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The ring rolling is a process of gradually forming the cross section of the ring material according to the outer shape of the working roll. In this study, process-induced defects in L-shaped cross section ring rolling process have been analyzed. Major defects in the L-shaped ring rolling process include folding, unfilling and groove on the bottom s...
Citations
... However, limited by rolling stability, only the minimum feed speed was selected [9]. Oh et al. analyzed the influence of blank shape, size, temperature, the rotational speed of main roll, the feed speed of mandrel, and other factors on the forming quality for the L-shaped parts in the rolling process based on the Forge software [10]. Hua et al. analyzed the plastic deformation law of spherical groove-section ring rolling process and found that the increase in radial thickness was not beneficial to forging penetration; on the contrary, the increase in feed speed is beneficial to forging penetration of ring [11]. ...
For the rolling process from rectangular blank to profiled ring, there is a lack of simple and rapid prediction method for geometric size. Based on the constant volume principle and the discrete idea from slab method, a rapid prediction model (RPM) describing the exact geometry of ring is established, and a simplified prediction formula for the section shape of profiled ring in the rolling filling process is proposed. This method is used to analyze the rolling process of typical profiled ring, and the results are compared with the rolling experiment, the finite element model (FEM), and the formula model (FM). The results show that this method has higher prediction accuracy than the constant volume formula method and higher calculation efficiency than the finite element method. The rapid prediction method proposed in this paper is of great significance for improving the analytical efficiency of profiled ring rolling.
... Xu et al. [16] proposed a ring blank design method for profile ring rolling combining the electric field method and the response surface method, which can accurately determine the dimensional range of reasonable billet to completely fill the cavity. Yeong et al. [17] investigated the effects of blank geometry, dimension and rotation speed, mandrel feed speed, and working temperature on the generation of defects during the L-shaped profile ring rolling process. ...
... Therefore, in this paper, based on the second-order model (Eq. 16), the least-squares method is applied to establish the response of the objective function with respect to the design variables 1 , 2 , 2 , and the response surface polynomial model is obtained as shown in Eq. (17). ...
During the rolling process of profile ring, the design of the rolling cavity directly affects the forming quality of the final ring and the production cost of the rolling process. To improve the cavity filling rate and reduce the production cost, the response surface method (RSM) is combined with a verified three-dimensional thermodynamic coupled finite element model to optimize the design of the rolling cavity for the profile ring rolling process. Firstly, a universally applicable design method for profile ring rolling cavity is proposed, and based on the description of the rolling cavity, three design variables and two corresponding response objectives are defined to achieve multi-objective optimization. Secondly, a verified finite element model is established to simulate the rolling process. Based on the simulation results, a response model is developed and modified by significance analysis and analysis of variance (ANOVA). Then through this response model, the effects of different variables on the optimization objectives are studied comprehensively. Finally, the optimal rolling cavity size is determined by combining the response optimization diagram, and the effectiveness of the optimization method is verified by forming experiments.
... This, they concede, requires a more complex process route for blank production such as blocker-type forging or die forging. One such process route was outlined by Oh et al. (2019), see Fig. 3a. The method uses a large shaped lower die and conical punch; in likelihood both would have to be custom-made for each part in question. ...
... Blank production method for L-Section rolling(Oh et al., 2019) Image reproduced with permission of copyright holder. ...
A novel ring rolling process is proposed to flexibly produce shaped rings without circumferential ring growth, potentially saving material and energy as well as reducing upstream and downstream processing requirements. In this paper, six circumferential constraint rolls are used constrain circumferential growth and enable L-shape profiles to be developed through axial material flow, via a compressive hoop stress. Process limits were studied in 22 experiments on lead rings and a set of axisymmetric thermally coupled simulations on a high value engineering material, Inconel 718. Profile depths of 75% of the original wall thickness were achieved in a range of rings and operating conditions, and material savings of up to 60% demonstrated over rectilinear rolling. There was no evidence of cracking or void formation, unlike processes where under-deformed regions are stretched circumferentially and are vulnerable to cracking. In several cases a non-circular ring shape developed, limiting the achievable profile depth especially for small wall thicknesses, large reductions in thickness per pass, or large profile heights. The constraint roll forces when this ‘collapse’ occurs was studied and an upper bound predicted by a plastic hinge model. The thermal simulations showed that in all except 4 cases reheats would be required to keep within safe temperature bounds, thus suggesting an optimum reduction in thickness per pass to avoid both excessive cooling and collapse.
... The main advantage of this process is that it can produce seamless forgings with material flow in the circumferential direction and requires less material than forging [6]. ...
During the rolling process of profile ring, the design of the rolling cavity directly affects the forming quality of the final ring. In order to improve the cavity filling rate and reduce the production cycle time, this paper proposes a general evaluation method of the filling difficulty for profile ring rolling cavity by combining the response surface method(RSM) and the finite element method(FEM) with the step-type ring as the research object. Firstly, a universally applicable design method for profile ring rolling cavity is proposed, and based on the description of the rolling cavity, three design variables and a corresponding response objective are defined to achieve multi-objective optimization. Secondly, a finite element model of this step-type ring rolling process is established, and the response model is built and improved by significance analysis and analysis of variance(ANOVA) based on the forming simulation results. Then, the effects of different variables on the optimization objectives are comprehensively investigated by this response model. Finally, the evaluation method of the filling difficulty for profile ring rolling cavity is obtained by combining the contour plot of the response objective.
Because of complicated geometric structure of C-section rings and the obvious difference of volume distribution along axial direction, the metal is difficult to flow along the radial direction to fill the profile section during ring rolling process. With a typical C-section ring of Inconel718 alloy as the research object, a blank design method was proposed for C-section ring rolling to redistribute the volume along axial direction. Then based on a verified 3D coupled thermo-mechanical FE model, response surface methodology (RSM) was employed to establish a response model with a high fitting accuracy of 98.31% to analyze the function relationship between the forming quality and blank size variables systematically. The results show that the blank design method proposed in this paper can be effectively applied to the C-section ring rolling. The C-section can be formed completely and about 10% of the material can be saved. Also, for multi-factor and multi-objective optimizations of ring rolling process, the optimal design method by combining FEM and RSM is an efficient and reliable method to obtain the best combination of parameters.
Groove-section profiled ring rolling (GSPRR) is a challenging forming process with high flexibility and complex deformation behavior. In the process, feeding strategy is a critical factor affecting the rolling stability and ring quality, thus should be carefully designed. In this work, towards the purpose of establishing a stable rolling process, simultaneously taking the different deformation behaviors during different forming stages into account, an advanced feeding strategy driven by staged growth velocity is proposed for GSPRR process, by which the feed rate of mandrel is adjusted in real time to maintain a constant ring growth velocity vD1 in most of the groove forming stage and a constant ring growth velocity vD2 in most of the pure diameter growth stage. To realize this, mathematical models clarifying the correlation between the ring growth velocity and mandrel feed rate in different forming stages are developed. Besides, the reasonable ranges of growth velocity in different forming stages are determined according to the gripping and penetrating conditions. Integrating the above mathematical correlations into the reliable FE model validated by experiment, the simulation of GSPRR with the feeding strategy driven by staged growth velocity is realized. Through simulations, it is demonstrated that better rolling stability and ring geometry accuracy are obtained under newly proposed feeding strategy compared to the traditional feeding strategy with predefined mandrel feed rate. In addition, it is found that with the increase of vD1 and vD2 in their reasonable ranges, the rolling stability and ring roundness become worse, while the uniformity of strain and temperature distribution become better. Therefore, for a comprehensive consideration, it is recommended to choose the vD1 and vD2 near the median of their reasonable ranges. This work can support the process design and optimization of GSPRR, meanwhile provide a theoretical and technical basis for upgrading industrial rolling mill by integrating the newly proposed feeding strategy into equipment control system.
In the conical-section profiled ring rolling (CSPRR), due to the asymmetrical geometric features and uncoordinated deformation of the ring along the axial direction, multiple geometric defects may occur, such as diameter error (i.e., the diameter of big and small ends cannot simultaneously reach the target values), roundness error and tilting. In this work, a growth velocity model, describing the ring diameter growing behavior at different axial positions, is developed through the theoretical analysis. Based on the growth velocity model, the largest growth velocity difference along the axial direction is expressed by a mathematical function which relates to the ring geometry parameters (including inner slope angle α1, outer slope angle α2, ring height H) and the mandrel feed rate vf. Further, combined with a mass of FE simulations, it is found that the growth velocity difference along the axial direction is the formation mechanism of multiple geometric defects in CSPRR process. By adjusting α1 or α2, reducing H or reducing vf, the largest growth velocity difference along the axial direction can be made close to zero, which is beneficial to improving geometric accuracy. Following the above understanding, three methods to avoid geometric defects are proposed, including the improved design of target rolled ring (forging drawing), the reduction of vf and the improved design of ring blank, which are applied in the process design for a complex conical-section casing ring. The corresponding simulations and industrial experiment indicate that the proposed methods work well to avoid multiple geometric defects.
