Examples of Current Research in“State Awareness” for Digital Models:

ICME and NDE Links to Structural Analysis

Michael EnrightCraig McClung

Southwest Research InstituteSan Antonio, Texas

Digital Twin Roadmap WorkshopNASA Langley Research Center

September 10-11, 2012

Examples of Current Research in “State Awareness” for Digital Models

Goal of “State Awareness”:

•Incorporate relevant digital information about the condition of the material/component into the digital models for calculation of life and reliability

Examples:

•Calculate full-field, location-specific bulk residual stress or microstructure resulting from the manufacturing process, and use the information to inform the fatigue crack growth life and reliability predictions

•Calculate location-specific Probability-of-Detection (POD) curves and use the information to inform the structural reliability prediction

DARWIN OverviewDesign Assessment of Reliability With INspection

Probabilistic Fracture Mechanics

Probability of DetectionAnomaly Distribution

Finite Element Stress Analysis

Material Crack Growth Data

NDE Inspection Schedule

Pf vs. Cycles

Risk Contribution FactorsLife Scatter

Stress Scatter

3Copyright 2012 Southwest Research Institute

Integration with Manufacturing Process Simulation

Link DEFORM output with DARWIN input Finite element geometry (nodes and elements) Finite element stress, temperature, and strain results Residual stresses at the end of processing / spin test Location specific microstructure / property data Tracked location and orientation of material anomalies

4Copyright 2012 Southwest Research Institute

DARWIN-DEFORM Links

Residual Stresses Microstructure

Anomaly Tracking and Deformation5

Copyright 2012 Southwest Research Institute

Effect of Material Processing Residual Stress on FCG Life

Stress

Life

Without Residual Stress With Residual Stress

6Copyright 2012 Southwest Research Institute

Effect of Material Processing Residual Stress on Risk

Life

Without Residual Stress With Residual Stress

Risk

7Copyright 2012 Southwest Research Institute

DARWIN-DEFORM Links

Residual Stresses Microstructure

Anomaly Tracking and Deformation8

Copyright 2012 Southwest Research Institute

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Demonstration Example: Influence of Grain Size Scaling on Life & Risk

ANSYSABAQUSDEFORM

DEFORM

DARWIN

StressResults

Files

Grain SizeResults

Filegrain size contour

service stress contour

Copyright 2012 Southwest Research Institute

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Influence of Grain Size Scaling on Crack Growth Rate

*

*

da D daf

dN D dN

grain size contour

crack growth rate multiplier

C=1.56 x 10-11

n2=3.66

Nominal values:

Copyright 2012 Southwest Research Institute

Effect of Location-Specific Grain Size Scaling on FCG Life

a=0.01”

Without Grain Size Scaling With Grain Size Scaling

a=0.02”

11Copyright 2012 Southwest Research Institute

Effect of Location-Specific Grain Size Scaling on Risk

Life

Without Grain Size Scaling With Grain Size Scaling

Risk

a=0.01”

12Copyright 2012 Southwest Research Institute

Overall Vision to LinkDEFORM & DARWIN

Phase I/II Work

Phase II Work

Future work

Residual Stresses

13Copyright 2012 Southwest Research Institute

Example: Random Residual Stress Modeling

• Design of Experiments Identify values of input variables for response surface

construction in DEFORM using Latin Hypercube sampling Perform deterministic DEFORM runs to determine residual

stress values at all nodes within FE model

• Response Surface Fitting Determine the residual stress response at selected locations

within the FE model in DARWIN using Gaussian Process (GP) model

Determine response along the crack path in DARWIN using GP model combined with Principal Components Analysis

• Monte Carlo Simulation Propagate random variables through response surface in

DARWIN to determine the random residual stresses along the crack path and influence on life and risk values

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Design of Experiments

Response Surface

Monte CarloCopyright 2012 Southwest Research Institute

Awareness of Existing Cracks:NDE POD Considerations

• The DARWIN analysis framework permits reduction of risk based on finding cracks during occasional NDE inspections

• Key random inputs to this calculation are the uncertain time of inspection and the POD curve

• The POD curve depends on inspection method/calibration and could also vary from location to location

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Linking DARWIN with MAPOD

• Model-assisted POD technology (based on the same digital component models) can be used to generate location-specific POD curves for improved reliability analysis

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Conclusions

• Some of the fundamental elements of “state awareness” for life and reliability management using digital structural models and advanced commercial software are already under development

• More work is needed!

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