Experiments and numerical simulations of initiation and growth of cracks under mixed mode i + iii loading

Abstract of the Talk

The problem of initiation and growth of cracks under combined mixed-mode I+III loading has received much attention in the literature over the past few decades both from experiments and analysis, but suitable failure criteria are still not available. Specifically, the existence of a threshold ratio of mode III to mode I stress intensity factors 〖K_III^∞/K〗_I^∞ below which fragmentation of the crack front (formation of daughter cracks) does not occur has been debated and the length scale associated with the spacing of the fragments when they do occur are still under debate. The continued growth of cracks under remote mode I + III loading is also of interest; it is observed that in some cases the fragmented cracks coalesce, while in others they maintain their independent development. We approach this problem through carefully designed experiments on polymers a nd gels to examine the physical aspects of crack initiation and growth. This is then explored further through numerical simulations of the stress state that explore the influence of perturbations on the formation of daughter cracks. Finally, the direct numerical simulation of crack initiation and growth is explored using a phase-field model. The model is first validated for in-plane modes I + II through comparison to experiments, and then used to explore combined modes I + III.

Biography of the Speaker :

Professor Ravi-Chandar received his bachelor’s degree in Physics from Bangalore University in 1973; and his diploma in Aeronautical Engineering, with honors, from the Madras Institute of Technology in 1976. He received his MS and Ph.D. in Aeronautics from the California Institute of Technology, in 1977 and 1982. He current ly holds the MC (Bud) and Mary Beth Baird Endowed Chair at the Department of Aerospace Engineering and Engineering Mechanics at The University of Texas at Austin. Dr. Ravi-Chandar’s research interests are in the general area of mechanics of materials. He is the Editor-in-Chief of the International Journal of Fracture. He has served on numerous professional organizations: member of the US National Committee on Theoretical and Applied Mechanics (2003-2022; Vice-Chair: 2016-2018; Chair 2018-2020; Past-Chair 2020-2022); member of the Congress Committee of the International Union of Theoretical and Applied Mechanics (2010-2018); President of the American Academy of Mechanics (2010-2012); and President of the International Congress on Fracture (2005-2009); Executive Committee of the Applied Mechanics Division of the ASME (2003-2008). He is a fellow of the ASME, the Society for Experimental Mechanics, and the American Academy of Mechanics, an Honorary Fellow of the International Congress on Fracture, and a Founding Fellow of the Indian Structural Integrity Society. He received the Murray Medal from the Society for Experimental Mechanics in 2004, the Drucker Medal for the American Society of Mechanical Engineers in 2015, the Prage r Medal from the Society for Engineering Science in 2020, and the Yakeo Yokobori Gold Medal from the International Congress on Fracture in 2023.

Organized by:

InSIS and Center for Structural Integrity of Safety Critical Systems, IIT Madras