SEMINAR: Multi-Scale Computational Models for Predicting Fatigue Crack Nucleation in Metallic Materials

Abstract:

Structural components are often subjected to cyclic loading and their fluctuations in service conditions. This results in their time-dependent fatigue failure. Fatigue in structural materials has been a topic of interest to researchers for decades. However, with the advent of recent research initiatives like the Integrated Computational Materials Engineering (ICME), research in this field has taken an exciting new dimension. By coupling sophisticated tools of Computational Mechanics and Computational Materials Science, these initiatives are enabling computational models to probe into the origins of cracking at multiple scales due to inhomogeneous plastic flow and follow their evolution to failure. This talk will introduce an approach to the development a multi-scale computational framework for physics-based modeling of fatigue crack nucleation and evolution, in polycrystalline metallic materials. Titanium alloys will be a specific focus in this study. The talk will begin with methods for generating 3D statistically equivalent representative virtual images and representative volume elements from experiments on material characterization. An experimentally validated crystal plasticity finite element (CPFE) model will be discussed for predicting microstructural deformation under monotonic and cyclic loading. The CPFE simulations will provide a platform for the development of physics-based crack nucleation model that accounts for microstructural inhomogeneity. Accelerated simulations for a large number of cycles leading to fatigue crack nucleation will be accomplished by a wavelet transformation based multi-time scaling (WATMUS) algorithm. This method significantly enhances computational efficiency in comparison with conventional single time-scale integration methods. Subsequently, the development of parametrically homogenized constitutive models (PHCM) will be discussed for macroscopic analysis. The PHCM explicitly accounts for microstructural morphology and crystallography through model parameters in the constitutive functions. The talk will conclude with a case study on the necessity of multi-scale models for predicting fatigue crack nucleation.

Biography:

Dr. Somnath Ghosh is the Michael G. Callas Professor in the Department of Civil Engineering and Professor of Mechanical Engineering and Materials Science & Engineering at Johns Hopkins University. He is the founding director of the JHU Center for Integrated Structure-Materials Modeling and Simulation (CISMMS) and was the director/PI of the Air Force Center of Excellence in Integrated Materials Modeling (CEIMM). His research focuses on multi-scale structure-materials analysis and simulations, multi-physics modeling and simulation of multi-functional materials, materials characterization, process modeling, and emerging fields like Integrated Computational Materials Engineering (ICME). He has conducted pioneering research to advance the field of integrated computational structure-materials modeling into new areas of importance and challenges.