Knowles Lecture

Friday, May 19, 2023
135 Gates•Thomas, Jim & Sandy Hall Auditorium

The 13th annual James K. Knowles Lectures and Caltech Solid Mechanics Symposium will be held on Friday, May 19, 2023, in the Jim & Sandy Hall Auditorium in Gates•Thomas. The James K. Knowles Lecture will be followed by the Solid Mechanics Symposium with presentations by current Caltech graduate students and postdocs.

The Lectures and Symposium are in memory of James K. Knowles, William J. Keenan, Jr. Professor of Applied Mechanics, Emeritus, who passed away on November 1, 2009. He is well known for his research contributions to the theory of nonlinear elasticity and the mathematical theories of materials and structures. Dr. Knowles inspired and influenced generations of students and scholars and authored over one hundred journal publications, as well as a textbook for graduate students entitled Linear Vector Spaces and Cartesian Tensors (Oxford University Press).

The Lectures and Symposium will be held annually and are made possible by the Division of Engineering and Applied Science and the support of family, friends and colleagues through donations to the James K. Knowles Memorial Fund.

James K. Knowles Lecture

R. Narasimhan, Department of Mechanical Engineering, Indian Institute of Science, Bangalore

Fracture Behavior of Magnesium: Mechanisms and Mechanics

Magnesium alloys are attractive from the standpoint of lightweight applications owing to their low density and high specific strength. However, their use has been limited due to poor ductility and fracture toughness at room temperature. In this lecture, fracture experiments conducted using single crystal Mg as well as a basal textured Mg alloy will be described. The former tests show that the crack grows stably along the twin-matrix interface and gets deflected at twin-twin intersections. The latter tests demonstrate that increase in notch root radius, temperature, loading rate and mode I component impede twinning near the tip leading to brittle-ductile transition and strong enhancement in the toughness. However, in all the experiments it is found that twinning can contribute significantly towards dissipation and toughness. Analyses conducted using crystal plasticity will also be described to understand some of these effects.

R. Narasimhan received his Bachelor's degree in Mechanical Engineering from Indian Institute of Technology, Madras, in 1982, and Masters and Doctoral degrees from California Institute of Technology in 1983 and 1986. After working for four years at Indian Institute of Technology, Bombay, he joined the Indian Institute of Science, Bangalore, in 1991, where he is presently Professor of Mechanical Engineering. His research interests are Computational Solid Mechanics, Nonlinear and Dynamic Fracture Mechanics. He is a Fellow of Indian National Science Academy, Indian Academy of Sciences and Indian National Academy of Engineering. Also, he has served as member of the Editorial Boards of International Journal of Fracture, Journal of the Mechanics and Physics of Solids and Mechanics of Materials.