Title: Numerical analysis of crack propagation during the burr formation process of metals

Authors: J. Regel, A. Stoll, J. Leopold

Addresses: Institute of Machine Tools and Production Processes, Chemnitz University of Technology, Germany. ' Department of Materials, University of Oxford, Oxford, UK. ' Fraunhofer Institute for Machine Tools and Forming Technology, Chemnitz, Germany

Abstract: Because of increased productivity demands in manufacturing the attention in burr problems is steadily turned to the avoidance of burr. With this initial point this paper contributes to the analysis and simulation of burr separation at workpiece material AISI 1045 steel (C45E). At first 12 known crack initiation criteria are investigated whether they are suitable to simulate crack initiation during burr formation. It is shown that eight criteria are suitable for the prediction of the crack, whereas the criterion from Cockcroft and Latham has to be pointed out. The implementation of the failure conception of ductile damage from Lemaitre and Sievert indicates the applicability for burr formation simulation with simultaneous simulation of segmented chips. In first calculation, a sliding of the chip could be simulated. At the end the hypothesis of the |hydrostatic bowl|, an area of highly negative pressure in the stage of burr formation, is used to predict the location of crack initiation. The established values correlate better to the experimental tests than these, which are determined by means of fracture criteria.

Keywords: burr formation; crack initiation; FEM; finite element method; hydrostatic pressure; metallic material; crack propagation; simulation; fracture.

DOI: 10.1504/IJMMM.2009.026927

International Journal of Machining and Machinability of Materials, 2009 Vol.6 No.1/2, pp.54 - 68

Published online: 09 Jul 2009 *

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