## Seminarium AMAS## Estimating crack closure characteristics - an example of optimal experimental design## dr T. Svensson |

Topper&Lam have developed a method for estimating crack closure characteristics without observations of the very phenomenon. This is done by postulating that

- the mean value influence on fatigue life depends solely on crack closure and
- that the crack closure level can be described by the Lam/Topper formula, including two parameters.

Fatigue tests on different mean values give then information about the closure characteristics and the parameters can be estimated. Topper&Lam propose that the tests should be performed at the R-ratios R=0 and R=-1. I will present the use of optimal statistical experimental design on the present problem, which leads to a test design that reduces the number of tests needed to about 60% of the original design.