Heavy-duty four-row roller bearings (FRRBs) are critical load-carrying components in high-speed hot rolling mills, where early-stage degradation is difficult to identify due to harsh operating conditions and limited accessibility. In industrial practice, bearing condition assessment is still largely dependent on an empirical judgement, leading to delayed maintenance actions and reduced reliability. This paper proposes a data-driven condition assessment framework based on acceleration signals for FRRBs operating under real industrial conditions. A multi-channel two-dimensional convolutional neural network (MC2DCNN) is developed to extract representative features from vibration signal representations, while a long short-term memory network (LSTM) is employed to characterize the temporal evolution of bearing health states. The proposed approach enables reliable classification of multiple degradation levels and provides practical decision support for bearing disassembly and maintenance scheduling. Beyond condition assessments, the identified degradation patterns are analyzed in conjunction with rolling mill operating characteristics. The results demonstrate that axial thrust forces and rolling force deviations induce internal load imbalances, which is a dominant factor governing bearing degradation. Based on these findings, targeted engineering measures, such as reducing mill stiffness asymmetry, optimizing bearing housing clearance, and improving mill structural symmetry-are implemented in an industrial plant. Field application results confirm that the proposed method effectively improves condition assessment reliability and significantly enhances the service performance of FRRBs in high-speed rolling mills.

In this study, the intrinsic correlation between dynamic mechanical behavior and microstructural evolution of spheroidized-annealed GCr15 bearing steel with a ferrite-carbide dual-phase structure has been investigated under high strain rates (3000-7000 s-1 ) and wide temperature ranges (20-650 degrees C). To more accurately characterize the dynamic mechanical response,the conventional TANH-Johnson-Cook (TANH-JC) constitutive model is optimized by incorporating the actual strain rate and the softening effect arising from adiabatic temperature rise observed in Split Hopkinson Pressure Bar (SHPB) experiments. This modification significantly improves the model's prediction accuracy. Furthermore, the coupling mechanisms among deformation parameters, dynamic recrystallization of ferrite, and carbide evolution are elucidated using multi-scale characterization techniques. Continuous dynamic recrystallization (CDRX) is identified as the primary grain refinement mechanism in the ferrite matrix, supplemented by particle-stimulated nucleation dynamic recrystallization (PSNDRX). The evolution of carbides is governed by the synergistic interaction of temperature and strain rate. The atomic diffusion capacity is enhanced with increased temperature, while numerous additional rapid diffusion pathways are introduced through its coupling with plastic deformation. These factors promote the dissolution of small carbides and the coarsening of large carbides. When thermal effects dominate, significant carbide dissolution weakens the Zener pinning effect, leading to coarsening of recrystallized grains. These microstructural evolution characteristics collectively govern the macroscopic mechanical response through three primary strengthening mechanisms: grain boundary strengthening, dislocation strengthening, and precipitation strengthening. This study provides practical engineering guidance for optimizing the turning process of material in subsequent machining operations.

During hot rolling, the coexistence of backward slip and forward slip regions within the deformation zone causes periodic reversal of the frictional shear direction acting on the work roll surface. However, the influence of the alternating shear induced by slip transition on wear damage evolution has not been adequately considered, resulting in an incomplete understanding of work roll wear behavior under actual hot rolling conditions. In this study, the wear damage evolution of hot rolling work roll was investigated under conditions considering the alternating shear effect associated with slip transition. The results show that slip transition leads to higher and more fluctuating friction coefficients, accompanied by more severe local spallation, debris accumulation, and ploughing damage. The oxide layer formed under alternating shear exhibits lower stability and is more susceptible to cracking and spallation. Continuous disruption of the oxide layer promotes the generation of oxide fragments and wear debris, which subsequently act as third body abrasives during sliding, aggravating ploughing damage and abrasive wear. In addition, pronounced grain refinement and increased local misorientation are observed in the near surface region after wear under hot rolling conditions, indicating substantial plastic deformation and strain accumulation beneath the worn surface. These microstructural evolution features reflect the continuous deformation of the near surface material during wear and correspond well with regions exhibiting local damage. Therefore, the alternating shear caused by slip transition should be considered when evaluating wear damage evolution of hot rolling work rolls. The findings provide further insight into the wear mechanisms of work rolls under hot rolling conditions and offer guidance for wear assessment and service life prediction.

The microstructural evolution and mechanical responses under multi-degree-of-freedom reciprocating torsion-compression deformations remain to be fully elucidated, particularly regarding the Swift and inverse Swift effects and their physical mechanisms, which constrain the design and formability of textured Mg alloys. Therefore, the multi-degree-of-freedom reciprocating pre-torsional-compressive loadings along extrusion direction (ED) were specifically designed. The twinning behaviours and the radial distribution of twin structures were systematically analysed. The driving mechanisms of the Swift and subsequent inverse Swift effects were discussed. Results demonstrated that free end torsion (FET) deformation induced radially linear-gradient twinning structure, while reverse FET (RFET) loading triggered FET twins detwinning and extensive {101(sic)2} tensile twin activation within the basal textures, driving the reverse FET twin texture further tend towards ED aggregation. FET twins inhibited the nucleation of RFET twins, resulting in the formation of a distinctive inverse-gradient twinning structure. 65% of the Swift-effect strain under low-strain FET (gamma < 0.12) was coordinated by dislocation slip, whereas the misfit strain induced by FET twins accommodated more than 85% of the axial shortening during gamma(FET) = 0.38. RFET-stage axial elongation was governed by detwinning, with subsequent axial shortening attributable to large-scale RFET twin activation. {102} tensile twins dominated initial free rotational compression (FRC) strain, the interactions between the release of residual shear stress and the reverse shear strain component induced by FRC twins results in the circumferential motionlessness during initial FRC. Proliferation of FRC twins promoted cumulative circumferential shear strain component, inducing further macroscopic reverse spontaneous rotation.

The key to model development lies in unifying the recrystallization behavior throughout multi-stage hot deformation processes. However, this integration has been hindered by three primary challenges: (1) the lack of a consistent criterion for the onset of dynamic recrystallization (DRX) during repeated deformation; (2) the insufficient consideration of the influence of DRX states on static recrystallization (SRX) mechanisms; and (3) the unclear treatment of recrystallization state transitions during successive deformation stages. To address these issues, this study introduces essential modifications to the internal state variable (ISV) model and extends its applicability to multi-stage hot deformation. Specifically, the critical dislocation density is employed as the criterion for DRX initiation, with a simplified method proposed for its determination. Furthermore, a SRX incubation fraction is incorporated to account for the influence of DRX states on static softening mechanisms. Additionally, a method is proposed to evaluate changes in the recrystallization fraction during repeated deformation by comparing the residual and critical dislocation densities, capturing the effects of recrystallized grain hardening and DRX recurrence. The predictive ability and underlying assumptions of the modified model are validated through double-pass hot deformation experiments. Furthermore, the applicability of the model under dynamically changing deformation conditions is verified. Finally, electron backscatter diffraction (EBSD) analysis of microstructural evolution under different inter-pass holding times is employed to elucidate the deformation mechanisms involved. The proposed model offers a theoretical framework for accurately predicting and controlling material states in multi-pass hot deformation processes.

During the early stage of angular contact ball bearing service, submicron-scale pits can still rapidly and extensively develop on raceway surfaces under nominal full-film lubrication. Consequently, the origin of these early submicron-scale pits cannot be adequately explained by conventional roughness-induced asperity-contact mechanisms. This study indicates that surface microdamage induced by superfinishing is the primary origin of these submicron-scale pits. Multi-scale characterization using stereomicroscopy, white-light interferometry, SEM, TEM, TKD, and PED reveals that a superfinished raceway surface is not damage-free but contains an approximately 600 nm-thick machining-affected layer with nanoscale microcracks, flow-line deformation microstructures, and pronounced strain localization. On this basis, a dualpathway mechanism governing damage evolution is established. First, nanoscale microcracks inherited from superfinishing directly evolve into submicron-scale pits, accounting for their rapid appearance. Second, strain-localized regions induced by severe non-uniform plastic deformation progressively accumulate damage under cyclic loading, thereby facilitating the initiation of fatigue cracks during service. Notably, cracks within the machining-affected layer consistently propagate along the flow-line direction, with propagation angles markedly deviating from those predicted by conventional RCF theory, confirming the guiding role of flow-line structures in crack propagation. Based on these findings, this study establishes a complete microstructural evolution pathway from superfinishing-induced microdamage to surface spalling failure, providing a theoretical basis for understanding the mechanism of bearing surface degradation.

To investigate the wear behavior of work rolls under hot rolling conditions, an experimental wear-testing apparatus capable of controlling load, slip ratio, cyclic temperature variation, and cooling was developed. The evolution of the friction coefficient and surface damage during rolling was systematically examined, while fractal theory was employed to characterize the evolution of surface morphology. The results reveal that abrasive wear and surface mechanical damage dominate during the initial stage, whereas oxidation-assisted and adhesive wear gradually become more significant with increasing rolling time because of the repeated formation and fracture of oxide layers. The formation of the oxide film may help reduce direct metal-to-metal contact and alleviate material removal. However, repeated cracking and spallation under coupled thermal and mechanical loading progressively weaken its protective effect. Under intensified thermo-mechanical loading, unstable oxide layers tend to undergo severe spallation, which is associated with accelerated surface degradation. A coupled wear model incorporating thermal, mechanical, and oxidation effects was established to describe the wear evolution, and the predicted results show reasonable agreement with the experimental observations. Sensitivity analysis further indicates that the fractal parameters D and G play important roles in wear evolution, while thermal and oxidation-related parameters also affect the wear process through coupled interactions. These findings provide useful insights into the wear evolution of work rolls under hot rolling conditions.

Multi-pass hot caliber rolling technology has significant advantages in producing continuous bars, which can be used as structural and connecting parts with essential applications. Simulation is an important tool for reproducing production processes. The simulation model must show the thermal state, microstructure, and hot workability during the bar’s high-temperature deformation process. However, such a multifunctional simulation model has not yet been reported. Here, a finite element simulation system for hot bar rolling is presented. It is based on the DEFORM-3D software and has been further developed. The most distinctive feature of the proposed simulation system is the integration of a material model that combines constitutive prediction with hot workability prediction. The constitutive model is formulated within an internal state variable framework, enabling the coupled prediction of microstructural evolution and stress response during multi-pass hot deformation. The hot workability prediction model is established based on a backpropagation neural network. By incorporating the microstructural state and deformation conditions as input variables, the model enables dynamic evaluation of hot workability throughout the deformation process. Based on the embedding of the material model, the simulation model can realize the coupled simulation of temperature, deformation, microstructure, and hot workability. Subsequently, the model is validated and applied based on an actual hot bar rolling production line. The simulation successfully predicts the surface cracks in rolled bars and provides insights into the underlying mechanisms of crack formation. The analysis indicates that the primary cause of cracking is the mismatch between the groove geometry and the workpiece geometry, which leads to localized deformation of the corner metal and a sharp temperature drop. Based on this understanding, a matching relationship between the groove geometry and the workpiece geometry is proposed, and the groove structure is optimized accordingly. After optimization, the surface quality pass rate of the rolled bars improved significantly, increasing from approximately 50.7% to about 95.3%. The simulation system can be applied to the hot bar rolling process and other multi-pass hot forming technologies. This is important for optimizing the production process and improving product quality.

As critical structural components in large-scale deep-sea equipment such as submarines and submersibles, cylindrical pressure shells require advanced manufacturing solutions to address the limitations of conventional methods characterized by prolonged production cycles and elevated costs. This study proposes an innovative corrugated rolling process (CRP) for high-performance, efficient fabrication of corrugated pressure shells. The theoretical foundations and critical parameters governing stable CRP operations were systematically established. Through comprehensive finite element simulations, systematic investigations were conducted on material flow patterns during corrugation formation, revealing three distinct processing stages classified into clamping, local forming, and global forming. Analytical results revealed that clamping-induced indentations progressively dissipated during subsequent forming stages. Distinct deformation zones within the billet were identified, consisting of active and passive deformation zones characterized by differential thickness reduction rates that synergistically ensured complete corrugation development. Given the complexity of metal flow in CRP, indicators such as corrugation saturation, uniformity of corrugation height, rib back depression rate, average spread and fishtail coefficient were defined to quantitatively assess the forming quality of corrugated pressure shells. The process rationality and technical feasibility of CRP were verified by the corrugated rolling test. This research establishes a theoretical foundation and provides practical technical guidance for manufacturing load-bearing structural components in large-scale deep-sea applications.

This study employs large-scale molecular dynamics simulations to investigate the influence of spherical nanovoids on the nanoindentation response of nickel single crystals. The interaction between nanovoid geometry—varied in size and depth—and the resulting plastic deformation behavior is systematically examined. The results show that nanovoids significantly affect dislocation evolution, acting as dislocation sinks. The absorption capacity increases with nanovoid size and proximity to the free surface. Post-nucleation dislocations propagate toward nanovoids, indicating a spatial coupling between defects and plastic slip activity. Mechanically, nanovoids cause a size- and location-dependent reduction in hardness, with surface-proximal and larger nanovoids having a more pronounced softening effect. Deeply embedded nanovoids show negligible impact. An empirical relation quantifies the hardness degradation based on nanovoid geometry, showing strong agreement with simulation data. These findings provide insights into defect-plasticity interactions and contribute to the design and performance evaluation of nickel-based materials in micro/nanoscale applications.

Asymmetric cryorolling demonstrates significant potential for producing materials with high strength and excellent electrical conductivity. This study presents an innovative Dynamic Offsets and Shear Force Adjustments Cryorolling (DSCR) technique coupled with short-time annealing (DSCRA), systematically investigating its synergy in tailoring mechanical properties, microstructural, recrystallization behavior, and thermal stability of pure copper. Compared to conventional symmetric rolling (SR) followed by annealing (SRA), the DSCRA specimens exhibit 27.9% higher microhardness and 18.3% enhanced ultimate tensile strength under annealing at 180 degrees C for 15 min, primarily driven by optimized dislocation strengthening and grain boundary strengthening. Both SRA and DSCRA specimens achieve >95% IACS electrical conductivity at elevated annealing temperatures. Microstructural analysis reveals that DSCRA specimens generate weaker and more homogeneous texture prior to recrystallization, resulting in 31.3% higher grain growth activation energy and superior thermal stability. These findings establish DSCRA as an industrially scalable strategy for manufacturing high-performance copper plates, providing critical insights for designing deformation-annealing protocols for conductive structural materials.

Aiming at the limitations of current monitoring methods in the accuracy of early fault diagnosis for rolling mill bearings, a structural design method for intelligent rolling mill bearings based on embedded multi-source microsensors was proposed.A multi-source microsensor module integrating temperature and acceleration signals was developed, and an optimized layout structure of axial sensing leads in the bearing housing was designed, breaking through the bottleneck of sensor integration under the space constraints of traditional bearings. A mechanical performance evaluation system for the slotted structure was established, and the reliability of the intelligent structure was verified through strength check and service life calculation.The results showed that when the slotted area was 10 mm×5 mm, the maximum equivalent stress was 99.71 MPa, which had sufficient safety margin compared with the material yield limit; the maximum overall deformation of the structure was only 0.24 mm, and the local deformation was less than 0.02 mm, with the theoretical service life consistent with that of conventional bearings. The optimized intelligent bearing ensured monitoring functionality while meeting industrial application requirements in terms of structural strength and service life.​The research results not only provide a high-precision monitoring method for early fault diagnosis of rolling mill bearings under extreme working conditions but also achieve an integrated "monitoring-structure" process through embedded design. Its strength check standards and service life evaluation methods can directly guide the transformation and upgrading of intelligent bearings in industrial sites, holding significant engineering value for improving the operation and maintenance efficiency of rolling production lines.

As a critical intermediate stage in the continuous casting and rolling process for bar production, the heating quality of a walking beam reheating furnace significantly affects billet shaping and the performance of the finished bars. To address issues such as uneven billet temperature distribution during heating, which leads to non-uniform deformation resistance in the rolling process, causing bending deformation, excessive thermal stress, and the initiation of microcracks and propagation of inherited casting cracks, this study uses 20CrNiMoA steel billets as the research object. The temperature field distribution inside the walking beam reheating furnace was simulated with ABAQUS finite element software. The accuracy of the simulation results was verified through ‘black box’ experiments, which demonstrated that the simulation precision meets the standards required for industrial applications. On this basis, the study systematically investigated the effects of temperature and time parameter settings in different heating zones of the furnace on billet temperature distribution and stress evolution. The results show that increasing the charging temperature improves temperature distribution and peak stress during the preheating stage, while lower furnace temperatures during the preheating phase reduce excessive thermal stress, and optimal furnace settings in heating zone I and II enhance heating efficiency and uniformity. The findings provide theoretical foundations and data support for optimizing on-site production heating process parameters and improving billet heating quality.

Anisotropic mechanical behavior and Luders strain are frequently observed during the deformation of dual-phase (DP) steels. The present study investigates the anisotropic Luders strain behavior exhibited by DP780 steel under cryogenic temperature tensile testing at varying strain rates. Based on electron backscattering diffraction (EBSD) technology, the effects of the texture evolution of the samples loaded in different directions and the Taylor factor distribution on the anisotropic Luders strain were revealed. It is found that the formation of anisotropic Luders strain is affected by the {110} slip system with lower dislocation slip resistance. IMPACT STATEMENT For the first time, the mechanism of anisotropic Luders strain of DP780 steel at cryogenic temperature was revealed from the perspective of texture evolution and main activated slip systems.

During practical forming processing, strong anisotropic mechanical behavior of dual phase (DP) steels is usually detected due to texture, which further determines subsequent processing optimization with loading paths changing. In order to clarify the underlying deformation mechanisms of DP steels under multi-axial loading, the mechanical response of DP780 under different biaxial loading paths was examined in detail. More precisely, anisotropic behavior of DP780 in complete "sigma xx-sigma yy" space was investigated through mechanical testing, microstructure characterization, and crystal plasticity computation based on dislocation density. In particular, biaxial compression test of thin plate is realized by using specifically designed fixture, and consequently yield loci in complete "sigma xx-sigma yy" space is detected experimentally. It is found that stronger anisotropy is observed under biaxial loading compared with that under uniaxial loading at macro scale, and biaxial Bauschinger effect is detected with biaxial preloading. At the micro scale, the texture evolution is affected directly by loading paths, and the compression load contributes more to the texture evolution. The distribution of the Taylor Factor under different biaxial loading paths reveals the impact of tension and compression on the main activated slip systems (MASS). Under biaxial tension and biaxial compression loading, the MASS of DP780 is the {112} slip system. Under combined biaxial tension and compression loading, the MASS is the {110} slip system. Using crystal plasticity, the evolution of dislocation density under different biaxial loading is captured. The relationship between the biaxial Bauschinger effect and MASS is clarified. It is found that the dislocation multiplication of the {112} slip system is more affected by changes in loading path than the {110} slip system. And during the subsequent loading process, the {110} slip system transform to {112} by preloading. Additionally, the relationship between the alteration of the MASS and the evolution of texture, as well as the resulting macroscopic anisotropic behavior has been elucidated.

The assembly clearance between the bearing housing and rolling mill stand affects the roll change and rolling stability. In order to improve the accuracy and real-time measurement of the bearing housing clearance of the rolling mill, four kinds of measuring methods were designed, namely the laser ranging method, external force measuring method, internal force measuring method, and eddy current ranging method, and the characteristics of the four measuring methods were introduced, respectively. The real-time measuring experiment of bearing housing clearance was carried out in a 100 mm two-high mill in laboratory and a 1580 mm four-high hot tandem mill in the Qian’an Iron and Steel Company. The results show that clearance measurement technology is helpful to improve the accuracy of real-time measurements and can provide guidance for the clearance control work. Finally, based on the real-time measurement technology of bearing housing clearance, the control strategy of bearing housing clearance was developed. This technology is of great significance to realize the fine management of rolling mill clearance and to improve the intelligence level of rolling mill systems.

The deformation mechanisms of Mg alloy under multi-degree-of-freedom axial, torsional, and combined loadings remains critically unclear. This is particularly significant in the case of the anisotropic evolution of yield loci and inverse Swift effect, which are crucial for optimizing the forming technologies for engineering parts. In order to clarify the underlying deformation mechanisms, combined multi-degree-of-freedom axial-torsional non-proportional loading paths are specially designed. The anisotropic evolution of the yield loci and Swift-inverse Swift effects in extruded AZ31 Mg alloys are investigated. The strong loading-path-dependent twinning activities and underlying deformation mechanisms are clarified in detail. The findings reveal that the inverse Swift effect during free rotational tension (FR_Ten) is attributed to the residual shear stress and initial texture heterogeneity, while the spontaneous macroscopic rotation during free rotational compression (FR_Com) is found to originate from the heterogeneous local strain induced by the interactions of the {1012} twins. Free end torsion (FE_Tor) pre-straining induces subsequent yield locus (SYL) rotation towards the positive tau axis and expansion along the negative sigma axis. The anisotropic Swift-inverse Swift effects are accurately captured by the plastic strain-components on the yield loci. Tensile twinning and basal slip coordinate the plastic deformation under FR_Com-dominated loading paths, owing to the low twin favourability, and the relative activities of non-basal slips under FR_Ten-dominated loading paths are significantly improved. The evolutions of the Swift-inverse Swift effects are determined by elastic preloadings, resulting in loading-path-dependent anisotropic evolutions of mechanical responses.

As an excellent pressure structure, circumferentially corrugated shells have been widely used in many fields, such as ocean engineering and aerospace. At present, the circumferentially corrugated shells have only obtained good buckling performance in tests and finite element analysis. However, the corrugated shells have not been further analyzed in theory, and some new problems have been found in tests. The geometrical parameters of shell structures determine the stress distributions and stiffness anisotropy, and the von Mises stress and local stiffness determine the collapse form and collapse location. The relationship between them has not been explained. The study of this problem will be beneficial to establish the active design theory of the circumferentially corrugated shells. Therefore, this paper aims to investigate the von Mises stress and stiffness anisotropy of the circumferentially corrugated shells. Some corrugated shells with uniform thickness and some corrugated shells with non-uniform thickness are established. The parameters used to represent the corrugated structure and the degree of stiffness anisotropy are proposed. The influence of corrugation parameters on the stress distributions and stiffness anisotropy is studied by finite element method and theoretical analysis, the mechanical behaviors of two types of shells under uniform lateral external pressure is perfectly explained. It provides a direction for the design and optimization of these shells. In addition, a new circumferentially corrugated shell is proposed at the end of this paper. It has good mechanical properties, which will make it possible to further reduce its weight.

Laser-based powder bed fusion (PBF-LB) of oxide dispersion strengthened (ODS)-FeCrAl steel commonly results in the generation of Y-Al-O oxide inclusions in the matrix. In this study, different heat inputs were obtained by adjusting the laser scanning speed, and systematic correlations were established between the heat input and both the molten pool geometry and oxide inclusions content. ODS-FeCrAl steel without Y-Al-O oxide inclusions was prepared when the heat input was 109 J/mm3, where the depth of molten pools was sufficient to remelt previously six deposited layers. The increased heat input of molten pools resulted in coarsening of both grains and nano-precipitates, and the yield strength of the oxide inclusions-free ODS-FeCrAl steel was reduced by 37 MPa. This study provides a feasible method for in-situ removal of oxide inclusions in alloys during the PBF-LB process.