100 Years and Still Cracking: A Griffith Fracture Symposium: Fracture and Cracks
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Megan Cordill, Erich Schmid Institute of Materials Science; William Gerberich, University of Minnesota; David Bahr, Purdue University; Christopher Schuh, Northwestern University; Daniel Kiener, Montanuniverstität Leoben; Neville Moody; Nathan Mara, University of Minnesota; Erica Lilleodden, Fraunhofer Insitute for Microstructure of Materials and Systems (IMWS)

Wednesday 8:30 AM
March 17, 2021
Room: RM 47
Location: TMS2021 Virtual

Session Chair: Nathan Mara, University of Minnesota

8:30 AM  Invited
Modeling Mechanics of Nanoparticles: Everything but Size: Jonathan Amodeo¹; Laurent Pizzagalli²; ¹MATEIS lab, INSA-Lyon Univ. Lyon CNRS; ²P' institute, Univ. Poitiers CNRS
     In recent years, several modeling groups focused on probing the strength, ductility and deformation processes of nanoparticles (NPs) using molecular dynamics, especially to support compression tests within the electron microscopes. Now, studies deal with most of materials classes (e.g., metals, semi-conductors, oxides) including various shapes (e.g. spheres, icosahedron structures, cubes). The NP size ranges from clusters of 1-5 nm up to one hundred nm, which overlaps with the experimental range. In this talk, we will first present the main features of NPs mechanical properties through a broad literature review and recent studies performed in our respective laboratories. A specific attention will be paid to the influence of several new key-parameters as shape, types of defects and surface state based on recent atomic scale and dislocation dynamics simulations. Finally, we will conclude this prospective talk by underlining the current strengths and weaknesses of existing investigation methods.

9:10 AM
The Curious Phenomenon of Prince Rupert's Drops: Koushik Viswanathan¹; Hillar Aben²; Munawar Chaudhri³; Srinivasan Chandrasekar⁴; ¹Indian Institute of Science; ²Tallinn University of Technology; ³University of Cambridge; ⁴Purdue University
    We discuss the peculiar fracture behavior of thermally quenched glass drops – first demonstrated dramatically by Prince Rupert of Bavaria in the 16th century, and hence bearing his name. Prince Rupert’s drops are tadpole-shaped drops, typically made from soda lime glass with high thermal expansion coefficient. The head of a drop can withstand impact or even compression loads of up to 15000 N, but its tail breaks with minimal finger pressure, with complete catastrophic disintegration. Using techniques of high-speed photography (~ two million fps) and integrated photoelasticity, we explain, both, the drop’s explosive disintegration, a consequence of repeated crack bifurcation events; and its high impact strength, arising from large surface compressive residual stress. We also provide a theoretical basis for these observations based on considerations of crack dynamics and thermal stresses. The phenomenon of Rupert’s drops offers a beautiful illustration of multiple aspects of Griffith’s pioneering work.

9:30 AM
Effect of Aspect Ratio on Stress Intensity Factor Solutions for Single Edge Notch Wire Fracture Test Specimen under Tensile and Clamped Bend Loading Conditions: Hrushikesh Sahasrabuddhe¹; Ashwini Mishra¹; Nagamani Jaya Balila¹; ¹India Institute of Technology Bombay
    Finite element analysis has been employed to evaluate the stress intensity factors ahead of a straight fronted surface crack in a cylindrical rod specimen in tension & clamped bend loading. Closed form 3-dimensional as well as 2-dimensional stress intensity factor solutions have been derived in terms of the relative crack depth, wire aspect ratio as alternatives to existing solutions. Our study establishes the strong influence of wire aspect ratio on the geometric factor which were ignored in the studies carried out earlier. Experimental validation of the geometric factor solutions is obtained by testing them against a brittle linear elastic polymeric material - PMMA, with a known mode 1 notch toughness (K_1Q). The results are explained in terms of the stress state ahead of such an asymmetric notch and the boundary conditions that result out of the loading constraints under tension and clamped bending.