Studies of the mechanical properties of solids with random porosity.
Item
-
Title
-
Studies of the mechanical properties of solids with random porosity.
-
Identifier
-
AAI9009757
-
identifier
-
9009757
-
Creator
-
Li, Rong.
-
Contributor
-
Adviser: Arthur Paskin
-
Date
-
1989
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Physics, General | Physics, Condensed Matter
-
Abstract
-
The 2-D and 3-D mechanical behavior of a solid with random porosity was studied experimentally. For 2-D samples, the elasticity and fracture stress could be well described by an effective modulus derived from an effective medium theory (EMT) in the dilute crack region. The elastic modulus and fracture stress decrease linearly with increasing {dollar}\phi{dollar}, the fraction of the missing bonds in the system where E {dollar}\sim{dollar} (1-{dollar}\alpha\phi{dollar}), with {dollar}\alpha{dollar} {dollar}\approx{dollar} 3.3 for honeycomb lattice and {dollar}\approx{dollar}2 for square lattice. According to EMT, the initial slope of the fracture stress as a function of {dollar}\phi{dollar} should be 3.6 for honeycomb lattice and 1.8 for square lattice. The fracture behavior of the system can be identified by the {dollar}\alpha{dollar} value in the Weibull distribution, which describes the dispersion of crack-size distributions of the specimen. In the scaling region, the experimental results show that the elastic modulus exponent, f, equals 3.1 {dollar}\pm{dollar} 0.2. The fracture exponent, F, obtained by applying the percolation concept to the Griffith relation, agrees with our experimental results which are 1.7 and 1.8 for honeycomb lattice and square lattice, respectively. The 3-D experiment involved a unique technique to prepare the specimen for a three-point bend test, namely an electrochemical dissolution process followed by an annealing process to form self-similar porous structures. The samples with larger-scale porosity had a lower Young's modulus and a higher fracture stress than samples with finer-scale porosity. In addition to these analytical differences in the sample, we discovered the existence of a ductile to brittle transition. We believe that this transition is effected by the size of the sample.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
