Micromechanics approach is employed to investigate the constraint effect on post-yield fracture toughness. Relationships between the conventional post-yield fracture toughness values, J1c and δc, and crack tip constraint characterized by the crack tip stress triaxiality are derived on the basis of an improved micromechanics criterion for ductile fracture. Then, new crack tip parameters Jmc and δmc (and associated new criteria for ductile fracture) are proposed, in which the effects of crack tip deformation and constraint are taken into account. Experiments show that both Jmc and δmc are material constant independent of stress state or specimen geometry. They can serve as new post-yield fracture toughness parameters to differentiate the fracture toughness of engineering materials, which provide new approaches for fracture assessments of engineering structures.

1.
Al-Ani
A. M.
, and
Hancock
J. W.
,
1991
, “
J-Dominance of Short Cracks in Tension and Bending
,”
Journal of the Mechanics and Physics of Solids
, Vol.
39
, pp.
23
43
.
2.
Hancock
J. W.
, and
Mackenzie
A. C.
,
1976
, “
On the Mechanisms of Ductile Fracture in High-Strength Steels Subjected to Multiaxial Stress-State
,”
Journal of the Mechanics and Physics of Solids
, Vol.
24
, pp.
147
169
.
3.
Hancock
J. W.
, and
Cowling
M. J.
,
1980
, “
Role of state of stress in crack tip failure process
,”
Metal Science
, Vol.
14
, pp.
293
304
.
4.
Hom
C. L.
, and
McMeeking
R. M.
,
1985
, “
Three-Dimensional Void Growth Before a Blunting Crack Tip
,”
Journal of the Mechanics and Physics of Solids
, Vol.
37
, pp.
395
415
.
5.
Li
G.
,
Li
X.
,
Li
C.
, and
Cao
S.
,
1989
, “
A Micro- and Macro Analysis of Strain at Crack-Tip
,”
Engineering Fracture Mechanics
, Vol.
32
, pp.
499
508
.
6.
Liu
H. W.
, and
Zhuang
T.
,
1985
, “
A Dual-Parameter Elastic-Plastic Fracture Criterion
,”
International Journal of Fracture
, Vol.
27
, pp.
R87–R91
R87–R91
.
7.
Marini
B.
,
Mudry
F.
, and
Pineau
A.
,
1985
, “
Study of Cavity Growth in Ductile Rupture of A508 Steel Under Nonradial Loading
,”
Engineering Fracture Mechanics
, Vol.
22
, pp.
375
386
.
8.
Matsoukas
G.
,
Cotterell
B.
, and
Mai
Y. W.
,
1986
, “
The Effect of Geometry on the Crack Opening Displacement of a Low Carbon Steel
,”
Engineering Fracture Mechanics
, Vol.
23
, pp.
661
665
.
9.
O’Dowd
N. P.
, and
Shih
C. F.
,
1991
, “
Family of Crack-Tip Fields Characterized by a Triaxiality Parameter: Part I—Structure of Fields
,”
Journal of the Mechanics and Physics of Solids
, Vol.
39
, pp.
989
1015
.
10.
Rice
J. R.
, and
Tracey
D. M.
,
1969
, “
On the Ductile Enlargement of Void in Triaxial Stress Fields
,”
Journal of the Mechanics and Physics of Solids
, Vol.
17
, pp.
201
217
.
11.
Ritchie
R. O.
, and
Thompson
A. W.
,
1985
, “
On Macroscopic and Microscopic Analyses for Crack Initiation and Crack Growth Toughness in Ductile Alloys
,”
Metallurgical Transactions A
, Vol.
16A
, pp.
233
248
.
12.
Shi
Y. W.
,
1989
, “
Critical Void Growth for Ductile Rupture of Steel Welds
,”
Engineering Fracture Mechanics
, Vol.
34
, pp.
901
907
.
13.
Shi, Y. W., Zhu, D. H., and Fu, J. M., 1986, “Fracture Strain and Void Development in Mild Steel and Weld Metals,” Proceedings of the Second International Conference on Structural Failure, Product Liability, and Technical Insurance, Vienna, Interscience Enterprises Ltd., pp. 648–656.
14.
Sun, J., 1989, “Ductile Damage and Elasto-Plastic Fracture Behaviour of Materials in Triaxial Stress State” (in Chinese), Ph.D. thesis, Xi’an Jiaotong University, Xi’an, China.
15.
Sun
J.
,
Deng
Z. J.
,
Li
Z. H.
, and
Tu
M. J.
,
1989
, “
Constraint Intensity in Crack Tip Field and Elasto-Plastic Fracture Criterion
,”
Engineering Fracture Mechanics
, Vol.
34
, pp.
413
418
.
16.
Sun
J.
,
Deng
Z. J.
,
Li
Z. H.
, and
Tu
M. J.
,
1990
, “
Stress Triaxiality in Crack Tip Region of Bend Specimens With Different Crack-Depth and Fracture Criterion at Initiation
,”
Engineering Fracture Mechanics
, Vol.
36
, pp.
321
326
.
17.
Wang
T. J.
,
1992
a, “
Improved Local Void Growth Ratio Criterion for Ductile Fracture
,”
International Journal of Fracture
, Vol.
57
, pp.
R3–R6
R3–R6
.
18.
Wang
T. J.
,
1992
b, “
Unified CDM Model and Local Criterion for Ductile Fracture II. Ductile Fracture Local Criterion Based on the CDM Model
,”
Engineering Fracture Mechanics
, Vol.
42
, pp.
185
193
.
19.
Wang
T. J.
,
1992
c, “
A Note on the New Local Damage Criterion for Ductile Fracture Under Non-Proportional Loading
,”
International Journal of Fracture
, Vol.
54
, pp.
R23–R29
R23–R29
.
20.
Wang
T. J.
,
1994
, “
Further Investigation of a New Continuum Damage Mechanics Criterion for Ductile Fracture: Experamental Verification and Applications
,”
Engineering Fracture Mechanics
, Vol.
48
, pp.
217
230
.
21.
Zheng, C. Q., Zhou, L., and Liu, J. M., 1987, “The Criterion of Critical Void Growth Rate and Its Applications,” Mechanical Behaviour of Materials-V, ICM-5, Vol. 1, Pergamon Press, Oxford, U.K., pp. 213–218.
22.
Zhuang
T.
,
1987
, “
Dual-Parameter Elastic-Plastic Fracture Criterion of Metals and Alloys in the Plane Strain Condition
,” (in Chinese),
Acta Mechanica Sinica
, Vol.
19
(Sup.), pp.
154
161
.
This content is only available via PDF.
You do not currently have access to this content.