Search Results (436)

Unsaturated polyester resin concrete (UPC) exhibits high strength and corrosion resistance, and it has been widely used in hydraulic engineering structures. However, the diffusion of water molecules inevitably induces matrix plasticization and debonding at the aggregate–resin interface, which leads to progressive degradation of mechanical performance under long-term aqueous service conditions. To elucidate the water-induced mechanical deterioration mechanism of UPC and to develop a temperature-adaptive model for long-term compressive strength prediction, we prepared UPC specimens using graded quartz sand aggregate, an unsaturated polyester binder, V388 curing agent, and KH570 coupling agent at a fixed mass mixing ratio, followed by 7 days of natural curing after demolding. Accelerated water aging tests were conducted at three temperature levels (25 °C, 40 °C, 60 °C) and four immersion durations (15 d, 30 d, 45 d, 60 d), including water absorption, compressive, splitting tensile, and flexural tests. Based on Fick’s second diffusion law and the Arrhenius equation, we quantitatively analyzed moisture diffusion behavior and the evolution of mechanical degradation. The results indicate that the water absorption of UPC strictly follows Fickian diffusion, and that elevated temperature increases both the water absorption rate and the saturated water absorption capacity. The saturated water absorption ratios reached 0.15%, 0.16%, and 0.22% at 25 °C, 40 °C, and 60 °C, respectively, corresponding to apparent diffusion coefficients of 1.13 × 10⁻⁶, 1.67 × 10⁻⁶, and 4.52 × 10⁻⁶ mm/s. Long-term water aging progressively degrades the mechanical properties of UPC; after 60 d of immersion at 60 °C, the retention rates of compressive, splitting tensile, and flexural strength decreased to 88%, 85%, and 78%, respectively. We developed a physically coupled compressive strength prediction model based on moisture erosion depth and the associated reduction in effective bearing area. The ratio of model predictions to experimental data ranged from 0.93 to 0.98, indicating favorable conservative accuracy for engineering applications. When further combined with the Arrhenius relationship, the model enables extrapolation of the long-term mechanical properties of UPC under arbitrary service temperatures. This work provides theoretical support and a quantitative calculation framework for assessing the durability and predicting the service life of UPC hydraulic structures. Full article

This study addresses the thermodynamic analysis of the thermal decomposition of solid compounds under a linear temperature increase. Starting from the Gibbs free energy formulation developed for isothermal–isobaric systems, a generalised description is derived for dynamic regimes by combining thermodynamic considerations with the three-parameter equation. The proposed approach enables the identification of temperature-invariant Gibbs free energy nodes and establishes a direct relationship between Gibbs free energy, conversion degree and heating rate. The application of the equilibrium criterion yielded insights into the enthalpy and entropy changes associated with the heating rate diagrams. This investigation utilises empirical findings on the high-temperature decomposition of calcite (case 1) and the low-temperature dehydration of calcium oxalate monohydrate (case 2), applying local thermodynamic analysis to an extensive experimental dataset of the relationship. The analysis shows that the thermodynamic behaviour of these systems depends strongly on heating rate and on the selection of the thermodynamic reference state. For calcite, increasing heating rate leads to a quasi-equilibrium condition characterised by $\Delta G$ approaching zero, whereas for calcium oxalate monohydrate, the observed behaviour reflects the coupled contributions of the chemical dehydration reaction and water-vapour transport. The proposed formulation also reveals the role of the enthalpy–entropy compensation effect in the interpretation of dynamic thermodynamic functions and provides a direct link between phenomenological thermodynamics and thermo-kinetic descriptions. The novelty of the approach lies in demonstrating how fundamental thermodynamic considerations can be transitioned into thermokinetic formulations, thereby opening up new paths for extending the analysis to determine Arrhenius parameters. Full article

In the current manuscript, the hot deformation behavior and the thermal processing map of 6082-T6 rolled aluminum alloy sheet were studied. A series of compression tests were conducted using the Gleeble-3500 thermal simulation machine under the conditions of 200–350 °C and 0.001–1 s⁻¹. In order to tackle the stress errors caused by friction and plastic deformation temperature rise, the friction correction model and the adiabatic temperature rise interpolation method were used, respectively, to correct the flow stress curve. Based on the corrected data, a strain-compensated Arrhenius constitutive equation was constructed. Through the 4th-order polynomial fitting of material parameters and strain, the measured and predicted stresses were compared, with the average relative error reaching 10.50%. The thermal processing map was drawn based on the dynamic material model, and the material instability region was concentrated in the low-temperature high-strain rate zone. Within the investigated temperature and strain rate range, the optimal processing window was 320–350 °C and 0.001–0.031 s⁻¹. Combined with microscopic characterization by Optical microscope and transmission electron microscope, it was found that deformation at low temperature and high strain rate was mainly dynamic recovery, and dynamic recrystallization could fully occur at high-temperature low-strain rate. The research results can provide theoretical support for the optimization of the hot forging and hot stamping processes of this alloy. Full article

Mg-Gd-Y-Zr alloys, with strong age-hardening and thermal stability, are ideal for lightweight load-bearing components, yet forming large complex parts is limited by high sensitivity to hot deformation parameters. This work investigates the hot deformation behavior and microstructure evolution of a Mg-9Gd-4Y-0.5Zr (wt.%) alloy via hot compression at 400 to 510 °C and strain rates of 0.001 to 10 s⁻¹. An Arrhenius constitutive equation with an activation energy Q of 158.63 kJ/mol was established, and a hot processing map was constructed. EBSD characterization revealed the dynamic recrystallization, grain size evolution, and texture transition. The results show that flow stress depends strongly on temperature and strain rate. At strain rates of 0.001~1 s⁻¹, a dynamic balance between work hardening and dynamic softening is achieved, and the post-peak flow stress gradually stabilizes. At a high strain rate of 10 s⁻¹, the flow stress continues to decrease because the competition between softening from dynamic recrystallization and work hardening is disrupted by deformation-induced heating. Low strain rates (≤0.01 s⁻¹) and high temperatures (≥470 °C) promote dynamic recrystallization and significant grain refinement. Two optimal processing windows were determined: 400 to 430 °C at 0.001 to 0.01 s⁻¹, giving fully recrystallized fine equiaxed grains, and 440 to 460 °C at 0.01 to 0.1 s⁻¹ with a power dissipation efficiency η of 0.43 to 0.51, balancing processing efficiency and microstructural uniformity. This work provides systematic theoretical and data support for optimizing hot forming parameters of large Mg-Gd-Y-Zr load-bearing components and offers guidance for applying high-strength magnesium alloys in high-end equipment. Full article

The quality of yellowfin tuna is highly vulnerable to microbial proliferation, which accelerates quality deterioration and spoilage throughout storage. In this study, the dynamic changes in biogenic amines (BAs), total volatile basic nitrogen (TVB-N), and total plate count (TPC) across a different storage temperature range of 0 to 25 °C were studied, followed by a shelf-life prediction based on kinetic models. The TPC, TVB-N, and most BAs increased significantly with increasing storage time and temperature. Correlation analysis was used as an exploratory approach and showed that only histamine and cadaverine exhibited significantly positive correlations (|r| ≥ 0.6, p < 0.05) with TPC and TVB-N within the present dataset. Histamine was selected as a candidate BA indicator for kinetic modeling because only this BA changed significantly during storage at different temperatures. Utilizing histamine, TPC, and TVB-N, preliminary kinetic equations for shelf-life estimation were developed using first-order kinetics and the Arrhenius equation. Among the tested indicators, TPC showed relatively greater temperature sensitivity and preliminary within-batch agreement. These results provide preliminary reference data for further validation of tuna during the refrigeration process. Full article

With the rapid development of recycling and secondary utilization of end-of-life battery materials, it is crucial to clarify the impact of full-lifecycle degradation on the thermal safety limits of lithium-ion batteries. This study focuses on a 16 Ah NCM613|graphite pouch battery. First, it analyzes the evolution of capacity decay, thickness expansion, and internal resistance during cycling at room temperature (25 °C) and high temperature (45 °C). Furthermore, an adiabatic accelerated calorimeter (ARC) is employed to investigate the influence of different states of health (SOH) levels (95% and 85%) on the battery’s thermal runaway characteristics. The findings indicate that, macroscopically, batteries in all states follow similar voltage–temperature failure pathways, with mass loss rates confined to a narrow range of approximately 16%, emphasizing the low catastrophic potential of mid-nickel chemistry. However, the microscopic kinetic mechanisms exhibit significant anisotropy: although thickness and internal resistance display no apparent abrupt increase during the late stage of room temperature aging, the capacity exhibits a highly nonlinear plunge behavior. The severe internal lithium plating side reaction triggered by this phenomenon causes the self-heating onset temperature to drop rapidly from 130.0 °C in the fresh state to 79.7 °C. Concurrently, the activation energy of the exothermic side reaction, fitted using a simplified Arrhenius equation, exhibits a non-monotonic variation with aging progress. In the early stages of aging at 95% SOH, due to high temperatures promoting more significant growth of the interfacial film or moderate film formation at room temperature enhancing interfacial thermal stability, the activation energies for both aged batteries increase, and the energy barrier at high temperatures is slightly higher than at room temperature; however, during the deep aging stage at 85% SOH, due to the degradation of active material components and the emergence of lithium plating characteristics, the energy barrier significantly decreases, with high-temperature-aged batteries exhibiting a greater reduction, highlighting the cumulative negative impact of prolonged high-temperature exposure on thermal safety. The research provides a core scientific basis for establishing a battery safety early warning and dynamic health management system covering the entire lifecycle. Full article

The increasing demand for sustainable bitumen modifiers has stimulated interest in bio-based materials capable of improving binder performance while reducing environmental impact. This study investigates the influence of corn starch on the thermo-oxidative aging kinetics of paving-grade bitumen. Unmodified 50/70 bitumen and binders containing 4, 6 and 8 wt.% corn starch were subjected to laboratory aging at 100 °C and 140 °C for up to 120 h. The aging process was evaluated using dynamic viscosity measurements, FTIR spectroscopy and Multiple Stress Creep Recovery (MSCR) testing. The obtained results demonstrated that corn starch significantly affected both the rate and temperature dependence of aging. The effect of corn starch was strongly dependent on both the aging temperature and modifier dosage, indicating that starch does not uniformly inhibit all aging processes but rather modifies their kinetics in a process-specific manner. Increasing the aging temperature from 100 to 140 °C accelerated the viscosity growth by approximately 9–11 times, depending on the binder composition. The apparent rate constants for carbonyl formation ranged from 9 × 10⁻⁶ to 7 × 10⁻⁵ h⁻¹ for the reference binder and from 1 × 10⁻⁵ to 5 × 10⁻⁵ h⁻¹ for starch-modified binders. The calculated apparent activation energies varied between 1.31 and 67.6 kJ mol⁻¹, confirming that starch altered the temperature sensitivity of oxidation and structural transformation reactions. Among the investigated formulation (4–8 wt.% corn starch), the binder containing 4 wt.% corn starch exhibited the most favorable balance between aging resistance and production cost. Overall, the results demonstrate that corn starch modifies rather than universally inhibits bitumen degradation, with the optimum performance depending on the investigated aging parameter, modifier dosage and aging temperature, with 4 wt.% providing the most favorable overall balance between chemical aging behavior, rheological performance and production cost. Full article

AA6061-T6 undergoes work hardening, dynamic recovery, and progressive flow softening during hot torsion, yet a systematic single-campaign dataset with quantified experimental uncertainty is absent from the literature. Gleeble hot torsion tests were conducted at eleven conditions from 250 to 450 °C and 0.91 to 9.07 s⁻¹. With the stress multiplier fixed a priori at α = 0.045 MPa⁻¹ from compression literature on this alloy, a two-stage calibration determined the remaining Garofalo–Arrhenius constants: the temperature-slope stage anchors Q = 151.1 kJ mol⁻¹ (consistent with Al lattice self-diffusion), and a global Zener–Hollomon regression conditional on Q yields n = 1.371 and A = 3.51 × 10¹⁰ s⁻¹; a fully simultaneous three-parameter fit is shown to be practically unidentifiable on the three-level matrix. Training AARE = 15.5% (R = 0.908); leave-one-out cross-validation gives AARE = 23.0%, bounding the predictive uncertainty. The Prasad instability map identifies 400–450 °C at 0.91–2.72 s⁻¹ as the optimal hot-forming window; flow instability is predicted at 350 °C (outright at 2.72 and 9.07 s⁻¹, with the 0.91 s⁻¹ condition at the map boundary), and macroscopic fracture was observed in all three specimens tested there. Optical microscopy in specimen T1 (ε_eq = 3.69) shows elongated subgrains at the gauge center and fine-grained zones near the fracture surface consistent with localized geometric dynamic recrystallization. The activation energy, smooth post-peak softening, and subgrain wall morphology identify dynamic recovery as the likely dominant restoration mechanism. Adiabatic heating and a 24% peak-stress repeatability scatter at the single repeated condition (450 °C, 9.07 s⁻¹) are quantified and propagated into the constitutive model uncertainty bounds. Because the training-to-cross-validation error gap (15.5% versus 23.0% AARE) reflects the limited three-level strain-rate matrix, the calibrated equation is recommended for interpolation within the tested window of 300 to 450 °C and 0.91 to 9.07 s⁻¹ (noting that 300 °C was tested only at 0.91 s⁻¹, so higher-rate predictions at that temperature are extrapolations) and for forming-window identification, not for extrapolation beyond this domain without additional validation data. Full article

To reveal the high-temperature hot deformation mechanism and optimize the thermal processing window of Zr-Nb alloy, hot compression tests were implemented via a thermal simulation apparatus over temperatures ranging from 500 to 900 °C and strain rates of 0.01~10 s⁻¹. The material’s flow performance, dynamic recrystallization (DRX) and phase transformation were systematically explored in this work. The results indicate that flow stress presents a negative correlation with deformation temperature and a positive correlation with strain rate. On the basis of measured stress–strain curves, the Arrhenius constitutive equation and processing map were established to quantitatively describe the alloy’s hot deformation behavior. Flow instability areas are mainly distributed in the low-temperature domain and the high strain rate region of medium-high temperature zones. The evolution of DRX under different strain rates and microstructural variations during phase transformation was analyzed in detail. Elevated strain rate leads to gradual grain refinement. Continuous dynamic recrystallization (CDRX) acts as the predominant DRX mode for Zr-Nb alloy, with merely minor discontinuous dynamic recrystallization (DDRX) features observed in the microstructure. Full article

Accurately predicting the degree of hydration in cement systems blended with slag and fly ash is difficult when experimental data are limited. Empirical kinetic models typically need recalibration for each specific blend, while purely data-driven approaches often fail to maintain physical consistency. In this work, we present a physics-informed neural network for predicting isothermal hydration by incorporating the Avrami–Erofeev–Arrhenius ordinary differential equation into the training loss and using a composition-focused sub-network to relate blend proportions to blend-specific kinetic parameters. The model was trained and tested on 29,379 calorimetry data points from 77 multi-component cement systems gathered from two open-access datasets. For previously unseen test systems, it reached an $R^2$ of 0.9864 and a symmetric mean absolute percentage error (sMAPE) of 25.3%. Its overall sMAPE was lower than that of a neural network with the same architecture but without physics-based constraints (34.9%); stage-resolved analysis showed that the largest difference occurred during early hydration. Across eight random seeds, the physics constraint did not confer a data-efficiency or training-stability advantage over the same-architecture network. The distinguishing features of the PINN are instead its explicit ODE and monotonicity regularization and its composition-conditioned effective parameters. Although random forest regression produced lower pointwise error, it failed to maintain physically consistent hydration-rate behavior. Overall, the framework provides a composition-conditioned surrogate that incorporates kinetic regularization within the composition range investigated. Full article

The hot deformation behavior of 7050 aluminum alloy was investigated by isothermal compression tests over a temperature range of 250 °C to 450 °C and a strain-rate range of 0.001 s⁻¹ to 1 s⁻¹. The flow stress was strongly dependent on both temperature and strain rate. At a strain rate of 0.1 s⁻¹, increasing the temperature from 250 °C to 450 °C reduced the peak stress by 72.7%. At 450 °C, decreasing the strain rate from 1 s⁻¹ to 0.001 s⁻¹ reduced the peak stress from 66.7 MPa to 14.6 MPa, corresponding to a decrease of 78.1%. Based on the peak stress, an Arrhenius-type constitutive equation was established, with a deformation activation energy of 179.35 kJ mol⁻¹. The predicted peak stresses agree well with the experimental values, giving a correlation coefficient (R²) of 0.98. The processing map indicates that the optimal hot working domain is located at 400–450 °C and 0.001–0.05 s⁻¹. Scanning electron microscopy (SEM) observations showed that increasing temperature promoted the reduction in second-phase particles, with their area fraction decreasing from 5.3% at 250 °C to 1.2% at 450 °C under 0.001 s⁻¹. In comparison, strain rate had a smaller effect on the particle area fraction at 450 °C. Electron backscatter diffraction (EBSD) analysis revealed that high temperature and low strain rate enhanced dynamic recovery and grain-boundary misorientation evolution. The fraction of low-angle grain boundaries (LAGBs) decreased from 71.5% to 38.8% as the temperature increased from 250 °C to 450 °C under 0.001 s⁻¹, and decreased from 48.2% to 38.8% when the strain rate decreased from 1 s⁻¹ to 0.001 s⁻¹ at 450 °C. Full article

Hypersonic air-breathing propulsion via the Oblique Detonation Wave Engine (ODWE) offers superior thermodynamic efficiency compared to conventional scramjets by utilizing a stationary oblique detonation wave (ODW). While fundamental research has predominantly focused on two-dimensional planar wedges, realistic applications feature axisymmetric conical configurations. Over a cone, radial Taylor–Maccoll (TM) compression decelerates the flow and, in the mixed flow regime, establishes a localized subsonic pocket near the cone surface. However, the unsteady structures, triple-point kinetics, and cellular evolution under the competing influences of stabilizing TM compression and destabilizing Prandtl–Meyer (PM) expansions induced by a finite-length cone remain poorly understood. To address this gap, high-resolution numerical simulations of axisymmetric conical ODWs on a finite cone (semi-cone angle θ = 49°) were conducted at an inflow Mach number of Ma₀ = 7.5 using OpenFOAM. The methodology solves the reactive Euler equations coupled with a single-step Arrhenius model and three levels of adaptive mesh refinement to resolve fine-scale wave structures. Numerical results reveal that the localized subsonic pocket completely obliterates the smooth ZND-like initiation zone typical of purely supersonic configurations. Within this subsonic channel, acoustic disturbances propagate upstream against the bulk flow at a relative velocity of c − u, bypassing the supersonic wave-blocking effect to continuously impinge upon the detonation front. This acoustic feedback loop disrupts shock–reaction coupling, accelerating wave front bifurcation into single triple-point, dual triple-point, and PM-affected segments. Shock polar analysis validates that upstream-facing triple points exhibit greater shock strength, driving slow upstream migration and causing adjacent triple points to collide and reform into distinct, chaotic cell morphologies. Trajectory tracking confirms that the mixed flow cells are substantially larger and more chaotic than supersonic cases, directly reflecting amplified perturbations from the subsonic pockets. These insights provide crucial design criteria for optimizing cone angles to suppress irregular modes and stabilize conical ODWs. Full article

To reveal the stress–strain response and microstructure evolution of 38MnVS6 non-quenching and non-tempering steel pistons during hot forging, this study combines finite element simulation with experimental validation to investigate the effects of deformation temperature and strain rate on equivalent stress, true stress–true strain curves, and grain evolution. The results show that the deformation resistance of 38MnVS6 steel decreases with increasing temperature and increases with higher strain rates. Under 1000–1050 °C and a strain rate of approximately 1 s⁻¹, the stress distribution in the forging is relatively uniform, and stress concentration is effectively relieved. An Arrhenius-type high-temperature constitutive equation is established based on peak stress data, yielding a deformation activation energy Q of 335.99 kJ·mol⁻¹, which accurately represents the flow stress variation under different hot deformation conditions. Grain evolution simulated using the CAFE model indicates that 50% deformation promotes dynamic recrystallization and refines the grains. Experimental results show that water cooling increases the tensile strength by approximately 35% compared with air cooling, although the plasticity slightly decreases. In contrast to existing studies on general operating conditions, this paper establishes a coupled correlation mechanism linking the thermal deformation parameters–cooling regime–microstructure–mechanical properties. The findings provide important theoretical foundations and engineering references for the optimization of precision forging processes for non-quenched and tempered steels, the precise control of the microstructure and properties, and the quality control of forgings. Full article

Magnetic hyperthermia relies on the ability of magnetic nanoparticles (MNPs) to dissipate heat under alternating magnetic fields, with the heating efficiency commonly quantified through the specific loss power (SLP). Accurate estimation of SLP requires realistic modeling of the dynamic magnetic response of nanoparticle ensembles, particularly in the ferromagnetic single-domain regime where hysteresis losses dominate. In the present work, we developed a computational framework in Mathematica based on the thermally activated Stoner–Wohlfarth model to simulate dynamic hysteresis loops and estimate SLP in ensembles of non-interacting magnetic nanoparticles. The model incorporates experimentally relevant distributions of particle diameter, magnetic anisotropy, and easy-axis orientation, enabling realistic representation of nanoparticle polydispersity and orientation disorder. Thermal activation was introduced through Arrhenius-type Néel switching probabilities, while the dynamic magnetization evolution was obtained numerically through solution of the corresponding rate equations. The framework was tested for magnetite nanoparticles, one of the most widely used materials in magnetic hyperthermia, considering typical single-domain ferromagnetic particle sizes in the range of 15–30 nm and effective anisotropy K_eff values representative, 3 kJ/m³ < K_eff < 20 kJ/m³ of experimentally reported systems. Simulations were performed under clinically relevant alternating magnetic fields with amplitudes up to 24 kA/m and frequencies ranging from 100 to 765 kHz. The model successfully reproduced dynamic hysteresis loop evolution and enabled systematic investigation of the influence of nanoparticle size, anisotropy, and orientation distributions on loop shape, symmetry, and SLP. The developed code provides a computationally accessible tool for researchers working in magnetic hyperthermia, allowing direct connection between microscopic nanoparticle properties and macroscopic heating performance. By enabling parametric mapping of dynamic hysteresis behavior and SLP dependence, the framework may support the rational optimization of magnetic nanoparticle systems for biomedical hyperthermia applications. Full article

This case study investigates the ageing behaviour of hydroxyl-terminated polybutadiene (HTPB)-based solid propellants, containing 0.5% iron oxide and a bimodal ammonium perchlorate (AP) distribution (300 µm coarse AP and 40 µm fine AP). To achieve higher burning rates in large solid rocket motors, burning-rate catalysts were preferred over ultra-fine oxidiser compositions due to processing advantages. Characterisation of the iron oxide burning rate catalyst, specific to its surface area, was attempted. The role of surface characteristics in burning rate augmentation and ageing reactions was studied. Particle size and surface area estimates were obtained, and propellant burning rates, pressure exponents, and propellant ageing behaviour were evaluated to support the study. Accelerated thermal ageing of composite solid propellant samples at three different temperatures is carried out. The Arrhenius equation was used to model the dependence of the initial modulus on ageing time and temperature. An activation energy of 68.18 kJ/mole was obtained, which is approximately 4–8% lower than previously reported values for conventional propellants. The study concludes that iron oxide with a specific surface area of 10 m²/g and proportions up to 0.5% by weight can be safely used in propellant formulations without a significant reduction in the propellant’s shelf life. Full article