Search Results (131)

In this study, graphite particles and short-cut carbon fibers were used to prepare a hybrid-reinforced composite with AZ91 magnesium alloy as the matrix via the powder metallurgy process. The effects of different added phase ratios on microstructure, density, compressive strength, and fracture morphology were investigated. The results show that the addition of 5% graphite particles alone reduced the compressive strength by 20.1% compared to pure magnesium, attributed to interfacial delamination and interlaminar peeling in the graphite’s layered structure. The introduction of carbon fibers effectively compensates for this degradation. When the carbon fiber content was increased to 10% (with graphite fixed at 5%), the compressive strength reached a peak of 375 MPa—a 63.0% increase over the graphite-only system—and the fracture strain rose to 16.98%. However, an excessive amount of carbon fibers (15%) led to agglomeration, causing the porosity to rise to 9.1% and resulting in a significant decline in mechanical properties. Microstructural analysis indicates that carbon fibers exert a reinforcing effect by sharing the load and constraining the lateral deformation of the matrix, while graphite particles induce microcracks and pores, resulting in a weakening effect; under appropriate ratios, the two can achieve synergistic reinforcement. This study provides experimental evidence for the component design and performance control of high-strength, rapidly dissolving magnesium-based composites. Full article

Ultra-deep lattice-like fractured carbonate reservoirs, formed by multi-period tectonic movements, feature strong heterogeneity, multi-scale fracture nesting, and anisotropic in situ stress. However, hydraulic fracture (HF) propagation behaviors within these complex formations remain poorly understood. In this study, using an unstructured fracture network approach, we simulated HF propagation in two typical fault-controlled lattice-like structures: compressive-torsion and pull-apart overlap zones. The performance of commingled, staged, and temporary plugging fracturing was evaluated, alongside sensitivity analyses of wellbore orientation, plugging timing, pump rate, and fluid viscosity. Results indicate that HFs in compressive-torsion zones exhibit long, straight geometries with local tensile activation points. Conversely, pull-apart overlap zones promote step-shaped, multi-branched fractures with superior lateral connectivity. The optimal timing for temporary plugging exhibits a delayed trend with increasing natural fracture density, ranging from 50% to 70% of the fracturing process in compressive-torsion zones, whereas an earlier implementation is preferred in pull-apart overlap zones, occurring at 33–65% of the fracturing process. Furthermore, HFs in compressive-torsion zones are less sensitive to viscosity and pump rate. To optimize stimulated volume, a moderate viscosity of 50–60 mPa·s is universally recommended. Regarding pump rates, 8–10 m³/min is ideal for balanced connectivity in pull-apart overlap zones, whereas >12 m³/min is required for compressive-torsion zones. These findings provide critical theoretical and engineering guidelines for differentiated fracturing strategies in ultra-deep reservoirs. Full article

Fly ash-metakaolin geopolymer has considerable potential for low-carbon and high-strength applications. However, its performance is highly dependent on preparation parameters and curing conditions, and its mix proportion optimization and nano-modification mechanism still require further clarification. In this study, under the condition that the mass ratio of metakaolin to fly ash was fixed at 9:1, an L₁₆ (4⁵) orthogonal experiment was carried out using nano-SiO₂ content, liquid-to-solid ratio, alkali equivalent, sodium silicate modulus, and curing temperature as independent variables. Range analysis and analysis of variance were employed to investigate the response patterns of slurry fluidity, setting time, and compressive strength under variations in these factors, while XRD, SEM-EDS, and FTIR were used to reveal the modification mechanism of nano-SiO₂. The results show that the early-age compressive strength is governed by alkali equivalent, whereas the later-age strength is jointly affected by multiple factors, with the differences among their effects gradually decreasing. Alkali equivalent and liquid-to-solid ratio have comparable effects on slurry fluidity, with contribution rates of 33.83% and 30.97%, respectively. Setting time is most sensitive to changes in sodium silicate modulus, which contributes 92.76% and 90.54% to the initial and final setting times, respectively. After the incorporation of an appropriate amount of nano-SiO₂, the amorphous gel characteristics, Si-O-T bonding structure, and fracture-surface compactness of the specimens were all enhanced. However, excessive incorporation tends to cause particle agglomeration and increase the water demand of the system, weakening the continuity of geopolymerization. The specimen with better overall performance was prepared with 1% nano-SiO₂, a liquid-to-solid ratio of 0.84, an alkali equivalent of 24%, and a sodium silicate modulus of 1.4, and cured at 40 °C. Full article

Predicting present-day pore pressure and 3D in situ stress in ultra-deep fold-thrust belts is severely hindered by the inadequacies of traditional 1D vertical compaction models, which fail to account for massive lateral tectonic compression and continuous elastoplastic yielding. To overcome this, a 3D poro-elastoplastic analytical framework is developed based on the Modified Cam-Clay model to decode the irreversible “geomechanical memory” of deeply buried argillaceous rocks. Applied to the highly compressed Kelasu Thrust Belt, this method links volumetric strain with mean and deviatoric stresses in stress-invariant space to reconstruct the maximum paleo-pore pressure and 3D paleo-stress tensor during the Coulomb Failure Period (CFP). The quantitative decoupling reveals an extreme state of geopressure prior to macroscopic faulting (pore pressure ratio α = 0.85–0.89). Crucially, the mean stress surge is identified as the dominant driver, generating ~91% of the excess overpressure. Consequently, horizontal tectonic compression accounts for 80–90% of the total overpressure anomaly, fundamentally overturning the classical assumption that vertical undercompaction (10–20%) is the primary mechanism. Furthermore, it is demonstrated that during subsequent tectonic uplift, the heavily compacted, salt-capped mudstones follow an undrained unloading path; the reduction in lithostatic burden is almost entirely offset by fluid depressurization, maintaining a constant effective stress state. This physically decoupled framework provides a rigorous basis for optimizing pre-drill safe mud-weight windows, designing hydraulic fracturing in highly deviatoric stress regimes, and assessing caprock integrity for deep geo-energy storage. Full article

Brittle geomaterials such as coal and rock are prone to unstable failure under high stress and dynamic disturbances, where rapid release of stored elastic strain energy can trigger dynamic disasters. Polyurea, a high-strength and high-ductility elastomer, can form a continuous flexible coating on the surface of coal/rock to regulate their deformation–fracture behavior. Here, uniaxial compression tests were performed on coal specimens coated with polyurea layers of different thicknesses (0–1.25 mm). Acoustic emission (AE) and digital image correlation (DIC) were jointly employed to characterize macroscopic deformation, microcrack evolution, fracture-mode transition, and energy partitioning. The results show that polyurea provides passive lateral confinement that suppresses lateral expansion and shifts macroscopic failure from brittle splitting to progressive ductile damage. AE-based AF–RA analysis indicates that thicker coatings increase the normal stress and shear resistance along potential fracture planes, promoting a microfracture transition from shear-dominated to tension-dominated cracking. Energy analysis demonstrates that the coating enhances pre-peak energy dissipation via coordinated deformation with the coal, while thicker coatings (≥1.00 mm) exhibit pronounced post-peak elastic tensile deformation to absorb and buffer fracture-released energy, impeding the instantaneous energy release typical of bare coal. Moreover, the elastic energy index shows that polyurea markedly reduces impact tendency, with an appropriate thickness stabilizing specimens from strong to weak/non-impact propensity. These findings clarify the coupled confinement–fracture–energy regulation mechanisms of polyurea coatings and provide quantitative guidance for coating-thickness design to mitigate dynamic failure hazards in brittle materials. Full article

Rock pillars in deep underground mines are subjected to complex stress environments. The combined effects of in situ stress and cyclic disturbances from mining activities lead to a redistribution of the surrounding rock mass stress field, which readily triggers instability and failure, posing severe threats to mining engineering safety. To investigate the damage mechanism of cyclic loading on rock and its weakening effect on the bearing capacity of mine pillars, this study takes limestone as the research object. A series of uniaxial compression tests were conducted on limestone specimens subjected to triaxial cyclic pre-damage, complemented by numerical simulations to further characterize the energy and deformation evolution of the damaged limestone under cyclic loading conditions. The findings are as follows: (i) Triaxial cyclic tests on limestone show that both the input energy and dissipated energy follow similar trends, decreasing rapidly in the initial stage before stabilizing. The elastic strain energy remains largely constant, with most of the input energy being stored as elastic strain energy. Under constant stress levels and cycle numbers, increases in confining pressure and frequency reduce the rock’s input energy, elastic strain energy, and dissipated energy. (ii) The peak stress of damaged limestone exhibits a positive correlation with the pre-damage confining pressure and cyclic frequency, while it decreases with an increasing number of cycles. Higher confining pressure and frequency raise the input energy, elastic potential energy, and dissipated energy at the peak stress point. (iii) Deformation and failure in damaged limestone originate from the development and propagation of localized deformation zones. Increased lateral displacement within these zones promotes the formation of macroscopic fractures. Due to significant structural heterogeneity inside the localized areas, the evolution of deformation energy is influenced by regional characteristics. (iv) Simulation results indicate that the uniaxial compressive failure of limestone involves the accumulation and propagation of micro-scale tensile cracks, which ultimately coalesce into macro-scale shear fracture surfaces. During uniaxial loading of pre-damaged limestone, newly generated cracks predominantly initiate around pre-existing cracks, with only a limited number distributed randomly. Their peak intensity shows a positive correlation with the pre-damage confining pressure. Full article

Objective: To describe the surgical technique and early clinical outcomes of prone-transpsoas single-position corpectomy (PTP-corpectomy) for the management of complex thoracolumbar spinal pathology. Background: PTP-corpectomy is an emerging technique for providing simultaneous lateral and posterior spinal access without patient repositioning. The previous literature describes the PTP approach for interbody fusions; however, evaluation of its use for corpectomy is limited. This case series reports our experience with the PTP-corpectomy procedure at our institution. Methods: We retrospectively reviewed seven patients who underwent PTP-corpectomy surgery for complex spinal pathologies, including severe kyphoscoliosis, traumatic burst fractures, and revision in 2022–2025. Collected variables included demographics, comorbidities, surgical history, perioperative details, radiographic imaging, and clinical outcomes. Results: All seven patients successfully underwent PTP-corpectomy. The average operative time was 460.6 ± 147.1 min, and the estimated blood loss (EBL) was 892.9 ± 898.3 mL. Average length of stay (LOS) postoperatively was 6.7 ± 3.0 days. One case required revision of a preexisting construct and complex wound closure with plastic surgery, which had significantly increased operative time and blood loss (767 min, 2700 mL). Excluding this complicated case, the average time was 409 ± 63.7 min, and EBL was 591.7 ± 454.3 mL. All seven patients maintained clinical stability postoperatively, demonstrating improvements in pain and functional status at latest follow-up. Follow-up time ranged from 41 to 375 days. Conclusions: Our experience adds to the limited body of evidence that the PTP approach is well suited for corpectomy procedures, and that it is feasible, safe, and effective at improving clinical outcomes for complex spinal pathologies. This series adds to the limited case volume describing this technique in the current literature. Future studies with larger patient populations are warranted to further validate these findings. Full article

Progressive collapse represents a catastrophic failure mode for reinforced concrete (RC) structures, yet the use of architected materials to mitigate this risk remains largely unexplored. This study presents a numerical feasibility investigation of RC beam–column sub-assemblages with auxetic metamaterial inserts embedded in critical joint regions. A hierarchical multiscale framework is developed to link the effective behavior of auxetic metamaterials with structure-scale collapse response. The framework couples macroscale structural analysis with mesoscale fracture simulations through a hybrid voxel–Voronoi discretization strategy. Baseline finite element models are validated against published experimental results for conventional RC specimens, while the auxetic-enhanced configurations are evaluated numerically. Under high tensile strain, the auxetic insert expands laterally because of its negative Poisson’s ratio and generates a localized confining stress field within the surrounding concrete. The simulations suggest that this mechanism may promote crack bifurcation, redistribute localized cracking into a more distributed damage pattern, and delay compressive crushing and crack coalescence. Compared with the corresponding conventional RC configurations, the auxetic-enhanced models predict a 25% increase in load redistribution capacity and a 20% enhancement in deformation ductility. These predicted improvements require future experimental validation using physical auxetic-enhanced RC specimens. The findings provide a computational basis for exploring material-by-design strategies aimed at improving the robustness of critical RC joint regions under progressive collapse demands. Full article

The long-term stability of rock–concrete composites largely depends on the mechanical properties and durability of the rock–concrete interface. This study investigated the coupling effect of interfacial roughness and acid sulfate corrosion on sandstone–concrete composites by using uniaxial compression tests combined with acoustic emission (AE) monitoring. The results showed that corrosion continuously reduces the mechanical properties of the specimens with peak strength and elastic modulus, exhibiting a two-stage evolution: rapid degradation in the early stage followed by a slow decline in the later stage. After 60 days of corrosion, the peak strength for composites with JRC = 5, JRC = 10, and JRC = 15 interfaces decreased by 46.59%, 44.34%, and 50.43%, respectively. The elastic modulus exhibited the same pattern of variation, and the decreasing rate was 68.90%, 66.96%, and 76.46% for the JRC = 5, JRC = 10, and JRC = 15 groups. Acoustic emission activities appeared earlier and were more significant after corrosion. With the effect of corrosion, the fracture mode evolved from tensile-dominated cracks to mixed tensile–shear cracks with a stronger shear component. Fractal analysis of AE energy revealed that the Hurst exponent decreased from 0.842–0.864 in the natural state to 0.503–0.567 after 60 days of immersion, whereas the fractal dimension increased from 1.136–1.182 to 1.433–1.497, indicating a decrease in the persistence and increase in complexity of the acoustic emission energy release process. Overall, the moderately rough interface (JRC = 10) achieved a better balance between initial strengthening and long-term corrosion resistance. These findings provide experimental support for evaluating the durability of sandstone–concrete composites in acidic sulfate environments. Full article

Accurately estimating the stress thresholds (crack closure stress σ_cc, crack initiation stress σ_ci and crack damage stress σ_cd) is of great significance to the study of failure mechanisms for hard rock. Uniaxial compression tests were conducted on four types of hard rock to investigate the rationality and applicability of four different identification methods. The stress thresholds obtained by different methods were compared and analyzed. The main research results are as follows. Both the two distinct energy dissipation rate (EDR) methods underestimate the value of σ_cc, and it is not applicable for hard rock with few primary fractures. Since the method of lateral strain response (LSR) method does not consider the closure process of primary fractures, it underestimates the value of σ_ci. The method of crack volume strain (CVS) or moving point regression (MPR) is recommended to calculate the σ_ci of hard rock. The EDR method overestimates the value of σ_cd. The method of CVS or MPR is recommended to identify the σ_cd of hard rock. Full article

Proximal femoral fractures associated with osteoporosis are an important clinical problem, yet how bone quality independently influences stress distribution remains insufficiently understood. This study aimed to quantitatively compare surface stress distribution between normal and osteoporotic proximal femoral models using thermoelastic stress analysis (TSA). Fourth-generation composite femurs with identical external geometries were subjected to cyclic compressive loading at a 9° adduction angle, with different maximum loads applied to avoid structural failure (normal: 1900 N; osteoporotic: 1000 N). TSA was performed using an infrared lock-in system to obtain surface stress maps, and stress values were evaluated across key proximal regions and along the medial and lateral cortices. The osteoporotic group showed higher maximum stress values in the medial neck (−37.79 vs. −11.52 MPa), lateral neck (24.70 vs. 8.75 MPa), and intertrochanteric crest (−17.98 vs. −6.05 MPa), corresponding to approximately 1.8–3.5-fold increases compared with the normal model values normalized to 1000 N. Mean stress values were also higher by approximately 1.9–2.4-fold across regions. These results suggest that reduced bone quality is associated with increased proximal stress concentration. They may also help guide implant and fixation strategies, including stem selection and fixation configuration, by identifying regions susceptible to stress concentration under different bone quality conditions. Full article

Surgical fixation techniques for bone fracture healing are well established and effective; however, opportunities remain to improve both functional outcomes and the patient experience. The Biofiligree^® concept integrates medicine, engineering, and design by reimagining conventional osteosynthesis plates as both therapeutic and aesthetic devices. Inspired by traditional Portuguese filigree, these plates allow patient participation through personalized geometries, patterns, or engravings and may later be transformed into wearable jewellery after removal, preserving them as symbolic artefacts of recovery. This study introduces and biomechanically evaluates a novel calcaneal fixation plate incorporating the biofiligree geometry concept. A biofiligree plate was designed for calcaneus fracture fixation and manufactured in stainless steel 306L. Experimental testing was conducted on synthetic composite calcaneus bone models to simulate anatomical conditions and compare the new design with a standard commercial plate. The biofiligree plate, 2 mm thick, was fixed using five screws and two percutaneous screws positioned at 45° to compress the fracture line. Results demonstrated comparable biomechanical performance between both systems, with similar strain distributions and fracture stabilization. The biofiligree plate showed stresses around 430 MPa and fracture displacement below 0.7 mm. Fixation stiffness values were 1445 N/mm for intact calcaneus, 1065 N/mm for the commercial plate, and 725 N/mm for the biofiligree plate, indicating adequate support for bone healing. Full article

Articular fractures require precise anatomical reduction and rigid fixation to heal appropriately. In veterinary cases that involve fracturing of the lateral humeral condyle, cortical bone screws inserted in lag fashion with Kirschner wire are the preferred method for surgical fixation. However, relatively high complication rates associated with cortical lag screws (CLSs) highlights the need to investigate alternate screw designs. Variable-pitch headless compression screws (VPHCSs) are unique as they advance beneath the cortical surface. Although the use of VPHCSs are widely utilised in human orthopaedics, the current use in veterinary orthopaedics is limited. This study aimed to evaluate the peak interfragmentary force (PIF) and area of compression (AOC) generated by a 3.5 mm self-tapping cortical screw placed in lag fashion and a 3.5 mm VPHCS inserted to four depths. PIF and AOC were measured using a pressure-sensitive film placed between two blocks of polyurethane foam (0.24 g/cm³), simulating a transverse fracture. CLSs were inserted by hand into predrilled 2.5 mm pilot holes. PIF and AOC were measured at full insertion. VPHCSs were placed into predrilled 2.5 mm pilot holes, followed by a 3.5 mm tapered countersink. The screw was inserted until the head was level with the surface. PIF and AOC were measured between the two blocks. The screw was continued until the head was at a depth of 2, 5, and 9 mm below the surface, and the PIF and AOC were measured again at each stage. There was no detectable difference in PIF and AOC between CLSs and VPHCSs countersunk to −2 mm (PIF–CLS: Mean = 12.886, SD = 2.370; 2 mm: Mean = 17.301, SD = 8.858, p = 0.319; AOC–CLS: Mean = 0.936, SD = 0.291; 2 mm: Mean = 0.925, SD = 0.447, p = 0.872). VPHCSs countersunk to −5 mm and −9 mm produced significantly greater PIF compared to CLSs (5 mm: Mean = 16.086, SD = 6.799, p = 0.002; 9 mm: Mean = 34.987, SD = 4.015, p < 0.001). VPHCSs countersunk to −5 and −9 mm produced significantly greater PIF and AOC compared to CLSs in this model. Further investigation is required to produce recommendations for clinical use. Full article

Introduction: An incomplete high anterior column fracture of the acetabulum is commonly considered to require completion of the fracture. However, reduction may become more difficult after completing the incomplete fracture due to plastic deformation. This study describes a surgical technique of compression osteosynthesis without completing the incomplete fracture and evaluates the clinical and radiographic outcomes. Materials and Methods: In this retrospective study, 25 patients with incomplete high anterior column fractures met the inclusion criteria. The fracture was reduced and stabilized by compression osteosynthesis through the anterior iliac approach without completing the incomplete fracture in the iliac wing. Patient demographics, the mechanism of injury, associated injuries, time to surgical reconstruction, operation time, and postoperative complications were analyzed. The quality of reduction and outcome were evaluated according to Matta’s criteria. Results: The mean operation time was 110 ± 23 min (range, 75–160). All fractures achieved bone union at a mean of 10.2 ± 1.4 weeks (range, 8–14). The quality of fracture reduction was graded as anatomical in 22 hips, imperfect in one and poor in two. Clinical results were excellent in 19 patients and good in six, and radiographic results were excellent in 22 patients and good in three. No statistically significant differences were observed between patients with and without quadrilateral plate fractures. Lateral femoral cutaneous nerve injury occurred in 13 patients (52%), mostly without significant symptoms. One patient experienced vascular injury. Conclusions: Incomplete high anterior column fractures can be effectively reduced and stabilized by compression osteosynthesis through the anterior iliac approach without completing the incomplete fracture in the iliac wing. This case series demonstrated favorable clinical and radiographic outcomes using this surgical technique. However, because this study was a retrospective case series with a small sample size and no comparative control group, further studies are required to confirm these findings. Full article

Understanding the changes in physical and mechanical properties of lignite during dehydration is crucial for its sustainability in coal mining, exploitation of coalbed methane, and carbon dioxide sequestration. Through SEM and Computed Tomography (CT) scanning, combined with fractal theory, this study investigates dynamic dehydration characteristics of macerals in lignite during normal temperature drying (NTD), and their effects on pore–fracture development and physic–mechanical property evolution. The results show that the hard layers of lignite are mainly composed of ulminite (Ul), while the soft layers are primarily composed of fusinite (Fu), densinite (De), and Ul. Ul exhibits low dehydration efficiency but is prone to shrinkage and cracking heavily, whereas Fu has high dehydration efficiency and excellent thermal stability. The layered enrichment of macerals controls the development of the three-dimensional (3D) pore–fracture structures of lignite during NTD and leads to distinct cracking characteristics of fracture structures between hard and soft layers. Unlike soft layers, hard layers tend to form long, straight fracture structures with large apertures and exhibit extremely high fracture connectivity and fractal dimension (FD). In addition, the differential drying behavior of macerals causes the physical parameters of lignite such as moisture ratio (MR), drying rate (DR), and density (ρ) to show a dynamic evolution characteristic of “initial rapid decline (or increase) in the early stage–subsequent gradual decline (or increase) and stabilization in the later stage” during NTD. The unique pore–fracture structure controlled by macerals significantly alters the deformation resistance and failure mode of dehydrated lignite under uniaxial compression but has limited effect on its uniaxial compressive strength. Full article