Search Results (622)

Gleeble-3800 thermal simulation testing machine was adopted to investigate the evolution laws of microstructure and properties in the coarse-grained heat-affected zone (CGHAZ) of pipeline steels with different Cr mass fractions (0.2, 0.5, 0.8 wt.%) under welding heat inputs ranging from 8 kJ/cm to 20 kJ/cm. Combined with optical microscopy, scanning electron microscopy and electron backscatter diffraction, the coupled influencing mechanism of heat input and Cr content on the properties of CGHAZ was systematically analyzed. The results show that as the Cr content increases, the range of valid welding heat input for maintaining satisfactory CGHAZ impact toughness gradually narrows with increasing Cr mass fraction of the steel. Specifically, the 0.2Cr experimental steel maintains high toughness under a thermal input ranging from 8 to 20 kJ/cm, the 0.5Cr experimental steel exhibits relatively high toughness in the range 8 to 13 kJ/cm, while the 0.8Cr experimental steel shows high toughness only at 15 kJ/cm. The coupled effect of weld heat input and Cr content on CGHAZ properties originates from a combination of microstructural composition types, phase fractions, substructures, and grain sizes. Increasing the heat input and Cr content leads to a reduction in the bainite ferrite with superior toughness and an increase in the large-sized granular bainite with inferior toughness. Meanwhile, the effective grain size of the overall microstructure first decreases and then rises. Grain coarsening and an increased fraction of Martensitic/Austenitic (M/A) constituent are the key factors responsible for the deterioration of CGHAZ toughness in deep-sea oil and gas transportation pipeline steel. Full article

Accurate tracking and localization of in-line inspection (ILI) tools are essential for mileage calibration, defect mapping, and blockage prevention in oil and gas pipelines. This review summarizes sensor-based approaches for external ILI-tool localization, emphasizing how sensing physics, deployment geometry, and signal interpretation determine practical performance. Extremely low-frequency (ELF) magnetic tracking is first examined through dipole modeling, sensor evolution, and weak-signal recovery under steel-pipe and soil shielding. Distributed fiber-optic sensing is then reviewed as a continuous-tracking alternative, with attention to fading mitigation, spatiotemporal denoising, and trajectory extraction from distributed acoustic sensing data. Acoustic arrays and hybrid schemes are discussed as complementary options for subsea or cable-free environments. Finally, the review assesses how data fusion and lightweight artificial intelligence (AI) can improve robustness while noting unresolved issues in field data availability, edge computing, and uncertainty quantification. The synthesis indicates that next-generation ILI tracking should combine heterogeneous sensing, physics-aware signal processing, and deployment-aware model design rather than rely on a single high-sensitivity sensor. Full article

Corrosion in carbon steel piping systems is a critical issue in hydroelectric power plants, as progressive wall thickness loss may compromise integrity and operational reliability. This study proposes a data-driven framework combining descriptive statistical analysis and distinct clustering methods to map and rank corrosion conditions in water pipeline systems of a hydroelectric power plant in Brazil. A total of 4916 pipe segments from 20 generators (generating units 1 and 2) were evaluated and the feature matrix included wall loss descriptors, measured thickness statistics, minimum allowable thickness, wall integrity indicators, pipe geometry, segment type, and system information. Descriptive analyses revealed heterogeneous corrosion patterns across generating units, segment types, diameters, and inspection points, with localized severe wall loss conditions in specific segments. A principal components analysis was applied to reduce the original feature space while preserving approximately 80% of the cumulative variance, as suggested by the literature. The best clustering solution was obtained using a weighted consensus model based on the Calinski–Harabasz index, resulting in five degradation/integrity profiles that support segment-level corrosion ranking and inspection prioritization. The proposed framework provides a structured basis for integrating inspection data, statistical descriptors, and integrity indicators into maintenance and decision support processes for hydroelectric power plant piping systems. Full article

Although steel pipelines constitute the primary infrastructure of agricultural irrigation systems, they are highly susceptible to moisture-induced pitting corrosion and severe operational conditions, including internal pressure fluctuations and heavy overburden loads. This study evaluated the structural performance and durability of full-diameter steel pipe specimens (311.5 mm in diameter and 2.0 m long) repaired using CFRP (single-layer) and GFRP (single- and multi-layer) sheet wrapping as well as overlay welding. A 60-mm pinhole defect corresponding to a 6% circumferential damage ratio was introduced to simulate advanced localized corrosion. The repaired pipelines were experimentally assessed under four-point bending, internal hydrostatic pressure, and accelerated salt spray exposure. Under service-level flexural loading, all specimens exhibited similar global load–deflection responses regardless of defect or repair condition. However, localized strain measurements revealed that the unrepaired defect produced tensile strains up to 12 times greater than those of the intact pipe, whereas all repair techniques effectively suppressed the localized strain concentration. The effectiveness of the FRP systems improved with increasing reinforcement thickness. Overlay welding provided the highest structural performance, restoring localized strain behavior to a level comparable to that of the intact pipe. Under an internal pressure of 2.0 MPa, welding and CFRP maintained 100% pressure retention, whereas single-layer GFRP exhibited minor radial bulging, reducing its pressure retention ratio to 73.5%. Increasing the GFRP thickness restored the retention ratio to 93.0%. Accelerated salt spray exposure further demonstrated that GFRP provided effective barrier protection against corrosion by acting as an impermeable dielectric barrier under short-term exposure, whereas welded specimens still exhibited localized corrosion around the heat-affected zone despite epoxy coating. These findings demonstrate that overlay welding offers the greatest immediate structural restoration, whereas adequately dimensioned FRP systems can provide a more balanced solution for multi-hazard durability by simultaneously enhancing structural performance and mitigating electrochemical degradation in aging agricultural steel pipelines. Full article

This study investigates adhesively bonded composite patch repair to enhance the load-carrying capacity of damaged metallic structures, introducing a novel FE-augmented machine learning (ML) framework that addresses the limited availability of experimental data in structural repair applications. To evaluate this approach, aluminum and steel specimens with central fatigue cracks were repaired using glass-fiber/epoxy and carbon-fiber/epoxy composite patches and tested under quasi-static loading at room ($70 \mathrm{F} °$), high ($145 \mathrm{F} °$), and low (−$60 \mathrm{F} °$) temperatures. Finite element (FE) models were then developed in ABAQUS© to predict the failure loads of the patched specimens under varying temperature conditions, showing excellent agreement with the experimental data. The high accuracy of the FE predictions enabled their use as additional training data, effectively augmenting the limited experimental dataset and allowing the development of more robust regression models. Ten machine learning (ML) regression models, including linear regression (LR), polynomial regression (PR), support vector regression (SVR), random forest (RF), gradient boosting (GB), XGBoost (XGB), LightGBM (LGBM), Gaussian process (GP) regression, artificial neural networks (ANNs), and Kolmogorov–Arnold networks (KANs), were trained to predict the failure load of both unpatched and patched specimens as a function of material type, temperature, specimen thickness, crack length, and, for patched specimens, patch type and thickness. The datasets combined a limited set of physical results (75 patched samples: 63 experimental and 12 finite-element; 72 unpatched samples: 27 experimental and 45 theoretical) with Gaussian-mixture-model synthetic samples used only to augment the training data up to 300 samples per case. Under a configuration-grouped, leakage-free nested cross-validation (entire configurations held out for testing, hyperparameters tuned on inner folds only), the best models predicted the failure load of unseen configurations with mean absolute percentage errors of 2.78% (Gradient Boosting, patched, $R^2=0.87$) and 3.33% (Gaussian Process, unpatched, $R^2=0.98$). A paired ablation showed that Gaussian-mixture-model augmentation did not improve accuracy and, for several models, actually reduced it; the final models therefore rely on the real multi-source (experimental, FE, and theoretical) data, with the synthetic pipeline reported as a validated but non-beneficial component for these datasets. Overall, this study provides a novel, data-efficient framework combining experimental testing, FE simulation, and validated regression modeling to predict the performance of adhesively bonded composite patch repairs under varying thermal and mechanical conditions. Full article

Non-contact metric inspection of metallic circular holes is essential for assembly quality control, yet remains difficult on reflective machined surfaces, where depth scale, stripe radiometry, and contour geometry degrade simultaneously. Pure monocular two-dimensional vision localizes hole boundaries efficiently but cannot resolve metric depth; multi-camera three-dimensional systems remove this ambiguity but with a heavier hardware and calibration cost; and conventional structured-light pipelines often improve stripe extraction or circle fitting in isolation, leaving the overall measurement chain fragile when reflection and edge defects co-occur. This paper proposes a monocular structured-light framework that treats sensing geometry, radiometric stripe reliability, and outlier-robust hole estimation as one coupled measurement chain. A single calibrated industrial camera is combined with an obliquely projected line laser to fuse top-view contour observation with light-plane-constrained depth recovery. Multi-exposure high-dynamic-range (HDR) fusion, adaptive Gaussian regularization, and distance-weighted gray-centroid refinement stabilize sub-pixel stripe centerlines under local saturation and uneven illumination, while geometry-aware contour screening and probabilistic multi-stage RANSAC fitting suppress burr-induced outliers during circle-parameter estimation. Experiments were conducted on a steel bolt-hole workpiece and a 6061 aluminum-alloy plate containing five holes with nominal diameters spanning approximately 30–78 mm. The original steel workpiece was evaluated for its diameter and two datum-related center-position quantities, while the five-hole plate was evaluated through three repeated optical diameter measurements and independent CMM references. For the five aluminum-alloy holes, the mean optical–CMM diameter differences ranged from 0.006 to 0.218 mm, with an average absolute difference of 0.096 mm. The results establish feasibility over the tested workpieces and calibrated measurement volume rather than generalization to arbitrary hole geometries, materials, or surface conditions. Full article

This study investigates hydrogen-assisted fatigue crack growth (FCG) in vintage pipeline steels to quantify grade-dependent degradation under hydrogen–natural gas blending conditions. Fatigue behavior was evaluated using compact-tension specimens extracted from API X52 and X70 pipeline steels and tested in natural gas–hydrogen mixtures at a total pressure of 6.9 MPa and ambient temperature. Hydrogen concentration was systematically varied from 0% to 100% H₂ to assess its influence on crack-length evolution, fatigue crack growth rate, and fracture morphology. Crack propagation was characterized as a function of the stress-intensity-factor range, and scanning electron microscopy was used to examine hydrogen-induced changes in fracture mechanisms. The results demonstrate that FCG accelerates as hydrogen concentration increases, with a strong dependence on steel grade. X70 exhibited substantially greater hydrogen-induced FCG acceleration than X52, despite showing better fatigue resistance under hydrogen-free conditions. Fatigue life reductions approached 60% for X70 at 100% hydrogen, compared with approximately 30% for X52 under the same conditions. Significant early-life sensitivity was observed in X70 even at low hydrogen concentrations, whereas X52 showed more pronounced acceleration during later stages of crack growth. The influence of hydrogen was nonlinear and tended to stabilize at elevated blend fractions, indicating a saturation-type response once hydrogen-assisted crack growth became dominant. Fractographic analyses revealed a transition from ductile tearing in natural gas environments to terrace- and facet-controlled crack propagation in hydrogen-rich environments, accompanied by secondary cracking and river-pattern features. These findings demonstrate that hydrogen–natural gas blending can significantly alter fatigue crack growth behavior and relative material performance in pipeline steels, highlighting the need for grade-specific integrity assessment of existing pipeline infrastructure. Full article

Budget overruns driven by unpredictable building material prices are a persistent challenge in emerging economies, yet reliable price forecasting tools for structural materials such as steel reinforcement bar (RFT) remain largely unavailable to building project teams. This study develops an Autoregressive Distributed-Lag (ARDL) model to forecast RFT prices in Egypt using macroeconomic leading indicators. A structured filtering pipeline—stationarity testing, Variance Inflation Factor (VIF) screening, and Granger causality testing—reduced 22 candidate variables to nine predictors: producer price index (PPI), loan rate (LR), discount rate (DR), Egyptian Stock Exchange Index (EGX30), money supply (M0), exchange rate (ER), iron ore prices (ORE), American stock index (S&P500), and Hang Seng Index (HSI). ARDL bounds testing confirmed cointegration across look-back periods (LBP) of 3, 6, and 9 months. Comprehensive diagnostics confirmed model stability, homoscedasticity, and the absence of serial correlation. The ARDL was benchmarked against an Ordinary Least Squares (OLS) baseline and a first-difference vector autoregression (VAR) model. Evaluated as genuine multi-step (dynamic) forecasts over the held-out crisis-period window, the 3-month model achieved an out-of-sample mean absolute error of approximately 5.9% in price terms, retaining a clear advantage over the OLS baseline at that horizon. The proposed framework provides quantity surveyors, cost consultants, and project managers with a practical tool for setting RFT budgets at the tendering stage and optimising procurement timing. It is transferable to other building materials (cement, structural steel sections, glazing) across emerging-market construction economies. Full article

Agricultural steel pipelines are essential components of pressurized irrigation systems, yet localized corrosion-induced pinholes severely compromise their structural integrity by creating critical stress concentrations. To address the lack of performance-based maintenance guidelines, this study experimentally evaluates three repair techniques—a multi-joint hinge clamp, a GFRP composite sleeve, and overlay welding—applied to steel pipes containing simulated pinhole defects representing 6% and 10% circumferential damage. Four-point bending and uniaxial tensile tests were conducted to simulate transverse overburden and longitudinal axial loading encountered in buried pipelines. Results reveal that repair effectiveness strongly depends on both loading mode and damage severity. At 6% damage, all methods effectively restored bending capacity, with the GFRP sleeve achieving near-complete recovery. Under tensile loading, however, external-confinement methods provided limited ductility improvement because they lack a direct axial load-transfer path. In contrast, overlay welding consistently achieved substantial structural restoration by eliminating stress concentrations and shifting fracture to the parent pipe material. Furthermore, a significant transition in repair performance was observed near the 6% damage level, beyond which confinement-based repairs exhibited reduced efficacy. These findings demonstrate that repair performance cannot be reliably assessed from bending behavior alone and highlight the importance of considering both loading conditions and damage severity in rehabilitation design. The study provides a quantitative framework for load-specific pipeline rehabilitation strategies. Full article

The transition to a decarbonized energy infrastructure relies on repurposing existing pipelines for hydrogen–methane mixtures, which introduces significant concerns regarding hydrogen embrittlement. Accordingly, a coupled Multiphysics phase-field model was developed to predict hydrogen-assisted failure in elastic–plastic solids. This framework is numerically implemented via the finite element method to predict the structural integrity of pipeline steel strength classes representative of API 5L X65, X70, and X80 by explicitly accounting for elastoplastic deformation, hydrogen trapping effects, and stress-driven diffusion. By computing crack growth resistance curves across various scenarios, it has been demonstrated the capability of the model to capture material sensitivities by varying hydrogen–methane blend compositions, operational pressures, and the elastoplastic deformation behavior of different strength grades. The investigation revealed that methane limits surface hydrogen coverage, thereby mitigating the crack-tip decohesion mechanism. Furthermore, the model indicates that at a pressure of 7.5 MPa, a 15 vol% hydrogen–methane blend enables these materials to retain 80–90% of their fracture toughness and exhibit ductile failure. Finally, higher-strength steel classes (representative of X80) demonstrate greater susceptibility to hydrogen embrittlement under these conditions due to yield stress-amplified hydrostatic stress, whereas lower-strength steels exhibit greater defect tolerance for the hydrogen-blend transition. Full article

Hydrogen embrittlement (HE) damages the fracture toughness, often promoting brittle fracture even at low stress levels. Since welded joints are sensitive to this kind of damage, there is a very high risk of failure. For this reason, this study systematically evaluates the fracture toughness and fracture behavior of X65 pipeline steel welded joints under a gaseous hydrogen environment. The crack tip opening displacement (CTOD) test and electron microscopy technology were adopted to carry out fracture toughness evaluation and microstructure analysis on the weld metal (WM) and heat-affected zone (HAZ) under hydrogen pressure conditions of 1.0 MPa, as well as 7.2 MPa. The results underscore that at the higher hydrogen pressure (7.2 MPa), the CTOD value decreased compared with that at 1.0 MPa; the reduction amplitudes of the CTOD values of the WM and HAZ were 79% and 84%, respectively. When the hydrogen pressure was 1.0 MPa, the WM and HAZ presented microvoid coalescence (MVC) fracture characteristics, the crack propagation path was tortuous, the plastic deformation at the crack tip was significant, and dislocations proliferated massively, leading to high fracture toughness. At 7.2 MPa, the fracture mechanism was into brittle fracture, the crack propagated along an almost straight path, plastic deformation and dislocation proliferation at the crack tip were significantly inhibited, and the fracture toughness decreased sharply. Full article

Hydrogen diffusion plays a central role in the susceptibility of steels to hydrogen embrittlement, yet reported diffusivity values often exhibit significant variability due to differences in experimental methodology. Gaseous hydrogen permeation experiments, while more representative of service conditions, are highly sensitive to surface boundary conditions and trapping effects, which can bias the diffusivity obtained from analysis. In this work, a gaseous hydrogen permeation methodology was developed at the High-Performance Powertrain Materials Laboratory (HPPM) at the University of British Columbia, Okanagan. A dedicated gas management system (GMS) was implemented to enable controlled pressure step transients, allowing partial permeation transients to be collected under gaseous charging conditions. This approach was applied to commercially pure iron and API 5L X60 pipeline steel to evaluate diffusion and trapping behaviour across materials with differing microstructural complexity. The results demonstrate that diffusivity obtained from transients spanning the full charging–discharging range (0–2 MPa) reflects an effective parameter influenced by reversible hydrogen trapping, whereas transients measured over incremental pressure steps (1–2 MPa) provide a more consistent estimate of lattice-controlled diffusion. The application of palladium coatings to the charging surface was found to promote hydrogen entry, reducing surface impedance effects and further improving agreement with Fickian diffusion behaviour. Full article

Hydrogen serves as a fundamental energy carrier essential for achieving global carbon neutrality, with long-distance pipeline transportation recognized as the most efficient approach for large-scale hydrogen delivery. Nevertheless, hydrogen embrittlement (HE) in pipeline steels constitutes a significant safety challenge for this infrastructure. This review presents a comprehensive and systematic analysis of HE in hydrogen pipeline steels, emphasizing the microstructural fracture mechanisms under hydrogen exposure, the microstructural regulation of hydrogen diffusion and trapping, the interplay of multiple influencing factors, strategies for HE mitigation, and numerical prediction methodologies. Critical factors including microstructural features, hydrogen transport dynamics, and the coupling effects between stress and hydrogen are examined in detail. The review systematically summarizes advanced HE mitigation techniques and strategies, encompassing microstructural engineering, surface modification, alloy composition optimization, finite element modeling, and machine learning applications. Additionally, several principal challenges confronting the field are identified: the ambiguous mechanisms underlying multi-field coupling effects, the limited translation of laboratory-scale findings to practical engineering contexts, especially with regard to multi-scale mitigation of hydrogen-induced fracture, and the incomplete advancement of artificial intelligence-based pipeline integrity assessment tools. To address these issues, the review proposes key research directions and recommendations for future investigations into HE in hydrogen pipeline steels. Full article

Buried steel frame-reinforced polyethylene (SRPE) pipelines are vulnerable to bending-compression buckling, sectional distortion, and tensile rupture when crossing reverse faults. Nevertheless, their multi-mode failure mechanisms and strain evaluation frameworks have not been systematically clarified. Given this challenge, a three-dimensional nonlinear finite element model considering pipe–soil contact, material elasto-plasticity, and large deformation is established in this study to investigate the deformation characteristics, strain evolution, and buckling performance of SRPE pipelines under reverse fault inclination angles from 0° to 150°. The effects of internal pressure, steel frame diameter, and soil properties on pipeline mechanical behavior are analyzed, with the results being compared with the strain limits specified in the GB 50470-2017, CSA Z662-2023, and EN 13476-3 standards. The pipeline is subjected to a three-stage failure process involving local compressive buckling, overall bending, and tensile necking. Notably, coupled bending-compression failure is typical at low inclination angles, while high angles are dominated by shear-tension coupling. Excessive internal pressure increases the local buckling and concentration of compressive strains. An increase in the steel frame diameter contributes to an effective improvement in the buckling resistance. When the soil has higher cohesion and stiffness, the critical buckling displacement becomes larger. The standard constant strain limits currently adopted do not account for the transition in failure mode arising from inclination control and are therefore overly conservative for SRPE pipelines. This study provides a theoretical foundation and quantitative reference for the seismic design and safety assessment of SRPE pipelines crossing reverse fault zones. Full article

Hydrogen embrittlement of the steel reinforcement layers poses a critical threat to the safe operation of steel-wire-reinforced thermoplastic pipes (SRP) in hydrogen transport. However, the mechanisms governing hydrogen diffusion in SRP under stress conditions remain poorly understood. This study develops a two-dimensional finite element model based on the theory of hydrogen diffusion under stress conditions. The model systematically examines the influence of four parameters on hydrogen diffusion in SRP: hydrogen pressure (1–20 MPa), steel wire diameter (1.0–2.0 mm), radial distance from the steel wire layer to the inner pipe wall (3.2–4.8 mm), and steel wire winding angle (8–15°). The key findings are as follows: (1) Increasing hydrogen pressure proportionally accelerates hydrogen diffusion and raises the local hydrogen concentration around the steel wires, thereby promoting hydrogen-induced crack initiation. (2) The effect of steel wire diameter is non-monotonic. Increasing the diameter from 1.0 mm to 1.2 mm lengthens diffusion paths and suppresses the local hydrogen concentration, whereas a further increase to 2.0 mm intensifies steric hindrance and hydrogen retention. Optimal hydrogen barrier performance is achieved at diameters of 1.2–1.4 mm. (3) Increasing the radial distance from the steel wire layer to the inner pipe wall strengthens the hydrogen concentration gradient across the inner and outer high-density polyethylene layers. This accelerates hydrogen diffusion and reduces the hydrogen concentration adjacent to the wires. (4) A winding angle of 9–10° minimizes the hydrogen concentration within the steel wire layer, thereby significantly improving resistance to hydrogen embrittlement. These findings elucidate the mechanisms governing hydrogen diffusion in SRP and provide quantitative design guidelines for mitigating hydrogen-induced damage in composite pipeline systems. Full article