Search Results (6,084)

Residual stress influences dimensional stability, fatigue, fracture and structural integrity in welded and additively manufactured components. Ultrasonic methods offer a non-destructive and deployable alternative to diffraction and strain-relief techniques because stress changes elastic-wave velocity through acoustoelasticity. This review traces ultrasonic residual stress measurement from nonlinear elasticity and single-element longitudinal critically refracted (LCR) waves to finite-element-assisted LCR, robotic phased-array inspection and Phased-Array Ultrasonics for Residual Stress Measurement (PAURS). It critically examines time-of-flight precision, depth and path averaging, reference-state uncertainty, temperature, coupling, geometry, Type I residual stress and its interaction with phase transformation, microstructure and texture. PAURS improves multi-path redundancy and diagnostic capability, while quantitative accuracy remains dependent on calibration and material-state effects. PAURS+ is proposed as the convergence of PAURS with phased-array microstructure characterisation; unlike experimentally demonstrated PAURS, it remains a conceptual multi-observable framework requiring quantitative validation. The review concludes that integrated in-process material-state measurement requires PAURS+ for multi-observable sensing, robotic high-temperature inspection for deployment, and coupled process, material and wave models for interpretation. Physics-informed AI, independent ground truth, uncertainty assessment and digital-twin updating are required to connect these capabilities to traceable manufacturing decisions. Full article

To improve the forming quality, microstructural characteristics, and mechanical properties of multi-track multilayer laser-clad H13 steel structures, a combined laser cladding and layer-by-layer remelting process was employed. The basic cladding parameters were comprehensively evaluated using an orthogonal experimental design combined with the entropy weight method–gray relational analysis (EWM-GRA), while the remelting parameters were determined through a full-factorial experiment. Multi-track multilayer specimens with and without layer-by-layer remelting were subsequently compared in terms of forming characteristics, microstructure, and mechanical properties. Within the investigated parameter range, the preferred cladding parameter combination was a laser power of 1300 W, scanning speed of 12 mm/s, and powder feed rate of 13 g/min, while the preferred remelting parameter combination was 780 W and 18 mm/s. Layer-by-layer remelting produced a smoother surface with less pronounced inter-track overlap traces. Qualitative examination of the cross-sections suggested a tendency toward fewer locally observed pores and reduced variation in microstructural morphology among regions at different heights. The average microhardness increased from 756.9 HV to 789.5 HV, while the ultimate tensile strength and yield strength increased from 1524.23 MPa and 1173.37 MPa to 1604.46 MPa and 1342.88 MPa, respectively. The increased strength was accompanied by reduced elongation after fracture, from 2.57% to 1.41%. These results provide a reference for process parameter selection and property tailoring of layer-by-layer remelting in multi-track multilayer laser-clad H13 steel structures. Full article

In the failure analysis of metallic materials, the observation of fracture-surface morphology by scanning electron microscopy (SEM) is an important means of determining the fracture mechanisms. In practice, however, interpretation of fracture-surface images relies heavily on expert experience and is readily affected by subjective factors when large batches of images must be examined. To address this issue, this paper proposes a classification model based on You Only Look Once version 8 (YOLOv8) and the convolutional block attention module (CBAM) for SEM images of metal fracture surfaces, aiming to identify four typical fracture-surface categories: cleavage, fatigue, dimple, and intergranular fracture. Considering that SEM images are mostly grayscale texture images, the model emphasizes the preservation of brightness, local texture, and edge-contour information during input processing and training augmentation, and introduces CBAM to optimize the channel and spatial responses of feature maps. Experimental results showed that at an input resolution of 1024, the YOLOv8-CBAM model achieved a Top-1 accuracy of 97.92% with only 1.53 M parameters. The proposed model achieved a favorable balance between observed classification performance and model complexity compared with the evaluated convolutional neural network (CNN) baselines. In addition, the gradient-weighted class activation mapping (Grad-CAM) results showed correspondence between the high-response regions of the model and certain fracture-surface morphology regions. Full article

Groundwater is vital for ecosystems and livelihoods in sub-Saharan Africa, particularly in Ethiopia, dubbed the “water tower of Africa.” Despite its significance, many areas face water scarcity due to data scarcity and an uneven distribution of resources. The Baro River watershed, covering over 23,000 km² in Southwestern Ethiopia, poses a critical study area that has been largely overlooked. A hydro-geospatial modeling framework, utilizing remote sensing (RS), Geographic Information Systems (GIS), and Multi-Criteria Decision Analysis (MCDA) via the Analytical Hierarchy Process (AHP), was employed to map Groundwater Potential Zones (GWPZ) across the region. Nine environmental parameters were assessed for their impact on groundwater recharge, with rainfall as the primary influencer. The analysis involved reclassifying and weighting each factor, yielding a Consistency Ratio (CR) of 0.067, well below the acceptable threshold of <0.10, indicating reliable results. The resulting groundwater potential map classified zones into five categories: very high, high, moderate, low, and very low potential. High-potential zones are predominantly located in the Gambella lowlands, benefiting from favorable groundwater infiltration conditions in fractured volcanic and alluvial deposits. In contrast, low-potential areas correspond to steep slopes with dense drainage. The findings reveal significant groundwater development opportunities, with over 90% of the watershed exhibiting moderate to very high potential, suggesting effective water management strategies through the integration of GIS and AHP for enhanced groundwater evaluation. Full article

Mafic–intermediate dikes provide useful constraints on mantle source characteristics, crust–mantle interaction, and regional tectono-magmatic evolution. Here we present field, petrographic, whole-rock geochemical, zircon U–Pb–Hf isotopic, and whole-rock Sr–Nd isotopic data for the Haojiang mafic–intermediate dike suite and its host granitoids in eastern Guangdong, SE China. Field observations show that dark, fine-grained dikes sharply intrude light-colored granitoids along fractures or joints. Zircon U–Pb dating of the host granitoid sample HJ-7-3 yields a crystallization age of 137.56 ± 0.76 Ma, whereas the representative dike sample HJ-1 yields a magmatic zircon age of 94.25 ± 0.64 Ma. These ages indicate that at least part of the Haojiang dike suite represents a Late Cretaceous mafic–intermediate magmatic event that postdated Early Cretaceous granitoid emplacement. An older zircon population in HJ-1 yielded an age of 135.8 ± 1.1 Ma and is interpreted as xenocrystic or inherited zircon probably related to interaction with Early Cretaceous granitoid crust or a coeval crustal component during magma ascent. The dike samples have SiO₂ contents of 50.10–58.52 wt.% and plot mainly in the basaltic andesite to andesite fields in the TAS diagram. Major-element variations, compatible trace elements, and weak Eu anomalies are consistent with variable fractional crystallization, although open-system processes cannot be excluded. The dikes are enriched in LILEs and LREEs and depleted in Nb, Ta, and Ti. Their initial ⁸⁷Sr/⁸⁶Sr ratios of 0.705232–0.705772, εNd(t) values of −3.10 to −0.12, and zircon εHf(t) values of −1.61 to +1.30 indicate weakly enriched isotopic compositions. Taken together, these features favor involvement of a subduction-modified enriched mantle source, although contributions from metasomatized lithospheric mantle and enriched asthenospheric mantle cannot be uniquely distinguished. Possible limited crustal interaction during magma ascent is also allowed. The ca. 94 Ma Haojiang dike therefore provides evidence for Late Cretaceous mantle-derived or mantle-influenced magmatism in eastern Guangdong, consistent with a regional extensional regime commonly associated with Paleo-Pacific slab rollback. Full article

Cemented sand and gravel (CSG), widely used in dams and cofferdams, is susceptible to fracture under coupled seepage and mechanical loading. This study combines wedge-splitting experiments and mesoscale numerical simulations to investigate the hydro-mechanical fracture behavior of CSG under crack-face water pressures of 0, 0.02, 0.05, 0.10, 0.15, and 0.20 MPa. A coupled model was developed by integrating the lattice discrete particle model (LDPM) with discrete poromechanics. In this framework, deformation and fracture of the solid phase are resolved through interactions among polyhedral cells, while water transport is represented by a dual-lattice seepage network and coupled to the solid response through the effective stress principle. After calibration using triaxial compression tests, the model was used to simulate pore-pressure evolution, crack initiation, and crack propagation. The results show that increasing hydraulic pressure accelerates crack propagation and localizes the fracture process zone, leading to more brittle failure. The peak load, initial fracture energy, and effective process-zone length all decrease with increasing water pressure. The simulated mean peak loads agree well with the experimental results, with relative errors of 0.26–6.58%, while the internal water-pressure histories recorded by three embedded sensors are reproduced with root-mean-square errors of 3.4–11.2%. The size-effect analysis further shows that the nominal strength follows Bažant’s size-effect law, confirming the quasibrittle nature of CSG fracture under seepage coupling. These results provide a mesoscale basis for evaluating fracture safety and optimizing seepage-control measures in CSG dams and cofferdams. Full article

Spontaneous imbibition (SI) is the key mechanism governing oil production in fractured carbonates, where capillary forces drive oil from the low-permeability matrix into the fractures. Its application is limited by the strongly oil-wet nature of carbonate rocks and by high interfacial tension (IFT), which restrict the capillary forces needed to mobilize oil from the matrix. This work examines whether a combined low-salinity water (LSW)-surfactant enhanced oil recovery (EOR) process can be optimized for SI by tuning the potential determining ions (PDIs) of the hybrid-stage brine. Experiments were performed with a fixed LSW preconditioning stage, while the hybrid-stage composition and surfactant concentration were varied. Contact angle screening of three ion-modified LSW formulations showed that LSW3Ca3Mg-SO₄, with tripled Ca²⁺ and Mg²⁺, reduced the contact angle from 178.5° to 47.3° within 6 days and lowered the IFT from 33.2 to 17.5 mN/m without surfactant. In SI tests on limestone cores, ion-modified hybrid systems showed substantially higher early-time imbibition rates than conventional LSW-surfactant systems, together with equal or higher ultimate recovery. Notably, with 0.5 wt.% surfactant the ion-modified system reached an early-time rate of 0.75%/h and 36.36% of the original oil in place (OOIP), compared with 0.36%/h and 35.94% OOIP for conventional LSW with 1.0 wt.% surfactant, i.e., at half the surfactant dosage. Wettability-controlled systems, such as ion-modified LSW without surfactant, accelerate early imbibition but recover only about 6-7% OOIP regardless of ionic tuning. IFT reduction, in contrast, is considered to lower the capillary resistance in tight pore throats, allowing much higher recovery even while the rock surface remains oil-wet (40.15% OOIP with the ion-modified hybrid system at 1.0 wt.% surfactant). These findings suggest that tuning the ionic composition of the hybrid-stage brine can accelerate SI and allow a lower surfactant dosage, pointing to a potentially cost-effective ionic design strategy for EOR in fractured carbonate reservoirs. Full article

The Honningsvåg Igneous Complex (Magerøya, N Norway) provides a unique window into the syn-tectonic crystallization and deformation of mafic-ultramafic cumulates within the Caledonian orogenic belt. This study integrates High-Resolution Electron Backscatter Diffraction (EBSD) mapping, Single-Crystal X-ray Diffraction (SC-XRD) analysis and refinement of the crystal structure, and Electron Probe Microanalysis (EPMA) to decipher the microstructural and chemical evolution of plagioharzburgites and troctolites. Our EBSD results reveal intense intra-crystalline plastic deformation in olivine, characterized by well-developed subgrain boundaries and translational deformation lamellae resulting from high-temperature dislocation creep. SC-XRD structural refinements substantiate this behavior, demonstrating that tectonic strain was accommodated by structural distortion restricted to the highly anisotropic M2 octahedral site. In contrast, clinopyroxene and plagioclase exhibit strong chemical and structural disequilibrium relative to the olivine framework (apparent olivine–orthopyroxene $K_D^{Fe-Mg}$ ≈ 1.08 vs. discordant olivine–clinopyroxene pairs), recording late-stage intercumulus crystallization from fractionated residual melts or episodic magma replenishment in an open system. Furthermore, plagioclase documents a continuous poly-rheological transition, shifting from magmatic alignment and dynamic recrystallization within a dense crystal mush to pervasive brittle micro-fracturing during late-stage tectonic exhumation. Finally, uniform crystallographic orientations of post-magmatic serpentine meshes reveal a strict epitaxial growth mechanism onto the parent olivine, proving that regional ductile deformation had entirely ceased prior to low-temperature H₂O–CO₂ hydrothermal fluid influx. These findings underscore the role of the Honningsvåg intrusion as a highly dynamic, open magmatic system evolving within an active orogenic environment, effectively bridging the gap between deep-seated magmatic processes and crustal-level tectonic deformation. Full article

Directed Energy Deposition (DED) is an additive manufacturing technology rapidly consolidating for the fabrication and repair of complex aerospace Ti-6Al-4V components, ensuring high deposition rates and large build volumes. However, in high build-rate regimes, process-induced phenomena, such as oxygen pick-up, overheating, and residual porosity, introduce material anisotropy. While residual porosity can largely be mitigated by Hot Isostatic Pressing (HIP), dissolved oxygen cannot be removed by any post-processing method, raising uncertainties regarding the final mechanical properties of large DED parts and limiting the predictive performance of design simulation tools. To fully exploit the advantage of design for additive manufacturing methods, it is fundamental to assess how the DED process influences the material performance of large Ti-6Al-4V builds. This work investigates the effect of build orientation and process parameter set on the final mechanical behaviour of DED Ti-6Al-4V samples in high-build-rate conditions. Compared to cast and annealed Ti-6Al-4V, all the realized samples exhibit an average 14% and 22.5% increase in yield strength and ultimate tensile strength, respectively, but 38% lower Elongation at Break. Microstructural analysis reveals that both the process parameter set and the build orientation influence DED material anisotropy, particularly ductility, with vertically built specimens showing 68% and 33% higher elongation at break than longitudinal and lateral specimens, respectively, highlighting a direction-dependent mechanical response consistent with the columnar prior β-grain morphology and extension. LECO analysis confirms that oxygen pick-up also occurs in an enclosed deposition environment and strongly increases material strength at the expense of ductility. Oxygen content varies with build orientation, from 0.15 ± 0.02 wt.% in vertical to 0.19 ± 0.01 wt.% in longitudinal specimens. Finally, fracture surface analysis indicates that lack-of-fusion defects act as preferential crack initiation sites. Full article

This study investigated the synthesis and microstructural evolution of AlFeCoNi medium-entropy alloy powder processed by ball milling, conventional uniaxial pressing, and vacuum sintering at 900 °C for 1 h. The mechanically milled powder exhibited a refined, irregular particle morphology with a broad size distribution, indicating extensive fracture and cold-welding during milling. SEM (scanning electron microscopy) and EDS (energy-dispersive spectroscopy) observations showed effective elemental mixing of Al, Fe, Co, and Ni, with only limited evidence of large-scale segregation, suggesting that mechanical alloying promoted compositional homogenization. After compaction and sintering, the powder compact exhibited noticeable changes in microstructural continuity and pore morphology, indicating further microstructural evolution during thermal treatment. Overall, the results demonstrate the microstructural evolution of AlFeCoNi MEA during ball milling and subsequent conventional sintering, while further investigation involving quantitative densification measurements and optimization of sintering conditions is required to establish the consolidation behavior and microstructural uniformity of the alloy. Full article

Fretting wear at metal O-ring sealing interfaces involves the coupled processes of debris generation, entrapment, and oxidation. Existing accelerated life testing relies on similarity theory, yet it overlooks the dominant role of third-body behavior in governing wear regime transitions, so equivalence between test and service conditions lacks a physical basis. This study investigates reciprocating fretting wear of an Inconel 718/304 stainless steel pair and reinterprets wear evolution using third-body dynamics. Laser scanning confocal microscopy, energy-dispersive spectroscopy, and real-time friction monitoring reveal three distinct stages: debris generation with mild damage, oxide layer formation with steady wear, and oxide layer fracture with material spalling. The friction coefficient passes through running-in, steady-state, and sharp-rise phases, while oxygen content on the wear track rises from 2.1 wt.% to 18.3 wt.%. One-way ANOVA shows significant differences among all stages. Based on Berthier’s theory, a state-evolution model is developed that treats third-body oxidation degree and cumulative friction energy dissipation as equivalence criteria. Friction energy and wear mass correlate linearly (R² = 0.94), giving an effective wear coefficient of 6.3 × 10⁻⁷ mg/J and acceleration exponents of m₁ = 9.77 for pressure and m₂ = −8.71 for frequency. Independent validation shows that the model compresses test duration by 51%, with relative errors below 18% for wear mass, fractal dimension, and fractal roughness. By shifting the focus of accelerated testing from dimensional analysis to mechanism-preserving state tracking, this work provides a failure analysis framework that identifies the root cause of seal degradation as third-body oxidative spalling and offers practical preventive actions for nuclear metal seal reliability assessment. Full article

Background: Tibial plateau fractures are complex knee injuries where timely and accurate diagnosis is critical to preventing long-term disability. In high-pressure emergency settings, the risk of missed fractures (false negatives) remains a significant challenge. Objective: This study aims to develop a robust, clinically safe automated detection model using advanced deep learning architectures. Methods: We utilized a dataset of 1489 real-world clinical X-ray images, annotated by orthopedic surgeons, to train and evaluate five versions of the You Only Look Once (YOLO) algorithm (v8, v9, v10, v11, and v12). A rigorous two-stage evaluation process was implemented. First, an initial screening excluded YOLOv8 and YOLOv10 due to critical detection failures (“background errors”), in which the models failed to detect any object in the target region. Second, a comprehensive performance analysis identified YOLOv11 as the optimal architecture. Based on these results, the YOLOv11 model was integrated into a user-friendly, web-based diagnostic system using the Python Flask framework. Results: The YOLOv11 model achieved the highest Mean Average Precision (mAP) of 99.3% and an Accuracy of 98.32%. Crucially for clinical safety, YOLOv11 demonstrated superior sensitivity (96.58%) with the lowest false negative rate, attributed to its enhanced feature aggregation capabilities which effectively distinguish subtle fracture lines from trabecular bone patterns. Independent web interface validation (n = 109 real-world cases) confirmed 98.17% accuracy, 98.00% sensitivity, 98.31% specificity, 98.00% Positive Predictive Value (PPV), and 98.31% Negative Predictive Value (NPV). Conclusions: This system is designed to support clinical workflows by providing real-time, highly accurate second opinions, thereby reducing diagnostic errors and alleviating radiologist workload. Full article

Many materials can be cleaved to produce ideal atomically flat surfaces. However, for many perovskite oxides it was observed that a well-defined concentration of adatoms remains on one of the crack surfaces, mirrored by an equivalent amount of vacancies on the other side, even though this violates the charge neutrality of the created surfaces. In this work, we show for three prototypical oxide perovskites, SrTiO₃, BaTiO₃, and KTaO₃, that these materials develop a large dielectric polarization by ferroelectric displacements of the atoms under the large strain at the crack tip. Upon fracture, the polarization creates a surface charge on the emerging surfaces, which is maintained by the transfer of ions between the crack surfaces and the formation of adatoms and vacancies. By quantifying the strain-induced ferroelectric atomic displacements at the point of fracture using density-functional theory calculations, we find a very good agreement between the surface charge from the evolving polarization and the experimentally observed concentration of adatoms, which are therefore a remnant of the cleaving process. When predicting results of fracture experiments, this strain-induced ferroelectric transition developing during fracture has to be taken into account even for oxide perovskites that are not intrinsically ferroelectric at room temperature. Full article

Efficient deployment of neural-network detectors on field-programmable gate array (FPGA) accelerators depends not only on model complexity but also on compiler-visible graph structure. On deep learning processing unit (DPU) platforms, unsupported operators can fragment execution between accelerator and host execution domains. We present C2fDeploy, a training-free rewrite for the YOLOv8 C2f block that moves channel splitting from the activation graph to an offline partition of the trained projection and batch-normalization parameters. The transformed block preserves the 32-bit floating-point (FP32) function without retraining or additional parameters. On the GRAZPEDWRI-DX fracture-detection task, the original and rewritten graphs produced identical FP32 test metrics and comparable 8-bit integer (INT8) accuracy. Direct tensor-level FP32 comparison at the outputs of all eight rewritten C2f blocks yielded an aggregate mean absolute error of $9.73\times {10}^{-8}$ and a relative $L_2$ error of $1.97\times {10}^{-7}$, providing numerical verification beyond detection-level metrics. Compilation for the Kria KV260 consolidated nine DPU subgraphs into one and removed the C2f-related host-side slicing operations. In a same-checkpoint whole-XModel benchmark, C2fDeploy improved whole-XModel graph execution throughput by $95.2\times$ and reduced energy per execution on the 5 V system-on-module (SOM) rail by 98.2%. Direct runtime profiling further showed that DPU compute-unit busy-time utilization increased from 0.36% to 90.75%, while system-wide CPU utilization decreased by 89.5%. Aggregate APM-observed external-memory bandwidth increased from 40.20 to 3250.56 MB/s as accelerator execution became more continuous, whereas normalized APM-observed traffic decreased by 14.8% per graph execution. These results show that compiler-aware graph rewriting can remove deployment bottlenecks without changing the trained detector. Full article

The presence of hydroxyapatite (HAp) in the Cuticle of laying-hen eggshells was investigated through a comprehensive characterization of its morphology, composition, crystallographic structure, and thermal behavior. Comparison with bone-derived hydroxyapatite confirmed the similarity of the mineral phase. Examination of the same region at different imaging contrasts revealed unidirectional (nanofibrous) calcite growth within the Vertical Layer (VL) and Palisade Layer (PL). Shell thickening in these layers appears to occur through an additive mechanism involving the successive deposition of nanodroplets containing, according to our hypothesis, the mineral phase, water, and organic components. This multiphasic system generates lamellae that progressively increase in thickness through the continuous incorporation of new nanodroplets onto the pre-existing surface. Such a nanodroplet-mediated growth mechanism also provides a plausible explanation for the formation of the micropores observed in the VL and PL. The proposed additive mechanism is further supported by the presence of nanohemispheres attached to growing lamellae and the similar diameters of cuticle nanospheres and Vertical Layer nanohemispheres. Fractures observed in the Vertical Layer indicate structural continuity between the Cuticle and the VL, suggesting that additive growth involves a continuous supply of HAp, possibly across the entire uterine surface, followed by a previously undescribed process in which calcium phosphate nanospheres dissolve and/or transform into calcium carbonate nanofibers. Full article