Publication detail

# A Magnetic Method for Testing of Homogeneity of Fibre Concrete

HOBST, L. ANTON, O. VALA, J. HORÁK, M.

Original Title

A Magnetic Method for Testing of Homogeneity of Fibre Concrete

English Title

A Magnetic Method for Testing of Homogeneity of Fibre Concrete

Type

conference paper

Language

en

Original Abstract

Homogeneity of fibre concrete structures, characterized, from the macroscopic point of view, by (nearly) constant volume fraction of randomly oriented fibre particles, determines their mechanical, thermal, etc. properties, consequently their long-time behaviour, reliability and range of user applications. Destructive validation of homogeneity is available under laboratory conditions, but frequently impossible in situ. A reasonable alternative to the radiographic control method can be based on stationary measurements of magnetic field strength, thanks to the composite structure with ferromagnetic particles, incorporated in the concrete matrix. The permanent magnet generates a (nearly) stationary magnetic field, whose distribution is described by the Laplace equation, supplied by appropriate boundary conditions, containing the effective relative magnetic permeability as just one material parameter; the crucial problem is then to estimate some formally homogenized (with a priori unknown permeability of fibres) as a function of , without the a priori knowledge of permeability of particles. The paper demonstrates that in such case the numerical analysis of solution of the Laplace equation can be avoided, thus is allowed to be evaluated directly, using local measurements of the magnetic field strength from the Hall-effect-based measurement and non-trivial MATLAB-supported computations, based on the least squares optimization, supported by the Newton method for the numerical evaluation of roots of nonlinear equations.

English abstract

Homogeneity of fibre concrete structures, characterized, from the macroscopic point of view, by (nearly) constant volume fraction of randomly oriented fibre particles, determines their mechanical, thermal, etc. properties, consequently their long-time behaviour, reliability and range of user applications. Destructive validation of homogeneity is available under laboratory conditions, but frequently impossible in situ. A reasonable alternative to the radiographic control method can be based on stationary measurements of magnetic field strength, thanks to the composite structure with ferromagnetic particles, incorporated in the concrete matrix. The permanent magnet generates a (nearly) stationary magnetic field, whose distribution is described by the Laplace equation, supplied by appropriate boundary conditions, containing the effective relative magnetic permeability as just one material parameter; the crucial problem is then to estimate some formally homogenized (with a priori unknown permeability of fibres) as a function of , without the a priori knowledge of permeability of particles. The paper demonstrates that in such case the numerical analysis of solution of the Laplace equation can be avoided, thus is allowed to be evaluated directly, using local measurements of the magnetic field strength from the Hall-effect-based measurement and non-trivial MATLAB-supported computations, based on the least squares optimization, supported by the Newton method for the numerical evaluation of roots of nonlinear equations.

Keywords

Fibre concrete, non-destructive testing, Laplace equation for magnetic fields, homogenization techniques, least square method, MATLAB-supported computations.

RIV year

2011

Released

07.12.2011

Location

Brno

ISBN

978-80-7204-774-1

Book

9th International Conference NDT 2011 Nedestruktivní testování v technických oborech

Pages from

19

Pages to

29

Pages count

10

Documents

BibTex

```
@inproceedings{BUT76539,
author="Leonard {Hobst} and Ondřej {Anton} and Jiří {Vala} and Michal {Horák}",
title="A Magnetic Method for Testing of Homogeneity of Fibre Concrete",
annote="Homogeneity of fibre concrete structures, characterized, from the macroscopic
point of view, by (nearly) constant volume fraction of randomly oriented fibre particles,
determines their mechanical, thermal, etc. properties, consequently their long-time behaviour,
reliability and range of user applications. Destructive validation of homogeneity is available
under laboratory conditions, but frequently impossible in situ. A reasonable alternative to the
radiographic control method can be based on stationary measurements of magnetic field
strength, thanks to the composite structure with ferromagnetic particles, incorporated in the
concrete matrix. The permanent magnet generates a (nearly) stationary magnetic field, whose
distribution is described by the Laplace equation, supplied by appropriate boundary
conditions, containing the effective relative magnetic permeability as just one material
parameter; the crucial problem is then to estimate some formally homogenized (with a
priori unknown permeability of fibres) as a function of , without the a priori knowledge of
permeability of particles. The paper demonstrates that in such case the numerical analysis of
solution of the Laplace equation can be avoided, thus is allowed to be evaluated directly,
using local measurements of the magnetic field strength from the Hall-effect-based
measurement and non-trivial MATLAB-supported computations, based on the least squares
optimization, supported by the Newton method for the numerical evaluation of roots of
nonlinear equations.",
booktitle="9th International Conference NDT 2011 Nedestruktivní testování v technických oborech",
chapter="76539",
howpublished="print",
year="2011",
month="december",
pages="19--29",
type="conference paper"
}
```