Hudak et al. (1978) presented data on crack growth data, which have been listed by Lu and Meeker (1993). There are 21 metallic specimens, each subjected to 120,000 loading cycles, with the crack lengths recorded every 10,000 cycles. We take t=no. cycles/100,000 here, so t(j)=j/1000 for j=1,...,12 coded by cycle. The crack increment sequences look rather irregular. Let l(i,j) be the crack length of the ith specimen at the jth observation and let y(i,j)=l(i,j)-l(i,j-1) be the corresponding increment of crack length, which has always a positive value. l(i,j-1) is coded by crack0 to use as a covariate.
A data frame with 241 observations of the following 4 variables.
Increment in crack length, y(i,j)=l(i,j)-l(i,j-1), where l(i,j) is the crack length of the ith specimen at the jth observation.
The previous crack length, l(i,j-1).
The specimen number for 21 metallic specimens.
The number of cycles/100,000; t(j)=j/100, j=1,...,12.
Hudak, S. J., Saxena, A. Bucci, R. J. and Malcom, R. C. (1978). Development of standard methods of testing and analyzing fatigue crack growth rate data. Technical report. AFML-TR-78-40. Westinghouse R & D Center, Wesinghouse Electric Corp., Pittsburgh, PA.
Lu, C. J. and Meeker, W. Q. (1993). Using degeneration measurements to estimate a time-to-failure distribution, Technometrics 35, 161–174.
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