ELFT HÍRADÓ

[Van Peter <vpet AT phyndi.fke.bme.hu>]

21. Termo Tea 

-------------------------------------------------
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.
---------------------------------
Kozreadta: Van Peter