Search Results (195)

This paper presents an investigation of the viability of Fiber Bragg Grating (FBG) accelerometers and load sensors for two diagnostic tasks in robotics: vibration analysis of industrial manipulators and slip detection in robotic grippers. The study synthesizes experimental results from two independent experiments, focusing on the use of optical sensors in place of traditional electromechanical devices such as MEMS accelerometers and resistive strain gauges. The experiments were performed on an ABB industrial robot with a parallel robotic gripper equipped with embedded optical fibers. Under the conditions tested, the optical chains provided good sensitivity and detected dynamic events such as slip onset and contact or movement-induced vibrations. Compared with the conventional chains recorded alongside them, the fiber-optic accelerometers delivered cleaner vibration spectra (SNR 36.7 dB against 13.7 dB), while the FBG load sensors measured gripping forces with a lower noise floor and less mains-band interference, although the force lost before a slip alarm favored the FBG chain only in the experiment carried out with brass. Obtained with a single specimen of each sensor type and a limited set of grasped objects, these findings indicate that optical sensing is a viable alternative for robotic diagnostics, but it comes at the cost of higher price and complexity. Full article

It has been established that hydrogen diffusion can significantly influence the mechanical response of metallic materials under various loading conditions. This phenomenon is particularly evident in reducing the ability for macroscopic plastic deformation. The formation and collapse of bubbles inside a fluid, i.e., cavitation, near a solid surface, generates one of the most complex loading scenarios. The characteristics of localized, high-velocity, and cyclic loading inherent to this process may lead to material removal from the surface, a phenomenon known as cavitation erosion. The mechanical properties of the metal surface, affected by hydrogen, may alter the resistance against erosion wear under cyclic loading conditions during cavitation. In this research, 316L stainless steel samples were electrochemically charged in H₂SO₄ to assess the effect of diffused hydrogen on mechanical behavior, as determined by tensile and micro-indentation testing. The cavitation erosion experiments were conducted on hydrogen-charged and uncharged samples in an ultrasonic cavitation test rig. The findings showed that hydrogen diffusion resulted in a significant reduction of up to 80% in cavitation erosion damage after 5 h of testing compared to the uncharged sample. After seven days of storage, however, the cavitation erosion damage of the hydrogen-charged specimens returned to a level comparable to that of the uncharged specimens, indicating that the beneficial effect of hydrogen on cavitation erosion resistance is reversible. Following short-term cavitation exposure, notable plastic deformation was observed on the eroded surfaces of the uncharged specimens, particularly as raised grain boundaries and slip bands. In contrast, the surfaces of the hydrogen-charged specimens predominantly retained their integrity, suggesting an increased resistance to plastic deformation following hydrogen charging. Full article

An angle-resolved scattered light sensor is a non-contact surface inspection technique that is robust and has a high resolution for roughness measurement at approximately 1 nm. Typically, during the early stage of cyclic loading in metals, persistent slip bands (PSBs) emerge on the surface as persistent slip markings (PSMs) which consist of extrusions and intrusions. It is commonly reported that the initiated crack is generated at the tip of one of those intrusions. Thus, the PSM formation is an important key for explaining the crack initiation behaviors in the early stage through surface development that was encouraged by the local plastic strain deformation. In this study, the optical-based measurement methods using the confocal microscope and the angle-resolved scattered light sensor were used to inspect and describe the crack formation during cyclic loading due to extrusion and intrusion formations. The specimens were fine-polished by diamond suspension (until 1 µm) and tested on a servo-hydraulic push–pull testing machine with the selected stress amplitude of 492 MPa (70% of the ultimate tensile strength), frequency (f) = 10 Hz, and load ratio (R) = −1. The extrusions and intrusions on the specimen were reliably observed and detected by our surface measurement techniques. The FIB–SEM results reported the emergence of PSMs and crack formations on the modified surface during fatigue loading. Moreover, the scattered light sensor has presented a remarkable result, which could be a potential technique for a new approach to study fatigue life estimation through the formation of extrusion and intrusion. Full article

Biogas-to-hydrogen production provides a renewable pathway to decarbonize hydrogen supply, yet consensus remains lacking regarding the most energetically and economically favorable process configuration. This study develops steady-state Aspen Plus models for two 40,000 Nm³·d⁻¹ biogas-to-hydrogen routes—pre-reforming decarbonization (Process A) and direct reforming (Process B)—and conducts a comprehensive evaluation across technical, economic, and environmental dimensions through combined techno-economic analysis (TEA) and life cycle assessment (LCA). Process B achieves a 7.8% higher hydrogen yield of 0.152 kg H₂ per Nm³ of biogas compared with Process A (0.141 kg·Nm⁻³), but consumes 9.9% more electricity per kilogram of hydrogen (14.37 vs. 13.08 kWh·kg⁻¹). Under baseline prices (0.6 CNY kWh⁻¹ electricity, 1.2 CNY Nm⁻³ biogas), Process B delivers a slightly lower net levelized cost of hydrogen (LCOH) of 16.21 CNY kg⁻¹ (2.25 USD kg⁻¹), compared with 16.63 CNY kg⁻¹ (2.31 USD kg⁻¹) for Process A. The economic break-even electricity price between the two routes is approximately 0.93 CNY kWh⁻¹. Environmentally, Process B yields a lower baseline 100-year global warming potential (GWP₁₀₀) of 8.34 kg CO₂-eq kg⁻¹ H₂ under the national grid mix, as methane slip from the pre-reforming PSA unit in Process A more than offsets the emission savings from lower electricity consumption. Under prevailing industrial electricity tariffs in China, direct reforming presents a slight overall competitive advantage, while pre-reforming decarbonization is more suitable for regions with high electricity prices. Full article

On-body robots that travel around a human limb must keep a firm enough grip to avoid slipping or detaching, while never pressing hard enough to hurt—a balance that is hardest to strike precisely when the robot is orbiting the limb and gravity continually redistributes the contact loads. This paper presents an open, non-anthropomorphic robot that wraps around a compliant cylindrical surface with a three-contact grasp: a central traction module with two in-line driven wheels, and two lateral spring-loaded arms with distal wheels. Its central contribution is an actuation-space decomposition in which the two lateral wheel torques, expressed in a common-mode/differential basis, simultaneously drive the orbital motion and regulate the central normal force. We show that this basis diagonalises both the rolling kinematics and the static force balance, so the differential (grip-regulating) channel is provably orthogonal to the common-mode (propulsion) channel: a single pair of actuators perform both tasks without mutual interference and without a dedicated force mechanism. A model-based feedforward law derived from the static contact model, corrected by a PI term fed back from the compliant arms—which double as the force sensor—keeps the central force within a safe band; in a full-revolution simulation the differential command reverses sign to counteract the gravitational load swing while leaving the orbit undisturbed. The same compliant arms yield a closed-form estimate of the cylinder radius and contact geometry, accurate to below one millimetre across a 45–87 mm diameter range, from proprioception alone. Preliminary prototype tests reproduce the predicted behaviour, supporting the approach for future wearable and assistive applications. Full article

To explore the effect of grain size on the tensile deformation mechanism of GH4169 nickel-based superalloy, specimens with average grain sizes of 10.7 μm and 70.6 μm were fabricated via different heat treatment processes, and in situ tensile experiments were carried out at room temperature using combined in situ SEM-EBSD technology. The results show that the fine-grained specimen exhibits a yield strength of 794 MPa and an ultimate tensile strength of 1372 MPa, while the coarse-grained specimen presents a yield strength of 317 MPa and an ultimate tensile strength of 782 MPa. During tensile loading, the fine-grained specimen undergoes uniform deformation with strong grain boundary coordination, accompanied by homogeneous grain orientation rotation; its average kernel average misorientation (KAM) value increases moderately from 0.82 to 0.89. In contrast, the coarse-grained specimen suffers severe inhomogeneous deformation and readily generates continuous slip bands, featuring abrupt local changes in grain orientation, with the KAM value rising from 0.8 to 1.04. Slip systems with high Schmid factors induce localized intragranular deformation. Benefiting from a high grain boundary density, the fine-grained specimen effectively restrains strain localization and achieves more uniform bulk deformation of the alloy. Full article

Compression tests over a wide range of strain rates were performed on cold-rolled and annealed, as well as annealed-and-aged, Fe-26Mn-8Al-1.2C-3Mo steel to elucidate the roles of Mo₂C precipitation and κ/Mo₂C co-precipitation in microstructural evolution and compressive behavior. The annealed microstructure consists of partially deformed and equiaxed ultrafine recrystallized austenite grains, with Mo₂C carbides uniformly dispersed throughout the matrix. Aging at 550 °C induces nanoscale spherical κ carbides, while the size and spacing of Mo₂C particles remain essentially unchanged. Both conditions exhibit pronounced strain-rate strengthening, primarily attributed to intensified dislocation–carbide interactions. In the annealed state, deformation is dominated by dislocation bypassing of Mo₂C carbides, resulting in discontinuous slip microbands. After aging, κ-carbide precipitation facilitates slip-band propagation and promotes interactions among adjacent slip bands. As the strain rate increases from 10⁻³ to 10⁰ s⁻¹, dislocation density increases, slip-band propagation is hindered, and the strain-hardening rate decreases. At 10³ s⁻¹, adiabatic thermal softening becomes significant, leading to a further reduction in strain hardening. Overall, aging increases strength but reduces strain-rate sensitivity in the low strain-rate regime due to κ-carbide-induced slip-plane softening and an increased effective slip distance. Full article

The fracture–cave carbonate reservoir in Unit S91 of the Tahe Oilfield is jointly controlled by strike-slip fault activity, karstification, and later-stage fracture development, resulting in reservoir spaces characterized by strong heterogeneity, strong discreteness, and multi-scale superimposition. The inter-well connectivity of this type of reservoir is not governed by the size of a single fracture–cave body or local fracture density, but rather by the spatial configuration among the main controlling fault, the associated fracture network, and the fracture–cave reservoir bodies. As the reservoir enters the middle–high-water-cut development stage, the production differential between dominant connecting channels and weakly connected fracture–cave bodies further enlarges, leading to marked heterogeneity in the remaining oil distribution. Integrating post-stack seismic data, fracture prediction, RGB attribute fusion, production performance, and numerical simulation data, this paper constructs a main fault-controlled fracture–vug coupling probability (MFC-FVCP) model under the constraint of the main controlling fault. Unlike conventional multi-attribute fusion methods that mainly enhance seismic anomaly visualization, the MFC-FVCP model transforms the main fault constraint, fracture connectivity, and fracture–cave reservoir-body effectiveness into a unified coupling probability. The model uses three core components—the main fault response field, the fracture attribute response field, and the fracture–cave reservoir body response field—to characterize the fault-control effect, fracture-network continuity, and effective reservoir-body response, respectively. By evaluating the coupling probability, the inter-well connectivity potential is assessed, the dominant connectivity areas where fractures and fracture–cave bodies synergistically develop under the constraint of the main controlling fault are identified, and potential remaining oil targets are clarified. The predicted connectivity pattern was further constrained by production performance, nitrogen injection response, and staged oil saturation simulation, which improves the reliability of remaining oil enrichment prediction. The results show that the T74 layer is the dominant development interval of fracture–cave reservoir bodies in Unit S91. These fracture–cave bodies are mainly distributed along the main controlling fault and associated fracture zones in beaded, chain-like, and banded patterns, exhibiting distinct fault-and-fracture control characteristics. Potential point A near well TK858XCH features both good reservoir physical properties and insufficient sweep efficiency, making it a key target for subsequent injection–production adjustment and remaining oil tapping. The MFC-FVCP model can incorporate static seismic responses, fracture–cave spatial structures, and dynamic development responses into a unified evaluation framework, providing a quantitative basis for characterizing inter-well connectivity and identifying remaining oil enrichment areas in fracture–cave carbonate reservoirs. Full article

In this work, 2.0 wt.% SiCp/AZ91D magnesium matrix composite was fabricated by stir casting, and its microstructure and properties were optimized through a coupled process of parallel equal-channel angular combined extrusion (PC-ECAP) and T6 heat treatment. The results indicate that the extrusion temperature has a significant influence on the microstructure and mechanical properties of the material. At an extrusion temperature of 350 °C followed by T6 heat treatment, the 2.0 wt.% SiCp/AZ91D composite exhibits a tensile strength of 221 MPa, an elongation of 19.2%, and a product of tensile strength and elongation (PSE) of 4.24 GPa%, which represent increases of 14.5%, 128.6%, and 161.7%, respectively, compared with the as-cast specimen. To elucidate the microscopic mechanism of the enhanced ductility, first-principles calculations were further performed. It is found that Al solute atoms can reduce the electron localization in the Mg–Mg bond region, causing a downward shift of the d-band center, thereby weakening the interatomic bonding strength on the slip plane. This effect is equivalent to reducing the stacking fault energy of non-basal slip. The finding provides a theoretical explanation for the activation of multiple slip systems and the suppression of twinning observed in the experiments. By combining experiments with calculations, this study systematically reveals the mechanism underlying the synergistic regulation of strength and ductility in the composite by PC-ECAP coupled with T6 heat treatment, offering a theoretical basis and process reference for the fabrication of high-performance magnesium matrix composites. Full article

After cold rolling of high-strength interstitial-free (IF) steel, the ferrite grains undergo plastic deformation associated with the formation of substructures and intense cold-rolling texture, which affects the microstructure and texture in the subsequent annealing process and determines the formability of the final sheet. To clarify the mechanisms of microstructure and texture formation during cold rolling of IF steel, a polycrystalline model was constructed based on the measured microstructure and texture features. A crystal plasticity model, along with a remeshing technique, was developed for IF steel. The model can calculate the deformation of the polycrystal after 70% cold rolling reduction, in which the calculated microstructure and texture features are consistent with the results from electron backscatter diffraction (EBSD). The results show that the deformed microstructure and texture are closely related to the initial crystal orientation, the interaction between neighbouring grains, and the cold rolling reduction. Grains with an initial texture orientation near <001>//ND are more stable during deformation and tend to retain their orientations after cold rolling. In contrast, grains initially deviating from the γ-fiber tend to rotate towards the <111>//ND orientation, while near-γ-fiber grains mainly retain their γ-fiber characteristics with intragranular orientation spreading during cold rolling. Multiple slip systems induce the formation of ingrain shear bands. These results establish a grain-scale link between initial orientation, intragranular substructure formation, and cold rolling texture evolution, and provide a mechanistic basis for optimizing cold rolling texture control and improving the formability of high-strength IF steel sheets. Full article

A multiphase high-strength steel austempered at 260 °C for 24 h was investigated by quasi-in-situ tensile characterization and EBSD-based crystal plasticity finite element modeling. The experimental observations reveal that local plastic deformation is strongly heterogeneous: von Mises strain concentrates preferentially near bainitic-ferrite packets, phase boundaries, and retained-austenite/martensite–austenite regions, whereas blocky retained austenite contributes to strain accommodation at the early deformation stage. To quantify the underlying stress–strain partitioning, a quasi-two-dimensional representative volume element was reconstructed from EBSD data and implemented in ABAQUS through a user-defined material subroutine. The model contained the real grain morphology, phase distribution, and crystal orientation information of the 24 h austempered specimen. A rate-dependent crystal plasticity constitutive framework with BCC matrix, FCC retained austenite, and transformed martensite branches was calibrated against the macroscopic tensile curve. The simulated tensile response agrees well with the experimental curve before macroscopic instability, and the predicted local fields are consistent with the quasi-in-situ strain maps. The results show that local plastic strain first accumulates in M/A-related regions and phase-boundary-neighboring zones, while high Mises stress migrates dynamically with slip activity and stress-induced martensitic transformation. Retained-austenite transformation increases the local load-bearing capacity, modifies interphase load transfer, and delays the direct linkage of strain-localization bands. The present work clarifies the coupling among retained-austenite stability, TRIP-assisted load redistribution, and microstructural strain partitioning in multiphase high-strength steel, providing a mesoscale basis for microstructure-guided strength–ductility optimization. Full article

Pretwinning followed by annealing was employed to modify the microstructure and texture of an AZ31 wrought magnesium alloy. A precompression step was applied to an as-rolled plate to introduce dense extension twin bands, after which annealing at 300 °C for 5, 15, and 60 min was conducted. The resulting microstructures were analyzed in terms of grain size, recrystallization behavior, and texture evolution. Mechanical properties were evaluated using uniaxial compression tests along the rolling, transverse, and normal directions to quantify changes in mechanical anisotropy. The results show that this thermomechanical treatment effectively reduces yield strength anisotropy through twin-assisted recrystallization and texture randomization. The mechanical response is interpreted based on microstructural changes and the activation of twining and slip systems. Full article

Clamp band separation mechanisms are widely used in spacecraft interfaces, and the clamp band preload is a key factor governing both connection reliability and separation performance. The conventional torque-control method is susceptible to friction-induced preload non-uniformity in clamp band separation mechanisms. To overcome this limitation, thermal preloading has been proposed as an alternative installation method. In this paper, a thermo-mechanical analytical model is established for clamp band separation mechanisms during thermal preloading based on curved-beam and thin-shell theories. Theoretical analysis shows that the preload distribution can be divided into three characteristic zones: a stick zone, a slip zone, and a separation zone. In the stick zone, the preload remains constant and is mainly governed by thermal stress and structural relative stiffness. In the slip zone, friction dominates the load transfer, leading to a non-uniform preload distribution. In the separation zone, local disengagement occurs near the clamp band joint end due to the eccentricity-induced bending moment. The proposed model is validated by finite element simulations, and parametric studies are conducted to reveal the effects of friction coefficient and structural geometric parameters on preload distribution. Based on the theoretical model, a zoned-heating method is proposed to improve preload uniformity, providing a useful reference for optimizing the thermal preloading method. Full article

Corrosion fatigue is an accelerated failure mechanism in metallic components and coated systems, where the effectiveness of the polymer coating is determined by the structural integrity and adhesion at the coating/substrate interface. This study investigated the corrosion fatigue interaction in AISI 410 steel with and without a poly(3-hexylthiophene)/poly (methyl methacrylate) (P3HT/PMMA) coating exposed to a 3 wt.% NaCl solution under four stress levels $\left(∆\sigma \right)$ at room temperature. Electrochemical noise (EN) was recorded during the test, the surface and interface were characterized using scanning electron microscopy (SEM), and the mechanical behavior was quantified using $da/dN$ vs. $∆K$ and $\sigma$ vs. N curves. The coated samples exhibited a wider potential range ($\approx \pm$400 mV) than the uncoated steel ($\approx \pm$200 mV), indicating localized electrochemical activity under the coating. SEM observations revealed microblisters at low stress levels and coating cracking at high stress levels, with localized substrate exposure, slip bands, and microcracks. Overall, the results showed that the corrosion fatigue is governed by electrochemical activity under the coating and cathodic delamination, which reduces adhesion, locally exposes the steel, and causes the initiation and propagation of cracks. Full article

Background: The plantaris muscle (PM) shows substantial variability in its proximal belly attachments. Although often deemed vestigial, specific variants may narrow or reshape the popliteal corridor and contribute to vascular (popliteal artery entrapment syndromes, PAES) and neural conflict (TN, CPN, sural nerves). Despite abundant anatomical descriptions of the plantaris, its contribution to neurovascular compression has not been organised into a classification-linked, imaging-integrated framework. Objective: To synthesise adult and foetal anatomical data with clinical–radiological evidence into a classification-linked framework that stratifies vascular and neural compression risk by proximal PM variants, and to propose an integrated risk matrix and variant-directed diagnostic/operative pathway. Methods: Narrative, classification-centred review centred on the Olewnik schema (Types I–VI) and multi-headed/accessory variants. We mapped variant geometry to (1) physiological compromise on provoked Doppler US and (2) anatomical correlates on MRI/MR angiography (MRA) (axial “band sign”), deriving graded risk for vascular and neural axes and an integrated, action-oriented grade per limb. Results: Baseline risk is low for canonical/compact footprints (Type I–IA, Type V), moderate for capsular-junction patterns (Types II/III), and potentially higher-risk for lateral linkage (Type IV; iliotibial band (ITB)/Kaplan fibres continuity) and multi-headed configurations (duplication, bifurcation, ≥3–4 heads; accessory proximal slips). The integrated matrix upgrades risk for a clear band sign, reproducible compromise on provoked Doppler US, or multi-headed/Type IV anatomy and downgrades when rigorous provocation is negative and muscle volume is small. We provide a variant-indexed imaging checklist, common pitfalls (e.g., Type IV misread as ITB thickening; multi-headed variants misread as cyst/tumour), and operative checkpoints to target capsular clefts, lateral bands, tunnels, and accessory slips. Conclusions: A classification-linked, imaging-integrated approach clarifies which proximal PM variants are plausibly associated with neurovascular entrapment (based on case-level evidence) and aligns work-up with targeted decompression and may improve diagnostic precision and inform surgical planning. Clinical relevance: The framework operationalises variant naming in reports, standardises dynamic provocation and axial mapping, and prioritises variants considered higher risk (Type IV; multi-headed) for early multidisciplinary review. Given that most clinical signals derive from case reports/series (Level IV), these recommendations are inferential and should be applied with clinical judgement. Full article