Search Results (919)

This study investigates the influence of solidification conditions on the high-cycle fatigue (HCF) behavior of a second-generation DD6 single-crystal superalloy. Single-crystal bars with a [⁰⁰¹] orientation were prepared using the high-rate solidification (HRS) and liquid-metal cooling (LMC) techniques under various pouring temperatures. The HCF performance of the heat-treated alloy was subsequently evaluated at 800 °C using rotary bending fatigue tests. The results demonstrate that increasing the pouring temperature effectively reduced the content and size of microporosity in the HRS alloys. At an identical pouring temperature, the LMC alloy exhibited a significant reduction in microporosity, with its content and maximum pore size being only 44.4% and 45.8% of those in the HRS alloy, respectively. Consequently, the HCF performance was enhanced with increasing pouring temperature for the HRS alloys. The LMC alloy outperformed its HRS counterpart processed at the same temperature, showing a 9.4% increase in the conditional fatigue limit (at 10⁷ cycles). Microporosity was identified as the dominant site for HCF crack initiation at 800 °C. The role of γ/γ′ eutectic in crack initiation diminished or even vanished as the solidification conditions were optimized. Fractographic analysis revealed that the HCF fracture mechanism was quasi-cleavage, independent of the solidification conditions. Under a typical stress amplitude of 550 MPa, the deformation mechanism was characterized by the slip of a/2<011> dislocations within the γ matrix channels, which was also unaffected by the solidification conditions. In conclusion, optimizing solidification conditions, such as by increasing the pouring temperature or employing the LMC process, enhances the HCF performance of the DD6 alloy primarily by refining microporosity, which in turn prolongs the fatigue crack initiation life. Full article

With the growing requirements for multi-particle process simulation, improving computational accuracy, efficiency, and scalability has become a critical challenge. This study generally focused on comprehensive analyses of existing numerical methods for simulating particle–substrate interactions in gas–thermal spraying (including gas–dynamic spraying processes), covering both single-particle and multi-particle models to develop practical recommendations for the optimization of modern coating spraying processes. First of all, this paper systematically analyzes the key limitations of current approaches, including their inability to handle high deformations effectively or high computational complexity and their insufficient accuracy in dynamic scenarios. A comparative evaluation of four numerical methods (Lagrangian, Arbitrary Lagrangian–Eulerian (ALE), Coupled Eulerian–Lagrangian (CEL), and Smoothed Particle Hydrodynamics (SPH)) revealed their strengths and weaknesses in modeling of real gas–thermal spraying processes. Furthermore, this study identifies the limitations of the widely used Johnson–Cook (JC) constitutive model under extreme conditions. The authors considered the Zerilli–Armstrong (ZA), Mechanical Threshold Stress (MTS), and Preston–Tonks–Wallace (PTW) models as more realistic alternatives to the Jonson–Cook model. Finally, comparative analyses of theoretical and realistic deformation and defect-generation processes in gas–thermal coatings emphasize the critical need for fundamental changes in the simulation strategy for modern gas–thermal spraying processes. Full article

The accurate modelling of material removal mechanisms in grinding processes requires precise constitutive equations describing dynamic material behaviour under extreme strain rates and large deformations. This study presents a novel methodology for optimising the Johnson–Cook (J–C) constitutive model parameters for micro-grinding applications, addressing the limitations of conventional mechanical testing at strain rates exceeding 10⁵ s⁻¹. The research employed single abrasive grain micro-cutting experiments using a diamond Vickers indenter on aluminium alloy 7075-T6 specimens. High-resolution topographic measurements (130 nm lateral resolution) were used to analyse the scratch geometry and lateral material displacement patterns. Ten modified J–C model variants (A1–A10) were systematically evaluated through finite element simulations, focusing on parameters governing plastic strengthening (B, n) and strain rate sensitivity (C). Quantitative non-conformity criteria assessed agreement between experimental and simulated results for cross-sectional areas and geometric shapes of material pile-ups and grooves. These criteria enable an objective evaluation by comparing the pile-up height (h), width (l), and horizontal distance to the peak (d). The results demonstrate that conventional J–C parameters from Hopkinson bar testing exhibit significant discrepancies in grinding conditions, with unrealistic stress values (17,000 MPa). The optimised model A3 (A = 473 MPa, B = 80 MPa, n = 0.5, C = 0.001) achieved superior convergence, reducing the non-conformity criteria to Σk_A = 0.46 and Σk_K = 1.16, compared to 0.88 and 1.67 for the baseline model. Strain mapping revealed deformation values from ε = 0.8 to ε = 11 in lateral pile-up regions, confirming the necessity of constitutive models describing material behaviour across wide strain ranges. The methodology successfully identified optimal parameter combinations, with convergence errors of 1–14% and 7–60% on the left and right scratch sides, respectively. The approach provides a cost-effective alternative to expensive dynamic testing methods, with applicability extending to other ductile materials in precision manufacturing. Full article

Laser-induced periodic surface structures (LIPSSs) on silicon, generated by ultrashort pulsed lasers, provide an efficient means to tailor surface functionality. This work presents a multiphysics finite element study on the thermomechanical dynamics of silicon wafers irradiated by picosecond laser pulses, focusing on the melting regime where thermomechanical and hydrodynamic effects dominate. To illustrate the sequential nature of laser scanning, single-pulse irradiation models are developed as thermomechanical analogues of sequential laser irradiations. By positioning the laser focus near reflective boundaries and corners of the target, these models reproduce the stress wave interference that would occur between successive pulses in laser scanning. The results show that periodic surface structures are enhanced from mechanical standing wave interference within the molten layer, forming ripples with near-wavelength periodicity. The penetration depth (PD) is identified as a key factor controlling the duration and stability of these ripples: shallow PDs (75–150 nm) yield distinct, persistent patterns, while deeper PDs (~2.5 μm) lead to extended melting and hydrodynamic smoothing. Simulations of sequential laser pulse irradiations confirm that residual stresses and strains from the first pulse amplify deformation during the second, enhancing ripple amplitude and uniformity. Thus, the role of controlled excitation of mechanical standing waves governed by PD, boundary geometry, and pulse sequencing, in deterministic LIPSSs formation on silicon is revealed. Full article

Compared to traditional single/double-row concrete cast-in-place piles or concrete walls commonly used in foundation pit engineering, pre-tensioned prestressed hollow concrete-filled steel tube piles (referred to as prestressed Steel Cylinder Piles, or prestressed SC piles) demonstrate superior advantages including high bearing capacity, light weight, enhanced stiffness, excellent crack resistance, and cost-effectiveness, indicating a promising future in foundation pit engineering. However, current research has paid limited attention to such piles. Only a few experimental studies have focused on their flexural performance. No studies have presented bearing behavior investigations considering soil–pile interactions and the differences between these kinds of piles and traditional piles. To address this gap, this paper conducts a systematic investigation into the bearing performance of prestressed SC piles. A refined finite element analysis model capable of accurately characterizing pile–soil interactions is developed to analyze the mechanical behavior. Subsequently, the elastic foundation beam method recommended by design codes is employed to analyze the internal forces and displacement variations of these piles during excavation. Finally, the predictions by the design code are compared against those from the refined model. Results shows that the established finite element model presents reasonable predictions on monitoring data and experimental results, with deviations in bending moments and deformations within the range of 10–15%; a comparative analysis of different pile types reveals that prestressed SC piles exhibit smaller horizontal displacements and higher bearing capacities; the bending moments and deformations predicted by design methods (elastic foundation beam method) are conservative, with the predicted values significantly higher than those predicted by the refined model. Full article

Background/Objectives: Distal biceps tendon rupture is a disabling injury that compromises elbow flexion and forearm supination strength, particularly in high-performance athletes. Although several fixation techniques have been proposed, no single method has proven optimal in combining mechanical stability, anatomical restoration, and early functional recovery. This study aimed to evaluate the efficacy, safety, and reproducibility of a hybrid dual-fixation technique combining a Tightrope^® cortical button (Arthrex, Naples, FL, USA) with a PEEK interference screw for anatomic reinsertion of the distal biceps tendon in athletic individuals. Methods: A prospective observational study was conducted on 13 high-performance athletes who underwent distal biceps tendon repair using the hybrid Tightrope–PEEK construct between March 2024 and September 2025. Functional recovery, muscle strength, esthetic contour, and patient satisfaction were evaluated using the Visual Analog Scale (VAS), Mayo Elbow Performance Score (MEPS), Quick Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH), and a 5-point Likert scale over a 12-month follow-up. Descriptive statistical analysis was performed using IBM SPSS Statistics, version 29.0. Results: All patients achieved secure fixation with no intraoperative or postoperative complications, loss of reduction, or hardware failure. Early controlled mobilization began within the first postoperative week. At 6 months, flexion and supination strength were fully restored, and at 12 months, all patients achieved full range of motion and optimal functional scores (mean MEPS 100; QuickDASH 0). No “Popeye” deformities or contour irregularities were observed, and mean patient satisfaction was 5/5. Conclusions: The hybrid Tightrope–PEEK dual-fixation technique provides excellent mechanical stability, allowing early mobilization and rapid functional recovery with minimal complications. Its reproducibility and cosmetic advantages suggest that it represents a safe and effective option for distal biceps tendon reinsertion in high-demand athletes. Full article

Syntheticaperture radar (SAR) object detection offers significant advantages in remote sensing applications, particularly under adverse weather conditions or low-light environments. However, single-modal SAR image object detection encounters numerous challenges, including speckle noise, limited texture information, and interference from complex backgrounds. To address these issues, we present Modality-Aware Adaptive Interaction Enhancement Network (MAIENet), a multimodal detection framework designed to effectively extract complementary information from both SAR and optical images, thereby enhancing object detection performance. MAIENet comprises three primary components: batch-wise splitting and channel-wise concatenation (BSCC) module, modality-aware adaptive interaction enhancement (MAIE) module, and multi-directional focus (MF) module. The BSCC module extracts and reorganizes features from each modality to preserve their distinct characteristics. The MAIE module component facilitates deeper cross-modal fusion through channel reweighting, deformable convolutions, atrous convolution, and attention mechanisms, enabling the network to emphasize critical modal information while reducing interference. By integrating features from various spatial directions, the MF module expands the receptive field, allowing the model to adapt more effectively to complex scenes. The MAIENet framework is end-to-end trainable and can be seamlessly integrated into existing detection networks with minimal modifications. Experimental results on the publicly available OGSOD-1.0 dataset demonstrate that MAIENet achieves superior performance compared with existing methods, achieving 90.8% ${\mathrm{mAP}}_{50}$. Full article

Background: Animation deformity (AD) is a well-known complication of submuscular implant placement. However, dynamic contour irregularities have also been reported in prepectoral reconstructions, but their mechanisms and classification remain unclear. Methods: In this prospective, single-center study, 67 patients underwent either direct-to-implant (DTI, n = 33) or tissue expander (TE, n = 34) reconstruction. Among these, 56 patients had subpectoral and 11 patients had prepectoral implant placement. Patient-reported outcome measures (PROMs) were assessed using the BREAST-Q. Aesthetic outcomes were rated by four plastic surgeons using the Breast Aesthetic Scale. Breast animation deformity was evaluated clinically and photographically by an expert panel using two distinct classification systems. Results: The mean follow-up period was 78 (±45) months. No significant differences were found between DTI and TE groups in BREAST-Q scores or overall aesthetic outcomes. Bilateral reconstructions showed significantly higher aesthetic ratings (p = 0.001). AD was observed in 61.2% of patients, with significantly higher prevalence in the DTI group (p = 0.02). Six patients with prepectoral reconstruction demonstrated dynamic contour irregularities distinct from classical AD. A new definition for this phenomenon is proposed. Conclusions: DTI and TE reconstructions achieve comparable long-term patient satisfaction and aesthetic outcomes. The observed cases of dynamic implant contour irregularities (DICI) in prepectoral implant placement underscore the need for a more nuanced classification of contour irregularities in implant-based breast reconstruction beyond the established concept of AD. Full article

To evaluate the shear performance of circumferential joints in super-large cross-section shield tunnels featuring inclined bolts and distributed mortises and tenons, refined numerical models were developed for three distinct configurations: single-bolt aligned mortise and tenon (SAB), single-bolt offset (SOB), and double-bolt offset (DOB). This study focuses on assessing how variations in bolt arrangement influence the shear behavior of these joints. The results are as follows: Under the effect of the ordinal shearing loading scenario (OSLS), bolts can significantly bear the load, resulting in the superior shear performance of DOB over SAB and SOB. Under the reverse shearing loading scenario (RSLS), bolts exhibit noticeable pullout phenomena, leading to minimal differences in the shear-dislocation curves of the three bolt arrangement pattern joints. The shear mechanical performance of SOB is notably better than that of SAB and SOB under OSLS, but this difference is less evident under RSLS. The mechanical behavior of bolts remains consistent across different bolt arrangement pattern joints during shear deformation. The bolt holes in SAB passing through the mortise and tenon weaken them, and contact failure between bolts and bolt holes further damages the mortise and tenon. Full article

Cold-formed thin-walled steel (CFS) members were widely used in steel structures but faced challenges in meeting bearing capacity and assembly efficiency requirements as single-limb members. To overcome the above limitations, a promising fold-fastened multi-cellular steel panel (FMSP) was proposed. The FMSP eliminated the need for discrete self-drilling screws, instead utilizing a continuous mechanical fold-fastened connection, which enhanced structural integrity and assembly efficiency. This approach also provided greater flexibility to meet the design requirements of complex structural configurations. This study investigated the flexural behaviors of panels—a key mechanical property governing their structural behavior. A bearing capacity test was conducted on five FMSP specimens, focusing on the failure modes, bending moment–deflection curves, deflection distributions under representative loading levels, and flexural bearing capacities of the specimens. Refined finite element models (FEMs) of the specimens were established, and the stress and deformation distributions were further studied. The comparison results showed that the numerical results were in good agreement with the experimental results. Finally, the parametric analysis was carried out, and the influence of key parameters on the flexural behavior was revealed. Analysis results demonstrated that doubling the steel plate thickness increased the flexural capacity by 207%, while a twofold increase in panel thickness resulted in a 123% improvement. In contrast, increasing the steel strength from 235 MPa to 460 MPa yielded only a 61% enhancement. This research laid a solid foundation for promoting the application and investigation of FMSPs, thus achieving high industrialization and meeting the requirements of complex structural design. Full article

This paper studies the influence of laser power and scanning speed through single laser scan tracks on AlNiCo5 and SS 304 substrates. Track morphologies and melt pool geometries were assessed to determine the prevailing melting modes. Cracking was observed only on AlNiCo5 substrates, while SS 304 substrates exhibited crack-free tracks, highlighting the advantages of its ductile FCC structure. Optimal laser powder bed fusion process parameters for AlNiCo5 fabrication were identified as 190 W and 600–900 mm/s for stable conduction melting, while for higher laser power processing, 270 W and 600–800 mm/s provided stable transition melting. Microhardness measurements, nanoindentation, and energy-dispersive X-ray spectroscopy were employed to analyze mechanical properties and compositional variation within the melt pools. Increased laser power led to noticeable dilution of the SS 304 substrate into the AlNiCo5 tracks, reducing the melt pool’s overall microhardness due to altered chemical composition. Nanoindentation analysis further confirmed localized mechanical heterogeneity within the melt pool, with Co- and Al-rich zones showing elevated nanohardness, elastic modulus, and resistance to plastic deformation (H/Er, H³/Er²), while substrate-diluted areas (Cr-enriched) exhibited softening linked to BCC-to-FCC phase transformation. Full article

As a critical element within the prefabricated structural system, the prefabricated shear wall connected by sleeve grouting is renowned for its superior mechanical performance and high construction efficiency. It is widely applied in mid- and high-rise buildings. However, under fire conditions, not only do the material properties degrade, but the structural connections may also fail, significantly compromising the structural stability and safety. Therefore, this study delves into the fire resistance performance of such prefabricated shear walls. The research primarily focuses on analyzing fire resistance characteristics, including deformation patterns, lateral and axial deformations, fire resistance limits, and other performance metrics, for both prefabricated and cast-in-place shear walls subjected to three hours of single-sided fire exposure. Additionally, a parametric analysis is performed. The results reveal that, after three hours of single-sided fire exposure, the temperature distribution patterns at the mid-width and mid-height sections of the prefabricated shear wall generally resemble those of the cast-in-place wall, displaying arch-shaped and strip-shaped distributions, respectively. However, due to the presence of sleeves, higher temperatures are observed near the sleeve areas in the prefabricated wall, along with a more extensive high-temperature zone. Throughout the three-hour fire exposure, both types of shear walls demonstrated satisfactory structural stability and thermal insulation performance, meeting the requirements for a first-level fire resistance rating (3 h). Nevertheless, greater axial and lateral deformations were noted in the prefabricated shear wall. Key factors influencing the fire resistance performance of the sleeve-connected prefabricated shear wall include the axial compression ratio, longitudinal reinforcement diameter, protective layer thickness, and height-to-thickness ratio. Specifically, axial deformation is found to be directly proportional to the axial compression ratio and height-to-thickness ratio, while inversely proportional to the longitudinal reinforcement diameter and protective layer thickness. Lateral deformation is directly proportional to the axial compression ratio and longitudinal reinforcement diameter, and exhibits a trend of initially increasing and then decreasing with an increase in protective layer thickness, and initially decreasing and then increasing with an increase in the height-to-thickness ratio. Full article

This study quantitatively investigates the influence of inter-particle rotation moment transition and mesoscopic friction on the macroscopic mechanical behavior of frozen sand by integrating plane strain tests with discrete element simulations. Two distinct contact models were employed under different temperatures and loading rates. The numerical results demonstrate that the parallel bond model, which accounts for particle rotation, accurately reproduces the full-range stress–strain response, including the strain-softening stage, whereas the contact bond model underestimates post-peak strength due to its inability to transmit moments. It is revealed that taking the influence of rotation moment transition into consideration promotes the uniformity of the local deformation distribution, thereby enhancing the material’s ductility, while mesoscopic friction parameters directly govern the shear band inclination angle at failure. Discrepancies in shear band morphology between experiments and simulations—single versus X-shaped bands—are explained by the inclination of loading plates in physical tests. This study establishes quantitative links between mesoscopic interaction mechanisms and macroscopic responses, offering valuable insights for developing advanced constitutive models for frozen soil in engineering applications. Full article

Mining above confined aquifers fundamentally depends on understanding the evolution of floor permeability for water hazard control and water conservation mining. A mechanical model was developed to characterize the coordinated deformation of floor aquiclude strata, accounting for non-uniform distributions of stress and water pressure. The competing mechanisms whereby neutral plane strain and flexural deflection dominantly control permeability at different dip angles were elucidated, and the influence of dip angle on the stability of the water-resistant key strata was quantified. On this basis, a quantitative method for assessing the feasibility of in situ water conservation mining above confined aquifers was developed and its effectiveness was verified through field application. The main findings are as follows: The deflection of the floor aquiclude increases with water pressure, advance distance, and panel length. Larger coal seam dip angles correspond to smaller aquiclude deflection, with a strong dependence on the water pressure treatment method. The equivalent permeability of the floor increases with water pressure, panel length, and advance distance, and its variation is most pronounced with water pressure. As the dip angle increases, the equivalent permeability exhibits a trend of first rising and then decreasing; the transition between deflection-dominated and neutral plane strain-dominated control occurs at a dip angle of 35°. Lithological assemblage is found to govern the position of the neutral plane and the bending stiffness matrix, while a soft–hard interbedded floor is effective in suppressing deformation and mitigating the increase in the equivalent permeability. For inclined aquiclude key strata, the ranking of zones most prone to failure and water inrush is as follows: lower end > upper end > coal wall position > behind the goaf. A quadratic multi-parameter response model for the mining-induced equivalent permeability at the Fenyuan Coal Mine is established, yielding the sensitivity ranking under single factor and interaction effects as follows: water pressure > panel length > advance distance > water pressure (quadratic) > water pressure × panel length interaction. The higher the water pressure, the stronger the influence of dip angle on the equivalent permeability. Groundwater ion evolution is dominated by dissolution/leaching, with sulfate (SO₄²⁻) serving as a diagnostic ion for source identification. The stepwise criteria and grouting-reinforcement parameters for in situ protection of confined aquifers are proposed. Using water quality and quantity as evaluation metrics, Working Face 5-103 at the Fenyuan Coal Mine, which is a large-inclination-angle and high-pressure working face, has achieved in situ protection of the floor water. Full article

Background and Objectives: Femoral malunion, defined as healing of a femoral fracture in an anatomically incorrect position, can lead to significant biomechanical and functional impairment despite modern fixation techniques achieving union rates near 99%. The lack of a universal definition and standardized management approach continues to hinder optimal outcomes. This review aims to synthesize the literature on the causes, clinical presentation, radiologic assessment, surgical indications, corrective procedures, and outcomes of femoral malunion to guide clinical decision-making and future research. Materials and Methods: A narrative review of peer-reviewed orthopedic literature was conducted, focusing on adult femoral malunions across anatomical regions. Articles detailing deformity thresholds, imaging modalities, corrective osteotomies, and fixation strategies were included. Particular emphasis was placed on region-specific deformities—femoral head, neck, intertrochanteric, diaphyseal, and distal femur—and their corresponding surgical correction methods, including valgus intertrochanteric osteotomy, clamshell osteotomy, and lengthening with external or magnetic intramedullary devices. Results: Malunion most commonly presents as angular, rotational, or length deformity, with thresholds of >5–10° angulation, >10° rotation, or >1–2 cm shortening being clinically significant. Patients may experience pain, limp, gait asymmetry, and early-onset arthritis. Corrective techniques tailored to the anatomical site yield favorable results: valgus intertrochanteric osteotomy restores leg length and alignment; diaphyseal malunions respond well to single- or multi-plane osteotomies with internal fixation or gradual correction; distal femoral malunions often require multiplanar osteotomy to reestablish the joint line. Most series report high union rates and functional improvement, though complications such as infection and hardware failure may occur. Conclusions: Femoral malunion remains a complex but treatable condition. Successful outcomes rely on accurate deformity characterization, patient-specific surgical planning, and restoration of mechanical alignment. Standardized deformity criteria and long-term functional outcome studies are needed to refine management algorithms and improve patient care. Full article