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

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

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

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

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

2 mm HD - Pullouts

Pullout Segmentation NC 2500 NC 500 NC 0.01 NC 0.0001

2-Point Statistics - Autocorrelations

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

PCA

PCA

Explained Variance

Basis Vectors

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)

Questions?

Band Segmentation

Pullout Segmentation

Brittle Facet Segmentation

Segmentation Results