Using Upper Bound Method to Analyze Force Parameters of Three-roll Piercing Process

The deformation process of the three-roll piercing mill is properly simplified,and thus there exist only the plane strains,i.e.,the axial strain and the radial strain. And the piercing deformation zone is divided into four areas,and the velocity field for each deformation area is set up. Accordingly,the deformation power of each individual deformation area is analyzed with the upper bound method,and the rolling force is identified by the rule that the rolling force equals to the sum of the power consumptions of all the deformation areas. Relevant operation cases demonstrate that when rolling light-wall tubes with D/S above 10.0,the relative difference between the theoretic value from the calculation with the above mentioned method and the measured value is small,which means that the former can be used for actual operation.