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Journal of Materials Processing Technology 209 (2009) 5167–5177

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Journal of Materials Processing Technology
journal homepage: www.elsevier.com/locate/jmatprotec

Computational modelling of 3D turning: Influence of edge micro-geometry on forces, stresses, friction and tool wear in PcBN tooling
Tugrul Özel ∗
Department of Industrial and SystemsEngineering, Rutgers University, Piscataway, NJ 08854, USA

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In this paper, computational modelling of 3D turning process in the presence of variable design cutting tool inserts is studied. Turning of alloy steel, AISI 4340, which utilized in high strength mechanical components for automotive and aerospace industry steel with uniform and variable edgedesign Polycrystalline cubic Boron Nitride (PcBN) inserts is performed. In the experiments chip geometry, forces and tool wear are measured. 3D computational modelling is utilized to predict chip formation, forces, stresses, temperatures and tool wear on uniform and variable edge design tools. Influence of variable edge tooling on resultant pressure-dependent friction has been investigated byutilizing 3D process simulations. Predicted forces are compared with experiments until pressure-dependent shear friction factor is solved. In general, a lower friction concentration is found for variable edge tooling. The temperature and stress distributions and tool wear contours reveal the advantages of variable edge micro-geometry design. © 2009 Elsevier B.V. All rights reserved.

Article history:Received 18 November 2008 Received in revised form 5 February 2009 Accepted 5 March 2009 Keywords: Computational machining Finite element method Variable edge design tool geometry

1. Introduction Machining is still indisputably the most popular manufacturing process in manufacturing of high precision discrete metal parts. Turning of hardened steels into finished parts by eliminating intermediatemachining and reducing grinding processes has been a cost-effective method for manufacturing high quality automotive components (Byrne et al., 2003). Besides, hard turning is a more flexible, more environmentally benign and higher throughput alternative to grinding. However, process reliability and surface quality is still considered behind grinding processes due to issues related to geometricallydefined cutting tools (Klocke et al., 2005). In hard turning, Polycrystalline cubic Boron Nitride (PcBN) cutting tools with various edge preparations (chamfer, radius, bi-radii oval or waterfall edges—see Fig. 1) are preferred to protect the cutting edge especially around the insert corner (nose) primarily from chipping (Matsumoto et al., 1999; Byrne et al., 2003; M’Saoubi and Chandrasekaran, 2004;Klocke et al., 2005). PcBN tools can withstand the extremely high temperatures but binder material in the polycrystalline tool body fails after cutting temperature exceeds a threshold (usually around 1200 ◦ C). Micro-geometry of the insert also has significant influence upon the surface integrity. Hence edge preparation must be carefully selected for a given application because it may generatesubsurface damage and result in highly tensile residual stress on the surface of the machined workpiece

(Klocke et al., 2005; Klocke and Kratz, 2005; Denkena et al., 2005; Özel et al., 2005). Heat generation during hard turning and heat distribution along the insert corner is also affected by micro-geometry due to change in work material flow around the cutting edge (Klocke and Kratz, 2005). Forexample, a chamfered face provides excessive negative angle to the cutting action and results in high heat generation. PcBN tools rapidly wear out during hard turning at high cutting speeds mainly due to dissolving binder material at attained high cutting temperatures (Byrne et al., 2003; Klocke and Kratz, 2005; Denkena et al., 2005). Flank wear occurs at flank face of the minor cutting edge where as...