Predicting elastic strain fields in defective microstructures using image colorization algorithms

In this work, an image colorization algorithm based on convolutional neural networks is explored as an approach to predict tensile plane-strain field components of microstructures featuring porosity defects. For the same, microstructures featuring porosity of various shapes, sizes, area fractions and number densities were sampled on the gage section of ASTM-E8 sized numerical specimens whose tensile deformation was simulated in plane strain mode using commercial finite element analysis package Abaqus. Subsequently, the image colorization algorithm was trained by treating the microstructure featuring porosity defects as the gray scale image, and its strain field components as its color layers, analogous to the red-green-blue color components of traditional digital representations of images. Towards the same, various CNN frameworks were tested for optimization of its parameters, viz. number of layers, number of filters in each layer, stride, padding, and activation function. An optimized CNN framework is presented that is able to predict strain fields on randomly sampled microstructures with high accuracy R²>0.91 at a fraction of the time that finite element analysis would take. Various cross-validation tests were performed to test the accuracy and robustness of the CNN in learning features of various microstructures. Results indicated that the CNN algorithm is extremely robust and can provide near-accurate strain fields in generic scenarios.