MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Direct In Situ Observation of Deformation Modes in Wedge Indentation of Metals
Anirudh UdupaNarayan SundaramTatsuya SugiharaSrinivasan Chandrasekar
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2019 Volume 60 Issue 8 Pages 1442-1449

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Abstract

We study deformation patterns in wedge indentation of annealed metals (e.g., copper) using high-resolution, in situ imaging and image correlation. Based on attributes of the deformation such as velocity fields, grid distortion and strain distributions, we discriminate between two modes of deformation — a cutting mode with narrow-angle (sharp) wedges, e.g., apex angle of 30°, and a radial-compression mode with wide-angle (blunt) wedges, e.g. apex angle of 120°. The cutting mode is characterized by significant material flow parallel to the wedge face; and a thin region of very high strain (∼3), that is located immediately adjacent to the indenter face (wall-layer), and arises from friction-induced deformation. The radial-compression mode is distinguished by material flow normal to and away from the indenter face, with negligible velocity component parallel to the indenter face. The corresponding strain field is one of bulk deformation, with the highly-strained region (strain ∼1) being of semicircular shape that extends from near the edge of indenter contact at the specimen surface, to well below the indenter tip. The observations show that indenter wall friction is likely to have a major influence on the deformation field only with narrow-angle indenters.

Based on the observations of material flow, a suggestion is made (and validated) as to how the challenges faced in computational modeling of narrow-angle wedge indentation can be overcome. Implications for use of narrow-angle wedge indentation to study tribology of metalworking contacts, and ductile failure and damage in metals, are briefly discussed.

Fig. 5 Grid deformation and background velocity fields for indentation with (a) 30°, (b) 90° and (c) 120° wedges. Prior to the indentation, each grid was rectangular. A, B and C indicate the positions of select points on the grid that were located initially close to the specimen surface and just below the indenter tip. A′, B′ and C′ are the locations of these points after the indentation. Fullsize Image
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© 2019 The Japan Institute of Metals and Materials
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