The quasi-brittle nature of Geopolymer Concrete (GPC) severely limits its broader structural viability. This study investigates the optimization of a Ground Granulated Blast-furnace Slag (GGBS) geopolymer concrete through sequential Styrene-Butadiene Rubber (SBR) latex modification and alkali-resistant (AR) glass fiber reinforcement. Polymer dosages from 0% to 25% were evaluated, validating a 15% SBR concentration as the microstructural baseline. Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis (SEM/EDAX) confirmed that this dosage facilitates a monolithic interpenetrating polymer network and enhances Calcium Aluminosilicate Hydrate (C-A-S-H) gel precipitation. Subsequently, AR glass fibers were incorporated (0% to 2.0%) into the optimized SBR-GPC matrix. Empirical testing isolated 1.5% as the absolute optimal fiber dosage, yielding peak 28-day compressive (31.70 MPa), flexural (5.39 MPa), and bearing (62.26 MPa) capacities. Furthermore, single-point loading fracture mechanics testing revealed that the 1.5% integration maximized both fracture energy and the critical stress intensity factor , while also achieving a 50.00% enhancement in ultimate impact energy absorption and reducing chloride permeability to 1350.20 Coulombs (Low). Dosages exceeding 1.5% induced severe agglomeration, systematically degrading structural integrity. Finally, mathematical regression models were compared against advanced Machine Learning architectures like Artificial Neural Networks (ANN) and Gaussian Process Regression (GPR). While simple empirical equations reliably predicted tensile and flexural capacities, the GPR framework demonstrated exceptional superiority in mapping the non-linear compressive strength behavior, achieving a Leave-One-Out Cross-Validation of 0.950.
Fatigue cracking at girth welds threatens offshore-pipeline integrity and requires uncertainty in flaw size, crack-growth behaviour, loading and weld geometry to be considered. A probabilistic fatigue-reliability framework is developed for a semi-elliptical surface crack in an API 5L X65 pipeline under cyclic global bending. Geometry-consistent stress-intensity-factor histories from a three-dimensional finite-element model provide 60 training and six case-wise held-out simulations. The Paris-law and loading distributions are identified as DNV code-calibrated benchmark inputs, not site-specific X65 measurements. For the fixed Paris exponent, normalisation by CeffΔσeq3 reduces the primary surrogate to a one-dimensional Gaussian process in initial crack depth. The model achieves R2 = 0.997 and MAPE = 4.04% on the test cases, and R2 = 0.996 with MAPE = 3.70% in leave-one-out validation. Using conditionally truncated inputs, the posterior-mean life distribution has a median of 6.84 × 108 cycles and a 95%-reliability design life of 2.12 × 108 cycles. Correlated latent-GP posterior-function propagation gives Pf = 4.147% at Nd = 2 × 108 cycles, with a 95% GP-posterior interval of 3.858–4.444%. Sensitivity analysis identifies the stress-range scale as dominant, showing that site-specific loading characterisation is essential for field application.
Closed wheel-tread cracks can remain compression-dominated during rolling contact while sustaining substantial in-plane and out-of-plane shear. A sequential ABAQUS–FRANC3D–Python framework resolves this response over ten crack-geometry updates. A closure-aware nominal driving force combines event-paired differences in the mode-II and mode-III stress-intensity factors. Four arc-length descriptors summarise its front distribution: mean, peak, peak coordinate and coefficient of variation. Controlled comparisons evaluate initial crack size and orientation, axle load, speed and wheel–rail friction. Thirty Latin-hypercube finite-element conditions provide 4,272 front points for condition-grouped machine-learning validation. ExtraTrees achieves a case-macro cross-validation RMSE of 16.9587 MPa·mm1/2. Four held-out numerical conditions, comprising 579 front points, give a pointwise RMSE of 8.5794 MPa·mm1/2. Front coordinate and initial orientation have the largest mean absolute SHAP contributions. The predicted terminal profiles quantify differences in driving-force magnitude and localisation across conditions within the sampled domain.
This study is dedicated to the investigation of the influence of the pre-impact loading on the residual properties of composite sandwich panels. The methodology was proposed for pre-impact testing followed by quasi-static and cyclic tension of structurally representative composite specimens and structural elements. The material was additively manufactured sandwich panels consisted of honeycomb core made of acrylonitrile butadiene styrene (ABS) thermoplastic and two load-bearing face sheets made of ABS reinforced with 15% carbon fibers. Novel experimental data was obtained on the residual load-bearing capacity and fatigue life after pre-impact loading at various impact energy. Several phenomenological models were used to approximate obtained data on impact sensitivity, that demonstrated high descriptive ability.
Friction Stir Welding (FSW) is widely validated as a solid-state joining process that has gained significant attention for the welding of aluminum alloys in aerospace and automotive applications. In this study, the effect of Tool Pin Profiles (TPP)—Taper Threaded (TTPP), Square (SPP), and Cylindrical Threaded (CTPP)—on the flow of material, mechanical properties, corrosion properties and microstructure of dissimilar aluminum alloys AA6061-T6 and AA2024-T3 was investigated. A Taguchi L9 orthogonal array (OA) was employed for the optimization of process parameters, which included Tool Pin Profile (TPP), Tool Rotational Speed (TRS) of 600, 700, and 800 rpm and Welding Speed (WS) of 25, 30, and 35 mm/min. Mechanical properties were evaluated in terms of Ultimate Tensile Strength (UTS), Stir Zone (SZ) microhardness, and Percentage elongation. Microstructural characterization was conducted using optical microscopy and Scanning Electron Microscopy (SEM). Post‑weld performance was evaluated using potentiodynamic polarization and immersion corrosion tests. The TTPP condition yielded the highest measured UTS (210 MPa), SZ microhardness (162 HV), and elongation (8.89%) within the tested parameter range. This performance is attributed to improved material mixing, refined grain structure, and a favourable thermal cycle during processing. Through Taguchi optimization analysis, it was confirmed that the most favorable conditions for joining AA6061-T6 and AA2024-T3 alloys are provided by the TTPP.
