanical properties. Second, a PCK surrogate model optimized by the LARS algorithm is developed to achieve high-precision replacement of finite element calculation results. Then, large-scale Monte Carlo simulations are conducted based on the surrogate model to obtain the probability distribution characteristics of slope safety factors and potential instability areas at different times. The research results show that the slope enters the most unstable stage during the middle of rainfall (36–54 h), with severe system response fluctuations and highly concentrated instability risks. Deterministic analysis generally overestimates slope safety and ignores extreme responses in tail samples. The proposed method can effectively identify the multi-source uncertainty effects of slope systems, providing theoretical support and technical pathways for risk early warning, zoning design, and protection optimization of slope engineering during rainfall periods. Full article

Delamination in fibre-reinforced polymer composites is a critical failure mechanism that can ultimately lead to a catastrophic failure. To characterise in-plane shear delamination (Mode II), several test setups have been proposed in the literature, with the End-Loaded Split (ELS) test being the most suitable for applications that require stable crack propagation (ISO 15114). This manuscript focuses on studying Mode II fatigue delamination in unidirectional carbon fibre-reinforced laminates using the ELS configuration. Experimental tests with varying displacement ratios and different initial energy levels were conducted to capture a wide range of stable crack propagation scenarios. To complement these experimental efforts, a numerical model based on cohesive zone models (CZM) was implemented in Abaqus, utilising a user-defined material subroutine (UMAT). The numerical results closely align with the experimental data, validating the model’s predictive capabilities. This combined approach deepens the understanding of Mode II fatigue delamination and provides a strong framework for designing and analysing composite structures. Full article

The present work develops an explicit dynamic finite element model of soil–disc interaction for a notched harrow disc, aiming to quantify how APS coatings, soil type and disc–soil friction influence stresses in the disc and surrounding soil. The model reproduces a four-gang offset harrow operating at 7 km/h, 0.15 m working depth, with 18°disc angle and 15° tilt angle, and compares an uncoated steel disc with three APS-coated variants (P1 Metco 71NS, P2 Metco 136F, P3 Metco 45C-NS). Mechanical properties of the substrate and coatings are obtained from micro-indentation tests and introduced via a bilinear steel model and Johnson–Cook plasticity for the coatings, while disc–soil friction coefficients are calibrated from microscratch measurements. Soil behaviour is described using the AUTODYN Granular model for four representative agricultural soils, spanning sandy loam to saturated heavy clay. Results show that the uncoated disc develops von Mises stresses in the disc–soil contact region of ≈150–220 MPa, with intermediate-stiffness soils being most critical. APS coatings significantly alter both the level and distribution of stresses: P2, the stiffest ceramic, yields the highest stresses (≈421–448 MPa), P1 keeps stresses near the baseline while shielding the substrate through extended plastic zones, and P3 provides an intermediate, more uniformly distributed stress regime. Increasing disc–soil friction systematically amplifies von Mises stresses in the contact region, especially for P2. Overall, the calibrated explicit model captures the coupled influence of soil properties, coating stiffness and friction, and indicates that P1 is better suited for light-to-medium soils, P3 offers the most balanced response in medium-to-stiff soils, whereas P2 should be reserved for highly abrasive conditions and used with caution in cohesive soils. Full article

The permeability of cohesive zone plays an important role in the stable operation and production efficiency of blast furnace. Fluidity of the primary slag in the cohesive zone is an important factor affecting the permeability and is usually characterized by the so-called fluidity index. In order to describe the relationship between the viscosity and the fluidity index of the FeO-CaO-SiO₂ ternary slag system (similar to the primary slag) generated by sinter, the fluidity and viscosity of FeO-CaO-SiO₂ ternary slag system was studied in this paper. It includes testing the fluidity under different temperatures and different compositions, calculating the viscosity of FeO-CaO-SiO₂ ternary slag system through the solid–liquid coexistence-phase viscosity model, and coupling the relationship between fluidity index and viscosity. The results show the following: (1) For the FeO-CaO-SiO₂ ternary slag system, when the temperature is constant, the fluidity index of primary slag in non-three-phase region increases with the increase in w (FeO), while that in three-phase region decreases with the increase in w (FeO). (2) The Kondratiev model and the Batchelor model were jointly employed to calculate the primary slag viscosity in the cohesive zone. (3) In FeO-CaO-SiO₂ ternary slag system, there is an approximate power function correlation between the solid–liquid coexistence-phase viscosity and the fluidity index. The research content and results of this paper have a certain theoretical guiding value for further research on more complex cohesive zone slag system and enhanced blast furnace smelting. Full article

To investigate the performance of horizontally reinforced composite foundations in resisting surface rupture of normal faults, this study designed and conducted a series of physical model tests. A systematic comparative analysis was performed on the fracture resistance of sites with three-layer sand, five-layer sand, and three-layer clay geogrid horizontally reinforced composite foundations under 70° normal fault dislocation. The results indicate that significant changes in earth pressure serve as a precursor indicator of fault rupture, and their evolution process reveals the internal energy accumulation and release mechanism. Increasing the number of geogrid layers significantly enhances the lateral confinement of the foundation, resulting in a narrower macro-rupture zone located farther from the structure in sand sites, and promotes the formation of a step-fault scarp deformation mode at the surface, which is more conducive to structural safety. Under identical reinforcement conditions, the clay site exhibited comprehensively superior fracture resistance compared to the sand site due to the soil cohesion and stronger interfacial interaction with the geogrids, manifested as more significant deviation of the rupture path, and lower microseismic accelerations and structural strains transmitted to the building. Comprehensive analysis confirms that employing geogrid-reinforced composite foundations can effectively guide the surface rupture path and improve the deformation pattern, representing an effective engineering measure for mitigating disaster risk for buildings spanning active faults. Full article

A multiscale model is developed to investigate the mechanical behavior and failure of in situ particle reinforced titanium matrix composites (PTMCs). Through the microstructural observation of the heterogeneous microscopic and mesoscopic structures in the in situ TiB/Ti55531 composites, multiscale heterogeneous models coupled to the finite element method are employed to simulate the mechanical behaviors and failures. In the atomic scale, molecular dynamics (MD) simulations are applied to determine the traction-separation (T-S) responses of the cohesive zone model (CZM) describing the Ti/TiB interface. Then, the mesoscale representative volume element (RVE) model with heterogeneous structure, including the Ti55531 matrix, the TiB particles, and their interfaces represented by the parameterized CZM, is established. The volume fraction and distribution morphology of TiB particles result from the microstructural analysis of titanium matrix composites. The simulation results show that the Young’s modulus, tensile strength and elongation of multiscale are in excellent agreement with experimental results. The stress transfer, damage evolution and fracture behavior of the TiB particles in the composites are also analyzed using this multiscale approach. Full article

In practical applications, steel storage racks include a wide range of beam-to-column connections (BCCs), which have a significant impact on their structural stability, particularly under various loading conditions. This systematic review focuses on the application of the finite element method (FEM) as a complementary tool to evaluate the mechanical behavior of these connections. Key parameters that influence connection performance include the connector’s class and hook configuration, column thickness, beam height and weld position on the connector. Although the Eurocode 3 standard provides design guidelines for connections, experimental testing remains the most reliable method due to the complexity of semi-rigid connections, particularly in the context of pallet racks. Validated FEM analysis emerges as a dependable and cost-effective alternative to experiments, enabling more detailed parametric studies and improving the prediction of structural response. This review focuses on the advantages of FEM integration into design workflows via quantitative synthesis, while also emphasizing the role of contact formulations in modeling accuracy. To establish FEM as an independent predictive tool for the design and optimization of steel storage racks, future research should focus on cohesive zone modeling, ductile damage criteria, advanced contact strategies and additional machine learning (ML) techniques. Full article

Adhesively bonded joints are extensively utilized in structural assemblies involving metals, composites, and hybrid materials due to their favorable mechanical and manufacturing characteristics. However, their performance under high-velocity impacts—common in aerospace, automotive, and defense applications—remains insufficiently understood. This work investigates the high-velocity performance and subsequent tensile response of adhesively bonded single-lap joints (SLJs) by integrating experimental testing with numerical simulations. High-velocity impacts were applied to SLJs fabricated from 4 mm aluminum adherends with overlap lengths of 15 mm and 25 mm, using a 1.25 g projectile at 288 m/s, followed by quasi-static tensile assessment. Experimental findings revealed substantial degradation in tensile strength for the 15 mm overlap configuration (reduced the load-bearing capacity by about 33% (from ~12 kN to ~8 kN)), while the 25 mm overlap retained its structural integrity. Finite element simulations conducted in ABAQUS 2021 employed the Johnson–Cook constitutive model for the adherends and a cohesive zone model for the adhesive layer, successfully replicating damage evolution and stress distributions. The results highlight the critical role of geometric parameters—particularly overlap length and adherend thickness—in determining the damage tolerance and residual load-bearing capacity of SLJs subjected to high-velocity impacts. These insights contribute to the development of more robust bonded joint designs for impact-prone environments. Full article

The mechanical behavior of fiber-reinforced concrete largely depends on the fiber morphology, geometry, and distribution. However, current numerical models do not take into account the stochastic properties of fibers with a spatial distribution, which limits their prediction accuracy and overlooks the critical impact of microstructural effects on macroscopic properties. To address this issue, a comprehensive numerical framework is developed using the Concrete Damage Plasticity (CDP) model for the concrete matrix, an elastoplastic model for steel fibers, and with cohesive zone elements applied to describe fiber–matrix interfacial debonding. Random fiber configurations are generated to represent statistical variability, and their effects on the elastic modulus, compressive strength, and tensile strength are systematically examined. A wide range of fiber parameters—including dimensions, volume fractions, stochastic orientation, and spatial distribution—is investigated to reveal microstructure-dependent mechanical behavior at the macroscale. The results highlight the critical roles of the fiber volume fraction and orientation control in enhancing mechanical behavior and provide practical guidelines for optimizing fiber incorporation strategies in concrete design. Full article

Externally bonded carbon-fiber-reinforced polymer (CFRP) can increase the flexural capacity of steel beams, but the benefit is often limited by the performance of the adhesive interface. This study develops and validates a three-dimensional finite-element model (FEM) with an explicit cohesive-zone representation of the adhesive layer. It reproduced benchmark four-point bending tests in terms of peak load, corresponding mid-span deflection, and the transition from end/intermediate debonding to laminate rupture. A one-factor-at-a-time parametric analysis is carried out to examine the influence of (i) member geometry (beam depth; flange and web thickness), (ii) CFRP configuration (bonded length; laminate thickness), and (iii) bond quality (cohesive normal strength). Within the ranges studied, cohesive strength and bonded length are the primary variables controlling both capacity and failure mode: strengths below about 25 MPa and short plates lead to debonding-governed response. Increasing strength to around 27 MPa and bonded length to 650–700 mm delays debonding, promotes CFRP rupture, and produces the largest incremental gains in peak load, while further increases in length give smaller additional gains. Increasing laminate thickness and steel depth or flange/web thickness always raises peak load, but under baseline bond conditions failure remains debonding and the added material is only partially mobilized. When cohesive strength is increased above the threshold, additional CFRP thickness becomes more effective. A linear regression model is fitted to the FEM dataset to express peak load as a function of bonded length, cohesive strength, laminate thickness, and steel dimensions, and is complemented by a failure-mode map and a cost–capacity chart based on material quantities. Together, these results provide quantitative trends and simple relations that can support preliminary design of CFRP-strengthened steel beams for similar configurations. Full article