fracture mechanics

Homework 1 - Self description

Submitted by Flavio Souza on Mon, 02/19/2007 - 21:06

Spring 2007

I am currently enrolled at University of Nebraska-Lincoln. The main courses I've taken in Solid Mechanics are Continuum Mechanics and Advanced Finite Element Method (currently taking). My undergraduate and Master major is Civil Engineering, both obtained in my home country Brazil. I would say that my strength related to this course is my motivation to understand the complex physical process of cracking, and my weakness is probably the fact that I don't have a good background in Fracture Mechanics. I am curretly pursuing my PhD at UNL under supervision of Dr. David Allen. Unfortunately our group doesn't have a published website. I am currently working on the development of a multi-scale computational model for predicting the evolution of damage in composites subject to impact loading. So, a better understanding of fracture mechanics and of the physical process underlying cracking will be of major importance to my research work. Finally, as fracture mechanics is present in any engineering application, I am sure it will greatly improve my education in a general basis.

Lecture 6 Channel cracks in thin films

Submitted by Zhigang Suo on Mon, 02/19/2007 - 20:50

Various cracks in thin films under tensile or compressive stresses
Micrographs of cracks in thin films
A micrograph of a channel crack
The origin of stress in a film
Stress in a thin film due to mismatch in the coefficients of thermal expansion
Stress in film due to bending
Measure redisual stress using wafer curvature
Channel crack: initiation vs. steady propagation
Steady-state energy release rate of a channel crack
Channel crack in patterned structure

lecture 5

Submitted by John W. Hutchinson on Fri, 02/16/2007 - 19:32

Lecture 5

Submitted by John W. Hutchinson on Thu, 02/15/2007 - 18:06

Lecture 5

Lecture 4

Submitted by John W. Hutchinson on Tue, 02/13/2007 - 14:23

Lecture 4

Interfacial toughness and mode mixity

Submitted by Jae-Hyun Kim on Mon, 02/12/2007 - 21:42

When I was a graduate student, I spent several months to measure interfacial toughness between metalic (Cu and Au) films and thick substrates(Si and Polycarbonate). My methods were bulge test (blistering test) and 4-point bending test. I had many problems such as making an initial crack(pre-cracking), changing load phase angle applied to specimens, preparing/patterning thin films, constructing my own test apparatus, etc. The biggest problem was to measure the interfacial toughness over a wide range of loading phase angle. For a bimaterial with a non-zero oscillatory index(epsilon), we don't know the phase angle for a minimum interfacial toughness beforehand. Therefore, we need to measure the interfacial toughness over a wide range of phage angle. For engineering purpose, we need a minimum interfacial toughness value for reliability design because this value will lead to a conservative design of systems.