Stochastic fracture network models are important tools for characterizing heterogeneity and seepage behavior in fractured rock masses in geotechnical engineering. To address the limitations of conventional models—poor generalization, high uncertainty in flow description, and susceptibility to distortion—this paper proposes a novel computational framework: a geometric-topologically constrained stochastic fracture network modeling method that accounts for the synergistic interplay between fracture geometry and topological connectivity. After validating the seepage reliability of the constrained model, uncertainty quantification analysis identifies the respective contributions of various geometric and topological parameters to fracture network connectivity efficiency. Furthermore, a practical modeling approach driven by dominant controlling factors is proposed. Results indicate that fractured rock samples exhibit pronounced dominant-flow characteristics. Fractures create preferential flow channels, accelerating gas migration from free space into the porous medium region. Uncertainty quantification reveals that the average number of connections per branch (CB), the average number of connections per fracture (CL), and the angle deviation of fracture (θ) are the core controlling factors governing system-scale seepage behavior. Fracture aperture (b), the number of X-type nodes (NX), and the number of fracture branches (NB) are identified as key influencing factors. Volumetric fracture intensity (P32) and the number of I-type nodes (NI) indirectly regulate seepage responses through interactions with other topological parameters. Based on these findings, a dominant-factor-driven modeling approach is proposed, which prioritizes accurate characterization of parameters controlling fracture network connectivity and the dominant seepage direction, while reasonably simplifying secondary factors that contribute less to seepage behavior. The fracture network model constructed using this new method achieves a consistency rate of approximately 96.6% with the reference model in terms of seepage behavior, demonstrating its robustness in effectively characterizing the baseline seepage response. These findings provide a practical solution for engineering-scale fractured rock mass modeling, offering a balance between accuracy and computational efficiency.
The transition from blast furnace to electric arc furnace steelmaking is a step toward enhancing circularity through increased scrap utilization, thereby reducing CO2 emissions. However, higher scrap use introduces tramp elements that may affect steel quality. This study investigates the influence of tramp elements on the phase transformation behavior of a low-alloyed steel by combining modeling and experiments. Dilatometry and optical microscopy are employed to analyze phase transformations and microstructures, enabling the construction of continuous cooling transformation diagrams. Prior austenite grain size is measured with a high-temperature laser scanning confocal microscope. To complement the experimental investigations, a computational modeling framework based on the CALPHAD method is performed using Thermo-Calc. Experiments reveal that tramp elements shift phase transformations to longer times and lower temperatures, decreasing critical cooling rates and enhancing hardenability. Refinement of prior austenite grain size with increasing tramp element content indicates segregation effects at grain boundaries. To identify the decisive mechanism driving the altered phase transformations, CALPHAD modeling highlighted the crucial role of element segregation in lowering grain boundary (GB) energy. These findings suggest that the segregation of tramp elements is likely to be an important factor in controlling phase transformation kinetics in scrap-based steels.
Diffusive gradients in thin films (DGT) coupled with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is increasingly applied for high-resolution chemical imaging of metal solutes, yet its effective lateral resolution has not been quantitatively assessed. This study provides the first targeted investigation of the lateral resolution achievable with state-of-the-art DGT LA-ICP-MS using copper (Cu) as a model analyte in three complementary experimental designs that isolate diffusion-controlled, geometry-controlled, and material-controlled constraints: (i) Controlled solute transport through a polytetrafluoroethylene (PTFE) foil with 5–100 µm holes revealed differential time-dependent broadening of solute and matrix patterns and the transition from geometry-preserving to diffusion-dominated behaviour. Full width at half maximum/minimum (FWHM)-based analysis showed very small apparent lateral “imaging-blur” coefficients for DGT-bound metals (Cu/Zn ≈10−15–10−13 m2 s−1), i.e., several orders of magnitude lower than typical ionic diffusion in hydrogels (≈10−10 m2 s−1), consistent with rapid immobilization at the DGT binding phases and modest lateral within-gel diffusion. (ii) Direct gel contact with Cu metal grids enabled quantitative comparison of nominal bar/hole dimensions with DGT-derived solute patterns, demonstrating that features down to 25 µm are detectable under optimal contact and laser ablation conditions. (iii) Application to printed circuit boards confirmed the method’s ability to reproduce sub-mm Cu features on technologically relevant materials. Across experiments, gel-phase lateral diffusion and imperfect gel-sample contact were the dominant factors limiting spatial accuracy. These results define the practical lateral resolution of DGT LA-ICP-MS and provide guidance for designing and interpreting high-resolution solute imaging experiments in environmental and materials science.
This study focuses on the formation, quantification and morphology of retained austenite in the heat-affected zone (HAZ) of a thermomechanically controlled processed high-strength steel. Physical simulation using dilatometry combined with high-energy X-ray diffraction was employed for in situ phase quantification, while various electron microscopy methods were used for microstructural investigation. Compared to the initial state, which contained approximately 1% retained austenite, the content increased by 1.9% in the coarse-grained HAZ and by 3.9% in the intercritically reheated coarse-grained HAZ. Some of the formed retained austenite appears as stand-alone phase in both zones. However, the majority seems to be present within various types of martensite-austenite constituents.
