An Accelerated Lifetime Approach for Estimating
the Durability of CDs & DVDs
Adriana Hornikova, James Filliben,
Statistical Engineering Division
Information Technology Laboratory
820 Bureau Dr., NIST North – 381
Mail stop: 8980-381
Phone: (301) 975 8118
Fax: (301) 990 4127
The durability & lifetime of storage media such as compact discs (CDs) and DVDs was investigated utilizing an accelerated testing experiment. An optimally designed experiment was used to minimize the bias and uncertainty of the predicted median lifetime at ambient conditions. This approach will apply for different CD/DVD manufactures and types.
The ISO /ANSI standard specifies five different stress conditions that are often used in the industry for predicting the ambient life expectancy of CDs and DVDs. These five conditions are combinations of elevated temperature and humidity that accelerate the wearout time of tested items. The data from accelerated testing is first censored (allowing for out those items that haven’t failed in the testing time) and then the median of each stress condition was computed, along with a bootstrapped estimate of the associated uncertainty.
For modeling the influences of elevated temperature and humidity we use the Eyring model:
where represents the median time to failure, T is the Kelvin temperature, RH is the relative humidity, is the activation energy per molecule (estimated), is the Boltzmann’s constant and are constants (estimated) that are unique to a particular brand and type of a CD. To assist in variance stabilization we use the natural logarithm for the least squares regression. We then generate predicted life time at ambient conditions (t = 25 ºC, RH = 50 %).
A comparative simulation was carried out to determine the optimal accelerated testing design for this study, and to determine uncertainty for the lifetime estimates. The results of this study will be presented in poster.
F. Byers: Care and Handling of CDs and DVDs, NIST 2003.
ISO 18 927: Imaging materials – Recordable compact disc systems – Method for estimating the life expectancy based on the effects of temperature and relative humidity, 2002.
W. Nelson: Accelerated testing, Statistical Models, Test Plans, and Data Analysis, 1990.
Keywords: Accelerated lifetime testing, durability, CDs & DVDs, simulation, uncertainty, Eyring Model, design of experiment.