Title: Investigations into micro-orthogonal cutting and material strengthening

Authors: Y.V. Srinivasa; M.S. Shunmugam

Addresses: Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai – 600 036, India ' Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai – 600 036, India

Abstract: When a scale of metal cutting process reduces to micrometer range, mechanics of material removal are affected by various factors such as workpiece material, cutting tool geometry and cutting conditions. A suitable model of constitutive behaviour of the material is needed to represent properties of the work material at the conditions existing during chip formation. In this paper, a material model based on theory of strain gradient plasticity is proposed for material strengthening in micro cutting, taking into account size effect in micro cutting with a tool having an edge radius. The proposed model effectively combines strain gradient plasticity and basic mechanics of orthogonal cutting. The material model thus developed is validated using results obtained from micro-orthogonal cutting experiments on mild steel (AISI 1019). Micro-orthogonal experiments with varying uncut chip thickness are also carried out to fine-tune the material model and investigate the mechanics of micro cutting considering the minimum uncut chip thickness effect. The results are encouraging and shear strength is predicted with an average absolute error of 11.8%. FE simulations carried out with flow stress obtained from Johnson-Cook relation yield cutting forces that follow the trend in the experimentally obtained force signals, but they are unable to capture the strain gradient and ploughing effects. [Received 4 July 2012; Revised 2 January 2013; Accepted 27 April 2013]

Keywords: micro-orthogonal cutting; edge radius; size effect; shear strength; minimum uncut chip thickness; mild steel; material strengthening; micromachining; simulation; finite element analysis; FEA; material removal rate; MRR; workpiece material; cutting tool geometry; cutting conditions; constitutive behaviour; chip formation; material modelling; strain gradient plasticity; flow stress; cutting forces; orthogonal cutting.

DOI: 10.1504/IJMR.2013.057749

International Journal of Manufacturing Research, 2013 Vol.8 No.4, pp.394 - 421

Available online: 26 Nov 2013 *

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