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ASTM Selected Technical Papers
Fracture Toughness and Slow-Stable Cracking
By
PC Paris
PC Paris
Chairman of symposium committee
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GR Irwin
GR Irwin
1Department of Mechanical Engineering,
University of Maryland
,
College Park, Md
.
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ISBN-10:
0-8031-0367-0
ISBN:
978-0-8031-0367-2
No. of Pages:
319
Publisher:
ASTM International
Publication date:
1974

Fracture mechanics, acoustic emission, and fractography were used to study the process of crack growth in 2-in. thick double cantilever beam specimens of a low-alloy steel over a wide temperature range. KIc values ranged from 33 ksi√in. at -200°C to 240 ksi√in. at +18°C. The acoustic emission rate rose steadily with load up to fast fracture. Changes in the emission amplitude distribution were observed shortly before fracture at one of the warmer temperatures. Emission during load holds was measured and emission waveforms were photographed. Fractography showed a small region of ductile tearing prior to fast fracture at warmer temperatures. A model of the interaction of ductile tearing and cleavage fracture is proposed. Ductile tearing is seen as a process taking time and strongly dependent on temperature. Cleavage is seen as a rapid process averted by ductile flow and tearing. Emissions are believed to be produced by plastic zone growth and by cleavage. The experimental facts can be consistently interpreted through this small set of assumptions.

1.
Turner
,
C. E.
and
Radon
,
J. C.
, “
Fracture Toughness Measurements in Low Strength Structural Steels
,” Paper 14,
Proceedings
, 2nd International Conference on Fracture,
Brighton
,
04
1969
.
2.
Pollock
,
A. A.
and
Radon
,
J. C.
, “
Acoustic Emission in the Fracture Toughness Test of a Mild Steel
,” Document IIW-X-595-70, Lausanne, Switz,
1970
.
3.
Nakamura
,
Y.
,
Veach
,
C. L.
, and
McCauley
,
B. O.
in
Acoustic Emission
, ASTM STP 505,
American Society for Testing and Materials
,
1972
, pp. 164–186.
4.
Pollock
,
A. A.
,
Nondestructive Testing
, Vol.
6
, No.
5
,
10
1973
, pp. 264–269.
5.
Harris
,
D. O.
,
Dunegan
,
H. L.
, and
Tetelman
,
A. S.
, “
Prediction of Fatigue Lifetime by Combined Fracture Mechanics and Acoustic Emission Techniques
,” Technical Bulletin DRC-105,
Dunegan/Endevco Corp.
,
1970
.
6.
Pollock
,
A. A.
and
Smith
,
B.
,
Nondestructive Testing
, Vol.
5
, No.
6
,
12
1972
.
7.
Radon
,
J. C.
and
Pollock
,
A. A.
,
Engineering Fracture Mechanics
 0013-7944, Vol.
4
,
1972
, pp. 295–310.
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