Abstract

An automated variable amplitude fatigue crack growth system has been developed using digital signal processing (DSP) technology to provide waveform generation, command-feedback verification, and crack growth monitoring. The system is designed to interface with existing analog or digital closed-loop servo-hydraulic mechanical test systems. An important parameter in the control of variable amplitude testing is the effect of loading errors on the fatigue crack growth rate response. A damage parameter (Γ) has been incorporated to quantify the magnitude and effect of loading errors. In this paper, a FALSTAFF, Mini-TWIST, and truncated Mini-TWIST aircraft spectrum were applied to an M(T) crack growth sample to demonstrate the correlation between the damage parameter and fatigue life.

References

1.
Donald
,
J. K.
, “
Automated Variable Amplitude Fatigue Crack Growth Technology
,”
Applications of Automation Technology to Fatigue and Fracture Testing
, ASTM STP 1092,
A. A.
Braun
,
N. E.
Ashbaugh
, and
F. M.
Smith
, Eds.,
ASTM International
,
West Conshohocken, PA
,
1990
, pp.
167
-
177
.
2.
McKeighan
,
P. C.
,
Fess
,
F. E.
 II
,
Petit
,
M.
, and
Campbell
,
F. S.
, “
Quantifying the Magnitude and Effect of Loading Errors During Fatigue Crack Growth Testing Under Constant and Variable Amplitude Loading
,”
Applications of Automation Technology in Fatigue and Fracture Testing and Analysis: Fourth Volume
, ASTM STP 1411,
A. A.
Braun
,
P. C.
McKeighan
,
A. M.
Nicolson
, and
R. D.
Lohr
, Eds.,
ASTM International
,
West Conshohocken, PA
,
2000
.
3.
Schutz
,
W.
, “
Standardized Stress-Time Histories — An Overview
,”
Development of Fatigue Loading Spectra
, ASTM STP 1006,
J. M.
Potter
and
R. T.
Watanabe
, Eds.,
ASTM International
,
West Conshohocken, PA
,
1989
, pp.
3
-
16
.
4.
Donald
,
J. K.
, “
Sampling Rate Effects in Automated Fatigue Crack Growth Rate Testing
,”
Automation in Fatigue and Fracture: Testing and Analysis
, ASTM STP 1231,
C.
Amzallag
, Eds.,
ASTM International
,
West Conshohocken, PA
,
1994
, pp.
124
-
145
.
5.
Paris
,
P. C.
and
Erdogan
,
F.
, “
A Critical Analysis of Crack Propagation Laws
,” ASME,
Journal of Basic Engineering
 0021-9223, Transactions of the ASME, Vol.
D85
,
1963
, pp.
528
-
534
.
6.
Clark
, ,
W. G.
 Jr.
and
Hudak
, ,
S. J.
 Jr.
, “
Variability in Fatigue Crack Growth Rate Testing
,”
Journal of Testing and Evaluation
 0090-3973, Vol.
3
, No.
6
,
1975
, pp.
454
-
476
.
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