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Speaker
Name/Affiliation: Anthony R. Ingraffea Cornell University

Date:

Friday March 30 2007

Start Time: 11:00a.m.

End Time: 12:0

0p.m.

Location (other): ACE 6.304

Host: Keshav Pingali
<

br>Talk Title: Multi-Scale Computational Simulation of Fatigue Cracking Pr

ocesses in Aluminum Alloys

Talk Abstract:
We are developing physi

cs-based models for simulating nucleation and propagation of fatigue cracks
in aluminum alloys. Our models are part of a DARPA-funded broad-team proj

ect on structural integrity prognosis. The salient features of our approach
are:

A.%09The use of statistically representative realistic micros

tructures as a starting point for our simulations. Using unique microstruc

ture builder tools we assemble three-dimensional digital material represen

tations from actual microstructural observations. These contain realistic

morphologies textures particle distributions etc. Constituents are assi

gned statistically representative distributions of properties such as yield
strengths and toughnesses.

B.%09The use of polycrystal plasticity

models to accurately compute stress and strain fields in polycrystals using
the finite element method. In polycrystalline metals the grain structure

and phenomena occurring on the grain scale such
as interactions betwee

n grains and particles and crystallographic slip strongly influence the fa

tigue behavior of the materials. Statistically realistic 3D microstructure

s are directly simulated in order to investigate the effect of elasto-plast

ic response within the microstructure on the fatigue behavior.

C.%0

9The use of an explicit geometric representational approach in a multi-scal

e methodology. At each length scale fatigue crack precursors such as grai

n boundary or particle decohesion are represented geometrically in the fin

ite element model and allowed to evolve through changes in the underlying

geometric and mesh models. The need for concomitant quantitative
ex

perimental data on microstructural damage nucleation (particle fracture de

bonding etc) becomes apparent.

I will report on progress in develop

ment verification and validation of our simulation models and show examp

le simulations.