Analysis of Tubular Stress-Strain Characteristics Evaluation with Bugling Test

In the present work, a new designed bugling test machine is introduced to evaluate the tubular material properties. Differing from previous studies, the new test method allows the tube to shrink along the axis without the end effect. The proposed method is viable to obtain the strength coefficient, work hardening exponent and initial strain in Krupkowsky-Swift work hardening model. To determinate a more accurate result, three common geometrical models (cosine, elliptical, circumferential) are applied to analyze the process of bugling and compared. Bugling test, uniaxial tensile test and a serial finite element simulation on rolled tubes are conducted to validate the results. It turns out that the properties from the bugling test are quite different from the tensile test ones, and implies that the cosine model is the best fit to the experiment. Therefore, it is concluded the parameters from bugling test can improve the accuracies of the numerical simulations of the tube hydroforming.