Search Results (2,854)

Austenitic–ferritic stainless steels are frequently selected for components in seawater-cooling pumps in power plants and nuclear stations due to their generally superior resistance to localized and stress corrosion cracking (SCC) in comparison with austenitic grades. However, during operation, these cast components are exposed to combined applied/residual stresses and chloride-rich seawater. This work addresses the research gap by investigating the SCC susceptibility of X6CrNiMoCu25-6 in the hyper-quenched state (45% ferrite–55% austenite) using slow strain-rate tensile (SSRT) tests in synthetic seawater at 70 °C at five imposed strain rates ranging from 2.38 × 10⁻⁷ s⁻¹ to 10⁻⁴ s⁻¹. The work is complemented by macrographic examination of crack initiation and SEM microfractographic analysis of the fracture surfaces. The findings indicate that the grade demonstrates only negligible susceptibility to SCC with respect to permissible stress, exhibiting a maximum reduction in tensile strength that is constrained to 5% relative to a neutral reference medium. However, a distinct critical strain rate of approximately 10⁻⁶ s⁻¹ has been identified. Further fractographic and microstructural analysis demonstrates that the susceptibility at this critical rate is governed by a localized mechanism. This mechanism is characterized by repeated pitting nucleation at slip-step emergence sites in the ferrite, selective ferrite dissolution, and progressive α/γ interfacial decohesion. These processes result in mixed intergranular/transgranular crack propagation, rather than by bulk mechanical softening. These findings address a particular lacuna in the duplex-steel SCC literature by providing a quantitative strain-rate/damage criterion, in conjunction with elongation-based rather than stress-based susceptibility indicators, for the assessment and management of the SCC risk of this cast duplex grade in real seawater-cooling pump service. From a fundamental standpoint, these findings indicate that the susceptibility of SCC in this duplex grade is governed by a competition between plastic-deformation kinetics and electrochemical dissolution kinetics. This competition reaches a maximum at an intermediate critical strain rate, thereby providing further experimental support for a general strain-rate/dissolution-competition model of SCC applicable to duplex steel. Full article

Understanding the role of faults in directing groundwater flow within bedrock aquifers is crucial, especially in the arid Southwestern United States, where water demand is exceptionally high. This study investigates the confined Coconino aquifer (Permian, 282–270 Ma), located between Springerville and Saint Johns, Arizona, and supplying the Springerville Generating Station. Using abundant well-pumping and water-level data, we analyzed how distinct regional geological structures, specifically the Coyote Wash fault (a steeply dipping normal fault; initially 70–30 Ma old with subsequent middle-to-late Quaternary and younger activity (<750 ka), the Cedar Mesa anticline, and the Buttes anticline, control local groundwater movement. Although the parallel Coyote Wash and Cedar Mesa structures experience similar regional stresses, model calibration yields hydraulic characteristics (hydraulic conductivity divided by barrier thickness) of 1.0 1/day for the Coyote Wash fault and 0.0001 1/day for the Cedar Mesa anticline, four orders of magnitude lower. Seismic reflection profiling reveals a disrupted zone, roughly 200 m wide, associated with the Cedar Mesa structures. Because these faults are perpendicular to the maximum horizontal stress direction, prevailing compressive forces theoretically close fracture apertures and severely restrict water flow. However, this study reveals that highly permeable regions exist where the structural damage zones of these prominent faults overlap. Ultimately, even in restrictive geological environments where ambient stresses predict sealed fractures, the overlapping damage zones of multiple intersecting faults can unexpectedly generate critical, highly permeable pathways for sustained deep groundwater flow today. Full article

Hydrogels used for fracture sealing during heavy-oil thermal recovery are repeatedly exposed to high-temperature steam, dehydration, pressure disturbance, and cooling, conditions that often lead to progressive network deterioration and loss of sealing efficiency. To address this limitation, a thermally triggered self-reinforcing covalent–physical double-network nanocomposite hydrogel was developed by combining a sparse MBAA-crosslinked P(NaAMPS-co-NVP-co-AM) covalent scaffold with a reversible Laponite-mediated physical network. The material response was systematically evaluated through cyclic hydrothermal treatment at 180 °C, while fracture-sealing and resealing performance was examined separately under steam-exposure conditions. Artifact-controlled experiments were further introduced to distinguish genuine cycle-induced reinforcement from dehydration, continued post-curing, and conventional thermal aging. The results show that the NaAMPS/NVP/AM molar ratio of 40/20/40 with 1.00 wt% Laponite provided a suitable balance between precursor processability, hydrothermal stability, and mature network stiffness. After five thermal cycles at 180 °C, the storage modulus of the Lap-DN hydrogel increased from 74.4 to 89.1 kPa, while the compressive stress at 50% strain increased from 0.641 to 0.842 MPa, corresponding to reinforcement ratios of 1.198 and 1.314, respectively. Meanwhile, the mean equivalent pore diameter decreased from 6.2 to 4.8 μm, indicating progressive refinement of the load-bearing network. The hydrogel retained 76.3% of its initial water and 81.6% of its initial volume after five cycles in the reference brine and preserved a cycle-5 modulus retention of 101.3% even at 150,000 mg/L salinity. In fracture-sealing tests, Lap-DN sustained a breakthrough pressure of 3.47 MPa and reduced fracture conductivity by 92.4% in a 1.60 mm fracture. More importantly, the same sealing body maintained a breakthrough pressure of 4.55 MPa after five steam impact–recovery cycles in a 1.20 mm fracture, corresponding to 106.1% of the first-cycle value, while 95.0% of the pre-breakthrough pressure resistance was restored within 30 min of cooling. These results are consistent with a cycle-induced reorganization of the Laponite-mediated physical constraints within the permanent covalent scaffold, although the transient dissociation and reassociation of individual polymer–Laponite junctions were not directly observed. Within this evidence-based interpretation, cyclic thermal perturbation is associated with mechanical reinforcement and repeated fracture resealing rather than acting solely as a damaging factor. This work provides a materials-design strategy for hydrogel sealing systems operating under cyclic steam and high-salinity conditions. Full article

Specimen-scale fitting can reproduce interlaminar fracture in carbon-fiber-reinforced aluminum laminates (CARALL) but obscures the physical origin of cohesive-zone parameters. We present a multiscale framework integrating molecular dynamics (MD), a representative volume element (RVE), finite element (FE) modeling, and opening-dominated asymmetric double-cantilever-beam (DCB) tests. At modeled high rates, an ideal nonbonded Al/epoxy interface exhibited normal and tangential strengths of 470.09 and 352.93 MPa, respectively. Across 0.001–0.005 Å/fs, normal and tangential peak tractions increased by 5.93% and 5.82%, respectively, whereas traction-separation integrals varied nonmonotonically. These single-atomistic-realization descriptors were transferred to an RVE containing Al/matrix and fiber/matrix interfaces. In this morphology, fiber/matrix debonding preceded Al/matrix damage in all three realizations, and the RVE yielded mean effective normal and tangential strengths of 27.42 ± 0.33 and 39.04 ± 0.65 MPa, together with mean Mode I and Mode II fracture energies of 0.36 ± 0.02 and 0.81 ± 0.04 N/mm, respectively, where the means and standard deviations are taken over the three stochastic fiber realizations. The RVE-derived strengths and fracture energies were assigned directly to the DCB model without fitting the experimental response. The FE peak load was 44.48 N, 5.50% above the four-specimen mean of 42.16 ± 1.22 N, and the predicted damage location was qualitatively consistent with the observed Al/matrix interfacial damage. Because the interface model is idealized and the comparison rests on load–displacement data without synchronized crack-length measurements or independent fracture-resistance data, these results are reported as a configuration-specific assessment of the transfer procedure rather than as a quantitative validation; the transferred parameters are not intended to predict the chemically and structurally complex anodized interface. Full article

Compressor rotor blades in marine engineering applications are exposed to harsh, corrosive environments and complex aerodynamic loads, making them prone to premature failure. This study investigates the fracture of 12th-stage 2Cr13 martensitic stainless-steel blades following a maintenance overhaul. Despite the replacement of several cracked blades, five blades fractured shortly after restart, accompanied by abnormal vibration. A comprehensive failure analysis was conducted, including macroscopic inspection, fractographic observation, energy-dispersive spectroscopy, metallographic examination, and mechanical property testing. The results indicate that the fractures are multi-source high-cycle fatigue. Crack initiation in the new blade originated from pre-existing transverse mechanical damage, while in the old blades, it initiated from sharp pits and microcracks introduced by sandblasting, which compromised surface integrity. The material exhibited a normal tempered sorbite structure and adequate mechanical properties, with slight strengthening due to service-induced precipitation and dislocation accumulation. The failure followed a typical evolution of multi-source initiation, propagation, crack coalescence, and final overload ductile fracture. These findings highlight the critical role of surface integrity in blade reliability. Full article

Conventional cement concrete has difficulty simultaneously achieving relatively high strength, large deformation capacity, and satisfactory post-cracking damage resistance, which limits its further use in demanding pavement applications. This study comprehensively evaluates the strength development, deformation capacity, post-cracking load-bearing behavior, repeated-impact response, fracture performance, and crack-evolution characteristics of a dense polyacrylate-modified concrete (PMC). Under the material composition and curing conditions adopted in this study, the PMC combines relatively high flexural strength with substantially enhanced deformability: its 28 d flexural strength and ultimate flexural strain are 51.5% and 505.1% higher, respectively, than those of conventional concrete, while exhibiting more stable post-cracking load-bearing and crack-propagation behavior. The repeated-impact and fracture responses further show that the material can sustain higher levels of cumulative nominal impact-energy input and provides greater fracture resistance and damage tolerance. SEM observations reveal film-like polymer connections on the surfaces of hydration products; this local morphology is consistent with the macroscopic toughness and stable crack-propagation characteristics, providing an experimental basis for further optimization of high-strength, high-toughness polymer-modified concrete for demanding service scenarios such as heavy-duty pavements and steel bridge-deck pavements. Full article

Mandibular fractures are a common injury in dogs and are associated with relatively high complication rates. The main goals of treatment are to provide stable fixation to promote bone healing, preserve the teeth and surrounding anatomical structures, and restore normal dental occlusion. Several treatment techniques have been described, including external skeletal fixation, bone plates and screws, interdental and intraosseous cerclage wiring, and dental splints used alone or in combination with cerclage fixation. However, all have inherent limitations. The objective of this study was to describe a novel intraoral fixation technique and evaluate its clinical application. The technique consists of a lingual arch anchored to the teeth or mandibular bone using cerclage wires and reinforced with bis-acrylic resin. Six dogs presenting with 11 mandibular body fractures, 10 of them opened toward oral cavity and with anatomically unfavorable configurations, were treated. The fractures were located rostral to or involved the alveolus of the first premolar. Ten fractures were open and potentially contaminated through the oral cavity, while one was closed. All patients achieved bone healing (mean, 70.8 days; range, 63–96 days). All patients recovered their pre-traumatic dental occlusion and showed no dental damage as a consequence of the intervention. The only complication observed in all cases was irritation of the oral mucosa at the contact points with the fixator. This resolved favorably within one week without antibiotic treatment. The potential advantages and limitations of the technique compared with existing fixation methods are also discussed. Full article

Variations in the electrical signals of rock masses can reflect the development of internal fractures, pore fluid migration, and damage evolution, showing broad potential for the monitoring and early warning of engineering rock mass disasters. In recent years, with the continuous development of electrical resistivity tomography, time-lapse electrical monitoring, digital rock technology, and multiscale numerical simulation, research on rock mass electrical properties has gradually expanded from traditional resistivity measurements to fracture evolution characterization, damage identification, and instability precursor prediction. However, the electrical responses of rock masses are governed by multiple interacting factors, and different physical processes may produce similar or even opposing electrical anomalies. Existing studies have largely addressed conduction theories, monitoring methods, and engineering applications as separate aspects, while a systematic understanding of the mechanisms governing rock-mass electrical responses under different conditions, as well as their intrinsic relationships with conductive network evolution, remains lacking. This review is mainly based on 153 representative publications indexed in the Web of Science Core Collection from 1998 to 2026 and systematically summarizes research progress on the electrical responses of rock masses over nearly three decades. With the conductive network as the central theme, this review comprehensively analyzes multiphase conduction theories, electrical monitoring techniques, conductive network evolution mechanisms, and engineering applications. Rock mass electrical responses originate from the charge transport process within the internal multiphase conductive network. The propagation of fractures, variation of pore structures, fluid migration, and multi-physics coupling continuously change the number, connectivity, and spatial distribution of conductive paths, thereby resulting in dynamic variations of electrical parameters such as resistivity. As rock masses evolve from stable damage to critical instability, the conductive network gradually shifts from local adjustment to rapid reconstruction and critical connectivity, accompanied by abrupt changes in resistivity, enhanced electrical anisotropy, and temporal anomalies. Even during quiet periods of acoustic emission, resistivity can continuously reflect crack propagation and conductive network reconstruction, providing complementary information for the identification of instability precursors. The main contribution of this review is to link the multiphase conduction mechanisms, electrical monitoring methods, resistivity variation characteristics, and damage-to-instability processes of rock masses and to systematically summarize the intrinsic relationships among charge transport, conductive network reconstruction, macroscopic electrical responses, and rock damage and instability. On this basis, an integrated analytical framework from conduction mechanisms to damage characterization and instability precursor identification is established, providing new insights into establishing quantitative relationships among conductive network structure, charge transport processes, and electrical responses, as well as developing electrical theories and intelligent monitoring and early-warning methods for rock masses under multiscale and multi-physics coupling conditions. Full article

In this work, a coupled Johnson-Cook (J-C) constitutive and damage modeling framework was established to investigate damage evolution during thread-rolling of TC16 titanium alloy. The J-C constitutive parameters were calibrated through tensile tests under different strain rates and temperatures, while the stress-triaxiality-dependent damage parameters were identified using specimens with different stress states. A finite element model of two-die radial thread rolling for MJ6 × 1 threads was developed using ABAQUS/Explicit. The mechanical response of the model was evaluated by comparing the numerically predicted and experimentally measured fracture displacements, with a maximum relative deviation of 7.63% in fracture displacement. The calibrated framework was subsequently applied to analyze stress distribution, plastic deformation localization, and damage evolution during the thread rolling process. The results indicate that damage accumulation is mainly concentrated at the thread root and the transition region between the thread flank and root. The damage of the thread can be attributed to the combined effects of high equivalent plastic strain, stress concentration, and an unfavorable stress state. The predicted damage localization agrees well with the experimentally observed fracture region under the investigated rolling condition. These findings demonstrate the applicability and limitations of the coupled Johnson-Cook constitutive damage framework for analyzing defect evolution in complex forming processes. Full article

This study investigated the quasi-static properties, fatigue behavior, and surface and fracture morphologies of pultruded glass/epoxy composites subjected to 24 months of natural outdoor exposure in Guangzhou, Hangzhou, and Suihua, China. Quasi-static tests were performed at scheduled exposure intervals, whereas fatigue tests on exposed specimens were conducted after 24 months. The quasi-static moduli and strengths fluctuated without consistent monotonic degradation. At both selected tensile stress levels, all exposed groups exhibited lower mean tension–tension fatigue lives than the unexposed reference, with the Guangzhou specimens showing the lowest means. Compression–compression fatigue exhibited greater scatter and no uniform reduction across the exposure groups. SEM observations revealed surface resin loss, fiber exposure, and local fiber–matrix separation, with more pronounced surface changes in the examined Guangzhou specimens. These observations suggest that local matrix and interfacial damage may contribute to the reduced fatigue resistance. Under the investigated conditions, tension–tension fatigue life showed a more pronounced response to 24-month natural exposure than the measured quasi-static properties, supporting its use as a complementary indicator in integrity assessment of pultruded GFRP composites. Full article

This paper proposes a repair-oriented steel tie beam joint with shape memory alloy (SMA) butterfly springs for double-column piers. In the proposed detail, the conventional welded connection is replaced by a bolted fuse region to redirect inelastic demand toward replaceable components. Joint component-level finite element simulations under cyclic loading were conducted to evaluate stress redistribution, cumulative plastic strain, hysteretic response, stiffness variation, cumulative energy dissipation, and residual deformation. The results indicate a repairability-oriented response characterized by damage localization and residual deformation control, rather than a strength-dominated enhancement. Compared with the non-SMA bolted reference joint, the SMA joints show a modest reduction in the peak stress of key plates, reduce the relative peak PEEQ indicator by $27.6\%$ within the adopted no-fracture finite element framework, and lower the residual deformation index by about $21.5\%$. The dual-row SMA arrangement provides better load sharing and slightly higher energy dissipation than the single-row arrangement. Although the SMA joints dissipate less cumulative energy than the non-SMA reference joint, the results suggest that the proposed detail may provide a repair-oriented connection concept when post-earthquake damage localization, replaceability, and residual deformation control are prioritized. Full article

This review examines the ballistic resistance of fiber-reinforced cement composites (FRCs) and related cementitious systems for protective structures, with emphasis on projectile–target interaction, penetration and scabbing mechanisms, and the governing roles of material and structural parameters. The synthesis indicates that ballistic resistance is controlled not only by compressive strength but also by the combined effects of dynamic tensile behavior, fracture energy, crack-bridging efficiency, aggregate characteristics, target thickness, projectile characteristics, and structural configuration. Steel and hybrid fiber systems generally provide the most consistent improvements in scabbing suppression and residual integrity, while hard aggregates and multilayer hard–soft–tough arrangements enhance penetration resistance, stress-wave attenuation, and staged energy dissipation. The review also evaluates current numerical approaches, including rate-sensitive constitutive models, cohesive and continuum damage formulations, smoothed particle hydrodynamics, and data-driven methods. Several calibrated and experimentally validated simulations reproduced penetration depth and major damage trends with useful engineering agreement; however, significant challenges remain in representing multi-hit degradation, fiber-scale pull-out, fragment ejection, and interface debonding. In addition, the review highlights the limited suitability of existing ballistic standards for quasi-brittle cementitious systems and emphasizes the need for FRC-specific testing, large-scale validation, and more sustainable protective material design. Full article

The laminated structure in shale rock plays a crucial role in fluid migration during shale gas exploitation. This study investigated the evolution patterns and mechanisms of shale permeability under the influence of laminae through multiple permeability experiments, including steady-state flow tests, confined pressure permeability tests, thermo-hydro-mechanical coupled permeability tests, fracture permeability tests, and fracturing fluid damage experiments. The results show that the permeability of the shale is significantly controlled by the laminated structure. Pores and micro-cracks develop along the laminated structure direction, which is conducive to the formation of seepage channels in vertical laminated specimens, while parallel laminated specimens are affected by multiple laminated structures, resulting in lower permeability. Increasing confining pressure leads to a rapid decrease in permeability, indicating that the closure of fractures is the key factor controlling the permeability characteristics of shale. Increasing temperature causes shale to further increase permeability under the effects of thermal stress, but the enhancement effect is weakened under high confining pressure. Artificial fractures significantly enhance the permeability of shale under low confining pressure, but the closure of artificial fractures reduces the permeability effect under high confining pressure. The effect of fracturing fluid leads to a decrease in shale permeability, and the damage to shale is more significant under high confining pressure. Full article

During the frequent charging, discharging, and storage processes of underground compressed air energy storage systems, the damage and degradation of sealing plugs directly affect the long-term stability of gas storage caverns. Using a self-developed cyclic charging–storage–discharging–restorage gas disturbance rock testing system, this study conducted cyclic gas disturbance tests on sealing plug specimens at different storage pressures, followed by post-disturbance uniaxial compression tests, to investigate the thermodynamic response during cyclic disturbances and elucidate the mechanical property degradation mechanism of sealing plug specimens after cyclic disturbances. The results show that, during a single cycle, the gas temperature exhibits staged responses characterized by compression heating, cooling during high-pressure storage, decompression cooling, and temperature recovery during low-pressure storage. As the storage pressure increases, the heating rate increases from 0.005 to 0.016 °C/s, while the cooling rate increases from 0.023 to 0.055 °C/s. During cyclic charging–storage–discharging–restorage processes, the gas temperature exhibits an overall logarithmic growth trend comprising three stages, namely a rapid increase, a slow increase, and stabilization, with the degree of heat accumulation increasing progressively with storage pressure. Cyclic alternating loading by high-pressure gas aggravates internal specimen damage. With increasing storage pressure, the peak strength of the specimens after cyclic disturbances decreases by 8.14%, 8.99%, 11.58%, and 15.05%, respectively, while the elastic modulus decreases by 2.12%, 6.45%, 8.88%, and 13.49%, respectively. Acoustic emission activity during failure becomes more pronounced, and deformation localization intensifies. With increasing storage pressure, the macroscopic failure mode gradually changes from localized cracking to multiple-crack coalescence and block fragmentation, while the increase in average fracture-surface porosity rises from 7.29% to 37.89%. These results are important for assessing the stability of sealing plugs in underground CAES caverns. Full article

To clarify the water-sensitive deterioration mechanisms of red-bed soft rocks under repeated wetting–drying cycles, mudstone samples from two representative sites in the Sichuan Basin were investigated through multiscale experiments combining mechanical testing, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that samples from Sampling Site ① exhibited higher compressive strength, elastic modulus, cohesion, and friction angle due to stronger cementation and greater structural integrity, whereas samples from Sampling Site ② showed weaker bonding and more initial structural defects. During wetting–drying cycling, both rock types experienced progressive mechanical degradation, with elastic modulus exhibiting the most pronounced deterioration after eight cycles. XRD analysis indicated that the main mineral assemblages remained stable without obvious phase transformation, while the reduction in calcite and clay minerals was associated with the weakening of cementing materials. SEM observations revealed distinct deterioration pathways: Site ① mainly underwent gradual damage characterized by particle-contact weakening, pore development, and shrinkage cracking, whereas Site ② experienced rapid structural degradation involving cement dissolution, particle debonding, and pore–fracture connectivity. These results indicate that wetting–drying deterioration is governed not only by mineral composition but also by bonding conditions and initial pore–fracture structures. The findings provide insights into the differentiated stability assessment and prevention of red-bed soft rock slopes and subgrades under water-sensitive environments. Full article