Conferences

Assignment of strain and stress values for the beginning of plastic yielding in materials by instrumented indentation method

  
E.Pechkovskiy
 

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Electron Microscopy and Strength of Materials - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2012, #18
http://www.materials.kiev.ua/article/584

Abstract

The method of an instrumented automatic indentation method with use of new methodology of processing and the analysis of results on a plenty of various materials analytically also experimentally establishes of strain εIT and stress σIT values which correspond to the beginning of plastic yielding of a material at simple circuits of a loading (tension, compression, bend). It is shown that value of stress σIT is close to proportional limit value σpl of a material, i. e. σIT » σpl. Connection of values εIT and σIT with hardness НIT of a material, its modulus of elasticity E and the contact module of elasticity Еr of pair a material — an indentor is established: εIT = 0,307(НIT/Еr) and σIT = 0,307НIT?(Е/Еr) (for Berkovich"s indentor). It is established that the value of the relation of hardness to a stress of material НITIT is determined by value of the relation of elastic moduluses Еr and Е as НITIT = 3,257(Еr/Е) and depending on a concrete material can change in limits НITIT = 1,78—3,257. It is shown that an instrumented automatic indentation method at room temperature it is possible to define concrete values of the beginning of plastic strain and a corresponding stress for brittle materials and superfirm coverings that is inaccessible to other known test methods. Full text download


DEFORMATION, HIGH-STRENGTH MATERIALS AND COVERINGS, INSTRUMENTED AUTOMATIC INDENTATION, RELATION OF HARDNESS TO STRESS, STRAIN