Short-rod elastic-plastic fracture toughness test using miniature specimens |
| |
Authors: | C T Wang R M Pilliar |
| |
Affiliation: | (1) Centre for Biomaterials, University of Toronto, 124 Edward Street, M5G 1G6 Toronto, Ontario, Canada |
| |
Abstract: | The standard ASTM-E399 plane-strain fracture toughness (K
IC) test requires (1) the test specimen dimensions to be greater than a minimum size and, (2) fatigue precracking of the specimen. These criteria render many materials impractical to test. The short-rod elastic-plastic plane-strain fracture toughness test proposed by Barker offers a method of testing not requiring fatigue precracking and furthermore, it appears that test specimens smaller than that stipulated by ASTM can be used to obtain validK
IC values. In this study, the use of a modified miniature short-rod fracture toughness test specimen was investigated. Our miniature short-rod specimen is approximately 7 mm long and 4 mm diameter. These mini specimens are well suited for the purpose of testing biomaterials. The value of the minimum stress intensity factor coefficient (Y
m
*
) for the mini short-rod specimens was determined experimentally using specimens machined from extruded acrylic rod stock. An elastic-plastic fracture toughness analysis using the mini specimens gave values ofK
IC for extruded acrylic (nominally PMMA) equal to 0.67 ± 0.06 MPa m1/2. The problem of testing non-flat crack growth resistance curve materials (such as PMMA) using the short-rod fracture toughness test method is discussed. A modification to the test procedure involving the use of aY
* value corresponding to a short crack length is suggested as a method of overcoming this difficulty.Nomenclature
a
crack length
-
a
0
initial crack length
-
a
1
length of the chevron notch on the mini short-rod specimen
-
a
m
critical crack length — crack length atY
m
*
-
C
specimen compliance
-
C
dimensionless specimen compliance = CED
-
D
mini short-rod specimen diameter
-
E
Young's modulus
-
K
1
stress intensity factor
-
K
1C
plane-strain fracture toughness
-
K
max
fracture toughness calculated usingP
max
- P
load applied to the test specimen during a short-rod fracture toughness test
-
P
c
load applied to the test specimen atY
m
*
-
P
max
maximum load applied to the specimen during a short-rod fracture toughness test
-
p
plasticity factor
-
W
mini short-rod specimen width
-
Y
*
stress intensity factor coefficient
-
Y
m
*
minimum of the stress intensity factor coefficient
-
dimensionless crack length =a/W
-
0
dimensionless initial crack length =
0/W
-
1
dimensionless chevron notch length =a
1/W
-
m
dimensionless critical crack length =a
m/W |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|