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To address the need for rapid repair and emergency support of traffic capacity in damaged tunnels, this study proposed a new structure combining arches assembled from steel plates and shotcrete with high early strength and performance (hereinafter referred to as the steel-shotcreting structure) based on the concept of "modular assembly, rapid formation, and temporary-permanent combination". It is designed to replace the traditional cast-in-place concrete arch repair technique. Based on the principle of equivalent stiffness, the load borne by the steel arches in the new support structure was analyzed. Numerical analyses were performed to examine the influences of steel arch spacing and the types of I beams and channel steel on the load-bearing capacity of the new structure under varying surrounding rock and tunnel span conditions. The new steel-shotcreting structure was applied in a tunnel in China and its load-bearing capacity was compared with that of traditional steel arch support structures. The results show that its load-bearing proportions were 13% and 18% under the conditions of grade IV and V surrounding rock, respectively. In large-span tunnels with unstable surrounding rock, reducing the longitudinal spacing of plate steel arches, upgrading the channel steel model for longitudinal connectors, and increasing the size of I beams can enhance the load-bearing performance of the whole structure. Compared to traditional steel arch support structures, the new structure is more adaptable, flexible, and stable and demonstrates better support effects. The research findings provide a theoretical basis and technical support for the rapid repair of damaged tunnels. [ABSTRACT FROM AUTHOR]

Predicting cutting forces in hard turning optimizes toolpaths, improving machining efficiency and precision, minimizing tool wear, and enhancing manufacturing processes. This study assesses the potential of ensemble machine learning models for predicting machining force components during the hard turning of AISI 52100 bearing steel. Firstly, it conducts a comprehensive evaluation of Random Forest, Gradient Boosting, XGBoost, and CatBoost machine learning models using experimental data collected during AISI 52100 bearing steel turning with a CBN cutting tool. Cubic Spline-based data augmentation is employed to enrich the data, further enhancing prediction quality. A comparative analysis of the considered models on both original and augmented datasets reveals significant performance improvements associated with the utilization of augmented data. Moreover, this study utilizes SHAP (SHapley Additive exPlanations) to elucidate model predictions, providing insights into the contribution of each feature. Results indicate that ensemble learning methods, particularly CatBoost and XGBoost, demonstrate satisfactory predictive results with an averaged R2 of 0.96 and 0.945, respectively. Ensemble models like CatBoost and XGBoost, coupled with data augmentation, prove effective in predicting cutting forces during hard turning, emphasizing the potential for enhanced machining optimization. [ABSTRACT FROM AUTHOR]

In this paper, ultrasonic surface rolling processing (USRP) is used to process GCr15 (AISI-52100), and a three-dimensional ultrasonic surface rolling processing simulation model is established by finite element method to analyze the influence mechanism of static pressure on residual stress. The design L9 orthogonal test studied the importance of USRP parameters on the surface roughness of GCr15 bearing steel. The influence mechanism of process parameters (feed, static pressure, and rotational speed) on the surface microhardness, microstructure, and wear resistance of GCr15 was also studied. The results show that when the process parameters 1400 N, 0.08, and 100 r/min (specimen A7) were selected for machining, the plastic deformation of the specimen was the most intense and the surface grains were refined, forming a grain refinement layer with a thickness of about 10 μm. The surface defects of the specimen are reduced, and the surface roughness is as low as 0.076 μm. The surface microhardness can reach up to 806.2 HV0.5. And the surface roughness, surface hardness, and residual stress increased by 12.56, 65.91, and 138.89%, respectively. After the USRP treatment, the coefficient of friction of the material is reduced, and the amount of wear is reduced by 30%. The wear mechanism also gradually changes from adhesive wear to abrasive wear. [ABSTRACT FROM AUTHOR]

Steel jacking pipes are potentially prone to buckling instability, a phenomenon that has received limited attention in hard rock formations. This study reports on the field monitoring of a water pipeline project in Zhongshan City, where the circumferential and hoop strains of steel pipe segments jacked in hard rocks were recorded. The buckling deformation observed during steel pipe jacking, as well as the critical buckling load, was analyzed with the aid of numerical simulations using finite element software. The initial defect for the post-buckling analysis of the steel pipe was selected as the first-order buckling mode. Field monitoring revealed that the loading conditions experienced by the steel pipe segments during the jacking process are complex, leading to significant deformation. Throughout the monitoring process, axial stress at each measurement point underwent tensile-compressive transitions. Numerical results showed the actual critical buckling load increases with wall thickness at a constant length-to-diameter ratio, which is significant for short pipes. For pipes with the same wall thickness and outer diameter, the actual critical buckling load of long pipes is significantly lower than that of short pipes. Additionally, initial defects were found to significantly reduce the actual critical buckling load of the steel pipe. Furthermore, the actual critical buckling load of long pipes is much lower than their yield load, whereas, for short pipes, the critical buckling load is limited by their yield load. Measures for managing buckling deformation of steel pipes in situ were also reported. The findings on critical buckling load and the countermeasures for managing buckling in situ would be valuable for the design and construction stages of similar projects employing pipe-jacking technology in hard rock formations. [ABSTRACT FROM AUTHOR]

The surface residual stress of the parts has an important influence on their performance. The generation mechanism of surface residual stress in ultrasonic vibration-assisted grinding (UVAG) of bearing steel was investigated, and the correlation between processing parameters and residual stresses was obtained. Based on the ultrasonic vibration-assisted grinding force and thermal model and the flow stress model considering the initial material microstructure, the mechanical and thermal stresses of the material were calculated. Finally, the theoretical model of residual stress is established based on the yield theory and experimentally verified. High-speed ultrasonic aerostatic spindle for ultrasonic vibration-assisted grinding, change the inlet pressure to realize the ultrasonic amplitude and frequency adjustment, the experimental results show that the cutting direction and the vertical cutting direction of the residual stress test results and the model prediction results of the average relative error of 11.4% and 11.7%, and the rule of change is more consistent. Based on the experimental results, the influence pattern of process parameters on the experimental results was analyzed. The results show that the residual compressive stress on the surface of ultrasonic vibration-assisted grinding is directly proportional to the grinding depth, feed rate, and inlet pressure of pneumatic ultrasonic wave and inversely proportional to the linear speed of the grinding wheel. This study provides a theoretical basis for the analysis of UVAG residual stress and optimization of UVAG process parameters. [ABSTRACT FROM AUTHOR]

Circular steel pipe concrete can give full play to the combination of steel pipes and concrete, resulting in an improvement in the steel pipe's concrete bearing capacity and ductility. In this study, the axial compression load capacities of nine steel pipe concrete columns, including one traditional steel pipe concrete column and eight steel pipe self-stressed concrete columns, were analyzed using an axial pressure test. The damage patterns and stress–strain curves of all the specimens under axial compression load were analyzed, and a comparison analysis was made between the test results of the different specimens. The test results show that the longitudinal expansion displacement of concrete increases with the increase in the expansion agent content. The greater the self-stress, the higher the bearing capacity of steel-tube concrete columns under axial compressive load within a certain range of the expansion agent, indicating that self-stress can increase the bearing capacity of steel-tube concrete columns under axial compressive load, but the effect of the magnitude of the self-stress on the damage pattern of the specimens is limited. The damage patterns of all the specimens were bulging in the center and concave at both ends. In addition, the existing theoretical calculation method of the bearing capacity of steel pipe concrete columns is modified, and a theoretical calculation method applicable to steel pipe self-stressed concrete columns is proposed to simplify the calculation method of the bearing capacity of steel pipe self-stressed concrete columns, which provides a basis for decision-making in practical engineering. [ABSTRACT FROM AUTHOR]

The document discusses the importance of heat treatment in modifying the microstructure of metals to achieve desired properties. It highlights research papers on various heat treatment methods and their effects on different alloys, including bearings, martensitic stainless steel, electrical steels, and high resistance steel. The studies focus on optimizing heat treatment parameters to enhance mechanical and magnetic properties, with implications for industrial applications. The document also presents a method for manufacturing low-cost heat pipes with specific properties and geometry using basic tools and 3D printers. [Extracted from the article]

Main-shaft bearings are vital safety components in aeroengines made of bearing steels with outstanding combinational properties. The material is supposed to exhibit high surface hardness, high fracture toughness, high temperature resistance, fatigue resistance and corrosion resistance. However, under harsh operation conditions bearing steels are prone to rolling contact fatigue (RCF) that leads to bearing failure, severely endangering flight. Therefore, accurately predicting the RCF lives of bearing steels is key to the reliability of aeroengine. This manuscript reviews important results and progress in the RCF and life prediction of aeroengine bearing steels and suggests future research directions. Firstly, special stress state as a result of the Hertzian contact between rolling element and raceway is introduced, where shear stress components peak at the subsurface. This explains the origin of complex subsurface-originated RCF mechanisms in bearing steels and indicates subsurface-originated RCF to be an important failure mode of bearing steels under ideal conditions. Meanwhile, with increasing contact pressure, the response of material evolves from elastic mode to plastic mode. Besides, due to the harsh service environment of aero-engine bearings, surface-originated also takes place and hence the competition between these two mechanisms is present. Next, three methodologies for RCF life prediction are summarized, being probabilistic models, mechanistic models and numerical models, with their advantages and limitations analyzed. Probabilistic models are well developed and widely employed by industry, but they are in nature a kind of statistical models without accounting for RCF mechanisms and are hence lacking scientificity; Deterministic models predict RCF life via describing physical processes, which are rich in science but poor in accuracy due to their simplification; numerical models balancing both engineering practice and scientific characteristic is a powerful tool to tackle the problem of RCF life prediction, although their accuracy requires further improvement. Finally, it is suggested that future research may focus on solving key scientific problems in RCF, modifying life prediction models via inserting RCF mechanisms and applying artificial intelligence in RCF life prediction. [ABSTRACT FROM AUTHOR]

The corrosion–wear coupling damage failure of 8Cr4Mo4V bearing steel under marine atmospheric conditions significantly limits aeroengine bearing applications. The present work aims to investigate the evolution of the corrosion–wear properties of 8Cr4Mo4V bearing steel at varied corrosion intervals and estimate the corrosion–wear interaction (CWI) effect. Neutral salt spray tests combined with tribological experiments were employed to explore the effect of corrosion on wear and the influence of wear on corrosion, and a quantitative characterization method of corrosion–wear interactions was proposed by establishing the component relationships of material losses in the corrosion–wear process. The results indicate that the corrosion rates initially increase and then decrease, ultimately resulting in a pattern characterized by predominant total corrosion and nested localized corrosion. The corroded surfaces tremendously influence the friction coefficient curves at the third stage, and a synergistic acceleration effect exists in the CWI behavior of 8Cr4Mo4V bearing steel under the action of corrosion and wear. A sample corroded for 6 h displayed the significant facilitative effect of corrosion on wear, exhibiting the highest CWI ratio and a greater total mass loss primarily attributed to corrosion. This study offers a significant reference for the quantitative assessment of the tribo-corrosion properties of bearings in a marine atmospheric environment. [ABSTRACT FROM AUTHOR]

To solve the problems of surface wear and fracture of bearing rings, tantalum carbide (TaC)-reinforced layer was prepared on the surface of GCr15 bearing steel by in-situ hot pressing diffusion method to improve the comprehensive properties of bearing steel surface. As-obtained TaC layer exhibited uniform thickness and dense structure, and the phase composition mainly consisted of TaC and very small amount of α-Fe phase. The interface between reinforcement layer and matrix showed good metallurgical bonding, and no other impurities were generated. Along normal direction of layer base, grain size of TaC in reinforcement layer decreased gradually (200-50 nm), showing gradient distribution. Volume fraction of TaC particles reached 98%, and the maximum microhardness of reinforcement layer reached 2400 HV0.05. Comprehensive analysis of tensile test shows that mainly intergranular fracture of TaC particles occurred inside reinforcement layer, indicating that bonding strength between reinforcement layer and matrix was higher than cohesive strength of reinforcement layer by 320 MPa. In friction and wear experiment, when wear distance of reinforcement layer was 8 times that of steel matrix, wear rate was only 0.33 times (loading 20 N), and wear mechanism was mainly adhesive wear and abrasive wear. Overall, reinforcement layer obtained by in-situ solid-state hot pressing diffusion exhibits good wear resistance and high bonding strength with the matrix and shows good protective effect on the steel matrix. [ABSTRACT FROM AUTHOR]

Over the past 30 years, screw piles with diverse geometries have gained popularity over conventional piles for deep foundations. The behavior of toe-wing screw piles is not widely recognized on a global scale, and the effect of toe-wing plate position on the performance of screw piles has not been explored. Therefore, this paper investigated the impact of toe-wing position on screw pile performance embedded in the bearing layer. The toe-wing plates were embedded (Ew) in the bearing layer at a depth equal to the wing plate diameter, while the embedment depth (Ed) of the central shaft (pile tip) increased from 0 mm to 90 mm, which reflects the change in the toe-wing position. The model ground was prepared in the steel container with bearing layer densities of 55, 80, and 90 %, while the soil above the bearing layer was placed at a relative density of 45 %. The experimental results indicated that the installation load and torque non-linearly increased with the increase in embedment depth ratio (Ed/Ew). However, if checked at the same embedment depth (Ed), the normalized installation load increased to Ed/Ew = 1.2 and then decreased. In contrast, the normalized installation torque is non-linearly reduced with an increased embedment ratio (Ed/Ew). The normalized ultimate pile capacity increased non-linearly with the increase in embedment ratio (Ed/Ew). Regression equations based on the above trends are presented in this study to quantify the effect of Ed/Ew on installation load, torque, and bearing response. [ABSTRACT FROM AUTHOR]

Residual δ-ferrite is ubiquitous in M50NiL bearing steel and seriously deteriorates impact toughness. In the present work, the formation mechanism of δ-ferrite in M50NiL steel and the influence of element segregation on its formation process were investigated. The residual δ-ferrite was proved to form directly from the final liquid phase at the end of solidification due to serious segregation of Mo and V elements. Calculation results indicate that the segregation of Mo and V elements expanded the “L + δ'' two-phase region and stabilized δ-ferrite. Due to the high concentration of Mo and V, large-sized V-rich MC and Mo-rich M2C carbides would precipitate in δ-ferrite at 900–1200 °C if the cooling rate is slow. When kept at 1200 °C for no more than 30 min, Mo and V elements derived from the decomposition of large-sized carbides are preferentially diffused into δ-ferrite, enhancing the stability of δ-ferrite. To achieve the effective elimination of δ-ferrite in M50NiL steel, it is necessary to keep the ingot at 1200 °C for at least 20 h.

The effects of cooling rate on isothermal spheroidizing annealing (SA) of hot-rolled GCr15 bearing steel have been investigated. The results show that controlling the cooling rate between austenitizing and secondary annealing within a specific range is crucial to prevent the formation of lamellar carbide (LC). With a suitable cooling rate, more uniform carbide distribution, lower dislocation density and hardness can be achieved. An increase in the cooling rate results in a decrease in Ar1 and an increase in undercooling. However, an excessively high cooling rate suppresses the divorced eutectoid transformation (DET), leading to an increase in the amount of LC, dislocation density and hardness in rapidly cooled samples. Conversely, in the sample cooled too slowly, the appearance of LC may be attributed to the sufficient precipitation and coarsening of carbides, resulting in a high density of carbides before phase transformation. LCs can be eliminated by extending the secondary annealing time appropriately. This work demonstrates that for isothermal SA, using an appropriate cooling rate can effectively reduce the secondary annealing time, which provides a new idea for the rapid and complete spheroidization of carbides in GCr15 bearing steel.

The reactions of rare earth elements (REEs) with refractory materials significantly affect their effective concentrations and inclusion modifications in molten steel. This study investigated the influence of steel-refractory reactions on the modification of inclusions in lanthanum-, cerium-, and yttrium-added steels utilizing three types of commonly used crucibles as smelting vessels. Steel-refractory reactions were found to strongly affect inclusions with different outcomes for smelting in MgO, Al 2 O 3 , and MgO·Al 2 O 3 crucibles. The RE-crucible reactions affected the evolution and size of inclusions in molten steel by influencing the content of [Mg] and [Al]. The RE-MgO crucible reactions increased [Mg] content, leading to more MgO inclusions and a smaller average size. The RE-Al 2 O 3 crucible reactions increased [Al] content, resulting in more REAlO 3 inclusions and a bigger average size. The reactions of La, Ce, and Y with MgO·Al 2 O 3 crucibles had varying effects on the evolution of inclusions. La and Ce selectively eroded the crucible, mostly reacting with the Al 2 O 3 component and generating REAlO 3 inclusions. In contrast, the slow reaction rate of Y with the crucible and the formation of the dense Y 2 O 3 layer at the steel/crucible interface made it react almost simultaneously with both MgO and Al 2 O 3 components, and the modification of inclusions was dominated by [Mg] rather than [Al]. The above conclusions provided more information on how the reactions between rare earth elements and refractory materials affected inclusions in rare earth steels during smelting. They also enriched the theory of inclusion control in steel and offered new controlling strategies. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties and microstructures of bearing steels with arsenic contents of 30, 40, and 120 ppm have been investigated. The results show that As‐40 steel has the highest tensile strength but lower fatigue strength than As‐120 steel. The fatigue crack propagation rate of As‐120 steel is relatively low, mainly due to the increase in ΔKth. After quenching and tempering, As‐120 steel has larger prior austenite grains and more undecomposed, elongated carbides appear, reducing the uniformity of the steel. For carbides with an aspect ratio greater than 2, they cannot grow by the Oswald mechanism of spontaneous migration but are spheroidized by self‐cracking. The undissolved elongated carbides have a lower chemical potential, which increases the diffusion tendency of arsenic in the matrix. SIMS and EPMA analyses show that there is no significant distortion of the trace element arsenic. Highlights: The arsenic content in bearing steel has property advantages within the optimal range.Trace element arsenic will diffuse near low chemical potential strip carbides.A certain amount of arsenic coarsening grains can improve the fatigue strength of steel [ABSTRACT FROM AUTHOR]

In this study, premature damage in cylindrical roller bearings made of 100Cr6 (SAE 52100) was investigated. For this purpose, full bearing tests were carried out using two different lubricant formulations with similar viscosities. Published research has pointed out the occurrence of tribo-chemical reactions that cause lubricant degradation and the release of hydrogen in tribo-contact. Hydrogen content measurements were conducted on tested samples, and these measurements showed dependence on the lubricant formulations. Hydrogen diffusion and trapping were identified as significant factors influencing premature damage. The measurement of trapping energies was conducted by thermal desorption spectroscopy, whereas residual stresses, which influence hydrogen diffusion and accumulation, were measured using X-ray diffraction. The measured trapping energies indicated that rolling contact caused the creation and release of hydrogen traps. Over-rolling resulted in changes in residual stress profiles in the materials, demonstrated by changes in stress gradients. These can be directly linked to subsurface hydrogen accumulation. Hence, it was possible to determine that the location of the microstructural damage (WEC) was correlated with the residual stress profiles and the subsurface von Mises stress peaks. [ABSTRACT FROM AUTHOR]

Bearing steel (GCr15) is widely used in key parts of mechanical transmission for its excellent mechanical properties. Electrochemical machining (ECM) is a potential method for machining GCr15, as the machining process is the electrochemical dissolution of GCr15 regardless of its high hardness (>50 HRC). In ECM, NaNO3 solution is a popular electrolyte, as it has the ability to help in the nonlinear dissolution of many metallic alloy materials, making it useful for precision machining. However, due to high carbon content of GCr15, the electrochemical dissolution of GCr15 is unique, and there is always a black layer with high roughness on the machined surface, reducing the surface quality. In order to improve the electrochemical machining of GCr15 with a high surface quality, the surface characteristics of GCr15 in ECM were investigated. The anodic polarisation curve in the NaNO3 electrolyte was measured and electrochemical dissolution experiments were conducted with different current densities. SEM, XRD, and XPS were employed to analyse the surface morphology and composition formed on the machined surface at different current densities. The initial results showed that there were two parts (black part and bright part) formed on the machined surface when a short circuit occurred, and the test results suggested that the black part contained a mass of Fe3O4 while the bright part was composed of mainly Fe and Fe3C. Further investigation uncovered that a black flocculent layer (Fe3O4) always formed in a low current density (32 A/cm2) with high roughness. With the current density increased, the amount of black flocculent layer was reduced, and Fe3C particles appeared on the machined surface. When the current density reached 81 A/cm2, the entire flocculent oxide layer was removed, only some spherical Fe3C particles were inserted on the machined surface, and the roughness was reduced from Ra7.743 μm to Ra1.783 μm. In addition, due to exposed Fe3C particles on the machined surface, the corrosion resistance of the machined surface was significantly improved. Finally, circular arc grooves of high quality were well manufactured with current density of 81 A/cm2 in NaNO3 electrolyte. [ABSTRACT FROM AUTHOR]

By means of microstructure observation and mechanical property tests, the influence of the laser pulse energy of the laser shock processing (LSP) on the surface residual stress, microstructure, microhardness and fatigue limits of the M50 steel was studied. Results show that when the laser pulse energy increases from 4, 6 to 8 J, the surface damage of the sample becomes more and more pronounced, which gradually changes from pits to long-strip ravines. LSP increases the hardness of the steel, the maximum hardness occurs on the impact surface, and the microhardness gradually decreases as the distance from the impact surface increases. When the laser pulse energy rises from 4 to 8 J, the maximum hardness of the surface increases from 741 to 845 HV1, which are 2.90 and 11.33% higher than the steel matrix respectively. The depth of the hardened layer of the samples produced by LSP is also deepened when the laser pulse energy increases. The hardened layer depth is approximately 0.3 mm when the laser pulse energy is 4 and 6 J, which reaches 0.5 mm when the laser pulse energy is 8 J. LSP generates residual compressive stresses of − 423, − 565 and − 809 MPa on the surface of the samples when the laser pulse energy are 4, 6 and 8 J respectively. The residual compressive stresses can inhibit the expansion of cracks, so that the steel is less prone to fracture, and thereby the fatigue limit of the steel is increased by 45.95% from 740 MPa of the sample without LSP to 1080 MPa after LSP with the laser pulse energy of 8 J. [ABSTRACT FROM AUTHOR]

Accurately predicting cutting forces in hard turning processes can lead to improved process control, reduced tool wear, and enhanced productivity. This study aims to predict machining force components during the hard turning of AISI 52100 bearing steel using machine learning models. Specifically, eight models were considered, and their prediction performance was assessed using experimental data collected during AISI 52100 bearing steel turning with a CBN cutting tool. The fivefold cross-validation technique has been adopted in training to obtain more reliable estimates of the performance of a model and reduce the risk of overfitting the data. Results showed that the Gaussian process regression (GPR) and decision tree regression outperformed the other models, with averaged root-mean-square error values of 14.44 and 12.72, respectively. GPR also provided prediction uncertainty. Additionally, feature selection was performed using two algorithms, namely Regressional Relief-F and F test, to identify the most important features impacting the cutting forces. The findings of this study can be useful in optimizing cutting parameters for hard turning processes to select cutting forces, reduce tool wear, and minimize the generated heat during the machining process. [ABSTRACT FROM AUTHOR]

The study aims to investigate the effects of carburizing (C), carburizing and nitriding (C+N) sequential treatment on microstructure, microhardness distribution, residual stress distribution and rolling contact fatigue (RCF) properties of M50NiL bearing steel. The results showed that the fatigue limit of the C+N samples was 14.4% higher than that of the C samples. According to analyses of fatigue crack initiation and propagation behavior of RCF specimens revealed that the failure mechanism of the C specimens was deep spalling caused by fatigue crack in a large-angle propagation mode; whereas the C+N specimens had higher surface hardness and residual compressive stresses, which suppressed fatigue crack initiation and propagation, and the failure mechanism was changed to fatigue crack in a small-angle propagation mode caused by shallow spalling. Transmission electron microscopy analysis of C+N specimens after RCF experiments revealed that the dislocations proliferate and shear the carbonitride precipitation phases during the RCF experiments, and the microstructure and precipitation phases of the M50NiL steel are refined, which effectively inhibited the rate of fatigue crack initiation and propagation, and substantially enhanced the RCF life of M50NiL steel. [ABSTRACT FROM AUTHOR]

Samples of AISI 52100 bearing steel were treated by using laminar plasma quenching methods with three optimized process parameters: input power, scanning speed, and scanning distance. The influence of process parameters on the surface morphology and quenching depth of AISI 52100 bearing steels was explored, as well as the influence on their microstructure and microhardness. Furthermore, the surface wear resistance was tested by using a reciprocating wear testing machine. The results showed that samples with a lower surface roughness and a deeper hardened layer could be obtained by treating with the combination of input power 10.6 kW, scanning speed 500 mm/min and distance 20 mm. Microstructure analysis indicated that finer acicular martensite formed at the surface layer. The microhardness analysis shows that the hardness was improved by 20%, and the wear volume was reduced by 37.7%. The treated AISI 52100 bearing steel sample only had some furrow-like abrasive wear, while the untreated sample had more spalling pits in addition to furrow-like wear. The excellent anti-wear performance could be attributed to the hardness of cryptocrystalline martensite, which formed a hardened layer on the surface of the material. Therefore, the plasma quenched AISI 52100 bearing steel exhibited excellent wear resistance, which could effectively improve the service life of the bearing steel and has broad prospects in the field of surface modification. [ABSTRACT FROM AUTHOR]

Grease lubrication is cost-effective and low-maintenance for motorized spindles, but standard steel bearings can fail at high speeds. This study focuses on high-speed full ceramic ball bearings lubricated with grease. The coefficient of friction torque in the empirical formula is corrected by establishing the heat generation model of full ceramic ball bearing and combining it with experiments. A simulation model of grease flow is established to study the influence of grease filling amount on grease distribution. The simulation model of the temperature field of a full ceramic ball bearing is established to analyze the influence of rotating speed on bearing heat generation, and experiments verify the calculation results of the theoretical model. The results show that an optimal grease filling amount of 15~25% ensures even distribution without accumulation. Additionally, when the amount of grease is constant, the outer ring temperature increases with higher rotating speeds. The test results show that when the grease filling is 0.9~1.2 g, it accounts for about 9~12% of the volume of the bearing cavity, and the temperature of the outer ring is the lowest. At a rotation speed of 24,000 rpm, the outer ring temperature of the grease-lubricated bearing is 50.1 °C, indicating a reasonable range for use in motorized spindles. It provides a theoretical basis for the optimization design of macro-structural parameters of full ceramic ball bearings in the future, which can minimize heat generation and maximize bearing capacity. [ABSTRACT FROM AUTHOR]

The fatigue behaviors of high-strength bearing steel were investigated with rotating bending fatigue loading with a frequency of 52.5 Hz. It was revealed that the high-strength steel tended to initiate at interior non-metallic inclusions in a very high-cycle fatigue regime. During fractography observation, it was also seen that the inclusion acting as a failure-originating site was seldom smaller than 10 μm. Moreover, prior austenite grains could also act as the originating source of failure when inclusion was absent. The crystal plasticity finite element method (CPFEM) was adopted to simulate the residual stress distribution around non-metallic inclusions of different sizes under different loading amplitudes. The accumulated plastic strain around the inclusion suggested that the existence of inclusion may reduce material strength and lead to more fatigue damage. The value of accumulated plastic strain around different inclusion sizes also resembled the crack nucleation or propagation of the materials. The simulation results also indicated that inclusions smaller than 5 μm had little influence on fatigue lifetimes, while inclusions larger than 10 μm had a significant influence on fatigue lifetimes. [ABSTRACT FROM AUTHOR]

Inclusions are an important parameter affecting the fatigue life of materials. In this paper, the type, size, and quantity of inclusions in bearing steel were quantitatively analyzed using scanning electron microscopy and automatic scanning electron microscopy with an X-ray energy dispersive spectroscopy function. The effects of the inclusion parameters and positions on the rotating bending fatigue properties were analyzed using the rotating bending fatigue test. The results proved that for samples 1 and 2, the inclusions were mainly sulfides, Ti-containing inclusions, and their composite inclusions. For samples 3 and 4, the inclusions were mainly oxides or sulfide–oxide complexes. The number and maximum size of inclusions in sample 2 were relatively small. This was mainly due to the difference in the content of Al, S, and Ca elements in the different samples. The inclusion distance to the surface and the maximum inclusion size had a larger influence on the rotating bending fatigue life in comparison to the inclusion type. Moreover, nitride–oxides had a more detrimental effect on the rotating bending fatigue life as compared to the sulfide–oxide complex inclusions. A model was established on the basis of the inclusion size, depth, and stress by using the Python software. The simulation demonstrated that using five parameters fit well with the experiment results. [ABSTRACT FROM AUTHOR]

The impact of rare earth treatment on the chemical morphology evolution of non-metallic inclusions in bearing steel under different initial cleanliness conditions was studied through simulation. Thermodynamic calculations indicate that at an oxygen content of 0.001%, the evolution route of inclusions with increasing Ce content was Al2O3 → CeAl11O18 + CeAlO3 → CeAlO3 + Ce2O2S → Ce2O2S → Ce2O2S + CeS. As the initial oxygen content decreases, the proportion of CeAlO3 decreases, leading to easier conversion of CeAlO3 to Ce2O2S. Vacuum induction furnace experiments demonstrated that with an oxygen content of 0.001%, an increase in Ce content results in a gradual rise in the proportion of inclusions in steel sized 1~2 μm. In contrast, the proportion of inclusions sized 2~5 μm decreases. Consequently, the overall content of inclusions in steel decreases, along with a reduction in both the number density and average size of inclusions. Introducing bearing steel melt with approximately 0.01% Ce rare earth to bearing steel with initial oxygen contents of 0.0005%, 0.001%, and 0.0015% showed an evolution of inclusions from Ce2O2S and CeS to Ce2O3, CeAlO3, etc. The average inclusion size significantly increased from 0.7 μm to 2.16 μm. Morphologically, the transition of inclusions from precipitated to polymerized forms occurred as the initial oxygen content rose. High-temperature laser confocal microscopy experiments demonstrated that inclusions in low cleanliness conditions tend to agglomerate more than those in high cleanliness conditions, contributing to the increase in average size. [ABSTRACT FROM AUTHOR]

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results. [ABSTRACT FROM AUTHOR]

The flange joint is an important connection in steel tube structures. In this paper, 11 groups of flange joint tests were conducted to investigate the influences of tube diameter, flange plate thickness, the distance from the bolt to the tube centroid, bolt numbers and material strength on the mechanical behavior. One of two failure modes in tests is that the excessive plastic deformation on the flange plate makes the flange plate lose the bearing capacity; the other is that the steel tube yield makes the joints fail. The results show that the calculating method for flange joint in Chinese design code is so safe that amplifying the calculating results of the code by 1.2 times would be closer to the bearing capacity of specimens. For a flange joint with different tube diameters, thickening the flange plate of thinner tube or thinning the flange plate of another tube are effective to ensure the deformations on both sides of the flange plates are equivalent. The ratio of the bearing capacity of the steel tube to that of flange plate should be greater than 1.7. And the thickness of the flange plate should be thicker than 14mm to reduce the deformation caused by cutting, drilling and welding during manufacturing. [ABSTRACT FROM AUTHOR]

Due to the strong reducibility and chemical activity of rare earths, the diffusion behavior and secondary oxidation of rare earths in the steel liquid will also have a significant impact on the modified products when rare earths are added to bearing steel, resulting in poor control of distribution behavior. Therefore, this paper studies the influence of time factors on the evolution of rare earth inclusions. The inclusion evolution behavior at different times when the bearing steel was treated with rare earths and subjected to secondary oxidation was simulated at 1873 K (1600 °C). At a cerium content of 0.012% in steel and a secondary oxidation of 0.0025%, the cerium content in steel and the total oxygen (T.O.) content in steel were determined at the 30 s, 3 min, 5 min, and 7 min after the addition and the inclusions were characterized by automatic scanning electron microscopy. The results demonstrated the formation of a cerium-enriched zone after the addition of the cerium alloy to the steel. As time progressed, a considerable number of inclusions were generated in the cerium-enriched zone, which subsequently disappeared. The trend in the composition of the inclusions can be described as Al2O3 → Ce2O2S + CeS → Ce2O2S. The final composition of the inclusions matches the thermodynamic phase diagram. Following the addition of the transient oxidant Fe2O3 to the molten steel, an oxygen-enriched zone was formed. As time progressed, a considerable number of inclusions were generated in the oxygen-enriched zone and subsequently disappeared. The trend of inclusions composition was as follows: Ce2O3 + CeAlO3 + Al2O3 → Ce2O3 + CeAlO3 → Ce2O2S + CeAlO3. The final inclusion composition coincides with the thermodynamic phase diagram. [ABSTRACT FROM AUTHOR]

The paper mainly studies the effect of surface carbon content on the deformation of M50 steel bearing ring, and the carbon content is changed by short-time carburizing on the surface of the bearing ring. By using the scanning electron microscope, x-ray diffraction analyzer, hardness tester and torsion spring tester to observe the microstructure and measure the hardness and size variation characteristic. The size and ovality variations of carburized and uncarburized samples are analyzed. Results show that austempering hardness decreases and tempering hardness increases with the increase of surface carbon content. The size of the bearing ring without carburizing is reduced by 0.31 mm after austempering, and the martensite in the surface layer plays a key role in inhibiting the size reduction. The size of the bearing ring with the carbon potential of 0.6% is reduced by 0.01 mm after austempering, and the size reduction is inhibited by the transformation of martensite in the core and surface. The ununiformity of carburizing layer makes the martensitic transition time in different regions inconsistent, resulting in the ovality of M50 steel increased by 0.14 mm. [ABSTRACT FROM AUTHOR]

In this study, GCr15 bearing steel with an ultrahigh strength was subjected to surface laser shock processing (LSP). The effects of the laser pulse energy (LPE) on the microstructure, microhardness, residual stress and tribological properties were studied systematically. The results indicated that the martensitic laths and carbide particles underwent severe plastic deformation and were refined into nanostructures. The grain refinement was aggravated with the increase of the LPE. A grain size of 50 nm was obtained on the sample's surface by LSP at 7 J. Many dislocation tangles and deformation twins were formed, which led to an increase in the microhardness. Furthermore, LSP induced compressive residual stress (CRS) with a high amplitude on the sample's surface. As the pulse energy of LSP rose, the impact layer of GCr15 steel deepened. The wear rate and the friction coefficient reduced, and the wear resistance increased as the LPE increased. The tribological properties of GCr15 steel were enhanced by the grain refinement and working hardening, and by the formation of a high CRS layer. [ABSTRACT FROM AUTHOR]

In this work, the effect of ion nitriding on the properties of high carbon chromium bearing steel containing rare earth (RE) elements was studied by micro-Vickers hardness, tensile test, and Charpy impact measurement. The original microstructure of the bearing steel was analyzed by electron backscatter diffraction measurement and x-ray diffraction analysis. The results implied that ion nitriding enhanced the hardness and strength of the bearing steel containing RE elements but decreased its impact toughness. The nitrided layer composed of Fe3N and Fe4N exhibited brittle cleavage fracture characteristics during the fracture process. [ABSTRACT FROM AUTHOR]

Biodegradable metallic materials are gaining attention for medical applications in short-term implants (15–500 days) because of their good mechanical properties, biocompatibility, and generalized corrosion. Most medical applications involve implant wear processes, particularly for bone fractures. Parallelepipedic specimens (dimensions 50 mm × 10 mm × 3 mm) were obtained by cutting the hot-rolled material processed from cast ingots of ZnMgY. To test the tribological performance of these stationary specimens, they were placed at the upper point of the machine's tribological contact. The rotating lower disk of the AMSLER machine (AMSLER & Co., Schaffhouse, Switzerland) is manufactured from AISI 52100 bearing steel with a 62–65 HRC hardness and a diameter of 59 mm both radially and axially. Frictional torque is the parameter that is measured. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to analyze the worn areas. The material behavior in the normal and wear states upon immersion in simulated body fluid (SBF) was evaluated. [ABSTRACT FROM AUTHOR]

The study investigates the effect of pulsed magnetic fields on undissolved carbides in high-carbon chromium bearing steel GCr15 billets. The billets were subjected to heat treatment at 950 °C, with a pulsed magnetic field of varying durations applied during the process. The influence of the pulsed magnetic field on the distribution of undissolved carbides within the billets was investigated, and the thermodynamic and kinetic mechanisms of undissolved carbides dissolution were explored. The results indicate that the area percentage of undissolved carbides in the microstructure decreases from 1.68% to 0.06% after applying a pulsed magnetic field for 10 min, and the size of undissolved carbides decreases from 17.5 μm to 4.9 μm. When a pulsed magnetic field is applied for 30 min, all undissolved carbides dissolve. The statistics demonstrate that the average size of undissolved carbides is reduced from 14.19 μm to 0.63 μm, with a reduction percentage reaching 96%. Over the same duration, the number density of the undissolved carbides decreases from (0.19~0.55)/mm2 to (0.03~0.1)/mm2, and the percentage area of the undissolved carbides decreases from (1.26~1.68)% to (0~0.02)%. Thermodynamically, applying a pulsed magnetic field lowers the dissolution energy barrier of undissolved carbides and modifies their transformation temperature. Kinetically, the rate of alloy element diffusion is enhanced by increasing the frequency of atomic jumps. This research aims to provide new insights into enhancing the contact fatigue life of bearing steel, increasing the proportion of special steel, and optimizing the steel deep-processing process. [ABSTRACT FROM AUTHOR]

The corrosion resistance of bearing materials is crucial for the long-term service and high precision of modern equipment, and has aroused widespread research interest. Inoculation treatment is beneficial for improving the mechanical properties of GCr15 bearing steel, but its impact on corrosion behavior remains to be investigated. In the present work, the influence of inoculation treatment on the corrosion morphology, open circuit potential, impedance spectrum, and polarization curve evolution of GCr15 steel was studied through in situ corrosion morphology analysis and electrochemical testing. The results showed that the samples treated after inoculation showed a reduced tendency for pitting corrosion and an obviously improved corrosion resistance. This improvement is related to the transformation of columnar grains into equiaxed grains during the inoculation process, which reduces the amount and distribution of inclusions and pores, thereby delaying the rapid development of pitting corrosion. This study provides new insights into the corrosion mechanism of gestational steel. [ABSTRACT FROM AUTHOR]

In order to enhance the surface properties of GCr15 bearing steel, a TiAlCN coating with a low friction coefficient, high hardness, and excellent adhesion was fabricated. The TiAlCN multilayer coating was deposited onto the GCr15 bearing steel surface using magnetron sputtering technology, and optimal coating parameters were achieved by adjusting the number of layers, sputtering power of the graphite target, and coating duration. The experimental results showed that adding Cr/CrN as a transition layer between GCr15 bearing steel and TiAlCN significantly improved multiple properties of the coating. Adding carbon atoms caused TiAlN to dissolve into a TiAlCN structure, enhancing multiple properties of the coating. With the increase in the sputtering power of the graphite target material, the hardness, friction, and wear performance of the coating showed a trend of first increasing and then decreasing. The hardness of the coating gradually increased with time, and the friction coefficient and wear amount first decreased and then increased. When the sputtering power of the graphite target material was 100 W and the coating time was 4800 s, the coating performance was optimal. The hardness was 876 HV, the friction coefficient was 0.42, the wear amount was 1 × 10−4 g, and the wear rate was 2.8 × 10−6 g/m·N under optimal process parameter conditions. [ABSTRACT FROM AUTHOR]

CSS-42L is a new generation carburized bearing steel for the critical service environment of aero-engine applications. Owing to the complex composition and heat treatment, this steel exhibits unique microstructural features at the subsurface, one of which is the formation of soft austenitic transition layers. So far, a plausible mechanism of this phenomenon is still absent. In this study, a systematic investigation into such austenitic transition layer formation process is conducted. By using various characterisation techniques along with thermodynamic analysis, it is found that the contents of Cr and C in the matrix are dominated by the formation of different types of carbides along depth. With increasing depth, the undissolved carbides vary from M7C3 and M23C6 to M6C and to nil. This is postulated to result in a drastic decrease of martensitic start (Ms) temperature in the M6C region, leading to the formation of austenitic transition layers. The simulations of both microstructure and Ms temperature evolution along depth during heat treatment are performed for different austenitic temperatures and compared against the experimental observation, with good agreement obtained. This study reveals the mechanism of austenitic transition layers for the first time and provides useful instructions for the further microstructural design of such high-performance bearing steels.

A new type of lightweight high aluminum bearing steel had been developed based on the widely used high carbon chromium bearing steel. Via multi-scale experimental characterizations and theoretical calculations, here we mainly focused on the evolution of microstructure including precipitates under different quenching temperatures. Accordingly, the mechanical properties, mechanisms and fracture features of the new high-Al steel after tempering were characterized in detail. As austenitizing temperature rose, matrix of steel varied from multiphase structure of martensite, retained austenite (RA) and ferrite to the full martensite and RA. RA was found in all four samples with the austenitizing temperature from 850 °C to 1000 °C. In terms of precipitates, a transformation from M3C to M7C3 were observed. As a phase newly introduced by Al, AlFe3C (κ carbides) would dissolve into matrix at 900 °C. Eventually, the yield strength of the researched steel could reach 1430 MPa with an unnotched impact energy of 35 J. Theoretical results showed that high strength of researched steel was mainly caused by solid solution effect of carbon and high density of dislocation. In terms of toughness and fracture observation, high impact energy was attributed to the highest density of grain boundary, and also, κ carbides were found at the origin of secondary crack. This study highlighted the significant effect of Al addition and quenching process based on the traditional bearing steel, which showed a novel method and idea to reduce significantly the weight of bearings.

Steel bearings have been commonly used to counteract induced loading from thermal and traffic conditions in numerous bridges. However, their effectiveness has been compromised due to aging and maintenance limitations, potentially impacting the overall bridge system performance. Existing monitoring techniques for detecting malfunctioning steel bearings lack automation and precision, making them inadequate for long-term and real-time bridge dynamics assessment. This study proposes a response-based approach to identify bearing malfunction by analyzing the traffic-induced response in the bearing vicinity. To implement this approach, laser displacement sensors and wireless acceleration sensors were employed to monitor both malfunctioning and well-functioning steel bridge bearings. Significant differences in bearing performance were observed through response analysis and comparison. Laser sensor measurements revealed larger vertical deflections in the girder at malfunctioned bearing under traffic loading. Moreover, the investigation of the acceleration response in the bearing locality indicated that bearing malfunction could alter the vibrational characteristics of the vicinity, significantly affecting Cross Power Spectral Density (CPSD) and cross-correlation. To quantitatively evaluate the performance of steel bearings, a Condition Score (CS) was introduced. The CS exhibited a strong correlation with bearing damage, providing valuable insights for maintenance and decision-making processes in bridge asset management. This study offers a comprehensive and automated method for identifying steel bridge bearing malfunction by utilizing advanced monitoring techniques and introducing the CS for assessment. The results obtained from this approach can enhance bridge maintenance strategies and contribute to effective bridge asset management. [ABSTRACT FROM AUTHOR]

The effect of Nb alloying on the suppression of austenite grain coarsening behavior during pseudo–carburizing is investigated in high–temperature–carburized SAE4320 bearing steel. To explore the role of the Nb element in the pseudo–carburizing process, the morphology, composition, size, and distribution of NbC precipitates were analyzed. The results show that the fine austenite grain observed in Nb micro–alloyed steel is caused by the pinning effect of NbC precipitates, which hinders the coarsening of austenite grains and changes the growth dynamics of austenite grains. After the SAE4320 carburized bearing steel with the addition of 0.45 wt.% Nb element is kept at 1150 °C for 4 h, the PAG size is still below 20 μm, which indicates the Nb element has obvious advantages in limiting PAG growth at high temperatures and shows great potential for the development of high–temperature carburized bearing steel. [ABSTRACT FROM AUTHOR]

The fatigue behavior of a high-strength bearing steel tempered under three different temperatures was investigated with ultrasonic frequency and conventional frequency loading. Three kinds of specimens with various yield strengths exhibited obvious higher fatigue strengths under ultrasonic frequency loading. Then, a 2D crystal plasticity finite element method was adopted to simulate the local stress distribution under different applied loads and loading frequencies. Simulations showed that the maximum residual local stress was much smaller under ultrasonic frequency loading in contrast to that under conventional frequency at the same applied load. It was also revealed that the maximum local stress increases with the applied load under both loading frequencies. The accumulated plastic strain was adopted as a fatigue indicator parameter to characterize the frequency effect, which was several orders smaller than that obtained under conventional loading frequencies when the applied load was fixed. The increment of accumulated plastic strain and the load stress amplitude exhibited a linear relationship in the double logarithmic coordinate system, and an improved fatigue life prediction model was established. [ABSTRACT FROM AUTHOR]

This study aimed to enhance the friction and wear characteristics of materials for wind turbine sliding-bearing bushes operating under low-speed and heavy-load conditions. To this end, a high-entropy CoCrFeNiMo alloy coating was applied to the surface of 9Cr18 bearing steel, and Ni-Cr-Mo-Si alloy coating was applied to MTCrMoCu30 wear-resistant cast iron using laser cladding. The effects of varying loads on the friction and wear properties of these coatings were investigated, and the friction and wear properties were compared. Furthermore, the overall priority indices for both groups of bearing bush coatings were assessed. The findings indicated that the friction coefficient, wear quality, and wear rate of CoCrFeNiMo high-entropy alloy coating initially decreased and then increased with the increase in applied load, dominated by abrasive wear. By contrast, the friction coefficient of the Ni-Cr-Mo-Si alloy coating increased, and wear quality and wear rate initially increased and then decreased, indicating the coexistence of adhesive wear and abrasive wear. Therefore, Ni-Cr-Mo-Si alloy coating exhibited a high overall priority index and favorable friction and wear properties. [ABSTRACT FROM AUTHOR]

This study introduces a low-friction composite based on PEEK to improve its friction and wear properties. The composite incorporates PTFE as a solid lubricant and utilizes PPTA as a reinforcing material within the PEEK matrix. These components were prepared utilizing a compression molding method, followed by a series of exploratory experiments to identify the optimal preparation conditions for PEEK. This research assesses how the PTFE/PPTA/PEEK composites perform in terms of friction and wear under dry and oil-lubricated conditions. By examining wear tracks using scanning electron microscopy and white light interference microscopy, this study aims to uncover the wear mechanisms of PEEK and its composites under different lubrication scenarios. Results show that the main wear mechanisms for the PTFE/PPTA/PEEK composites and bearing steel are ploughing and adhesive wear. The presence of PPTA helps reduce wear by leveraging its strong fibers and thermal stability, while the coefficient of friction decreases as PTFE creates a smooth, solid lubricating film on the surface. Notably, PEEK composites containing 25 wt% PTFE and 6 wt% PPTA demonstrate the lowest wear rates and reduced coefficient of friction in both dry and oil-lubricated conditions. [ABSTRACT FROM AUTHOR]

A proposed low-temperature forging method is presented to enhance stainless steel bearings by creating a martensitic subsurface layer, significantly boosting bearing fatigue life due to increased surface hardness. This technique induces beneficial residual stresses, particularly in axial bearings, streamlining their construction and improving machine elements. Challenges persist, especially with radial bearings, but simplicity in axial bearing forging promotes compact, resource-efficient facility construction. Future research will focus on applying this technique to axial bearing washers, potentially replicating success in other bearing components. Despite the energy expenditure on cooling during forging, the substantial increase in bearing fatigue life offsets this, enhancing overall durability and reliability of critical machine components. Integration of this forging technique into bearing fabrication appears seamless, offering a promising trade-off between energy use and enhanced performance. [ABSTRACT FROM AUTHOR]

The re-excavation roadway in the filling body is a common engineering demand in mines. In order to solve the problem of instability and failure of the filling body caused by the excavation disturbance in the filling body and improve the comprehensive economic benefits of the technology, it is proposed to use the filling body formed by membrane bag filling in the goaf and the steel arch frame to form a prefabricated load-bearing structure, reserve the required roadway space, avoid the safety risks caused by roadway excavation, and reduce the difficulty and cost of roadway support in the later stage. Based on the background of a mine goaf, the mechanical model of the load-bearing structure is established, and the analytical solution of the bearing capacity of the steel arch is obtained. The optimal ratio of the membrane bag filling of the load-bearing structure is obtained by indoor test, and the deformation of the surrounding rock and the distribution range of the plastic zone after the formation of the reserved roadway are numerically simulated and analyzed. The results show that the best cementing material is cement : fly ash of 8 : 2, and the ratio of cement to sand is 1 : 3. The vertical displacement of the roof is 45.1 mm, the vertical displacement of the floor is 5.1 mm, and the horizontal displacement of the left side is 55.5 mm. The load on the load-bearing structure is within the allowable range, and the field monitoring results show that the deformation of the reserved roadway is small. The research results can provide reference for the prefabricated roadway engineering in the filling body. [ABSTRACT FROM AUTHOR]

This paper presents a rolling contact fatigue life prediction model for bearing steel. In the initial stage of rolling contact, the gradient structure appears in the subsurface region of bearing steel and the hardness shows a gradient distribution along the contact depth direction due to the roller compaction effect. This indicates that the fatigue resistance of bearing steel varies in the subsurface region. Besides, each subsurface material volume element is subject to different stress cycles. Based on Weibull theory, the survival possibility of subsurface volume elements is formulated. Then the rolling contact fatigue life is evaluated considering the stress state and anti-fatigue performance of each elementary volume of the subsurface material. According to the phenomenon and assumption, the model proposed for gradient material was applied in the rolling contact fatigue life prediction of the bearing steel GCr15 and validated with the fatigue experiment data in the open literature. Furthermore, the accuracy of the proposed model results was compared with the traditional empirical rolling contact fatigue life prediction models. [ABSTRACT FROM AUTHOR]

In recent years, due to the changing climate conditions and the continuous deepening of water resource conservation measures, the groundwater level in northern China has gradually risen, leading to the increasingly prominent issue of anti-floating in existing buildings and structures. The development and adoption of reliable anti-floating reinforcement techniques for existing structures are crucial for ensuring the quality of such reinforcements. Therefore, focusing on the limitations of the anchor method for anti-floating reinforcement, this paper proposes a new type of anti-floating prestressed compression anchor that features a full-length anti-compressive steel pipe with a bearing body at the end and uses non-bonding tendons throughout its length. Firstly, the structural form of this pressure-type anchor is introduced; subsequently, combined with the results of on-site pull-out tests of the anchor, an analysis is conducted on the working principle, lateral resistance distribution, and internal force transfer mechanism of the new anti-floating anchor, and its load-bearing characteristics are elucidated. Finally, relying on actual anti-floating reinforcement projects and through numerical calculations, the changes in internal forces under different anti-floating conditions of existing structures reinforced with the new anchor compared to conventional anchors are contrasted. Research findings and engineering practice indicate that this new anti-floating anchor improves the mechanical performance of the grout body of the anchor, solves the water seepage problem at the anchor location of the waterproof slab, effectively suppresses cracking of the foundation waterproof slab after reinforcement, and enhances the anti-floating and durability of existing structures. [ABSTRACT FROM AUTHOR]

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