1 engineering background

Rolling is rotating rolls into the gap between the material and deformation process. Close to the end of deformation of the head rolled piece is stable deformation, and in the other part, along the direction of rolled piece on conditions are not dramatically changed, reason for stable state. Rolling production, material of plastic deformation law, roll and rolled piece of the friction between the phenomenon, material in the change of temperature and microstructure, in the process of rolling pressure the rate, such as the ratio of generous of rolled piece and the influence on the quality of, is very complicated problem. Affect production efficiency and production quality for many reasons, from the scene and experiment of the rules and it is difficult to get covered all aspects of theory, and enormous consumption. The numerical simulation method for the numerical experiment is in recent years in the theoretical research trend will finite element method is applied to the study of the theory of the rolling process could not only save the cost, and because its high-speed and reliability can not easily in the process of rolling on experimental study deeply discuss the issues.

2 problems introduced

Plate rolling technology on the surface looks very simple, but the actual production the problems of many, and some have not yet very good solution. Such as rolling deformation region of three dimensional stress and strain distribution law, medium thickness plate shape rules, bite into the plane and cast steel stage of the stable deformation etc. Therefore, using the finite element method especially elastic-plastic finite element method to analyze the rolling process is still very necessary.

In the process of rolling elastic-plastic finite element analysis, according to the use of the finite element method can be classified into two categories: iterative algorithm is presented to solve the differential equation of the implicit algorithm and finite difference method to solve the differential equation integral explicit. This paper briefly describes the laboratory of plate rolling to simulate the process of some, this paper introduces using ANSYS and ANSYS/ls-dyna plate rolling process simulation on the basic ideas, and by explicit and implicit algorithm of some of the differences are compared.

3 model describes

3.1 implicit 2 d rigid roll process simulation
Using ANSYS implicit algorithm is 2 d rigid roll, roll for the rigid roller, roll the movement of the PILOT nodes through control, can make the roll rotation at a constant speed. The PLANE42 unit rolled pieces by mesh division, and according to the asymmetry take only the first half of the sensibility analysis, in a symmetrical boundary on the symmetric constraint. Roll with rolled piece of contact between the coulomb's friction. Roll rotation and rolling a forward movement when a suitable
distance calculated, until the complete rolling process.

3.2 implicit 2 d elastic roll process simulation
Implicit 2 d elastic roll, and roll for elastic roller, the elastic roll PLANE42 grid division, the rotation of the roll by add in the roll with rotational degree of freedom to put the beam element, roll with rolled piece of contact between still use the coulomb's friction.

3.3 implicit 3 d rigid roll process simulation
Implicit 3 d rigid roll, and roll for the rigid cylinder, rely on the PILOT node control, make its moving around the axis rotation. According to the asymmetry, rolled piece take of the part of model building, the SOLID45 by mesh division, roll with rolled piece of contact between still using the coulomb's friction. Other calculation with the foregoing conditions similar.

3.4 explicit 3 d rigid roll process simulation
Explicit 3 d rigid roll, and roll the rigid roller, but with the analysis of the implicit roll form different, for rigid roller but also units classification, in calculating the cost calculation time these units is not. Rolled piece using a quarter model, roll and rolled piece of the friction between the coulomb's friction. Roll and rolled piece USES SOLID164 unit grid partition. Calculation when giving the rolling piece at a certain initial velocity, to roll gap movement into the gap by for contact friction after rolling.

3.5 explicit 3 d elastic roll process simulation
Explicit 3 d elastic roll of the two hole shape vertical roll for the rigid roller, two flat roller is the elastic roller, contact friction is using the coulomb's friction, roll with rolling piece is using SOLID164 unit grid partition. Rolled piece at a certain initial velocity to roll gap movement into the gap by friction after finish rolling process. In addition the model of the rolled piece along the wide temperature to increase gradually, gradually reduce the deformation resistance.

4 result analysis

For the implicit algorithm analysis and by explicit algorithm analysis, from theory and practice can be calculated the comparison. In theory, the implicit algorithm is unconditional stability, and the explicit is conditions stable, that the only time step in the calculation of less than certain time step calculation is when stable, otherwise the result is not available. Implicit algorithm needs when iterative process, the convergence of the iterative with many factors, expend in the adjustment of the convergence on the question of the time will be very much, this is actually reduces the computational efficiency. And explicit with explicit scheme, so no iterative and convergence problem, take in the adjustment of the less time in calculation, also can pass quality zoom to shorten the time calculation, it is implicit algorithm does not have, finally make by explicit algorithm of the calculation efficiency is higher.

From the calculation for practice, the implicit algorithm rolling process simulation, when the pressure the rate is bigger, rolling a bite the difficulties, but through the in rolling piece bite fashionable add a proper thrust, or first by the vertical pressure the bite into the rolling method to solve. But on the whole, the implicit analysis method of rolled piece bite into is always a more difficult problem, in specific problems but to the more detailed adjustment. And by explicit method to calculate, due to the large deformation contact problem to deal with very convenient, for rolling simulation can well solve the problems bite. Even in pressure the rate is bigger, the rolling piece bite into also won't appear difficult. On the other hand, in the elastic roll process, because of the elastic deformation and rolling roll a large plastic deformation of the coupling analytical, making implicit calculation iterative process is very not easy convergence, must pass through many times to get a stable adjustment of the results. Especially in the pressure the rate is bigger, the grid distortion is more serious is even more so. And explicit analysis does not exist convergence problem, so it can greatly shorten the adjustment process, so as to improve the calculation efficiency. Moreover, implicit analysis, calculation of time




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