The objective of this research was to obtain and compare constant and variable amplitude fatigue behavior of AZ91E-T6 cast magnesium alloy in both an air and 3.5 percent NaCl aqueous corrosive environment. An additional objective was to determine if commonly used models that describe fatigue behavior and fatigue life are applicable to this material and test environment. Fatigue tests included constant amplitude strain-controlled low cycle fatigue with strain ratio, R, equal to 0, −1 and −2, Region II constant amplitude fatigue crack growth with load ratio, R, equal to 0.05 and 0.5 and variable amplitude fatigue tests using keyhole notched specimens. In all fatigue tests, the corrosion environment was significantly detrimental relative to the air environment. Mean strains influenced fatigue life only if accompanied by significant mean stress. The Morrow and Smith, Watson, and Topper mean stress models provided both accurate and inaccurate fatigue life calculations. Likewise, variable amplitude fatigue life calculations using the local strain approach and based upon the formation ofal mm crack at the keyhole notch were both accurate and fairly inaccurate depending on the specific model used.

1.
Glinka
G.
,
1985
, “
Energy Density Approach to Calculation of Inelastic Strain-Stress Near Notches and Cracks
,”
Engineering Fracture Mechanics
, Vol.
22
, No.
3
, pp.
485
508
.
2.
Goodenberger
D. L.
, and
Stephens
R. I.
,
1993
, “
Fatigue of AZ91-T6 Cast Magnesium Alloy
,”
Journal of Materials and Technology
, Vol.
115
, pp.
391
397
.
3.
Graham, J. A., 1968, ed., Fatigue Design Handbook, Society of Automotive Engineers, Vol. 4.
4.
Lease, K. B., and Stephens, R. I., 1991, “Verification of Variable Amplitude Fatigue Life Methodologies for a Cast Aluminum Alloy,” SAE, Paper No. 910163.
5.
Liaw
P. K.
,
Hartmann
H. R.
, and
Helm
E. J.
,
1983
, “
Corrosion Fatigue Crack Propagation Testing with the Krak-Gage® in Salt Water
,”
Engineering Fracture Mechanics
, Vol.
18
, No.
1
, pp.
121
131
.
6.
LifEst, 1988, Software Users Manual, SoMat Corporation.
7.
Neuber
H.
,
1961
, “
Theory of Stress Concentration for Shear-Strained Prismatical Bodies with Arbitrary Nonlinear Stress-Strain Laws
,”
ASME Journal of Applied Mechanics
, Vol.
28
, pp.
544
550
.
8.
Perov
S. N.
,
Ogarevic
V. V.
, and
Stephens
R. I.
,
1993
, “
Application and Verification of Fatigue Life Calculation Methods for AZ91E-T6 Cast Magnesium Alloy Under Variable Amplitude Loading
,”
ASME JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY
, Vol.
115
, pp.
385
390
.
9.
Smith
K. N.
,
Watson
P.
, and
Topper
T. M.
,
1970
, “
A Stress-Strain Function for the Fatigue of Metals
,”
Journal of Materials
, Vol.
5
, No.
4
, pp.
767
778
.
10.
Stephens, R. I., Schrader, C. D., Goodenberger, D. L., Lease, K. B., Ogarevic, V. V., and Perov, S. N., 1993, “Corrosion Fatigue and Stress Corrosion Cracking of AZ91E-T6 Cast Magnesium Alloy in a 3.5% NaCl Solution,” SAE paper number 930752.
This content is only available via PDF.
You do not currently have access to this content.