Abstract

Alternate immersion stress corrosion testing according to ASTM G 44, Practice for Alternate Immersion Stress Corrosion Testing in 3.5% Sodium Chloride Solution, has proves to be representative for alumimum alloys in natural environments resembling the actual eavironmental conditions for aircraft. A simple automated stress corrosion testing method called the ASCOR (automated stress corrosion ring) test was developed to test aluminum alloys according to ASTM G 44 and using direct stressing as in ASTM G 49. Recommended Practice for Preparation and Use of Direct Tension Stress Corrosion Test Specimens. The method involves testing cylindrical or pin-loaded flat tension test specimens in a loading sing provided with strain gages to measure the load. Initiation of a stress corrosion crack (SCC) results in a small load decrease. During the test the load is measured periodically and stored in a data acquisition system controlled by a personal computer. A specific load decrease is used as the criterion for SCC initiation. The main advantages of the method are that a large number of specimens can be tested simultaneously in a climate chamber and that SCC initiation lives can be determined according to a clearly defined criterion without time consuming and subjective inspections, and without disturbing the test procedure.

References

1.
Gray
,
J. A.
, “
A Comparison of Various Stress Corrosion Test Procedures Applied to Three Aluminium Alloy Plates
,” Royal Aircraft Establishment Technical Report 79117, Farmborough, U.K.,
09
1979
.
2.
Schra
,
L.
and
Wanhill
,
R. J. H.
, “
The Influence of Different Environments on Stress Corrosion Cracking of High Strength Aluminium Alloy Forgings
,”
Aluminium
, Vol.
59
, No.
3
,
1983
, pp.
191
-
194
.
3.
Schra
,
L. and't
,
Hart
,
W. G. J.
, “
Long-Term Outdoor Stress Corrosion Testing of Overaged 7000 Series Aluminium Alloys
,” National Aerospace Laboratory NLR Technical Report 88012U, Amsterdam, The Netherlands,
01
1988
.
4.
Schra
,
L.
, “
Accelerated and Real-Time Corrosion Testing of Aluminium-Lithium Alloys
,”
Sixth Internationed Aluminium-Lithium Conference
, October 7–11, 1991,
Garmisch-Parteskirchen
,
FRG
, To be published by the Deutsche Gesellschaft fur Maserialkunde.
5.
Braun
,
R.
, “
On the Exfoliation Corrosion and Stress Corrosion Cracking Behaviour of 2091-T8X51 Plate Material
.”
Sixth International Aluminium-Lithium Conference
. October 7–11, 1991,
Garmisch-Partenkirchen
,
FRG
. To be published by the Deutsche Gesellschaft für Materialkunde.
6.
Kolkman
,
H. J.
and
Schra
,
L.
, “
Stress Corrosion Resistance of Damage Tolerant Aluminium-Lithium Sheet Materials
.” National Aerospace Laboratory NLR Technical Publication 91399L.
Amsterdam. The Netherlands
,
09
1991
.
7.
Investigations on Aluminium-Lithium Alloys for Damage Tolerant Applications. Task 2: Understanding of Corrosion Behaviour
.”
Brite-Euram Project
3250
, To be published.
8.
Schra
,
L.
, “
Corrosion Properties of Al-Li-Cu-Mg-Zr Sheet Materials
,” National Aerospace Laboratory NLR Technical Report 88047L, Amsterdam. The Netherlands.
03
1988
.
9.
Stress Corrosion Resistance of 8090-T81 Sheet
,” Personal Communication from R. Braun, DLR. Porz-Wahn. FRG.
10.
Schra
,
L.
and
Kuijpers
,
T. B. A.
,”
The Breaking Load Method for Stress Corrosion Testing: A First Evaluation
,” National Aerospace Laboratory NLR Technical Report 88182L. Amsterdam. The Netherlands,
12
1988
.
11.
Bucci
,
R. J.
,
Brazill
,
R. L.
,
Sprowls
,
D. O.
,
Ponchel
,
B. M.
,
Bretz
,
P. E.
, “
The Breaking Load Method: A New Approach for Assessing Resistance to Growth of Earty Stage Stress Corrosion Cracks
,”
Presented at the ASM International Conference and Exposition on Fatigue, Corrosion Cracking, Fracture Mechanics and Failure Analysis
,”
Salt Lake City, UT
. December 2–6. 1985.
This content is only available via PDF.
You do not currently have access to this content.