1. Fracture Surface Analysis of Dual-Phase Steel
CSE 8803 – Materials Informatics
Karla Wagner
November 20, 2017

2. Goals: Objective Review
Failure mechanisms of DP980 are significant to automobile industry
No coating (NC) vs Galvannealed (GAN) DP980 Steels
Tested at distinct strain rates
Range over 7 orders of magnitude
Goals:
P-S linkage between microstructure, strain rate, and fracture mechanisms
f (ms, ) = fracture surfaces

3. Proposed Work Segment Fracture Surfaces Quantify Fracture Surfaces
Number and size distribution of various fracture features
Area fractions of all fracture features
Quantify Fracture Surfaces
2-pt Statistics
PCA
Model Building
Create model for process-structure linkage
Inputs: Original microstructure & strain rate
Output: Fracture surface statistics

4. Fracture Surface Segmentation
Experimental data – must be segmented
Feature definitions based on hand calculations
Some challenges:
4 “phases” – fracture features
Variance from image to image
Methods Used
Filters
Thresholding
Image closing and opening
Edge detection
Superpixels
Further Improvements
Customize code for each set of images

5. Segmentation Results
All provided images segmented
Area fractions of features calculated
Further improvements can only improve any modelling efforts
Dimples
Brittle Facets
Bands
Pullouts
Fully Segmented Image
Original Image

6. 2 mm HD - Pullouts

7. Pullout Segmentation
NC 2500
NC 500
NC 0.01 NC

8. 2-Point Statistics - Autocorrelations

9. PCA Results
May change based on segmentation improvements
May separate GAN and NC – dependent on model creation

10. PCA

11. PCA

12. Explained Variance

13. Basis Vectors

14. Improvements on segmentation
Next Steps
Improvements on segmentation
Customize segmentation code to images & image sets for accuracy
Iterate PCA if necessary
Include the rest of the GAN images
Possibly use these to validate model
Process-structure linkage
Regression based model(s)

15. Questions?

16. Band Segmentation

17. Pullout Segmentation

18. Brittle Facet Segmentation

19. Segmentation Results