Numerical modelling of material fracture caused by the Mannesmann effect

Abstract

This paper relates to the problem of modelling material fracture caused by the so-called Mannesmann effect, a phenomenon that frequently occurs in cross and skew rolling processes. First, previous studies on numerical modelling fracture in rotary tube piercing and cross wedge rolling processes are described. The literature review shows a lack of studies investigating the propagation of cracks due to the Mannesmann effect. To fill this knowledge gap, a study involving both numerical analyses and experiments was undertaken. The study used a test based on rotary compression of a cylindrical specimen; the test is used for material damage function calibration. Rotary compression was performed under cold forming conditions for aluminium alloy Al99.7 and under hot forming conditions for steel C45. Based on results of the rotary compression test for aluminium, a new method was developed for determining the critical value of damage using cylindrical specimens with initiated fracture. Following the establishment of the critical damage value for alloy Al99.7, the rotary compression process was simulated numerically, which consisted of 3D modelling the axial crack propagation caused by the Mannesmann effect. In addition to that, the effect of the formed crack on the state of stress in the workpiece was determined. After that, the critical damage of steel C45 in the temperature range 950 °C–1100 °C was determined. The obtained critical damage value was validated by simulating material fracture in a cross wedge rolling process that was earlier conducted under laboratory conditions. The numerical and experimental results of material fracture showed very high agreement.