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**From**: Van Peter <vpet AT phyndi.fke.bme.hu>**To**: fizinfo AT sunserv.kfki.hu**Cc**:**Subject**: [Fizinfo] Termo Tea**Date**: Tue, 30 Sep 2003 14:56:37 +0200**List-archive**: <http://sunserv.kfki.hu/pipermail/fizinfo>**List-id**: ELFT HÍRADÓ <fizinfo.lists.kfki.hu>

21. Termo Tea

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2003, oktober 6. hetfo, 14.00

BME, Kemiai Fizika Tanszek, F ep. III lcsh. I em., jobbra

Christina Papenfuss (Technical University of Berlin, Germany)

Mesoscopic theory of material damage

Abstract:

The subject of the presentation is the damage of brittle

materials caused by growth of microcracks. In the model the cracks

are penny shaped. They can only enlarge, but not heal, a fact that

is denoted as unilateral dynamics. For the single crack a simple

growth law is assumed: There is crack growth only if tension is

applied normal to the crack surface, exceeding a critical value.

This critical tension is taken from a Griffith-type energetic

consideration. For the length change velocity an expression is

assumed, which is motivated by Rice model, i.e. by thermodynamic

considerations.

The aim is to investigate the effect of crack growth on

macroscopic constitutive quantities. A possible approach taking

into account such an internal structure within continuum mechanics

is the so called mesoscopic theory. A distribution of crack

lengths and crack orientations within the continuum element is

introduced, and a differential equation for this distribution

function is derived. Macroscopic quantities are calculated as

averages with the distribution function. A macroscopic measure of

the progressing damage, i.e. a damage parameter, is the average

crack length. For this damage parameter we derive an evolution

equation. The differential equations for the crack distribution

function, as well as that for the average crack length are solved.

Finally, a simple model of opening cracks, is discussed. In this

case a (nonlinear) stress-strain relation can be predicted.

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Kozreadta: Van Peter

**[Fizinfo] Termo Tea**,*Van Peter, 09/30/2003*

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