Optimal experimental-design for estimating crack closure features

Recently, a new method for determining crack closure properties of a material has been presented. The method is convenient for engineering purposes, since it does not include any observations of the closure, but only uses results from fatigue life tests. In this paper we introduce the concept of optimal experimental design and use it for finding an optimal test design for the closure determining method. The resulting design is shown to give the same precision as the design used in previous investigations using only 60% of the number of tests. A new series of fatigue tests was made according to the new design and the closure model parameters were estimated.