Search Results (1,262)

This work proposes a novel design configuration for an elasto-poro-hydrodynamic damper (EPHD damper) that consists of an imbibed, soft, elastic, porous material enclosed by a rubber membrane. The core innovation lies in the device’s ability to collect and re-imbibe expelled fluid during decompression, ensuring potential functionality and durability across repetitive loading cycles. Damping is achieved through the synergy of three mechanisms: friction of the membrane and of the piston with solid boundaries, squeeze flow inside the porous layer, and compression of the poro-elastic structure. The EPHD damper’s behavior was evaluated both theoretically and experimentally through quasi-static, low-speed compression tests, with dynamic evaluation being reserved for future work. A numerical model successfully validated stress-deformation behavior against experimental data, with a simplified analytical model providing a good approximation. The study also identifies that the piston–membrane friction coefficient significantly influences the EPHD damper’s performance. These findings provide a valuable framework for optimizing the design and expanding its potential application to repetitive damping systems. Full article

The present work numerically investigates the mechanical behavior of six 6061-T6 aluminum profiles during roll bending, considering, in two specific cases, the application of the process in different bending directions (vertical and horizontal), totaling eight cases analyzed, with emphasis on the influence of multiple bending radii. Notably, two of the profiles are characterized by high geometric complexity, making their analysis particularly relevant within the scope of this study. Using the finite element method in ANSYS^® (version 2022 R2) (SOLID187 element), the study expands the previously validated model to a broader range of geometries and includes an additional validation and verification stage. The results reveal: (i) an inverse relationship between bending radius and von Mises stress, with critical values close to the material’s strength limit at smaller radii; (ii) characteristic displacement patterns for each profile, quantified through specific curve fittings; and (iii) a systematic comparison among the six profiles, highlighting stress concentrations and deformations differentiated by geometry. The simulations provide criteria for predicting forming defects and optimizing process parameters, expanding the database for industrial designs with multiple extruded profiles. Full article

The hot deformation behavior of a Mg-9.2Er-4.9Sm-2.2Zn-0.6Zr (wt.%) alloy, with emphasis on the role of grain size and long-period stacking-ordered (LPSO) phases, was examined via comparison experiments. Two types of samples were obtained through distinct heat treatment schedules: sample A had a smaller grain size, featuring block-shaped LPSO phases at grain boundaries and lamellar LPSO phases within grains, while sample B had a larger grain size and few LPSO phases. The hot deformation behavior was characterized by the true stress–strain curve within the processing window of 300–450 °C and 0.001–1 s⁻¹. The block-shaped LPSO phases contributed more significantly to strain hardening, leading to elevated flow stress in sample A, particularly under low-temperature and high-strain-rate conditions. Through the particle-stimulated nucleation (PSN) mechanism, block-shaped LPSO phases demonstrated greater efficiency in promoting Dynamic recrystallization (DRX) compared to lamellar LPSO phases; additionally, the synergistic effect between LPSO phases and grain boundary density further improved DRX efficiency. During hot deformation, dynamic precipitation of both block-shaped and lamellar LPSO phases occurred. The formation of block-shaped phases required a longer duration than that of lamellar ones. The presence of the LPSO kink exerted an influence on DRX, while a significant angle kink can promote DRX. Full article

Wellbore stability is a crucial factor affecting the safe exploitation of offshore natural gas hydrates. As a sustainable energy source, natural gas hydrate has significant reserves, high energy density, and low environmental impact, making it an important candidate for alternative energy. Although research on the stability of screen pipes during horizontal-well hydrate production is currently limited, its importance in sustainable energy extraction is growing. This study therefore considers the effects of hydrate phase change, gas–water seepage, energy and mass exchange, reservoir deformation, and screen pipe influence and develops a coupled thermal–fluid–solid–chemical field model for horizontal-well natural gas hydrate production. The model results were validated using experimental data and standard test cases from the literature. The results obtained by applying this model in COMSOL Multiphysics 6.1 showed that the errors in all simulations were less than 2%, with errors of 12% and 6% observed at effective stresses of 0.5 MPa and 3 MPa, respectively. The simulation results indicate that the presence of the screen pipe in the hydrate reservoir exerts little effect on the decomposition of gas hydrates, but it effectively mitigates stress concentration in the near-wellbore region, redistributing the effective stress and significantly reducing the instability risk of the hydrate reservoir. Furthermore, the distribution of mechanical parameters around the screen pipe is uneven, with maximum values of equivalent Mises stress, volumetric strain, and displacement generally occurring on the inner side of the screen pipe in the horizontal crustal stress direction, making plastic instability most likely to occur in this area. With other basic parameters held constant, the maximum equivalent Mises stress and the instability area within the screen increase with the rise in the production pressure drop and wellbore size, and the decrease in screen pipe thickness. The results of this study lay the foundation for wellbore instability control in the production of offshore natural gas hydrates via depressurization. The study provides new insights into sustainable energy extraction, as improving wellbore stability during the extraction process can enhance resource utilization, reduce environmental impact, and promote sustainable development in energy exploitation. Full article

Thermoset fibre-reinforced composites are widely used in high-end industries, but a growing demand for more sustainable and recyclable alternatives conveyed the research efforts towards thermoplastics. To expand their usage, new approaches to their manufacture and mechanical performance must be tackled and tailored to each engineering challenge. The present study designed, manufactured and tested advanced multi-layer laminated composites of thermoplastic polypropylene prepreg reinforced with continuous woven fibreglass with interlayer toughening through thermoplastic polyurethane elastomer (TPU) layers manufactured by fused filament fabrication. The manufacturing process was iteratively optimized, resulting in successful adhesion between layers. Three composite configurations were produced: baseline glass fibre polypropylene (GFPP) prepreg and two multi-layer composites, with solid and honeycomb structured TPU layers. Thermal and mechanical analyses were conducted with both the polyurethane elastomer and the manufactured laminates. Tensile testing was conducted on additively manufactured polyurethane elastomer specimens, while laminated composites were tested in three-point bending. The results demonstrated the potential of the developed laminates. TPU multi-layer laminates exhibit higher thermal stability compared to the baseline GFPP prepreg-based composites. The addition of elastomeric layers decreases the flexural modulus but increases the ability to sustain plastic deformation. Multi-layer laminate composites presenting honeycomb TPU layers exhibit improved geometric and mechanical consistency, lower delamination and fibre breakage, and a high elastic recoverability after testing. Full article

To address the challenge of asymmetric deformation and failure in the surrounding rock of main roadways within extra-thick coal seams caused by level differences under intense mining disturbance, this study systematically analyzed the evolution laws of principal stress fields, deviatoric stress fields, and their impact on surrounding rock stability in upper-, middle-, and lower-level roadways within a 20 m extra-thick coal seam during mining retreat. The analysis employed numerical simulation, similarity simulation, and field monitoring. Key findings include the following: ① As the working face advances, the principal stress vector lines deflect following a bias-unloading pattern, while the peak value of the deviatoric stress field (PVDSF) exhibits asymmetric bias-loading characteristics. The lower-layer roadway emerges as the primary load-bearing layer controlling surrounding rock stability. ② The evolution trend of the maximum principal stress vector orientation is consistent across different layers. The deflection trajectory manifests as “the deflection of the goaf side → the near layer orientation → the deflection of the solid coal side”. ③ The deviatoric stress peak zones (DSPZs) at all layers exhibit a characteristic “three-stage” evolution. The deviatoric loading pattern for the lower-layer roadway surrounding rock is the following: initial state double peak region crescent-shaped non-layer distribution type → the range of the bimodal region and the extreme value increased simultaneously, distributed in a non-layer manner → the asymmetrical distribution type of steep drop in the peak area of non-mining deviator stress. ④ The junctions between the mining-side rib and floor and the non-mining-side rib and roof were identified as critical control zones. An innovative zonal asymmetric directional anchoring control technology, “anchor cable foundation support + concrete floor + asymmetric reinforcing anchor cable support”, along with a “One Directional Penetration and Three Synergies” control methodology, was proposed. Field monitoring confirmed the significant effectiveness of the optimized support system. Full article

Timely and reliable surface deformation monitoring is critical for hazard prevention and resource management in mining areas. However, traditional Time-Series Interferometric (TSI) Synthetic Aperture Radar techniques often suffer from low coherent point density in mining environments, limiting their effectiveness. To overcome this limitation, we propose an adaptive Polarimetric TSI (PolTSI) method that exploits dual-polarization Sentinel-1 data to achieve more reliable deformation monitoring in complex mining terrains. The method employs a dual-strategy optimization: amplitude dispersion–based optimization for Permanent Scatterer (PS) pixels and minimum mean square error (MMSE)-based polarimetric filtering followed by coherence maximization for Distributed Scatterer (DS) pixels. Experimental results from an open-pit mining area demonstrate that the proposed approach significantly improves phase quality and spatial coverage. In particular, the number of coherent monitoring points increased from 31,183 with conventional TSI to 465,328 using the proposed approach, corresponding to a 1392% improvement. This substantial enhancement confirms the method’s robustness in extracting deformation signals from low-coherence, heterogeneous mining surfaces. As one of the few studies to apply Polarimetric InSAR (Pol-InSAR) in active mining regions, our work demonstrates the underexplored potential of dual-pol SAR data for improving both the spatial density and reliability of time-series deformation mapping. The results provide a solid technical foundation for large-scale, high-precision surface monitoring in complex mining environments. Full article

The measurement accuracy and equipment stability of superposition-type force sensors are primarily influenced by the layout and number of individual force sensors. Analyzing this impact effect through experimental testing for each configuration would consume significant manpower, material resources, and financial costs. To efficiently analyze the influence of the number of paralleled individual sensors and their layout within a superposition-type force measurement instrument on overall device stability and force measurement accuracy, this paper employs SolidWorks to establish models of force instruments based on common superposition schemes. Subsequently, ANSYS is utilized to perform finite element analysis on models of different schemes, obtaining corresponding data on total deformation, stress, and simulated force values. The analysis results indicate that a relatively sparse sensor layout with symmetric arrangement around the center point of the base plate enhances overall stability, and the force measurement error can be controlled within several ten-thousandths. Furthermore, the more stable and higher-accuracy schemes identified through simulation analysis were compared with practical experimental results to analyze theoretical versus actual errors. The test results showed that when the three single force sensors are placed in a “Pin font” shape, the sum of the forces measured by each individual sensor differs from the sum of the forces measured by the superimposed sensors by only a few ten-thousandths, which is within the acceptable range. Full article

Composite breakwater is a commonly employed structure for coastal and harbor protection. However, strong hydrodynamic impact can lead to failure and instability of these protective structures. In this study, a two-dimensional fluid-porous-solid coupling model is developed to investigate the stability of composite breakwaters. The fluid-porous model is based on the Volume-Averaged Reynolds-Averaged Navier-Stokes equations, in which the nonlinear Forchheimer equations are added to describe the porous layer. The solid model employs the Nodal-based Discontinuous Deformation Analysis (NDDA) method to analyze the displacement of the caisson. NDDA is a nodal-based method that couples FEM and DDA to improve non-linear processes. This proposed coupled model permits the examination of the influence of the thickness and porosity of the porous layer on maximum impacting wave height (${\mathrm{IWH}}_{\max }$) and the turbulent kinetic energy (TKE) generation. The results show that high porosity values lead to the dissipation of TKE and reduce the ${\mathrm{IWH}}_{\max }$. However, the reduction in the ${\mathrm{IWH}}_{\max }$ is not monotonic with increasing porous layer thickness. We observed that ${\mathrm{IWH}}_{\max }$ reaches an optimum value as the porous layer thickness continues to increase. These results can contribute to improve the design of composite breakwaters. Full article

This work aimed to address the severe deformation and uncontrollable instability of surrounding rocks in gob-side roadways of ultra-thick coal seams under intense mining disturbances. Theoretical analysis, numerical simulation, and field practice were used to investigate the reasonable width of deteriorated coal pillars and surrounding rock control technology. The following items were clarified, including the structural characteristics of the overlying strata, the fracture location of main roof, and the stress, failure, and deformation patterns of surrounding rocks based on coal pillar width. In terms of the load-bearing characteristics of coal pillars, the reasonable width of deteriorated coal pillars in roadways was determined. According to the differential deformation characteristics of roadway roof and sides, an adaptive and targeted asymmetric control scheme was proposed for surrounding rocks. Key strata above the ultra-thick coal seam working face formed a structure of low-level cantilever beam and high-level articulated rock beam. The fracture position of the main roof cantilever beam was located 15.4 m from the coal wall of the goaf. When the pillar width reached 8 m during roadway excavation, the internal stress exceeded the original rock stress. The lateral deterioration range of the coal seam extended to 25 m from the coal wall after mining the upper working face. The protective coal pillars within the reasonable width range were all in a fully plastic failure state. The plastic-bearing zone within the deteriorated coal pillar occupied a high proportion when the coal pillar width ranged from 8 to 10 m, demonstrating convenient load-bearing capacity. Considering economic and safety factors, the reasonable width for deteriorated coal pillars was determined to be 8 m. The deformation of roof and side on the coal pillar side of the roadway was greater than that on the solid coal side, showing obvious asymmetric characteristics. A targeted asymmetric support scheme using truss anchor cables was proposed for surrounding rocks. This scheme formed an effective prestress field in the surrounding rocks, enabling enhanced control of severely deformed areas. Field practice has verified the rationality of the designed deteriorated coal pillar width and support system, ensuring safe production in the working face. This provides reference and inspiration for the reasonable width and surrounding rock control technology of deteriorated coal pillars under similar geological conditions. Full article

Polyhedral cages (p-cages) are Euclidean geometric structures corresponding to polyhedra with holes. They are a good example of the geometry of some artificial protein cages. In this paper we identify p-cages made out of two families of equivalent polygonal faces, where the face of one family is attached to three other faces while the faces of the other family are attached to three, four, five or six other faces. To restrict ourselves to p-cages with small holes, we consider p-cages where each hole comprises at most four faces. The construction starts from planar graphs made out of two families of equivalent nodes. One can then construct the dual of the solid corresponding to that graph and tile its faces with regular or nearly regular polygons. An energy function is then defined to quantify the amount of irregularity of the p-cages which is then minimised using a simulated annealing algorithm. We have analysed nearly 100,000 possible configurations, ruling out the p-cages made out of faces with deformations exceeding 10%. We then present graphically some of the most interesting geometries. Full article

As infrastructure construction expands, the massive consumption of traditional concrete materials has led to resource shortages and environmental pollution. Utilizing industrial wastes such as coal gangue and fly ash to produce high-performance concrete is an important pathway toward a greener construction industry. However, concrete incorporating high volumes of fly ash and coal gangue (i.e., high-volume fly-ash coal-gangue self-compacting concrete, CGSC) suffers from low strength and high brittleness due to the inherent deficiencies of its constituents. This study proposes using glass fiber-reinforced polymer (GFRP) tubes for external confinement to improve the axial compressive capacity and deformability of CGSC. A total of 27 concrete cylinders were prepared and tested under axial compression, with real-time acoustic emission (AE) monitoring. The variables examined include the coarse aggregate type (coal-gangue and natural gravel), GFRP tube thickness (5 mm and 8 mm), and fly-ash content (80%, 85%, 90%). The stress–strain response of each specimen and the failure evolution of internal cracks were recorded throughout the loading process. The results show that GFRP tube confinement markedly increases the axial strength and ductility of CGSC. AE features exhibited staged behavior that closely mirrored the stress–strain curves. This correspondence reveals the progression of internal cracks under confinement and indicates that AE is an effective tool for damage monitoring in such composites. The findings provide a new technical approach for the efficient reuse of solid waste in concrete and offer a theoretical and practical basis for applying FRP composite structures in underground support engineering. Full article

Landslide InSAR monitoring is crucial for understanding the evolutionary mechanisms of geological disasters and enhancing risk prevention and control capabilities. However, for complex terrains and large-scale landslides, satellite-based SAR monitoring faces challenges such as a low observation frequency and limited spatial deformation interpretation capabilities. Additionally, two-dimensional monitoring struggles to comprehensively capture multi-directional movements. Taking the post-disaster monitoring of the landslide in Yunchuan, Sichuan Province, as an example, this study proposes a method for three-dimensional deformation dynamic monitoring by integrating dual-view MIMO ground-based synthetic aperture radar (GB-InSAR) data with high-resolution digital elevation model (DEM) data, successfully reconstructing the three-dimensional displacement fields in the east–west, north–south, and vertical directions. The results show that deformation in the landslide area evolved from slow accumulation to rapid failure, particularly concentrated in the middle and lower regions of the landslide. The average three-dimensional deformation of the main slip zone was approximately 60% greater than that of the original slope, with a maximum deformation of −100 mm. These deformation characteristics are highly consistent with the topographic structure and sliding direction. Field investigations further validated the radar data, with observed surface cracks and accumulation zones consistent with the high-deformation regions identified by the monitoring system. This system provides a solid foundation for geological disaster early warning systems, mechanism research, and risk prevention and control. Full article

Pure copper joints (PCJs) were fabricated using pinless friction stir spot welding (P-FSSW), a solid-state welding technique, to investigate the influence of plunge depth, rotational speed, and dwell time on PCJ performance. Thermal cycles under different welding parameters were recorded, while the microstructure at various locations within the welded zone was characterized using electron backscatter diffraction (EBSD). The microhardness and tensile–shear force (T-SF) of the PCJs were evaluated, and the fracture types together with fracture evolution were analyzed. The experimental results reveal that, under the combined effect of thermal cycles and mechanical stirring, subgrains in the welded zone transformed into recrystallized grains, whereas intense material flow contributed to an increased fraction of deformed grains. At the Hook region and the interface between the upper and lower sheets, grains were tightly bonded, resulting in effective metallurgical joining. Higher microhardness values were observed in the stir zone (SZ), whereas lower values appeared in the heat-affected zone beneath the interface. With increasing plunge depth, rotational speed, and dwell time, the T-SF of the PCJs first increased and then decreased, achieving a relatively high value at a plunge depth of 0.4 mm, a rotational speed of 1500 rpm, and a dwell time of 9 s. The fracture types of the PCJs were shear fracture and plug fracture, with the Hook region identified as the weakest zone. Full article

Mining-induced surface subsidence is a typical geological hazard. Loose layer drainage disturbed by coal mining can exacerbate surface subsidence in terms of both the extent and amount, thereby increasing the risk of building deformation and environmental degradation in mining areas. However, currently the prediction results of surface subsidence considering these two factors are not precise enough, which contradicts the principles of green coal mining. Firstly, this paper introduces the probability integral method, which predicts mining-induced surface subsidence. Subsequently, based on the soil–water coupled theory and the derived characteristic curve of groundwater level decline, a surface subsidence prediction model that considers loose layer drainage is constructed using triple integral transformation. Finally, a more precise surface subsidence prediction model considering both factors is proposed based on the principle of superposition. The model is applied to the mining of working panel 1309 in Shanxi province, China, an area rich in coal yet scarce in water resources. When compared with the measured subsidence data, the proposed model achieves a root mean square error (RMSE) of 27 mm, while the RMSEs of existing models are 78 mm and 123 mm, respectively. The prediction accuracy has been significantly improved. In addition, the proposed model is further validated through fluid–solid coupling numerical calculations in FLAC3D. The subsidence results considering the single effect of each factor also demonstrated good validation accuracy. Overall, the proposed model can accurately describe the surface subsidence considering both factors. This research can provide a theoretical guide for assessing the environmental impact and building damage, while contributing to the sustainable development of land use and groundwater resource in mining areas. Full article