Mechanisms and Kinetics of Brittle Fracture
Alexander Chudnovsky
Department of Civil and Material Engineering, University of Illinois at Chicago
Abstract
A domain of dense strain localization surrounding and preceding the crack growth (plastic zone, damage zone or, in general, process zone (PZ)) is commonly observed in engineering materials. A closely coupled system of crack and PZ is referred to as crack layer (CL). Slow CL growth results from a) strong interactions between the crack, process zone (PZ) and the rest of the solid, and b) degradation processes of the PZ material. CL thermodynamic forces are conventionally presented as the negative derivative of Gibbs free energy of the solid containing CL with respect to CL parameters. CL constitutive equations are formulated in form of Onsager equations, i.e., linear relations between the rates of crack and PZ growth and corresponding thermodynamic forces. Numerical solution of CL growth equations suggests a complex kinetics of slow CL growth. Continuous, discontinuous and transient CL growth predicted by CL model is experimentally confirmed.
The experimental examination of CL model is conducted using specially design experimental setup, since it is difficult to observe in-situ the mechanisms and kinetics of crack and PZ growth in non-transparent materials. The micro-mechanisms of CL growth is observed by means of optical and SEM microscopy. It is shown that the complexity of CL growth is related to a ductile-brittle transition taking place on the micro scale within PZ. Applications of CL model and the challenges for accelerated testing for lifetime are also discussed.
Biography
Presently A. Chudnovsky is UIC Distinguished Professor Emeritus and Director of Fracture Mechanics & Materials Durability Laboratory at Civil and Materials Engineering Department of The University of Illinois at Chicago. Professor Chudnovsky received his education in the former Soviet Union. In 1980 he became a professor at Case Western Reserve University, Cleveland, OH. From 1987 till 2010 he is Professor of Mechanics and Materials at Civil and Materials Engineering Department of UIC and Director of UIC Fracture Mechanics and Materials Durability Laboratory. In 2001 he is awarded the title of UIC Distinguished Professor.
Among scientific accomplishments of Professor Chudnovsky there are Mathematical Theory of Elastomers, Entropy Criterion of Local Failure, Statistical Fracture Mechanics, Crack Layer Model and more recent Geometrical Modeling of Material Aging. He has published a monograph (in Russian) and more than 300 technical papers; graduated 42 Ph.D. students. Prof. Chudnovsky has a wide range of research interests: Statistical Thermodynamics and Thermodynamics of Irreversible Processes, Critical Phenomena, Fracture Mechanics, Application of Probability and Statistics in Engineering Design, Materials Durability and Structural Reliability. In his consulting services he conducts forensic studies, reliability assessments of engineering structures and lifetime prediction for metals, polymers, composites and rocks, as well as for new breed of materials for microelectronics and photonics applications.