Plastic Deformation Zone Size during Indenter Scratch Tests of Materials
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NOSTICS AND MECHANICAL TEST TECHNIQUES
Plastic Deformation Zone Size during Indenter Scratch Tests of Materials A. Yu. Marchenkova, *, D. V. Chernovb, D. A. Zhguta, E. V. Terent’eva, and N. Abusaifa aMoscow bBlagonravov
Power Engineering Institute, National Research University, Moscow, 111250 Russia Institute of Engineering Science, Russian Academy of Sciences, Moscow, 101000 Russia *e-mail: [email protected]
Received September 16, 2019; revised October 17, 2019; accepted October 30, 2019
Abstract—The plastic deformation zone sizes in various metallic materials (steel, copper, armco-iron) are studied during tests by scratching with a tetrahedral Vickers pyramid under the scratch formation conditions at a constant depth. The ratio of the plastic deformation zone depth under a scratch to the scratch depth is found to weakly depend on the scratch depth and to be 6.3–8.5 for the materials under study. Based on these results, we concluded that, when the mechanical properties of a metallic material are determined by scratching, the ratio of the material thickness to the scratch depth should be at least 8.5. Keywords: indentation, scratching, deformed volume, hardness DOI: 10.1134/S0036029520100171
INTRODUCTION The creation of new technologies and the improvement of the existing technologies for the manufacture of parts and structures of various purposes require the improvement of quality control methods, including methods for determining the mechanical properties. To control products of small thickness, for example, thin tapes, strips, coatings, researchers often use the indentation method, which in some cases is the only suitable method to reliably and accurately determine a wide range of the mechanical properties of a material, including its hardness, strength, and fracture toughness. Note that, along with the indentation techniques based on pressing an indenter, the indenter scratching method (scratch test) is also applied. The methods of controlling the mechanical properties by scratching with an indenter are very diverse and find application in solving a number of production and research problems [1–3]. The method of scratching at a constant indenter penetration depth is most widely used to analyze the mechanical properties of structural materials. It makes it possible to increase the information of a control procedure due to the possibility of evaluating the hardness, the strength, and the ductility of a metal in developed plastic deformation and fracture zones [4]. At the same time, there is a limitation on the use of indentation methods by both indentation and scratching, which consists in observing a certain ratio of the indentation/scratch depth and the material thickness.
This is especially true for determining the hardness of thin coatings, treated layers of a material, and tapes, when it is necessary to exclude the influence of the substrate material (in the case of coating) or equipment (in the case of products of small thickness) on the result of measuring the hardness. For example, in the case
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