Experimental study of frictional forces at the boundary between tool and workpiece during expansion of large diameter pipes

Most rigidly geometric characteristics of the cross section is regulated to pipes intended for offshore sites where permissible deviation from the theoretical circumference of pipe body 1…1.5 % of the diameter and 0.75…1 % of the diameter at the ends. The sectional shape of large diameter pipes formed during the complex forming operations deformation of billets strip adjusting this geometry under the influence of welding stresses and calibration in the process of finishing operations of expansion. The results of operations of expansion depends on the geometry of the workpiece in front of the operation and to the dynamics of contact interaction between tool and workpiece directly at of expansion. An important role is played by the frictional force between the contacting surfaces of the pipe expander head and because under the influence of these forces redistribution tangential deformation can occur and, consequently, the distortion geometry. The paper presents experimental data to determine the coefficient of friction, resulting in conditions as close as possible to the conditions of expansion of large diameter pipes. The technique of the experiment, a description of the laboratory setup with the necessary measurement tools. The estimation of influence of the main technological factors on the value of the coefficient of friction.