SIMULATION OF A THREE-STAGE PROCESS FOR FORMING A CLOSED CONE FROM A PLATE

摘要

High geometrical quality of bent cones is required in assembling several cone segments into a crown of Francis turbines. Although closed cones were successfully obtained using pyramidal three-roll conical bending machines with cylindrical rolls which is more adaptive and less expensive, the zones close to the leading and trailing edges of the plate never pass under the inner roll and remain planar. For the purpose of obtaining high geometrical quality, a three-stage process is proposed to obtain a jointed cone with no planar zones. The planar zones resulted from the first stage of the conical bending is eliminated after the repassing of the bent cone in the bending machine with the leading and trailing edges jointed together by forces. Numerical simulations with commercial software ANSYS/LS-DYNA in explicit scheme and ANSYS in implicit scheme are performed and bent cones with improved qualities are obtained.