A method for the prediction of ductile fracture by central bursts in axisymmetric extrusion

Abstract

A new approach for the prediction of central burst defects in extrusion and wire drawing is proposed. Central burst defects are troublesome in industry as it is impossible to detect these defects by simple visual examination alone. It is therefore important to identify the combination of process parameters that will reduce the probability of these defects occurring. The proposed approach is capable of accurately predicting when and where a central burst is likely to occur. The influence of die geometry on damage development and subsequent central burst formation is examined using the modelling capabilities of Abaqus finite element software. The ductile fracture criteria of Cockcroft and Latham, Oyane and Chaouadi were employed using a Fortran subroutine, and their ability to predict the onset and evolution of the central burst defect was examined. For relatively lower area reductions and die angles the considered criteria are capable of accurately predicting the morphology of the defect. Under these conditions, the proposed approach shows good agreement with experimental results, confirming its effectiveness and suitability for industrial application. The failure criteria are inadequate in predicting central burst defect formation during conditions of large reduction in area and large semi-die angles. Further development of ductile failure criteria is necessary to accurately simulate defect evolution for all die angles and area reductions.

Ductile Fracture by Central Bursts in Drawn 2011 Aluminium Wire

“…In addition, due to the complexity of the equations involved, the applications of such criteria are only suitable for simple geometries and boundary conditions. The availability of finite element computer programs has resulted in the implementation of fracture criteria to metal forming analysis by numerous researchers (Clift et al, 1989;Chevalier, 1992;Chaouadi et al, 1994;Gouveia et al, 1996;Campos and Cetlin, 1998;Choi et al, 1998;Phelan et al, 1999;Ko and Kim, 2000;McAllen and Phelan, 2005). This approach has resulted in some success.…”

Numerical analysis of axisymmetric wire drawing by means of a coupled damage model

“…For low reduction ratios and large die angles, the distortion of the elements is small enough to allow a good discretization of the problem, thereby enabling an accurate simulation of defect evolution. A more detailed discussion on the implementation of the USDFLD subroutine has been reported elsewhere in literature [11].…”

“…The availability of finite element computer programs has resulted in the implementation of fracture criteria to metal forming analysis by numerous researchers [10][11][12][13][14][15][16][17][18]. This approach has resulted in some success.…”

Damage dependent stress limit model for failure prediction in bulk forming processes

“…Successful predictions have been reported in many works, e. g. [5,6]. On the other hand, the accuracy of the Oyane criterion is not sufficient if the identical critical values are applied for different forming cases.…”