The kinematic and dynamic characteristics of the grinding media during the wet grinding process are investigated using a coupled Discrete Element Method (DEM)–Computational Fluid Dynamics (CFD) approach. Firstly, a coupled DEM-CFD model of the vertical spiral agitator mill is established and validated with experimental torque measurements. Subsequently, a velocity analysis model is established using the vector decomposition method. The cylinder is then divided into multiple regions along its radial and axial directions. The effects of spiral agitator rotational speed, diameter, pitch, and media filling level are investigated with respect to the circumferential velocity, axial velocity, collision frequency, effective energy between media, and energy loss of the grinding media. The average effective energy between media is an innovative metric for evaluating the grinding effect. The results indicate that the peripheral region of the spiral agitator demonstrates superior kinematic and dynamic performance. The rotational speed of the spiral agitator exerts a highly significant influence on the kinematic and dynamic characteristics of the media. With a maximum rise of 0.2 m/s in circumferential velocity and a 16.7 J gain in total energy. The media filling level demonstrates a negligible influence on media kinematics, while it profoundly affects dynamic properties, evidenced by a substantial increase of 83.09 J in the total media–media energy. As the diameter increases, the peak media circumferential velocity shifts outward, and the total media–media energy rises by 5.4 J. The spiral agitator pitch has a minimal impact on both the kinematic and dynamic characteristics of the media.

As wind turbines trend toward larger sizes, higher rotational speeds, and extended service lives, higher demands are emerging for the dimensional accuracy, mechanical properties, and service reliability of the main shaft bearings. The hot bulging process is a critical process in bearing ring manufacturing. The stress–strain and dimensional evolution during the hot bulging process are crucial for the fatigue life and dimensional accuracy of rings with non-circular cross-sections. Therefore, based on the residual stress field from rolling as an initial condition, this paper established a coupled finite element model for the entire rolling-to-bulging process of GCr15SiMn bearing steel rings and verified the accuracy of the model. A stepwise rotation hot bulging process was innovatively designed. The stresses, strains, and deformation rates of the rings were thoroughly evaluated at different steps of the bulging process. Additionally, the effect of the bulge amount on the stress–strain uniformity and dimensional accuracy of the fabricated rings was also evaluated. Results indicate that based on the stepwise rotation hot bulging process conducted at 870–930 °C, when the first-step bulging amount is 1.50 mm, the secondary and third-step amounts are both 0.50 mm, and the bulging speed is 1.00 mm/s, while the roundness error of ring #3 stabilizes within 0.28–0.35 mm. The standard deviation of the axial equivalent strain was decreased by 92%, and the stress peak was also decreased by 39%. Above all, the stepwise rotation hot bulging process is an effective approach to improve the distribution uniformity of the stress–strain and the dimensional consistency of the bearing rings. This paper provides theoretical foundations and process guidance for the precision forming of large wind turbine bearing rings with non-standard sections.

Recently, near-net-shape rolling has emerged as a key manufacturing technology for producing high-precision, fatigue-resistant bearing rings with irregular cross-sections, particularly for the production of Wind Turbine Shaft Bearings (WTSBs). The deformation behavior of the material during this rolling process is governed by temperature and rolling speed. Therefore, based on a thermomechanical coupled analysis, a simulation model for the deformation process of GCr15SiMn profiled rings during variable-speed rolling was developed in this study. The model was experimentally validated, confirming a dimensional error of less than 3‰. And then, the distribution of strain and temperature were analyzed during the rolling of the profiled ring. As the initial temperature increased from 1040 °C to 1160 °C, the standard deviation of strain (SDP) decreased from 6.12 to 4.05. Correspondingly, the standard deviation of temperature (SDT) was raised from 4.32 to 4.74. When the drive roll speed was increased from 2.5 rad/s to 4.0 rad/s, the SDP was reduced from 4.24 to 3.42. In addition, the SDT decreased from 4.42 to 3.21. The research indicates that SDP is primarily affected by initial temperature, whereas SDT is significantly influenced by drive roller speed. On the one hand, this study provides a clearly defined optimization framework, parameter ranges for achieving optimal uniformity in GCr15SiMn material (temperature of 1100–1130 °C, speed of 3.0–3.5 rad/s), and their anticipated benefits (an SDP reduction of 32% and an SDT reduction of 15%). On the other hand, it also establishes quantifiable industrial control targets, defining key quality assurance values (SDP ≤ 5.0, SDT ≤ 4.5). The rolling stability and precision can be improved through the selection of optimized rolling temperatures and speeds. This finding provides a theoretical foundation and technical framework for improving the rolling process stability of profiled cross-section bearing rings. Furthermore, this study is of positive significance for reducing the manufacturing costs of high-performance WTSBs.

The forming quality of large wind turbine main shaft bearing inner rings directly determines the service life and operational reliability of wind energy equipment. Yet the plastic deformation mechanism and stress–strain evolution of GCr15SiMn bearing inner rings during asymmetric cross-section radial–axial rolling remain poorly understood. Stress–strain curves from isothermal hot compression tests were used to build a three-dimensional finite element (FE) model of inner ring radial–axial rolling, validated by dedicated rolling experiments. The effects of drive roll rotational speed, initial rolling temperature, and radial–axial feed speeds on the stress and strain fields were systematically investigated. Results show that material flow velocity on the outer surface of the radial deformation zone is 100–200 mm/s higher than on the inner surface. The velocity difference between the upper and lower end faces in the axial deformation zone stays below 100 mm/s, confirming synchronous end-face forming. Peak equivalent stress reaches 81.5 MPa in the radial rolling stage and 75.6 MPa in the axial rolling stage. Standard deviation of stress (SDS) and plastic strain (SDP) quantify field uniformity; the most uniform distributions occur at 3.5 rad/s (SDS = 15.09) and 1100 °C (SDP = 4.18). These findings provide a theoretical basis for rolling process optimization and precision forming quality control of asymmetric cross-section wind turbine bearing inner rings.

Wind turbine main bearing rings with non-standard cross-sections are large, and a single rolling operation can hardly satisfy the simultaneous requirements of stress uniformity and dimensional accuracy; how the as-rolled state is inherited by the subsequent hot bulging remains unclear. A coupled thermo-mechanical model of the rolling-bulging sequence of a GCr15SiMn ring was therefore established in Abaqus/Explicit, transferring the geometry and the stress, plastic-strain and temperature fields across the two operations. With all bulging parameters fixed, five initial rolling temperatures (1040–1160 °C) were compared. The rolling stage was validated experimentally, the relative errors of the predicted outer diameter, inner diameter and wall thickness being below 0.37%, 0.28% and 2.5%, respectively, and the mesh-convergence deviation below 2%. Bulging reduced the mean stress by 21.9–35.6% and preserved the as-rolled uniformity ranking, the lowest stress standard deviation (3.46 MPa) occurring at 1130 °C. The outer- and inner-diameter roundness errors decreased from 6.29–7.61 and 4.13–5.14 mm to 1.05–1.44 and 0.80–1.35 mm, corresponding to correction ratios of 81–83% and 74–81%; the retained fractions stayed within 17–19% and 19–26% of the as-rolled error, so bulging scales the inherited shape error rather than equalising it. Considering dimensional accuracy and the stress state together, 1130 °C is recommended as the optimum, with 1100–1130 °C as the preferred process window. The bulging results are simulation predictions pending full-size experiments.