Establishment of minimum relative bending radius of thin-walled tube no-mandrel bending

The steel tube bending stress and strain were briefly analyzed,the relationship between the minimum relative bending radius and the tube bending tangential strains was explored,the calculation method of the minimum relative bending radius was determined,and then the calculated minimum relative bending radius formulas according to the material hardening exponent,elongation and deformation of the geometric condition were deduced respectively.It was modified further through the steel tube bending tests.This method can precisely determine the actual minimum relative bending radius based on the small amount of steel tube bending tests,which has a strong reference value.