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Topic Summary of the Dissertation
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4. Two types of FEM analyses are often carried out to simulate heat
rolling processes. One of these is the steady-state, Eulerian model by
neglecting end effects and using rigid-plastic or viscoplastic behavior. The
other is an incremental, updated Lagrangian model used when end effects are
being investigated and/or elastoplastic or elastovisoplastic rheology is
assumed. Quite a number of investigations have been carried out with various FEM
models in the simulation of the rolling process of slab and in stretching
grooves. With respect to FEM investigation of shape rolling, a few results have
also been published such as the works relating to the rolling of rail, beam and
angle steel. Some researcher did the simulation under the application of
existing source programs, others tried to, however, directly write their own
programs and then analyze the rolling process with the finished program. In a
number of investigations some calculated parameters were compared with those of
experiment and the FEM was thus examined and optimized. The comparison of local
material flow exists, especially in the relatively simple rolling processes such
as rolling in stretching grooves. Since the FEM simulation of shape rolling is
normally very time consuming, the analysis of the shape rolling was often done
through a combination of FEM with other methods (such as slab method, energy
method, etc.), in order to cut down the calculation cost. But sometimes such a
combination leads to a little sacrifice of the calculation accuracy.
Most of the published research works for the simulation of shape
rolling are inadequate. Many researchers only managed to solve part of the
problems of the simulation, or tried to simulate the process with simplified
material data and boundary conditions. The dependence of the material data and
boundary conditions on the forming parameters such as temperature, strain,
strain rate, were not adequately taken into consideration in most of these
investigations. Some parameters such as forward and backward slip were often
neglected. Only in very few of the investigations were sufficient optimization
of boundary conditions and an extensive assessment of the calculation performed,
especially with the rolling tests.
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