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Incubation & Nucleation Validation Study. SIPS TIM, October 22 nd 2007 Cornell and RPI. Eight peer-reviewed journal papers will be produced from the SIPS-related work being completed by Cornell and our M&S colleagues:

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Incubation nucleation validation study

Incubation & Nucleation Validation Study

SIPS TIM, October 22nd 2007

Cornell and RPI


Eight peer-reviewed journal papers will be produced from the SIPS-related work being completed by Cornell and our M&S colleagues:

  • January, 2008 – “A geometric approach to creating and meshing statistically accurate finite element models of AA7075-T651 microstructures”

  • January, 2008 – “A geometric approach to modeling microstructurally small crack fatigue crack formation part I: probabilistic simulation of constituent particle cracking in AA7075-T651”

  • May, 2008 – “A three-dimensional multiscale procedure for microstructurally small fatigue crack nucleation”

  • May, 2008 – “A geometric approach to modeling microstructurally small crack fatigue crack formation part II: verification and validation of incubation and nucleation criteria”

  • July, 2008 – “A geometric approach to modeling microstructurally small crack fatigue crack formation part III: simulation of stage I, intra-granular crack propagation in AA7075-T651”

  • January, 2009 – “A geometric approach to modeling microstructurally small crack formation, part IV: simulation of stage I, trans-granular crack propagation in AA7075-T651”

  • March, 2009 – “A geometric approach to modeling microstructurally small crack formation, part V: probabilistic simulation of stage I crack propagation in AA7075-T651”

  • May, 2009 – “A geometric approach to modeling microstructurally small crack formation, part VI: a probabilistic multiscale method for predicting microstructurally small fatigue life of AA7075-T651


Outline
Outline SIPS-related work being completed by Cornell and our M&S colleagues:

  • Previous Work

    • Incubation Filter

    • Nucleation Damage Metrics

  • Calibration & Validation

    • Objectives

  • Microstructure Replication Process

    • Model Generation

    • Preparation & Analysis

    • Results & Observations


Previous work incubation filter
Previous Work: Incubation Filter SIPS-related work being completed by Cornell and our M&S colleagues:

ND

RD

Determine particle strength,scr~ KIC / sqrt(particle size)

sp scr

no

yes


Max. accumulated slip on a single system: SIPS-related work being completed by Cornell and our M&S colleagues:

Max. accumulated slip on a single plane:

Total accumulated slip:

Work-based damage:

Fatemi-Socie damage:

Previous Work: Nucleation Damage Metrics

Definitions of relevant slip-based damage metrics:

Criterion: Nucleation occurs when Di ≥ Di,0


Calibration & Validation: Objectives SIPS-related work being completed by Cornell and our M&S colleagues:

Calibrate incubation & nucleation criteria:

  • Using 1 experimental observation of crack incubation, back calculate the parameter ‘C’

  • Using 1 experimental observation of crack nucleation, calibrate the parameter ‘Di,0’ for each damage metric

Using 13 additional observations, validate incubation criterion assumptions :

  • Maximum particle stress is accurately obtained when:

    • idealizing particle as an ellipsoid

    • only attaching the surrounding grain

  • Parameter ‘C’ is a material constant

Evaluate nucleation criteria using 5 additional observations:

  • Do any of the 5 slip-based damage metrics predict nucleation events for all observations?


Outline1
Outline SIPS-related work being completed by Cornell and our M&S colleagues:

7

  • Previous Work

    • Incubation Filter

    • Nucleation Damage Metrics

  • Calibration & Validation

    • Objectives

  • Microstructure Replication Process

    • Model Generation

    • Preparation & Analysis

    • Results & Observations


Microstructure Replication Process SIPS-related work being completed by Cornell and our M&S colleagues:

Detailed Microstructure

OIM

SEM

Physical Data

(from Northrop Grumman)

Particle

Particle

  • Take detailed microstructure from EBSD/OIM

  • Generate a simplified microstructure derivative based on phenomenological information

  • Assign crystal plasticity model, with measured orientations, to each grain

  • Mesh and apply notch strain

Computational Modeling

  • Test effect of simplifying the microstructure by comparing with results from detailed geometry

  • Record results, check for mesh convergence, and note numerical advantages for each simplified microstructure derivative


Model Generation: Detailed Microstructure SIPS-related work being completed by Cornell and our M&S colleagues:


Model Generation: Simplified Microstructure Derivatives SIPS-related work being completed by Cornell and our M&S colleagues:

No Small Grains @ Distance

Surrounding Grains Only

All Grains

No Small Grains

Small Grains Above/Below


Model Generation: Automated Routine SIPS-related work being completed by Cornell and our M&S colleagues:


Preparation and Analysis: Mesh SIPS-related work being completed by Cornell and our M&S colleagues:

All grains

Surrounding grains only


Preparation and Analysis: Notch Strain SIPS-related work being completed by Cornell and our M&S colleagues:

Questions for Northrop Grumman Inc.:

What is the exact notch strain for the first load cycle?

What is the notch strain history for subsequent load cycles?


Results and Observations SIPS-related work being completed by Cornell and our M&S colleagues:

sxx MPa

Surrounding Grains Only

All Grains

75 mm

100 mm

Coarse Mesh

Medium Mesh

Fine Mesh

x


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