NDTnet 1998 Aug, Vol.3 No.8

Abstract

One of the most widespread methods of indirect determination of the mechanical characteristics of a material is research of residual deformation parameters caused by penetration of an indentor a material and determination of the mechanical characteristics with the help of empirical dependencies. The possibilities of modern research methods (for example, optical electronics in combination with PC) permit determining deformation parameters during impact penetration of the indentor and by that expanding possibility of identification of the material properties provided availability of adequate mathematical model and algorithm of identification. The same significance has the important problem of determination of those parameters, being a subject to measurement, which are "responsible" for qualitatively determined properties of the material.

Iterative model of process of the indentor impact penetration in the elasto-plastic material based on the FE model of the media and special finite difference representation of deformation process in a time is developed. It is possible to formulate the problem of determination of prescribed parameters of the material model based on the results of measurements as follows: to find values of qualitatively determined components of material model parameters vector with the help of minimisation of given criterion of quality; at the same time the quantities of the minimum of criterion of quality themselves are optimised with the help of measured parameters control. The control functions can be considered as determining the model of measuring process ensuring sufficient information for determination of parameters of researched system model. As a result the initial problem reduces to two: the identification problem and the control one.

On the basis of developed model of the process of impact penetration of the indentor in the elasto-plastic material the algorithm is constructed of the identification of physical material parameters and control of qualitative definiteness of measured parameters necessary for adequate description of material properties. Optimum criterion of chosen set of measured parameters is introduced. Examples of determination of necessary measurement parameters are resulted for the qualitatively given vector of parameters describing "stress-strain" diagram of the material. The developed technique permits determining the mechanical characteristics of the material of the finished product without experiments with specimens.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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