Search Results (1,173)

The unplanned failure of the drive ring gear of a horizontal ball mill is one of the most severe unscheduled shutdowns a cement plant can face, since replacement lead times of 9–18 months make on-site repair the only viable option for maintaining production continuity. This paper reports an industrially validated emergency repair framework applied to a two-piece EN-GJS-800-2 nodular cast-iron ring gear (6531.50 mm pitch diameter, 216 teeth) affected by multiple cracks, including a 750 mm through-crack. Because the material combines high strength with markedly low ductility, five shielded metal arc welding (SMAW) procedure specifications (WPS 1–WPS 5) were developed and evaluated sequentially in the field over approximately thirteen months (December 2024–January 2026) while progressively varying preheating temperature (150–600 °C), joint geometry, filler metal chemistry, and mechanical restraint strategy. WPS 1 and WPS 2 were limited by, respectively, transverse post-weld cracking under the lower-preheat condition and severe geometric distortion (up to −2.8 mm radial run-out) from excessive restraint at 600 °C. WPS 3 and WPS 4 progressively introduced a root land, dissimilar ASTM A36 reinforcement plates, and post-weld heat treatment. WPS 5, a hybrid procedure combining nickel buttering (ENi-CI), a nickel–iron dissimilar filler (ENiFe-CI), and controlled interpass peening, produced no reported surface-breaking crack indications on post-weld liquid penetrant testing (PT) and preserved the corrected gear concentricity. During the distortion period, broadband root mean square (RMS) vibration velocity at the main bearing housings was reduced from 20 mm/s to 7 mm/s by temporarily lowering the ball-charge filling degree from 37% to 29% and production from 90 to 55 t/h. Following WPS 5, the repaired ring gear operated continuously for approximately three months, from October 2025 until the replacement gear was installed in January 2026. The results provide field-scale evidence, rarely documented in the open literature, on how welding procedure variables, geometric distortion, and operational vibration interact during the emergency repair of large gear components incorporating dissimilar materials. Full article

This study investigates a hybrid composite comprising an ultra-high-performance concrete (UHPC) matrix, short alkali-resistant (AR) glass fibers, and an embedded AR-glass textile grid (GF-UHPTRC), with emphasis on measured mechanical response, elevated-temperature residual performance, and short-term sulfate-exposure behavior. Fourteen UHPC matrix formulations were screened, including seven plain matrices and seven containing 2% AR-glass fibers by cement mass. The mixtures were evaluated for flowability, compressive strength, and 28-day matrix flexural strength, and UHPC-P7 and UHPC-GF7 were selected for subsequent testing. The maximum 28-day compressive strengths were 115.3 MPa for UHPC-P7 and 105.2 MPa for UHPC-GF7. UHPC-GF7 reached a 28-day modulus of rupture of 10.45 MPa, approximately 39% higher than UHPC-P7. In TRC beam tests, GF-UHPTRC reached an average ultimate flexural strength of 47.5 MPa compared with 34.06 MPa for UHPC-TRC. After exposure to 400 °C, the residual compressive strengths were 66.0 MPa for UHPC-GF7 and 54.9 MPa for UHPC-P7; severe damage and spalling were observed at higher temperatures. After 28 days in 5% Na₂SO₄ solution, both mixtures showed mass gain and measurable length increase. The results demonstrate improved measured flexural strength with short AR-glass fibers, while conclusions regarding long-term durability, ductility, crack control, and structural-scale performance remain outside the scope of the available data. Full article

Controlling prior austenite morphology during single-pass hot rolling is essential for improving the strength–ductility balance of strip casting high-strength steels. In this study, Fe–0.24C–1.5Si–1.8Mn steels with and without 0.03 wt.% Nb were deformed by 50% at 950–1100 °C and subsequently held at 350 °C for 60 min for bainitic transformation. The effects of deformation temperature and Nb addition on austenite dynamic recrystallization, bainitic microstructure, and mechanical properties were investigated. For the Nb-free steel, recrystallization occurred at all these investigated deformation temperatures. The addition of 0.03 wt.% Nb markedly suppressed austenite recrystallization during hot deformation, resulting in the retention of elongated deformed austenite after deformation at 950 °C. Compared with the bainitic microstructure formed from fine recrystallized austenite in the 0Nb steel (without Nb addition), that formed from elongated austenite in the 03Nb steel (with 0.03 wt.% Nb) deformed at 950 °C exhibited a smaller lath width and higher HAGB and dislocation densities. In addition, the volume fraction of retained austenite increased from 4.5% to 9.8%, while its average thickness decreased from 105.6 nm to 49.1 nm. Consequently, under identical deformation conditions (50% reduction at 950 °C), Nb addition increased the yield and tensile strengths from 1064 MPa and 1261 MPa to 1088 MPa and 1323 MPa, respectively, while the total elongation remained nearly unchanged (24.8% vs 24.6%). These findings provide new insights into the optimization of thermomechanical processing for strip casting bainitic steels. Full article

We investigated the deformation and tensile behavior of crystallized polypropylene (PP)/poly(butylene terephthalate) (PBT) blends across a wide range of PBT compositions. Low-PBT-content blends (100/1 and 100/3 PP/PBT) exhibited enhanced yield stresses at room temperature, as well as superior or comparable tensile ductility and creep resistance at 100 °C compared to neat PP. These improvements were driven by robust interfacial adhesion established via crystallization-induced mechanical interlocking derived from surface-induced nucleation of PP from small PBT domains. This robust interfacial adhesion, suggested by a high-temperature shift in the αc-relaxation reflecting enhanced interfacial constraint in dynamic mechanical analysis, promoted a specific deformation sequence wherein matrix fibrillation preceded interfacial debonding, thereby suppressing transverse craze propagation and enabling stable large-strain drawing. Conversely, the high-PBT-content blend (100/20 PP/PBT) exhibited brittle fracture behavior governed by a weakest-link-dominated failure mechanism, in which premature interfacial debonding at coarse domain boundaries under intense triaxial stress concentration triggered extensive transverse crazing prior to matrix fibrillation. These findings provide valuable fundamental insights for designing tough, heat-resistant polymer blends without conventional chemical compatibilizers, which can serve as a conceptual framework for upcycling mixed polymer waste streams. Full article

Selective laser melting (SLM) produces elemental segregation and nonequilibrium secondary phases in GH4169 superalloys, but the effects of P and C variations on grain-boundary phase evolution and high-temperature tensile behavior remain unclear. Alloys with primarily varied P (0.034–0.058 wt.%) and C (0.009–0.066 wt.%) contents were fabricated and heat treated identically. Microstructures were characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), and tensile properties were evaluated at 650 °C. The as-built alloys exhibited columnar grains, cellular substructures, cell-wall segregation, and Nb-rich Laves-phase particles. After heat treatment, cellular substructures largely disappeared, γ″ precipitates formed in the γ matrix, and fine Ti/Al-rich particles were tentatively attributed to γ′; δ phase, residual Laves phase, and MC-type carbides were present at grain boundaries. Increasing P reduced the δ-phase area fraction from 2.20% to 1.38% and changed its distribution from continuous chains to semi-continuous and discrete arrangements. Increasing C raised the MC-type carbide area fraction from 0.34% to 1.48% while decreasing the δ-phase area fraction from 1.68% to 0.98%, accompanied by carbide coarsening. The 0.050P alloy exhibited the highest yield and ultimate tensile strengths, whereas the 0.009C alloy showed the best strength–ductility balance. These results reveal distinct P- and C-related changes in grain-boundary phase evolution and tensile behavior at 650 °C. Full article

First-principles FP-LAPW calculations were used to investigate the structural, mechanical, electronic, optical, and thermoelectric properties of the double halide perovskites Rb₂NaTaBr₆ and Rb₂LiTaBr₆. Structural optimization confirmed their stable cubic phase. Elastic analysis shows they are mechanically stable, ductile, and anisotropic. Spin-polarized calculations reveal that both compounds are half-metallic ferromagnets with an integer total magnetic moment of 2 μB per formula unit, dominated by the Ta-d states. They exhibit strong dielectric response and strong UV light absorption originating from interband electronic transitions, despite their intrinsic metallic ground state. Boltzmann transport theory revealed a temperature-dependent enhancement of electrical conductivity and power factor. Both materials, especially Rb₂LiTaBr₆, show promise for high-temperature thermoelectric and UV optoelectronic applications. Full article

Ti65 is a promising structural material for lightweight high-temperature aerospace components, yet the heat-treatment response of Ti65 fabricated by electron beam powder bed fusion (EB-PBF) remains insufficiently understood. In this study, EB-PBF Ti65 specimens were subjected to solution treatments at 800–1000 °C for different holding times followed by aging at 650 °C for 2–8 h. Microstructural evolution was characterized and tensile properties were evaluated at room temperature and 650 °C along the XY and Z directions. The as-built alloy exhibited a fine basketweave α + β lamellar microstructure with evident anisotropy. Increasing the solution temperature promoted α-lamella dissolution, elemental homogenization, discontinuity of grain-boundary α, and microstructural reconstruction. The 1000 °C/2 h + 650 °C/2 h treatment significantly improved room-temperature strength and transverse ductility, giving ultimate tensile strengths of approximately 1050 MPa and reducing anisotropy. At 650 °C, all specimens showed reduced strength but increased ductility; low-temperature solution treatment favored ductility, whereas 1000 °C-based treatments combined with appropriate aging improved elevated-temperature strength. Aging for 4 h provided a balanced strength–ductility combination, while longer aging enhanced yield strength but reduced ductility. These results demonstrate that tailoring solution and aging parameters is essential for optimizing the microstructure and mechanical performance of EB-PBF Ti65 alloy. Specifically, the 1000 °C/2 h + 650 °C/2–4 h regime achieved UTS of ~1050 MPa at room temperature and ~608 MPa at 650 °C, with XY-direction elongation increasing from 5.4% to 11.5%, representing a quantitative anisotropy reduction of approximately 53%. Full article

This study investigates the effects of Cr content on the microstructure, room-temperature and 600 °C mechanical properties and high-temperature oxidation behavior of TiVNbTaCr_x (x = 0, 0.25, and 0.5). Cr addition significantly intensified Ti segregation in the interdendritic regions during solidification, inducing the formation of an Face-Centered Cubic (FCC) Ti-rich precipitate phase. As the Cr content increases from 0 to 0.5, the Ti-rich phases evolve from a straw-like morphology to a blocky morphology, and the mechanical properties at room temperature continue to decrease. Fracture analysis reveals that cracks initiate at grain boundaries associated with the FCC Ti-rich phase, leading to a transition from ductile to brittle fracture in the Cr-containing alloys. At 600 °C, all Cr-containing alloys exhibit elongations below 0.20%, indicating that the precipitation of the FCC Ti-rich phase severely degrades the deformation capability of the alloys at 600 °C. Oxidation tests demonstrate that Cr addition provides only a marginal beneficial effect on the mass gain rate during the initial stage (0–10 h at 600 °C), while the Cr-containing alloys continue to gain mass upon prolonged exposure due to the reduced integrity of the oxide film. The oxide scale consists primarily of (Ta, Nb)₉VO₂₅, and no protective Cr₂O₃ scale was observed under the present experimental conditions. In summary, within the composition range studied, the FCC Ti-rich phase precipitates at Cr contents of 5.88 and 11.11 at.%, resulting in the fragmentation of the body-centered cubic lattice (BCC) matrix continuity and a comprehensive deterioration of mechanical properties at both room temperature and 600 °C, while failing to improve the oxidation resistance at 600–700 °C. Full article

Centrifugally cast 35Cr45NiNb alloy has been widely employed in ethylene-cracking furnace tubes owing to its excellent carburization and creep resistance. However, the influence of microstructural degradation and temperature on its high-temperature tensile behavior remains poorly investigated. In this study, an accelerated aging method at 1200 °C for 230 h (A1) and 430 h (A2) was employed to simulate approximately 4 and 8 years of service at 1050 °C, based on the Larson-Miller parameter. The equivalence was validated by the nearly identical precipitate area fractions of the A1 specimen (16.6%) and an ex-service specimen (14.8%). Combined with SEM and EBSD characterization, tensile tests at 950, 1000, and 1050 °C were conducted to elucidate the relationship between microstructure and high-temperature tensile properties. During aging, the skeletal interdendritic M₇C₃ carbides transformed into blocky M₂₃C₆, NbC evolved into the brittle G-phase (Ni₁₆Nb₆Si₇), fine secondary M₂₃C₆ precipitates formed, and the initially continuous primary-carbide network progressively coarsened. Yield and ultimate tensile strengths decreased monotonically with increasing temperature, whereas aging produced pronounced hardening at the expense of ductility, as secondary-carbide precipitation strengthening outweighed the weakening of the primary carbide network. The fracture mode transitioned from mixed quasi-cleavage fracture at 950 °C, initiated by stress concentration at coarse phase interfaces, to ductile rupture at 1000 and 1050 °C. GND analysis further revealed an aging-dependent transition in the dominant deformation mechanism, from dislocation pile-up at the carbide network, to recrystallization after prolonged aging. Full article

Global oil and gas exploration and development are gradually expanding into deep and ultra-deep formations. Deep limestone exists in a long-term multi-field coupled environment featuring high temperature, high in situ stress and high pore pressure, which brings great challenges to reservoir stimulation and wellbore stability. To investigate the effects of confining pressure and pore pressure on limestone under high temperatures, triaxial compression tests were conducted on limestone at various temperatures (25~150 °C) using the GCTS RTR-2000 rock mechanics testing system. This paper investigates the evolution laws of strength and deformation parameters of limestone under varied temperature, confining pressure and pore pressure. The results indicate that: (1) Within the 25~150 °C range, the peak strength and elastic modulus of limestone exhibit a “decrease-then-increase” trend, with a strength rebound occurring at 150 °C driven by the “thermal expansion and compaction” effect. (2) Under a pore pressure of 50 MPa, temperature and confining pressure exert a significant coupled control effect on the mechanical properties of the rock, characterized by a critical confining pressure threshold of approximately 100–110 MPa. Below this threshold, high temperature acts as a weakening factor, whereas above it, high temperature acts as a strengthening factor and induces intense brittle failure under high pressure. (3) In the pore pressure coupling tests, the rock undergoes ductile failure as confining pressure increases at normal/room temperature, while a temperature of 100 °C strengthens the rock under high confining pressure. (4) Energy evolution analysis reveals that within the 75~125 °C range, the thermal pressurization of pore water and local thermal stresses induce massive microcracks, causing the dissipated energy to surge sharply to nearly 80%. The research findings provide a theoretical basis for wellbore stability analysis and fracturing parameter optimization in deep carbonate reservoirs. Full article

7xxx series aluminum alloys exhibit high strength and low density; however, their high degree of alloying results in a pronounced hot-cracking tendency, making direct casting forming challenging. In this study, a rheo-squeeze-cast AA7075 alloy was investigated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and room-temperature tensile testing were employed to systematically examine the effects of the solution treatment window on the microstructure and mechanical properties of the castings. The distinctive contribution of this work is the quantitative correlation of solution-time-dependent second-phase evolution and porosity with the tensile behavior of ECSC-assisted rheo-squeeze-cast AA7075. The results show that, with increasing solution treatment time, the intergranular eutectic phases gradually dissolved, and their morphology evolved from lamellar structures into fine rod-like features. When the solution treatment time was extended to 12 h, a small number of pore defects appeared in the microstructure. Under the conditions of solution treatment at 470 °C for 8 h followed by aging at 120 °C for 24 h, uniformly distributed Zn–Mg-rich aging precipitates were observed in the matrix, resulting in the best comprehensive mechanical properties, with an ultimate tensile strength, yield strength, and elongation of 498.1 MPa, 413.7 MPa, and 8.2%, respectively. The optimized heat-treatment condition provides a practical route for achieving a favorable strength–ductility balance in rheo-squeeze-cast AA7075 components. Full article

Ta-2.5W alloy is a promising liner material for high-performance shaped-charge warheads because of its high density and excellent dynamic mechanical properties. However, conventional machining and hot-forming routes suffer from low material utilization, limited dimensional accuracy, and oxidation-related defects. In this study, near-net-shape cold pressing and annealing treatments were investigated for Ta-2.5W liners. The initial microstructure and mechanical properties of the starting sheet were characterized, compression tests were performed to establish a room-temperature constitutive model, and 16 combinations of deformation and annealing temperature were designed to clarify the evolution of grain morphology and crack sensitivity. To compensate for elastic die deformation and blank springback, a coupled simulation-based die correction strategy was further developed. The results show that the starting alloy exhibits an excellent strength–ductility balance with weak anisotropy. Increasing cold deformation refines the grains, whereas increasing annealing temperature initially promotes grain refinement but subsequently causes grain coarsening. Excessive deformation combined with high annealing temperature increases crack susceptibility. Based on the single-specimen screening experiments in this study, a preliminary processing range of 20–40% cold deformation and 1200 °C annealing produced the most favorable microstructural condition without obvious cracking. After iterative die compensation, trial-manufactured parts satisfied the target contour requirements and showed uniform, crack-free microstructures after annealing. Full article

Data-driven prediction of crumb–rubber modified asphalt (CRMA) binder properties is usually reported on datasets in which a small number of mix-designs is swept across several test temperatures, so that the row count greatly exceeds the number of independent experiments. This study asks what such a dataset can actually support. Using 221 laboratory measurements drawn from 20 independent CRMA mix designs, we evaluate a task-adaptive mixture-of-experts multi-task network (TA-MoE-MTL), a locked Huber-anchored hybrid extension, and fourteen deep and classical reference models for the joint prediction of penetration, softening point, ductility and rutting factor. Three methodological elements are introduced. First, model selection is made strictly nested and group-aware: the stopping epoch is chosen on an inner split of the training designs and the held-out designs are used once. Second, we bound what the recorded inputs can explain before any model is fitted: because the consistency targets are constant within a mix design and because eight designs share identical input vectors while their rutting factors differ, the attainable coefficient of determination for the rutting factor is 0.790 rather than unity. Third, performance is reported with each mix design weighted equally, so that high replication designs cannot dominate. The locked hybrid assigns 90% weight to a Huber-anchored robust expert branch and 10% to a freshly trained TA-MoE-MTL branch. It attains pooled out-of-fold coefficients of determination of 0.613/0.594/0.878/0.685 and ranks first of 16 models at a mean pooled R² 0.693, exceeding MLP–sklearn (0.656) by 0.037. Across three seeds, seeds 42/43/44 give mean pooled R² values of 0.693/0.689/0.693 (mean 0.691 ± 0.002), and all three runs remain above the frozen MLP sklearn reference. A learning curve over the number of training designs is still rising at the largest size the data allow. The contribution of this work is an evaluation protocol for replicated mix design datasets, a way of bounding their information content, and a robust hybrid that exposes rather than hides the value of a simple small-sample anchor. Full article

Asphalt pavements suffer from progressive deterioration during service life due to aging, while conventional polymer modifiers raise environmental concerns regarding recyclability and volatile organic compound emissions. Functionalized-biochar derived from renewable biomass offers a sustainable alternative through its tunable surface chemistry and porous structure. This study develops and evaluates a nitrogen-rich, surface-functionalized biochar as a multifunctional asphalt binder modifier and elucidates the synergistic roles of inherent nitrogen and post-synthetic functionalization in governing binder performance. To this end, soybean powder was pyrolyzed to prepare the biochar precursor, which was subsequently characterized to determine its suitable pyrolysis temperature and surface properties. These analyses identified 300 °C as the preferable pyrolysis temperature within the tested range of 200–500 °C, maximizing biochar yield and achieving favorable surface physicochemical properties including the iodine adsorption value, oil absorption value, surface functional groups and pore morphology. To improve surface functionality, the biochar underwent a two-step modification: nitric acid oxidation followed by hydroxymethylation, hereinafter referred to as functionalized-biochar. The influence of functionalized-biochar content on asphalt binder performance was evaluated across dosages of 10–20 wt%, and 15 wt% was identified as the recommended content. Asphalt binder modified with 15 wt% functionalized-biochar exhibited improved high-temperature performance, as evidenced by enhanced rutting resistance factor G*/sin δ values obtained from dynamic shear rheometer testing. Aging resistance also improved, reflected in a lower complex modulus aging index and a higher phase angle aging index. At 15 wt% dosage, the softening point increased by 6 °C, and ductility rose by 10.6 cm relative to the base asphalt (1.9 cm), corresponding to a 557.9% improvement. Penetration declined by 17%, while the complex modulus aging index decreased from 3.44 to 1.68. Notably, the experimental program in this study was limited to binder-scale characterization. Full article

This research investigates the systematic nanomechanical behavior of tetragraphene-based nanotubes (TGCNTs) using classical molecular dynamics (CMD) simulations performed via the LAMMPS package with the reactive AIREBO-Morse potential. Tetragraphene is a novel carbon allotrope characterized by a unique mixture of $s{p}^2$ and $s{p}^3$ hybridization. We analyzed the nanomechanical properties of zigzag-like TGCNTs under uniaxial tensile loading, systematically examining the effects of chirality, diameter, length, and temperature ranging from 300 K to 2100 K, while maintaining a constant nanotube length. Our results reveal a distinct nanostructural degradation at high temperatures, where the nanotubes completely lose their structural stability above 1500 K. Under mechanical strain, the stress–strain curves highlight a strong dependence on chirality. The $(0,n)$ TGCNTs exhibit brittle behavior, characterized by a short, nearly linear curve that terminates abruptly at a rapid fracture point without significant plastic deformation. In contrast, the $(n,0)$ TGCNTs demonstrate remarkable ductility and irreversible plastic deformation flow. This is evidenced by a distinct plateau effect with constant stress up to 20% strain, followed by ultimate fracture at a strain over $40\%$, indicating a stress-induced structural phase transition. To map their transverse elasticity, Poisson’s ratio ($\nu$) was evaluated within the elastic regime, revealing an ultra-low value of $\nu =0.07$ for the TGCNT $(0,10)$ in close agreement with density functional theory (DFT) benchmarks, contrasting with an anomalously high value of $\nu =1.19$ for the TGCNT $(14,0)$ due to severe chiral anisotropy. The calculated Young modulus values range from 2379.90 to 3499.20 GPa.Å for $(n,0)$ TGCNTs and 1886.70 to 2374.40 GPa.Å for $(0,n)$ TGCNTs. These insights into the nanostructure–property relationships of TGCNTs provide essential design guidelines for their application in flexible electronics, nanocomposites, and advanced nanoelectromechanical systems (NEMSs). Full article