Search Results (248)

With the electrification of generator sets, electric locomotives, new energy vehicles, and other industries, AC motors subject bearings to an electric field environment, leading to galvanic corrosion due to the use of variable frequency power supply drives. The phenomenon of bearing discharge breakdown in subway traction motors is a critical issue in understanding the relationship between shaft current strength and the extent of bearing damage. This paper analyzes the mechanism of impulse discharge that leads to galvanic corrosion damage in bearings at a microscopic level and conducts electric thermal coupling simulations of the traction motor bearing discharge breakdown process. It examines the temperature rise associated with lubricant film discharge breakdown during the dynamic operation of the bearing and investigates how breakdown channel parameters and operational conditions affect the temperature rise in the micro-region of bearing lubrication. Ultimately, the results of the electric thermal coupling simulation are validated through experimental tests. This study revealed that in an electric field environment, the load-bearing area of the outer ring experiences significantly more severe corrosion damage than the inner ring, whereas non-bearing areas remain unaffected by electrolytic corrosion. When the inner ring reaches a speed of 4500_rpm, the maximum widths of electrolytic corrosion pits for the outer and inner rings are measured at 89 um and 51 um, respectively. Additionally, the highest recorded temperatures for the breakdown channels in the outer and inner rings are 932 °C and 802 °C, respectively. Furthermore, as the inner ring speed increases, both the width of the electrolytic corrosion pits and the temperature of the breakdown channels rise. Specifically, at inner ring speeds of 2500_rpm, 3500_rpm, and 4500_rpm, the widths of the electrolytic pits in the outer ring raceway load zone were measured at 34 um, 56 um, and 89 um, respectively. The highest temperatures of the lubrication film breakdown channels were recorded as 612 °C, 788 °C, and 932 °C, respectively. This study provides a theoretical basis and data support for the protective and maintenance practices of traction motor bearings. Full article

The aim of this paper is to present the results of an experimental and numerical investigation into the degradation of reinforced concrete (RC) specimens subjected to an accelerated corrosion process using impressed current in the presence of chloride ions. The corrosion of the rebars was carried out using three current densities (50, 100, and 200 µA/cm²) and various exposure times. The experimental results characterised the internal degradation of the RC specimens through measurement of the corrosion product thicknesses at the steel–concrete interface; the widths, lengths and orientations of internal concrete cracks; and the external concrete crack widths. In addition, numerical modelling of the corroded RC specimens was conducted to describe the crack patterns. The comparison between the experimental and numerical results demonstrated a high degree of correlation, providing insights into the degradation process of RC specimens due to corrosion. Full article

The operation of heavy-haul railway trains with large loads results in significant cracking issues in reinforced concrete beams. Atmospheric carbon dioxide, oxygen, and moisture from the atmosphere penetrate into the beam interior through these cracks, accelerating the carbonation of the concrete and the corrosion of the steel bars. The rust-induced expansion of steel bars further exacerbates the cracking of the beam. The interaction between environmental factors and beam cracks leads to a rapid decline in the durability of the beam. To address this issue, a multi-physics field coupling durability assessment method was proposed, considering concrete beam cracking, concrete carbonation, and steel bar corrosion. The interaction among these three factors is achieved through sequential coupling, using crack width, carbonation passivation time, and steel bar corrosion rate as interaction parameters. Using this method, the deterioration morphology and stiffness degradation laws of 8 m reinforced concrete beams under different load conditions, including those of heavy and light trains in heavy-haul railways, are compared and assessed. The analysis reveals that within a 100-year service cycle, the maximum relative stiffness reduction for beams on the heavy train line is 20.0%, whereas for the light train line, it is only 7.4%. The degree of structural stiffness degradation is closely related to operational load levels, and beam cracking plays a critical role in this difference. Full article

The corrosion of high-strength steel wires is a key factor impacting the durability and reliability of cable-stayed bridges. In this study, the corrosion pit features on a high-strength steel wire, which had been in service for 27 years, were extracted and modeled using three-dimensional point cloud data obtained through 3D surface scanning. The Otsu method was applied for image binarization, and each corrosion pit was geometrically represented as an ellipse. Key pit parameters—including length, width, depth, aspect ratio, and a defect parameter—were statistically analyzed. Results of the Kolmogorov–Smirnov (K–S) test at a 95% confidence level indicated that the directional angle component (θ) did not conform to any known probability distribution. In contrast, the pit width (b) and defect parameter (Φ) followed a generalized extreme value distribution, the aspect ratio (b/a) matched a Beta distribution, and both the pit length (a) and depth (d) were best described by a Gaussian mixture model. The obtained results provide valuable reference for assessing the stress state, in-service performance, and predicted remaining service life of operational stay cables. Full article

This study focuses on the optimization of valve assemblies in downhole rod pumping units (DRPUs), which remain the predominant artificial lift technology in oil production worldwide. The research addresses the critical issue of premature failures in DRPUs caused by leakage in valve pairs, i.e., a problem that accounts for approximately 15% of all failures, as identified in a statistical analysis of the 2022 operational data from the Uzen oilfield in Kazakhstan. The leakage is primarily attributed to the accumulation of mechanical impurities and paraffin deposits between the valve ball and seat, leading to concentrated surface wear and compromised sealing. To mitigate this issue, a novel valve assembly design was developed featuring a flow turbulizer positioned beneath the valve seat. The turbulizer generates controlled vortex motion in the fluid flow, which increases the rotational frequency of the valve ball during operation. This motion promotes more uniform wear across the contact surfaces and reduces the risk of localized degradation. The turbulizers were manufactured using additive FDM technology, and several design variants were tested in a full-scale laboratory setup simulating downhole conditions. Experimental results revealed that the most effective configuration was a spiral plate turbulizer with a 7.5 mm width, installed without axis deviation from the vertical, which achieved the highest ball rotation frequency and enhanced lapping effect between the ball and the seat. Subsequent field trials using valves with duralumin-based turbulizers demonstrated increased operational lifespans compared to standard valves, confirming the viability of the proposed solution. However, cases of abrasive wear were observed under conditions of high mechanical impurity concentration, indicating the need for more durable materials. To address this, the study recommends transitioning to 316 L stainless steel for turbulizer fabrication due to its superior tensile strength, corrosion resistance, and wear resistance. Implementing this design improvement can significantly reduce maintenance intervals, improve pump reliability, and lower operating costs in mature oilfields with high water cut and solid content. The findings of this research contribute to the broader efforts in petroleum engineering to enhance the longevity and performance of artificial lift systems through targeted mechanical design improvements and material innovation. Full article

Stainless steel, due to its exceptional comprehensive properties, has been widely adopted as the primary material for liquid cargo tank containment systems and pipelines in liquefied natural gas (LNG) carriers. However, challenges such as hot cracking, excessive deformation, and the deterioration of welded joint performance during stainless steel welding significantly constrain the construction quality and safety of LNG carriers. While conventional tungsten inert gas (TIG) welding can produce high-integrity welds, it is inherently limited by shallow penetration depth and low efficiency. Magnetic field-assisted TIG welding technology addresses these limitations by introducing an external magnetic field, which effectively modifies arc morphology, refines grain structure, enhances penetration depth, and improves corrosion resistance. In this study, TIG bead-on-plate welding was performed on 304 stainless steel plates, with a systematic investigation into the dynamic arc behavior during welding, as well as the microstructure and anti-corrosion properties of the deposited metal. The experimental results demonstrate that, in the absence of a magnetic field, the welding arc remains stable without deflection. As the intensity of the alternating magnetic field intensity increases, the arc exhibits pronounced periodic oscillations. At an applied magnetic field intensity of 30 mT, the maximum arc deflection angle reaches 76°. With increasing alternating magnetic field intensity, the weld penetration depth gradually decreases, while the weld width progressively expands. Specifically, at 30 mT, the penetration depth reaches a minimum value of 1.8 mm, representing a 44% reduction compared to the non-magnetic condition, whereas the weld width peaks at 9.3 mm, corresponding to a 9.4% increase. Furthermore, the ferrite grains in the weld metal are significantly refined at higher alternating magnetic field intensities. The weld metal subjected to a 30 mT alternating magnetic field exhibits the highest breakdown potential, the lowest corrosion rate, and the most protective passive film, indicating superior corrosion resistance compared to other tested conditions. Full article

Vegetable oil is regarded as a medium that can replace kerosene in electrical discharge machining (EDM) hole processing due to its renewability and environmental friendliness. Meanwhile, numerical simulation serves as an effective means to study the behavior of the gap flow field during EDM processing. Based on this, this study explored the influence of hole size and different vegetable oil dielectrics (sunflower seed oil, canola oil, and soybean oil) on the movement of electro-corrosion residues in the processing gap. The simulation results demonstrate that the viscosity of the oil affects the escape rate of the particles. In holes of 1 mm and 4 mm of size, the escape rate of canola oil at any time period is superior to that of sunflower seed oil and soybean oil. In a 1 mm hole, its average escape rate reached 19.683%, which was 0.24% and 0.19% higher than that of sunflower seed oil and soybean oil, respectively. Subsequently, experiments were conducted in combination with the simulation results to explore the influence of current, pulse width, and pulse interval on hole processing. This further confirmed the application potential of vegetable oil in electrical discharge micro-hole processing and provided theoretical support and experimental basis for optimizing the green manufacturing process. Full article

Ferritic stainless steels (FSSs) have attracted considerable attention due to their excellent corrosion resistance and significantly lower cost compared with nickel-bearing austenitic stainless steels. However, the high-temperature wear behavior of additively manufactured FSS 430 has not yet been thoroughly investigated. This study aims to examine the microstructural characteristics and wear properties of laser powder directed energy deposition (LP-DED) FSS 430 fabricated under varying laser powers and hatch distances. Wear testing was conducted at 25 °C and 300 °C after subjecting the samples to solution heat treating at 815 °C and 980 °C for 1 h, followed by forced fan cooling. For comparison, an AISI 430 commercial plate was also tested under the same test conditions. The microstructural evolution and worn surfaces were analyzed using SEM-EDS and EBSD techniques. The wear performance was evaluated based on the friction coefficients and cross-sectional profiles of wear tracks, including wear volume, maximum depth, and scar width. The average friction coefficients (AFCs) of the samples solution heat treated at 980 °C were higher than those treated at 815 °C. Additionally, the AFCs increased with hatch distance at both testing temperatures. A strong correlation was observed between Rockwell hardness and wear resistance, indicating that higher hardness generally results in improved wear performance. Full article

Bond behavior between steel bars and concrete is fundamental to the structural integrity and durability of reinforced concrete. However, corrosion-induced deterioration severely impairs bond performance, highlighting the need for advanced and reliable assessment methods. This paper pioneers an algorithm for an advanced ensemble learning framework to predict bond strength between corroded steel bars and concrete. In this framework, a novel Stacked Boosted Bond Model (SBBM) is developed, in which a Fusion-Based Feature Selection (FBFS) strategy is integrated to optimize input variables, and SHapley Additive exPlanations (SHAP) are employed to enhance interpretability. A merit of the framework is that it can effectively identify critical factors such as crack width, transverse confinement, and corrosion level, which have often been neglected by traditional models. The proposed SBBM achieves superior predictive performance, with a coefficient of determination (R²) of 0.94 and a mean absolute error (MAE) of 1.33 MPa. Compared to traditional machine learning and analytical models, it demonstrates enhanced accuracy, generalization, and interpretability. This paper provides a reliable and transparent tool for structural performance evaluation, service life prediction, and the design of strengthening measures for corroded reinforced concrete structures, contributing to safer and more durable concrete structures. Full article

Tunnel lining structures, which are subjected to the combined effects of water and soil pressure as well as a water-rich erosion environment, undergo a corrosion-induced damage and degradation process in the reinforced concrete, gradually leading to structural failure and a significant decline in service performance. By introducing the Cohesive Zone Model (CZM) and the concrete damage plastic model (CDP), a three-dimensional numerical model of the tunnel lining structure in mining method tunnels was established. This model takes into account the multiple effects caused by steel reinforcement corrosion, including the degradation of the reinforcement’s performance, the loss of an effective concrete cross section, and the deterioration of the bond between the steel reinforcement and the concrete. Through this model, the deformation, internal forces, damage evolution, and degradation characteristics of the structure under the effects of the surrounding rock water–soil pressure and steel reinforcement corrosion are identified. The simulation results reveal the following: (1) Corrosion leads to a reduction in the stiffness of the lining structure, exacerbating its deformation. For example, under high water pressure conditions, the displacement at the vault of the lining before and after corrosion is 4.31 mm and 7.14 mm, respectively, with an additional displacement increase of 65.7% due to corrosion. (2) The reinforced concrete lining structure, which is affected by the surrounding rock loads and expansion due to steel reinforcement corrosion, experiences progressive degradation, resulting in a redistribution of internal forces within the structure. The overall axial force in the lining slightly increases, while the bending moment at the vault, spandrel, and invert decreases and the bending moment at the hance and arch foot increases. (3) The damage range of the tunnel lining structure continuously increases as corrosion progresses, with significant differences between the surrounding rock side and the free face side. Among the various parts of the lining, the vault exhibits the greatest damage depth and the widest cracks. (4) Water pressure significantly impacts the internal forces and crack width of the lining structure. As the water level drops, both the bending moment and the axial force diminish, while the damage range and crack width increase, with crack width increasing by 15.1% under low water pressure conditions. Full article

The miniaturization of smart materials has become a new trend in the modern manufacturing industry due to its enormous application in the aerospace, biomedical, and automobile sectors. Nickel–titanium (NiTi)-based binary shape memory alloys (SMAs) are one of the smart materials with certain supreme features like shape memory effect, pseudo-elasticity, high ductility, strong corrosion-resistance, and elevated wear resistance. For this, several micro-machining processes have been developed to machine NiTi SMAs. This paper summarizes all of the conventional and non-conventional micro-machining processes employed to machine NiTi SMAs. In this review process, the surface integrity, dimensional accuracy of the machined surface, cutting force and tool wear analysis during conventional and non-conventional micro-machining of NiTi SMA are evaluated mostly with the aid of input process variables like cutting speed, depth of cut, width of cut, types of coolants, tool coating, discharge voltage, capacitance, laser fluence, pulse duration, scan speed, electrolysis concentration and gap voltage. The optimization of process parameters using different methods during conventional and non-conventional micro-machining of NiTi SMAs is also analyzed. The problems faced during conventional micro-machining of NiTi SMAs are overcome by non-conventional micro-machining processes as discussed. The present study aims to recognize potential developments in the improvement of the micro-machinability of NiTi SMAs. Full article

With the rapid development of urban construction, the demand for safety monitoring of reinforced concrete structures has been increasing. However, current crack detection methods still struggle with limited accuracy, poor real-time performance, and difficulty recognizing extremely small or low-contrast cracks in complex environments. To address these challenges, this study proposes a new method that combines the improved Visual Geometry Group Network 16, U-Net, and You Only Look Once target detection technologies. A new model for detecting concrete corrosion cracks has been developed based on this method. After 100 training epochs, the model achieved a precision of 94.4% and a loss rate of 2.6%, with an average Intersection over Union exceeding 85.0%. In high-roughness field tests, the proposed model achieved a crack width detection error of ±4.0 mm. For cracks that were soil-covered or partially occluded, the detection errors were ±5.4 mm and ±5.1 mm, respectively. Based on the original model, two additional lightweight variants were constructed, with the inference speeds of the three models recorded as 36 ms, 28 ms, and 24 ms in descending order. The results demonstrate that the proposed detection model offers an efficient and intelligent solution for structural health monitoring, with strong potential for engineering applications and urban infrastructure renewal. However, the model still presents a risk of misclassification when identifying fine cracks under low-contrast or complex background conditions. Future work will incorporate adaptive image enhancement and more refined feature extraction algorithms to further improve detection robustness and real-time performance. Full article

9Cr18MoV stainless steel is widely employed in cutting-tool applications owing to its exceptional hardness and corrosion resistance. In this study, we systematically optimized the wire electrical discharge machining (WEDM) process parameters for 9Cr18MoV stainless steel through an L₁₆ (4⁴) orthogonal experimental design. The key parameters investigated include pulse width (T_on), pulse interval (T_off), peak current (IP), and wire feed speed (WS), with cutting efficiency (CE) and surface roughness (R_a) serving as the primary optimization objectives. A signal-to-noise ratio (SNR) analysis was applied to assess the effects of the individual parameters and derive single-objective optimal configurations. Subsequently, grey relational analysis (GRA) integrated with analytic hierarchy process (AHP)-based weighting was employed to establish a multi-objective optimal parameter set, which was experimentally validated. The results reveal that the optimal multi-objective performance was attained at T_on = 28 μs, T_off = 3 μs, IP = 9 A, and WS = level 3. SEM characterization confirmed that this parameter combination yields a more uniform surface morphology, with diminished oxidation and molten debris deposition, thereby significantly enhancing surface integrity. The adoption of this optimized parameter set not only ensures superior machining efficiency but also results in improved surface quality. Full article

This study investigates the influence of crack width on the time to chloride-induced corrosion initiation in reinforced concrete (RC) bridge decks, incorporating climate change projections through the year 2100 under IPCC scenarios (RCP2.6 and RCP8.5). A probabilistic modelling approach using Monte Carlo simulations (MCSs) was applied to assess corrosion initiation across a range of environmental and structural conditions, including normal and high-performance concrete (HPC), varying concrete cover depths, and the use of supplementary cementing materials (SCMs). The results indicate that increasing the crack width significantly accelerates chloride ingress, reducing the time to corrosion initiation by up to 41% compared with that under uncracked conditions. HPC demonstrated superior durability, delaying corrosion initiation by nearly twice as long as normal concrete under identical chloride exposure. Elevated temperatures projected under high-emission scenarios further reduce service life by increasing chloride diffusion rates. Polynomial regression models were developed to relate crack width and concrete cover to corrosion initiation time, offering practical tools for durability-based design and service life prediction. These findings highlight the importance of enhanced crack control, climate-adaptive material selection, and updated durability standards to improve the resilience of RC bridge infrastructure in the face of climate change. Full article

The inspection of corrosion and pitting-type defects is critical in the petrochemical, marine, and offshore industries. Guided wave inspection is widely used to detect these flaws and control operational costs. Higher order modes cluster (HOMC) guided waves, composed of higher-order Lamb wave modes, offer enhanced resolution compared to low-frequency guided waves. They exhibit minimal dispersion, reduced sensitivity to surface features such as T-joints, and retain most of their energy upon interacting with surface defects. This study employs two-dimensional finite element simulations to investigate the propagation and interaction of HOMC guided waves with defects in a T-joint and an aluminum plate. Both conventional fitting methods and machine learning (ML) models are used to estimate the depth of sharp defects reaching up to half the plate thickness. The results demonstrate that both approaches can utilize data from defects of one width to predict the depth of defects with a different width. The ML model outperforms the fitting method, achieving higher prediction accuracy while reducing dependence on expert knowledge. The developed method shows strong potential for characterizing sharp defects of varying widths, closely resembling real-world pitting corrosion scenarios. Full article