Multiscale and multicycle instrumented indentation to determine mechanical properties: Application to the BK7 crown boro
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Benzaama École Nationale Polytechnique d’Oran, ENPO, Oran 31000, Algérie
A. Mejias Arts et Métiers ParisTech, MSMP, ENSAM 8 Boulevard Louis XIV, Lille 59046, France; and Facultad de Ingeniería, CIMEC, Universidad de Carabobo, Valencia 2005, Venezuela
S. Kossman Univ. Lille, FRE 3723-LML-Laboratoire de Mécanique de Lille, Lille 59000, France
A. Montagne and A. Iost Arts et Métiers ParisTech, MSMP, ENSAM 8, Lille 59046, France
D. Chicot Univ. Lille, FRE 3723-LML-Laboratoire de Mécanique de Lille, Lille 59000, France (Received 2 September 2016; accepted 22 December 2016)
In this work, nano, micro, and macro-indentation tests under standard or multicycle loading conditions were performed for studying the mechanical behavior of a crown borosilicate glass sample with the objective to study the scale effect in indentation and the influence of cracks formation on the assessment of mechanical properties. When no cracks were initiated during the indenter penetration, especially for low indentation loads, the mechanical properties were deduced by applying different methodologies, (i) Standard (or monocyclic) loading, (ii) Continuous Stiffness Measurement mode, (iii) Constant and progressive multicycle loading, and (iv) Dynamic hardness computation. It has been found independently of the loading conditions, Martens hardness and elastic modulus are approximately 3.3 and 70 GPa, respectively. However, when cracking and chipping are produced during the indentation test, two damage parameters related to hardness and elastic modulus can be used for representing the decrease of the mechanical properties as a function of the relative penetration depth.
I. INTRODUCTION
Optical glasses are mainly used for lenses and mirrors in optical devices which are the most often intended for telescopes, microscopes, and photographic targets (sights, collimators, and eye pieces). The main types of glasses belong to the crown and flint families. These materials are appropriate for optical transmission in a range between 380 and 2100 nm; due to their homogeneous microstructure, their low porosity and their easy machinability. As an example, a concave lens of crown combined with another convex lens in flint is known to correct chromatic aberration of an optical device.1,2 To optimize their performance in service and for obtaining high quality optical devices, the reflective
Contributing Editor: George M. Pharr a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.523
surface must be carefully prepared to have a smooth surface and “zero” defects like pores or nano-cracks. The surface must also be flat to avoid any optical wave’s deflections. Additionally, the surface preparation process must minimize the introduction of residual stresses at the surface. Within this compulsory objective, the surface preparation process must follow specific steps. The first pre-polishing step consists of a lapping phase with agglomerate tools or abrasive particles in suspension.3–7 This stage is used to eliminate the macro-geomet
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