Search Results (46)

Surface roughening is a common defect in plastic deformation processing, directly affecting product surface quality and service performance. This study investigates the mechanisms of surface roughness evolution during plastic deformation by considering both intrinsic and extrinsic factors. A macro–meso-scale modelling framework is developed by coupling crystal plasticity finite element modelling, fluid–solid interaction modelling, and macro–meso boundary conditions. The crystal plasticity model incorporates a constitutive model based on crystal plasticity theory, a Voronoi-based geometric model, and a real rough-surface topography model to capture non-uniform grain-scale plastic deformation. Fluid–solid interaction modelling is introduced to analyze the influence of liquid lubricant on the deforming solid material. Boundary interpolation and continuous displacement theories are then used to transfer macro-scale boundary constraints to the meso scale. The proposed framework is numerically implemented and applied to the aluminum alloy tube drawing process. The effects of intrinsic factors, including grain size, grain orientation, and initial surface roughness, and extrinsic factors, including deformation path, strain rate, and lubrication condition, are systematically examined. From a practical point of view, effective strategies to improve surface quality are by reducing grain size, lowering initial surface roughness, decreasing the strain rate and using low-viscosity lubricants. Full article

This study presents a multiscale numerical simulation of the behavior of crack growth in the heat-affected zone (HAZ) of AH36 marine steel welded joints under fatigue loading from the micro-scale to the macro-scale. The MD-FEM method and the multiscale coupling-optimized XFEM method were used to simulate fatigue crack propagation from micro-scale to meso-scale and from meso-scale to macro-scale. A total of 10,900,788 tension–tension fatigue cycles was realized. Information across different scales was transferred via boundary displacement transfer, crack morphology equivalence, and tip tracking. Building upon our previous investigation into fatigue crack growth behavior at the micro-scale, in which crack extension was limited to 469 Å, the present study encompasses the complete process of fatigue cracking from micro-scale initiation to macro-scale instability. Furthermore, the crack tip morphology and propagation pathways obtained from micro-scale molecular dynamics simulations are employed to optimize and calibrate the corresponding XFEM simulations at both the meso- and macro-scales. Results demonstrate that the phenomenon of interconnection between voids and the main crack near the crack tip has a significant influence on the crack propagation rate and path. During cycling, the propagation rate of the main crack increases significantly during its interconnection with voids, whereas crack propagation is significantly hindered when the interconnection is completed or when voids undergo self-closure. Furthermore, both theoretical simulations and experiments revealed the occurrence of crack propagation instability at the meso-scale. The present examination of the entire fatigue crack propagation process indicates that the MD-FEM method and the multiscale coupling optimized XFEM method in this study are fundamentally accurate in representing both the crack propagation process and the crack tip morphology. The results obtained in this paper can serve as a reasonable prediction of fatigue damage mechanisms in the HAZ of AH36 marine steel welded joints. Full article

Accurately predicting the mechanical response and failure of composite–metal hybrid bolted joints under thermo-mechanical coupled loads remains a critical challenge in aerospace engineering. This paper develops a temperature-dependent multi-scale progressive failure analysis model based on micromechanical failure theory. A hexagonal representative volume element (RVE) incorporating fibers, matrix and interphase is constructed, with a stress amplification factor enabling macro–meso stress–strain transformation. Dimensionless temperature corrections are applied to resin and interphase mechanical properties, and temperature-influenced mesoscopic failure criteria with corresponding stiffness degradation schemes are proposed. The nonlinear progressive damage simulation is implemented via the ABAQUS/UMAT subroutine. Static tensile tests on AC531/CCF800H composite-7075 aluminum alloy three-bolt double-shear joints are conducted at −70 °C, 20 °C and 120 °C. The results show excellent agreement between the simulations and experiments, with ultimate load errors < 5%. Low temperature increases load capacity by 3.91% via resin hardening and enhanced interfacial bonding, while high temperature reduces it by 9.07% due to resin softening. Failure modes shift from end-hole tensile fracture (−70 °C, 20 °C) to full-hole bearing failure (120 °C), governed by altered bolt load distribution and damage evolution paths. The proposed model provides reliable support for thermo-mechanical design and strength verification of aerospace composite structures. Full article

An explicit dynamic framework based on the Nonlocal Macro-Meso-scale Consistent Damage (NMMD) model is proposed to simulate complex multiple-crack evolution in quasi-brittle materials subjected to blast loading. Three numerical examples—a single-edge-notched half-plate, a thick ring, and a hollow mortar cylinder containing a small borehole—are analyzed. The results show that crack initiation, propagation, branching, and coalescence can be naturally captured by the proposed framework without remeshing. Reliable predictions are obtained only when sufficient mesh resolution is used to resolve nonlocal interactions and the time step satisfies the explicit stability criterion. Comparisons indicate that fewer but more dominant crack paths are predicted by the model, suggesting a conservative tendency in estimating the number of fragments. Crack-path selection is significantly influenced by material heterogeneity, which enables secondary cracks to evolve into dominant crack paths. Crack multiplication and network connectivity are promoted by increased blast pressure, whereas crack complexity and spatial extent are reduced by higher damping coefficients. Full article

Heap bioleaching is widely used to extract copper from low-grade sulfide ores thanks to its operational simplicity, low cost, and environmental sustainability. However, current control strategies rely primarily on single-factor optimization and often overlook the synergistic interactions of multiple key parameters, such as ore particle size, pore structure, pH, temperature, microbial activity, and oxygen transfer efficiency. As a result, issues such as low recovery rates, extended leaching periods, and high operational costs persist. Moreover, the “gray-box” nature of heap systems impedes real-time monitoring of internal physical, chemical, and biological processes. In addition, empirical multi-parameter optimization is time-consuming and inadequate for capturing complex interdependencies. This review was conducted to systematically examine the key factors influencing heap bioleaching efficiency and critically evaluate recent advances in numerical simulation and intelligent control strategies. As a result, we identified a major research gap: the existing models—including microscale shrinking core models (SCMs), mesoscale pore-network models based on CT reconstruction, and macroscale continuum models—have inherent limitations. SCMs assume idealized spherical particles with uniform mineral distribution while neglecting pore structure evolution and biofilm dynamics. Mesoscale models offer detailed pore characterization but lack robust multi-physics coupling (thermal–hydro–mechanical–chemical–biological, or THMCB). Macroscale models rely on homogenization assumptions that oversimplify spatial heterogeneity and temporal variations in permeability. This analysis covers the relevant literature from 1985 to 2025, with a focus on three methodological scales (micro, meso, and macro) and their integration with machine learning approaches. A notable finding is that hybrid neural network models (e.g., BP and RBF architectures) outperform purely physics-based models in predicting leaching kinetics under varying operational conditions. However, their accuracy depends heavily on high-quality field data—a limitation rarely addressed in prior reviews. By clearly delineating these model-specific limitations and scale-dependent trade-offs, this review makes two unique contributions: a structured framework for selecting and coupling numerical methods according to process requirements and a roadmap for integrating artificial neural networks with multi-physics simulations to achieve real-time intelligent control of heap bioleaching. The findings offer both theoretical guidance and practical references for optimizing the processing of low-grade copper sulfide ores. Full article

In resin impregnation processes for composite manufacturing, proper infusion of the preform is essential to achieve optimal component quality. Manufacturing-induced defects, such as voids, are commonly present in the final product; however, minimizing their occurrence is critical to preserving the component’s mechanical properties. This study aims to provide a predictive tool for defect analysis and composite manufacturing process optimization. A finite element-based multi-scale framework is developed to simulate resin impregnation, coupling macro-scale multiphase flow analysis with meso-scale modeling of unsaturated porous media. The model is verified against commercial software and used to perform a parametric study. Results demonstrate the framework capability to predict filling times, resin front progression, and defect formation, providing insights onto the correlation between material behavior and flow kinetics. The proposed simulation tool enables process optimization and defect minimization, offering a flexible and efficient alternative to heuristic process setting. Full article

Quantitative characterization of internal stress fields in fracture-dominated geological materials remains a significant challenge due to the limitations of conventional measurement techniques. This study presents the first quantitative full-field stress analysis of slightly sandy dolomite (Level I sandification) using an enhanced CT-3D printing–photoelasticity workflow. Five transparent physical models were fabricated from CT-scanned dolomite specimens to replicate the natural fracture-matrix structure and tested under diametrical compression (800 N) using ten-step phase-shifting digital photoelasticity. To overcome the severe optical noise generated by dense fracture networks, a robust phase unwrapping procedure (CPULSI) was incorporated into the data processing pipeline, enabling continuous stress parameter retrieval where conventional unwrapping methods fail. The recovered full-field principal stress-difference maps reveal that the internal stress field is dominated by meso-scale fracture geometry: Stress concentrations localize at fracture tips and narrow intact matrix bridges, reaching 3–5 times the far-field stress, while the macro-scale loading pattern becomes progressively obscured as fracture complexity increases across the five models. Quantitative validation against CT-based finite element simulations (RFPA-3D) demonstrates good agreement in intact matrix regions, with mean relative errors of 9–18%. These results provide new experimental evidence for the meso-scale stress distribution mechanisms governing the mechanical behavior of sandy dolomite—a geomaterial of significant engineering relevance in Southwest China—and establish a validated experimental pathway for investigating stress fields in other fracture-dominated geomaterials. Full article

The development of green building materials and high-performance concrete has promoted the use of manufactured sand (MS) in self-compacting concrete (SCC). To investigate the effect of MS lithology on concrete performance, this study prepared C40-SCC using basalt, limestone, and granite manufactured sand, as well as river sand. Workability and mechanical properties were measured via macro-scale tests. A meso-scale random aggregate model, including mortar, aggregate, and interfacial transition zone (ITZ), was established to simulate uniaxial compression. The macro-test results indicate that workability decreases in the order of river sand, granite, limestone, and basalt, while mechanical strength decreases in the order of granite, limestone, basalt, and river sand. The meso-scale simulation reveals that damage initiates at the ITZ and extends into mortar. The simulated stress–strain curves match the experimental data in the ascending branch, with peak stress errors between 1.1% and 6.9%. The failure modes also align with experimental observations. The consistency between the simulation and experimental results verifies the reliability of the meso-scale model. By combining macro-experiments and meso-simulation, this study compares concrete performance and explains the differences from the perspective of damage evolution. The results indicate that MS lithology affects interfacial properties and damage development, thereby determining macro-mechanical behavior. This research provides a theoretical basis for the appropriate selection of MS in SCC. Full article

Polypropylene fibers provide an innovative solution for enhancing the crack resistance of tunnel lining segments. However, existing macro-models obscure the distinct effects of fibers on the mortar and ITZ, while explicit meso-modeling remains computationally prohibitive. This study develops a multi-scale modeling framework to investigate PFRC segment fracture under bending. The framework integrates a 3D meso-scale module for calibrating fracture-related material properties, a 3D macro-scale module for predicting global displacements, and a 2D meso-scale module for resolving local fracture processes. A full-scale bending test was performed to validate the framework and to examine the effects of fiber content at both scales. Both the full-scale test and numerical simulations show that the segment response exhibits three stages: elastic, damage development, and cracking at the design load. Numerical simulations further reveal that an optimal fiber content of 0.4% reduces the vertical displacement at the load point by 9.8% and the horizontal displacement at the edge point by 2.9% relative to the fiber-free case. Meso-scale simulations show that 0.4% fibers decrease the bottom crack width from 0.0868 to 0.0770 mm (−11.29%) and limit internal crack connectivity. Although fibers may locally promote ITZ cracking due to reduced mortar–aggregate bonding, a strengthened mortar matrix suppresses crack penetration and connected crack networks. A pronounced high-damage peak in the ITZ near the failure threshold confirms the ITZ as the governing weak link; therefore, further improvements may require ITZ-strengthening strategies. Full article

Corrosion damage is a vital factor that causes strength weakening or even failure of offshore derrick. To study the influence of local corrosion on the derrick, a regular spherical pitting model was adopted to analyze the evolution mode of pitting corrosion damage and the corresponding pitting corrosion damage models with different morphology. The connection technique for the across-scale interface was discussed, a method for constructing multi-scale models of derrick with pitting corrosion damage was proposed. The pitting damage simulation and ultimate bearing capacity analysis are carried out for an offshore derrick in service. The results show that the interaction between meso-scale pitting corrosion damage and macro-scale structure can be effectively considered, the stress distribution of the pitting corrosion damage and its effect on stress concentration coefficient can be obtained, and the influence of local random pitting distribution location, style, and density on the ultimate bearing capacity can be determined. In addition, the ultimate bearing capacity can be predicted. It provides a new idea for bearing capacity prediction and safety assessment of large steel frame structures in service with local damage. Full article

Commercial pedestrian streets serve as vital urban public spaces for residents’ daily leisure and social interaction. However, amid rapid urbanization, many such streets exhibit a tendency towards homogenization, raising practical concerns about the capacity of these environments to consistently deliver rich psychological restorative experiences. Existing research on the restorativeness of urban streets has primarily focused on macro or meso scales, leaving the restorative impacts of micro-scale elements, such as public art within streetscapes, insufficiently explored. To address this research gap, this study takes Tanhualin Historic Cultural Street in Wuhan as its research setting. Employing a streetscape image simulation experiment combined with an online questionnaire survey, it assesses the influence of public art on the perceived restorativeness of commercial pedestrian streets. The results indicate that public art substantially enhances the perceived restorative capacity of commercial pedestrian streets. Further analysis reveals clear independent main effects of both the form and theme of public art on perceived restorativeness, with the influence of form being more pronounced, and no statistically significant interaction effect between the two. These findings offer novel insights for enhancing the restorative potential of commercial pedestrian streets and provide design recommendations for future urban street renewal and sustainable development. Full article

Heat exchangers–adsorbers (HEX-As) are emerging as innovative technologies in many applications (CO₂ capture, gas purification and separation, thermal energy storage, etc). This review addresses the theoretical challenges within computational fluid dynamics (CFD) in modeling and simulating coupled heat and mass transfer within gas separation by using adsorbing porous media in fixed beds. Conservation equations of mass, momentum, and energy from different studies (1D, 2D-CFD, and 3D-CFD models) are presented and discussed with an emphasis on their ability to predict the complex multi-physics multi-scale heat and mass transfer phenomena involved, such as the adsorption kinematics, the thermal front propagation, and the multi-component fluid flow dynamics inside the beds. For the fist time, we show that mathematical theoretical modeling in CFD has been differently developed and applied by many authors in the literature in order to model the same physical phenomena. This sheds light on the present challenges and bottlenecks in theoretical and computational fluid dynamics when it comes to complex coupled heat and mass transfer in multi-component gas dynamics in porous media. This review make it easier for readers to understand the different models that exist in the literature for modeling and simulating HEX-As. It also opens questions on how accurately one can model multi-functional heat exchangers–adsorbers using CFD, e.g., physics multi-scale extrapolation from nano- to meso- and then to macro-scale behavior. Full article

Supercritical carbon dioxide (SC-CO₂) jetting has emerged as a promising technique for rock fracturing due to its superior physical properties such as low viscosity, high diffusivity, and zero surface tension. However, the complex interaction mechanisms between SC-CO₂ jets and heterogeneous rock media remain inadequately understood. In this study, a coupled Smooth Particle Hydrodynamics–Finite Element Method (SPH-FEM) framework is established to simulate the dynamic fracturing process of rocks under SC-CO₂ jet impact. The Riedel–Hiermaier–Thoma (RHT) constitutive model is incorporated to describe the nonlinear damage evolution of brittle rocks, and key material parameters are calibrated via sensitivity analysis and SHPB experimental validation. A series of numerical simulations are performed to investigate the effects of jet standoff distance, jet velocity, and rock lithology (marble, granite, red sandstone) on fracturing efficiency. Damage area, damage volume, and a novel metric—block size distribution—are employed to quantify the fracturing quality from both macro and meso scales. The results indicate that SC-CO₂ jets outperform conventional water jets in creating more extensive and homogeneous fracture networks. An optimal standoff distance of 1–2 cm and a velocity threshold of 0.2 cm/μs are identified for maximum fracturing efficiency in marble. Furthermore, smaller block sizes are achieved under higher velocities, indicating a more complete and efficient rock fragmentation process. This study provides a comprehensive numerical insight into SC-CO₂ jet-induced rock failure and offers theoretical guidance for optimizing green and water-free rock fracturing techniques in complex geological environments. Full article

Resettlement communities in Qinghai are located in cold, high-altitude regions with dry climates and strong solar radiation. Although not extremely cold, the moderate heating demand aligns well with high solar availability, making passive design highly effective for reducing energy use. This study investigates solar-optimized spatial configurations that enhance passive energy performance while addressing functional settlement needs. Through parametric modeling and climate-responsive simulations, four key spatial parameters are examined: building spacing, courtyard depth, density, and volumetric ratio. The findings highlight the dominant role of front–rear spacing in solar access, with optimal values at 3–4 m for single-story and 5–10 m for two-story buildings, balancing radiation gain and land use efficiency. Courtyard depths under 2.7 m significantly limit south façade exposure due to shading from the opposite courtyard wall under low-angle winter sun. This reduction results in the south façade attaining only 55.7–79.6% of the solar radiation acquisition by an unobstructed south façade (the baseline). Meanwhile, clustered orientations reduce inter-building shading losses by 38–42% compared to dispersed layouts. A three-tiered design framework is proposed: (1) macro-scale solar orientation zoning, (2) meso-scale spacing tailored to building height, and (3) micro-scale courtyard modulation for low-angle winter radiation. Together, these strategies provide practical, scalable guidelines for energy-efficient, climate-responsive settlement design in the alpine regions of Qinghai. Full article

The nonlocal macro–meso-scale damage (NMMD) model, implemented in the framework of the finite element method, has been demonstrated to be a promising numerical approach in simulating crack initiation and propagation with reliable efficacy and high accuracy. In this study, the NMMD model was further enhanced by employing an identical degradation mechanism for both the tensile and shear components of shear stiffness, thereby overcoming the limitation of equal degradation in shear and tensile stiffness inherent in the original model. Additionally, a more refined and physically sound seepage evolution function was introduced to characterize the variation in permeability in porous media with geometric damage, leading to the development of an improved NMMD model suitable for simulating coupled seepage–stress problems. The reliability of the enhanced NMMD model was verified by the semi-analytical solutions of the classical KGD problem. Finally, based on the modified NMMD model, the effects of preset fracture spacing and natural voids on hydraulic fracture propagation were investigated. Full article