Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol Applicability of cutting theory to nanocutting of metallic glasses: Atomistic simulation Karina E. Avila a , Vardan Hoviki Vardanyan a , Iyad Alabd Alhafez a , Marco Zimmermann b , Benjamin Kirsch b , Herbert M. Urbassek ⁎ ,1,a a Physics Department and Research Center OPTIMAS, TU Kaiserslautern, Erwin-Schrödinger-Straße, Kaiserslautern D-67663, Germany b Institute for Manufacturing Technology and Production Systems, TU Kaiserslautern, Kaiserslautern D-67663, Germany ARTICLE INFO Keywords: Cutting Metallic glass Shear bands Molecular dynamics Shear angle ABSTRACT Using molecular dynamics simulation, we perform simulations of cutting a CuZr metallic glass at a wide range of rake angles. Plasticity in the metallic glass is governed by the formation of parallel shear bands in the chip. The chip is clearly separated from the uncut workpiece by a primary shear zone, from which the shear angle can be easily determined. The dependence of the shear angle on the rake angle and the friction angle follows closely Merchant’s theory of cutting. This agreement is particularly pronounced in the case that the force exerted on the workpiece is far from the cutting direction; this occurs for negative rake angles. 1. Introduction Orthogonal cutting is a well investigated machining process. The basic mechanical description has been set up decades ago [1,2] and describes the cutting in terms of the geometrical relations between the cut geometry and the forces. However, for the important case of (crystalline) ductile metals, the agreement between theory and ex- periment is not convincing and several refnements – inclusion of ma- terial-specifc quantities such as the yield strength or the surface spe- cifc work – have been included [3–5]. In addition, the model was set up for macro-scale machining. In the last years, signifcant improvements in micro and nano-scale machining have been achieved with regard to the (small) dimension and accuracy of the achievable structures [6]. However, the cutting mechanisms at very small scales with very small chip thicknesses are not yet fully understood [7]. This is due to the small sizes of the cutting zone, making it hardly observable. Metallic glasses are a class of materials with properties that are quite distinct from those of crystalline metals; thus they exhibit high strength and allow for large elastic strains [8–11]. Their plasticity is controlled by shear localization, which limits ductility with the increase of plastic strain [12–14]. Shear localization manifests itself in micro- scopic regions called shear transformation zones [15–18], which ar- range into macroscopic groups of atoms moving jointly, called shear bands (SBs) [19–22]. These plastic regions have been widely studied in several deformation processes [23–35], including the mechanical process of cutting, which has been investigated both by experiment [36–44] and by simulation [45–49]. Up to now, cutting theories have not been tested for metallic glasses. Due to their fundamentally diferent plastic behavior, it is unclear whether they follow the traditional cutting theories [1,2] better or worse than crystalline metals. In the present paper, we use molecular dynamics simulation to study the processes occurring under cutting of a metallic glass. By using physics-based molecular dynamics simulation, chip removal mechanisms at smallest scales can be assessed. We will hence examine if classic cutting theories can be applied to small scales. Since the simulation allows one to monitor not only the forces and the geometry of the forming chip, but also the plasticity processes, we obtain a complete picture of cutting in this material. Finally, by varying the rake angle of the tool, we can test to what extent available theories of cutting apply to metallic glasses. Note that the rake angle serves as an easy-to-control parameter to change the force kinematics during cut- ting, cf. for example the ultra-precision micro-cutting experiments by Chau et al. [43]. We will conclude that metallic glasses follow well Merchant’s theory of orthogonal cutting [1,2]. This is in strong contrast to the cutting of single-crystalline metals [50]. 2. Simulation details We use a Cu 64.5 Zr 35.5 metallic glass containing 1,404,928 atoms with dimensions of 44.95 nm × 11.21 nm × 45.00 nm in x, y and z https://doi.org/10.1016/j.jnoncrysol.2020.120363 Received 2 June 2020; Received in revised form 16 July 2020; Accepted 10 August 2020 ⁎ Corresponding author. E-mail address: urbassek@rhrk.uni-kl.de (H.M. Urbassek). 1 http://www.physik.uni-kl.de/urbassek/ Journal of Non-Crystalline Solids 550 (2020) 120363 0022-3093/ © 2020 Elsevier B.V. All rights reserved. T