Search Results (1,837)

This study systematically investigates the tensile anisotropic mechanical behavior of ferritic steel under different orientations through an integrated experimental, theoretical modeling, and simulation approach employing advanced characterization techniques including electron backscatter diffraction (EBSD), digital image correlation (DIC), scanning electron microscopy (SEM), and finite element analysis. The results demonstrate pronounced orientation dependence in mechanical response, with initial yield strengths of 391, 391, and 405 MPa and fracture strains of 0.237, 0.220, and 0.212 observed for 0°, 45°, and 90° orientations, respectively, corresponding to orientation-induced variations of 3.6% in yield strength and 11.8% in fracture strain. These anisotropic characteristics are primarily attributed to the predominant α-fiber texture <110>||RD, which accounts for 59.8% of the texture components. Furthermore, crystallographic texture significantly influences fracture behavior, as evidenced by the distinct orientation-dependent macroscopic contraction characteristics and morphological features of fracture surfaces. Full article

Background and Objectives: Intramedullary headless screw (IMHS) fixation is a minimally invasive and biomechanically stable option for metacarpal fractures. However, the suitability of commonly used screw diameters may be limited by the morphometric features of the intramedullary canal. This study evaluated the isthmus morphology of the second to fifth metacarpals using computed tomography (CT)-based morphometric analysis and virtual screw simulation. Materials and Methods: A retrospective morphometric study was conducted using 75 hand CT scans, representing 300 metacarpals (second to fifth). Three-dimensional reconstructions were created with Mimics software (Materialise, Leuven, Belgium), and the isthmus level was identified by serial axial CT analysis. Canal diameters were measured at this level, and bone-specific virtual screw models were generated in Rhinoceros 3D and imported into Mimics for virtual implantation and canal conformity assessment. Feasibility rates were calculated for screw diameters between 2.75 mm and 4.00 mm. The effects of age and gender were also analyzed. Results: The fourth metacarpal had the smallest mean isthmus diameter (2.64 ± 0.89 mm), while the fifth had the largest (3.21 ± 0.84 mm). Feasibility decreased as screw diameter increased across all metacarpals. The fourth metacarpal showed the lowest compatibility, with feasibility rates of 10.7% for 3.5 mm screws and 4.0% for 4.0 mm screws. In contrast, the fifth metacarpal had the highest feasibility at smaller diameters, with 74.7% compatibility for 2.75 mm screws and 62.7% for 3.0 mm screws. Positive correlations were found between age and isthmus diameters of the second and third metacarpals, indicating age-related canal widening. Conclusions: The anatomical feasibility of IMHS fixation in the second to fifth metacarpals is influenced by isthmus morphology. The fourth metacarpal appears to be the most restrictive, particularly for screws ≥ 3.5 mm. These findings support individualized CT-based preoperative templating rather than standardized implant selection to improve screw canal compatibility and reduce cortical compromise risk. Full article

Background: Over the past 25 years, advances in knee surgery have been driven by an improved understanding of fracture morphology and associated injuries, as well as by significant technological progress. The introduction of novel classification systems has led to the refinement of treatment strategies, particularly with respect to the selection of surgical approaches. Furthermore, advances in biomechanical understanding have facilitated the development of new osteosyntheses designed to promote earlier rehabilitation while simultaneously reducing complication rates. Research Question: Which key milestones over the last 25 years have significantly influenced treatment strategies for knee joint fractures, with a perspective on unresolved issues? Results: Recent advances in fracture management, osteosynthesis, imaging techniques, and biomechanical research have substantially improved clinical outcomes, including a reduction in infection rates and improved postoperative results. The implementation of new classification systems has enabled more precise preoperative planning, allowing surgeons to define approaches that ensure adequate visualization of the articular surface while facilitating optimal positioning of the osteosynthesis. In terms of osteosynthesis, the introduction of locking plate technology has become widely established and supported by biomechanical evidence and has largely replaced traditional methods such as tension-band wiring of the patella. Despite these advances, fracture management in geriatric patients remains a considerable challenge, as compromised bone quality frequently limits the ability to achieve sufficiently load-stable osteosynthesis. Direct visualization of the articular surface is essential for adequate assessment and reduction of the affected articular segment. However, there is currently no consensus on which surgical approach or possible extension is most appropriate while simultaneously ensuring a low complication rate. Full article

A detailed analysis of the effects of magnesium on the microstructure of hypereutectic Al–20Si alloys is provided in this study. Experimental results show that the addition of Mg significantly refines the primary silicon phase relative to the unmodified Al–20Si alloy, transforming its morphology from a complex form to a singular plate-like structure. Notably, for the first time, equiaxed aluminum grains appear in the aluminum matrix under conventional solidification conditions. The generation of these grains is closely related to the quenching effect caused by rapid cooling during metal mold casting, which promotes the generation of equiaxed aluminum grains within tightly constrained temporal and spatial parameters. The Al–Si eutectic structure exhibits a regular lamellar morphology, with an average eutectic silicon spacing of 930.97 nm. The phase analysis shows that the alloy mainly consists of Al, Si, and Mg₂Si phases after the addition of Mg. With the increase in Mg concentration, the diffraction peaks for Al(200) and Si(220) first shift to lower angles and then move to higher angles, along with significant peak broadening. Ambient temperature mechanical testing indicates that tensile strength first increases with increasing Mg concentration, then declines, with the highest tensile strength of 235.1 MPa at 3 wt.% Mg in the Al–20Si alloy. The fracture mechanism of the testing specimens changes from cleavage fracture to ductile fracture. Microhardness testing indicates a continuous increase in the hardness of the aluminum matrix with rising Mg concentration; the hardness of primary silicon declines first and then increases, whereas the hardness of the eutectic structure exhibits a first increase followed by a decline. Full article

The complex propagation behavior of hydraulic fractures (HFs) in strongly heterogeneous conglomerate reservoirs poses significant challenges for effective reservoir stimulation. In particular, the interaction between fractures and gravel-induced heterogeneity often leads to highly tortuous fracture networks and uneven stimulation efficiency. To address this issue, a series of laboratory true triaxial hydraulic fracturing experiments were conducted on artificially prepared conglomerate specimens with controlled gravel size and distribution. A quantitative evaluation index, termed the Fracture Complexity Index (FCI), was proposed to characterize the tortuosity and complexity of fracture networks by integrating multiple geological and engineering factors. The effects of cluster spacing and fracturing fluid viscosity on multi-fracture propagation behavior were systematically investigated. The results show that increasing cluster spacing enhances inter-fracture interaction and promotes fracture tortuosity, while lower fluid viscosity facilitates fracture branching but may limit effective propagation distance due to energy dissipation. To further quantify the trade-off between fracture complexity and propagation extent, a dimensionless fracture length was introduced and combined with FCI to establish a fracture morphology evaluation framework. This framework enables the classification of fracture patterns and reveals the coupling relationship between engineering parameters and fracture geometry. The findings provide new insights into the mechanisms of fracture propagation in conglomerate reservoirs and offer a quantitative basis for optimizing fracturing design, particularly in balancing fracture complexity and effective stimulation range in strongly heterogeneous formations. Full article

This study investigated the comparative effects of various maleic anhydride-grafted polymeric compatibilizers such as polyethylene-graft-maleic anhydride, polypropylene-graft-maleic anhydride, polyethylene(alt)-graft-maleic anhydride and poly(styrene-ethylene/butylene-styrene)-graft-maleic anhydride on the final properties of polypropylene (PP) carbon nanotube (CNT) composites. Polypropylene nanocomposites (PP-CNT) were prepared by melt mixing using a laboratory scale twin-screw extruder. The mechanical test results showed that the incorporation of CNTs along with various compatibilizers increased the tensile strength (10.3%) and tensile modulus (24.2%). The tensile modulus and yield stress of the PP-CNT nanocomposites were significantly higher than those of the pristine PP. Differential Scanning Calorimetry (DSC) analysis revealed that the addition of CNTs slightly increased the melting temperature of the crystallization peaks. In the compatibilized PP-CNT composites, the CNTs were well dispersed to enhance the onset of degradation and maximum decomposition temperatures. The frequency-dependent rheological behaviors of PP-CNT nanocomposites indicated that the storage modulus (G’), loss modulus (G”), and complex viscosity (η*) PP increased for the compatibilized system. The XRD results indicated that the addition of CNTs and compatibilizers slightly affected the crystalline nature of PP. Scanning electron microscopic images of the fractured surfaces presented in the micrographs showed the brittle nature of the surface morphology of PP-CNT nanocomposites. Full article

To clarify the migration and structural evolution of mining-induced overburden following grouting reconstruction of the Fourth Aquifer, the inner section of Panel 1022-2 in Wugou Coal Mine was taken as the engineering background. The evolution law of overburden movement and the development characteristics of the caving zone were systematically investigated via theoretical analysis, similar-material simulation, and numerical simulation. In addition, the maximum caving-zone height of Panel 1022-2 was calculated based on the measured caving-to-mining ratio of the adjacent Panel 1010-1. The results show that following grouting reconstruction of the Fourth Aquifer, the water inflow and permeability coefficient decreased significantly, the mining-induced water-body grade was classified as Grade III, and the required coal pillar type was converted from a waterproof safety coal (rock) pillar to an anti-collapse safety coal (rock) pillar. The bedrock failure morphology evolved sequentially from a symmetrical trapezoid to a stepped shape and finally to an asymmetrical saddle shape, with a maximum caving-zone height of 19.0 m, whereas the Fourth Aquifer evolved from fracture initiation and bed separation to asymmetrical overall subsidence. Overburden migration is jointly controlled by bedrock thickness and the mechanical properties of the unconsolidated layer, presenting a distinct three-stage evolution pattern. As the size of the reserved safety coal (rock) pillar decreases, the overburden failure mode changes from overall plastic failure under relatively thick bedrock, to semi-block failure with longitudinal fractures penetrating to the base of the Fourth Aquifer and transverse fractures and interlayer separation initiating inside the aquifer, and finally to intensified failure under thin-bedrock conditions. Based on field analogy with Panel 1010-1, the maximum caving-zone height of Panel 1022-2 was calculated to be 19.73 m, which is in good agreement with the numerical and similar-material simulation results, verifying the reliability of the three-stage overburden evolution law and the caving-zone height evaluation. Full article

In this study, scanning electron microscopy (SEM) analysis is used to reveal the real microstructure of C75S steel and to compare grain morphology and deformation features with numerical predictions. A micro-scale finite element model of C75S steel is developed to investigate its tensile response in order to understand how steel actually deforms and fails at the microstructure level. Subsequently, the validated microstructural model is employed to simulate the cutting process using the finite element method, focusing on stress concentration and damage initiation at the grain and interface zones. The results demonstrate that microstructural modelling provides improved insight into deformation and fracture mechanisms compared to homogenised approaches, highlighting the critical role of cementite distribution and interfacial behaviour during tensile loading and micro-scale cutting. The cementite particle sizes in C75S steel range from approximately 0.5 to 2.0 µm, with circularity values between 0.7 and 0.95 and a volume fraction of about 10–12%. The proposed framework offers a robust basis for predicting the cutting performance of high-carbon steels. Full article

Background: Adiponectin (ADPN) is a key adipokine with osteogenic potential, but its clinical translation for bone regeneration is hindered by poor in vivo stability. This study aimed to develop poly lactic-co-glycolic acid (PLGA) microparticles as a stable and biocompatible carrier for sustained ADPN delivery to enhance bone repair. Methods: ADPN-loaded PLGA microparticles (ADPN-MPs) were fabricated via emulsion solvent evaporation. Their physicochemical properties were characterized using scanning electron microscopy (SEM) and circular dichroism (CD) spectroscopy. Loading efficiency and drug loading were quantified. In vitro release kinetics and stability under physiological conditions were assessed. Biocompatibility was evaluated using MC3T3-E1 osteoblasts and BMSCs, and in vivo efficacy was tested in a fracture model via gait analysis. Results: Employing CD to evaluate the secondary structure of ADPN, emulsion solvent evaporation for microparticles preparation, and SEM for morphological analysis, we quantitatively assessed the loading efficiency (69.83 ± 4.24%) and drug loading (0.97 ± 0.06%) of ADPN-MPs. Results indicated that ADPN-MPs maintained significant stability under varied pH and temperature conditions and exhibited a controlled release profile, with an average initial rapid release of 14.25% within 24 h and an average cumulative release of 55.00% by day 28. Furthermore, ADPN-MPs promoted the proliferation of MC3T3-E1 and BMSCs without toxicity, demonstrating excellent biocompatibility. Notably, gait analysis in a fracture model showed improved healing in both ADPN and ADPN-MPs groups compared to controls, with ADPN-MPs demonstrating comparable efficacy to free ADPN, supporting its potential as a stable delivery system for bone regeneration. Conclusions: PLGA microparticles serve as an effective, stable, and biocompatible delivery platform for ADPN, significantly promoting bone regeneration in vitro and in vivo. This delivery system enhances the therapeutic potential of ADPN for clinical bone repair applications. Full article

Materials derived from renewable and recycled resources offer a promising route toward more sustainable thermoset composites. In this study, waste poly(ethylene terephthalate) (PET) was depolymerized by glycolysis with propylene glycol to obtain a glycolysate, and subsequently polycondensed with biobased propylene glycol, maleic anhydride, and trimethylolpropane diallyl ether to synthesize biobased UV-curable unsaturated polyester resin (UV-bUPR). The composites were prepared with acryloyl-modified Kraft lignin (K_rL-A) as a reactive bio-filler using a dual-curing approach, in which rapid UV curing was followed by thermal/redox post-curing to improve conversion and network homogeneity. The structure of the synthesized resin and composites was confirmed by FTIR and NMR spectroscopy. Mechanical properties were evaluated by tensile testing and hardness measurements, while morphology and fracture behavior were analyzed by scanning electron microscopy. The unmodified lignin decreased tensile performance due to limited compatibility with the polyester matrix and the formation of interfacial defects and agglomerates. In contrast, K_rL-A exhibited improved dispersion and stronger filler–matrix interactions, resulting in superior mechanical performance. The most pronounced effect of lignin modification was observed at 15 wt.% filler loading, where the tensile strength reached 27.83 MPa, compared with 13.91 MPa for the corresponding unmodified system. The developed composites also showed improved sustainability, assessed through the E-factor, due to the combined use of recycled PET and renewable lignin. Full article

Background/Objectives: Vertebral body stenting (VBS) and balloon kyphoplasty (BKP) are widely used for the treatment of osteoporotic vertebral fractures (OVFs). However, it remains unclear whether the theoretical biomechanical advantages of VBS translate to superior clinical or radiographic outcomes. This study aimed to compare VBS and BKP with respect to clinical outcomes, radiographic parameters, and complications. Methods: In this multicenter retrospective comparative cohort study, 123 patients with OVF treated with VBS (n = 24) or BKP (n = 99) were analyzed. VBS was indicated for complex fracture patterns, including severe endplate injury, split-type fractures, and absence of interbody sclerosis; other fractures were treated with BKP. Pain outcomes, operative parameters, cement volume and leakage, and radiographic measures of vertebral kyphosis angle (VKA) and local kyphosis angle (LKA) were assessed. For group comparisons, we used independent-samples t tests or Mann–Whitney U tests for continuous variables and chi-squared or Fisher’s exact tests for categorical variables. Results: Baseline demographics and bone mineral density were comparable between groups. Surgical time was longer for VBS (39 ± 6 vs. 35 ± 9 min, p = 0.007). Both procedures produced significant pain reductions (p < 0.001), and postoperative VAS did not differ between VBS and BKP (18 ± 11 vs. 13 ± 12 mm, p = 0.06). Although VKA immediately after surgery was lower for VBS (4.8 ± 4.4° vs. 7.0 ± 4.9°, p = 0.03), the magnitude of correction, VKA, and LKA at final follow-up were comparable. Cement volume was similar (6.4 ± 1.4 vs. 6.7 ± 1.9 mL, p = 0.45), but cement leakage occurred more frequently with VBS (54% vs. 24%, p = 0.005). Rates of adjacent vertebral fracture (13% vs. 26%, p = 0.12) and revision surgery (4% vs. 8%, p = 0.44) were comparable between groups. Conclusions: Despite VBS being reserved for more complex fracture morphologies with split-type fractures and severe endplate defects, while BKP was generally used for uncomplicated OVF cases, VBS provided pain relief and radiographic correction comparable to BKP. Full article

In this paper, the effects of 4 wt.% of silicon on the microstructure and mechanical properties of AM50 magnesium alloys fabricated by the casting method are presented. New AM50/Si material and the base AM50 alloy were gravity cast into a metal mould under the same conditions for comparison. Analyses of the alloys’ microstructures were carried out by light microscopy (with differential interface contrast), scanning electron microscopy (with an energy dispersive X-ray spectrometer), as well as X-ray diffraction (XRD). In as-cast conditions, both materials were composed of α-Mg solid solution, α + γ eutectic (where γ is Al₁₂Mg₁₇), Al₈Mn₅ intermetallic phases and discontinuous γ precipitates. The AM50/Si material also consisted of the Mg₂Si phase. This structural constituent appeared in the form of primary crystals with regular polygonal morphology and an α + Mg₂Si eutectic in the form of “Chinese script”. In the microstructure of the AM50/Si material, the Mn₃SiAl₉ ternary phase was also identified. The detailed analyses presented in this paper revealed that the new ternary Mn₃SiAl₉ structural compound caused a reduction in the volume fraction of the Al₈Mn₅ phase but did not completely replace it. These two phases formed competitively. The fabricated material exhibited higher tensile and compression strength as well as yield strength in comparison with the AM50 alloy. Additionally, analyses of the fracture surfaces of the AM50/Si material carried out using scanning electron microscopy (SEM) were presented. Full article

During the production, storage, and use of solid rocket motors, the impact generated by unexpected accidents, such as collision or drop, will cause damage to the propellant and affect the safety of the motor. However, the progressive evolution mechanism of mesoscopic damage in NEPE propellant under such impact conditions has not been fully elucidated, and there is still a lack of quantitative method to evaluate the impact-induced damage degree, which restricts the engineering safety assessment of solid rocket motors. To investigate the influence mechanism, the mesoscale damage characteristics of NEPE propellant under drop-weight impact is systematically studied. First, damaged NEPE specimens are obtained by conducting drop-weight experiments with a 10 kg hammer, where the drop height is varied to apply different impact impulses. The internal meso-structure of the propellant is then characterized using micro-CT, yielding detailed imagery of the refined meso-structural features and damage morphologies in the NEPE propellant. To capture the dynamic evolution process of mesoscale damage, a mesoscopic model incorporating AP, Al, HMX particles and voids, is subsequently constructed based on the high-precision mesoscopic morphology characterized by micro-CT. By integrating the deviatoric constitutive model, Gurson plastic damage model, and bilinear cohesive zone model, high-fidelity numerical simulations of the drop-weight impact damage process are performed using the advanced SPH-FEM coupling algorithm. The results indicate that no significant damage occurs when the impact impulse is less than 13.85 N·s. As the impulse increases, phenomena including matrix microcracks, void collapse, particle/matrix interface debonding, and main crack formation appear sequentially. When the impulse exceeds 24.25 N·s, particle fragmentation and transgranular fracture occur, accompanied by plastic flow and frictional heating that induce ignition. Finally, the overall damage degree is fitted by the Boltzmann function, and a function for quantitatively describing the damage degree is obtained, which can provide theoretical support for the impact safety assessment of solid rocket motors. Full article

Objective: This study aims to analyze the dynamic changes in lymphatic endothelial cell (LEC) markers during the progression of intervertebral disk degeneration (IDD) and to investigate their association with the progression of IDD. Method: In this study, intervertebral disk (IVD) specimens were first collected from patients who underwent open lumbar fusion surgery for spinal fractures (control group, n = 10) and lumbar disk herniation (IDD group, n = 10). Concurrently, a mouse IDD model was established, and IVD specimens were collected from mouse in the Sham group and the IDD group 1, 3, and 6 weeks after modeling (n = 5 per group at each time point). Pathological morphological changes in human and mouse IVD specimens were observed using Hematoxylin and Eosin (H&E) and Masson’s Trichrome staining. The degree of degeneration in the mouse IVD specimens was quantified using a histopathological scoring system. Subsequently, real-time quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry (IHC), and immunofluorescence (IF) staining were employed to examine LEC markers in IVD tissue, including lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), podoplanin (PDPN), prospero homeobox protein 1 (PROX-1), and vascular endothelial growth factor receptor 3 (VEGFR-3), as well as matrix metabolism-related markers such as matrix metalloproteinase 13 (MMP-13) and collagen II (Col II). Finally, we performed Spearman’s rank correlation analysis between the histopathological scores of all mouse IVD specimens and the corresponding expression levels of LEC markers. Results: In human IVD tissue, expression levels of LYVE-1, PDPN, PROX-1, and VEGFR-3 were extremely low in the normal group. In contrast, expression of these markers was significantly upregulated in the IDD group. In the mouse IDD model, compared with the Sham group at the same time point, the IDD group exhibited higher histopathological scores in IVD tissue, accompanied by upregulation of LYVE-1, PDPN, PROX-1, and MMP-13, as well as downregulation of Col II. In-depth analysis revealed that these differences between the Sham and IDD groups were not static but exhibited a dynamic pattern of increasing magnitude over time. Concurrently, as the modeling period progressed, the histopathological scores of mouse IVD in the IDD group, as well as the expression levels of LYVE-1, PDPN, PROX-1, and MMP-13, showed a progressive upward trend, while Col II expression progressively decreased. In addition, Spearman’s rank correlation analysis revealed that the expression levels of LYVE-1, PDPN, and PROX-1 in mouse IVD tissue were all significantly positively correlated with histopathological scores. Conclusions: In the process of IDD, the dynamic upregulation of LEC markers is highly consistent with its severity in the time dimension. At the same time, there was also a significant positive correlation between the expression level of LEC markers and the severity of IDD. Taken together, these findings suggest that the dynamic upregulation of LEC markers may be potentially associated with the pathological progression of IDD. Full article

Metal Digital light processing (MDLP) offers high resolution and excellent surface quality, but the final properties of printed parts are highly dependent on post-processing. In this study, the effects of debinding, decarburization, and sintering on the shape fidelity, microstructure, and mechanical properties of MDLP-fabricated 316L stainless steel were systematically investigated. The optimal post-processing route consisted of debinding in an inert atmosphere, decarburization in air within 400–600 °C, and sintering at 1370 °C for 4 h under flowing nitrogen. Under these conditions, the sintered parts achieved a relative density of 98.03 ± 0.23%, hardness of 380.63 ± 9.15 HV, elastic modulus of 213.47 ± 5.5 GPa, tensile strength of 519.7 ± 22 MPa, and elongation at fracture of 76.8 ± 9.3%. Microstructural analysis showed that increasing the sintering temperature reduced porosity and smoothed the morphology of Cr-rich oxygen-containing second phase regions, thereby alleviating stress concentration and improving mechanical properties. This study provides an effective post-processing strategy for MDLP-fabricated 316L stainless steel and examines the microstructural origins of the observed property evolution. Full article