Introduction to ring rolling technology

At present, ring rolling process is applicable to ring parts or blanks of various shapes, sizes and materials. Ring rolled parts have a large processing range in diameter, height, wall thickness and ring quality. Therefore, they are increasingly widely used in many industrial fields, such as machinery, automobile, train, ship, petrochemical industry, aerospace, energy and power and so on. The materials of rings are usually carbon steel, alloy steel and other metal alloys. Common ring rolling products include gear ring, flange ring, bearing ring, train wheel and hub, gas turbine ring, collector ring, high-voltage switch, wind power tower body and other rings. Now ring rolling technology has become an advanced and efficient process mainly used to produce ring mechanical parts, and is developing rapidly in the direction of large complex ring rolling, cold precision ring rolling, flexible ring rolling and so on.

Since 1968, the ring rolling process has been an important topic in scientific research. In the subsequent time, a variety of analysis methods have been used in the ring rolling process, such as the upper bound method and the modified upper bound method. Boucly et al. Described the development process of physical simulator for ring rolling process, and formed rings with an outer diameter of 700mm, making it possible to study the influence of various parameters on ring rolling process. The use of finite element method to study the ring rolling process was also developed in the same year. This method is quite accurate, but it takes a long time due to the following three main factors. Firstly, because the ring rolling is different from the standard plane forming, the material is in an unstable flow state, and the cross-section size of the ring changes continuously. Therefore, the contact conditions between the ring and the roll change continuously, which will lead to a significant increase in calculation time. The second factor is that in order to obtain the required ring shape, the number of meshes required for finite element analysis is very high compared with a standard deformation process (such as forging). For this reason, the calculation time increases significantly. The third factor is to describe the nonlinearity of material flow curve. In each simulation step of ring rolling process, it is necessary to carry out iteration to realize linearization, which will further increase the calculation time.

In order to reduce the calculation time, different simplified models of mathematical incremental model have been proposed in previous studies. Yang et al. Proposed a method to simplify the ring rolling process, which is simplified as a plane strain process. Tszeng et al. Developed a pseudo plane strain theory based on Yang’s research, which mathematically decomposes 3D deformation into a 2D in-plane flow and a 1D out of plane flow. Xu et al. [40] simulated the process of 3D forming, mainly focusing on the design of roll pass. The disadvantage of the above methods is that the geometric accuracy is not accurate and is limited to simulating the simple ring rolling process without end roll and guide roll.

Davey et al. Proposed Lagrange Eulerian (ALE) finite element method to simulate 3D ring rolling process, and achieved good results. Hu et al. Developed an arbitrary Lagrange Euler method, which is a finite element formula, in which the calculation system is not limited by space (Euler formula) or material (Lagrange formula). In the process of engineering simulation using ale technology, the arbitrary movement of the computational grid area can be used to optimize the shape of the workpiece, and the grid divided at the boundary and area can accurately locate the interface and boundary of the multi-material system with the movement of materials.

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