Volume 3, Issue 2 (February 2006)
The Challenge of Multiple Particles in Extreme Value Inclusion Rating
The presence of multiple types of defect is a challenge for Extreme Value Inclusion Rating since it can lead to serious underestimation of extreme inclusion size and it can in practice make methods less robust than expected. First the paper deals with the results being obtained by ESIS TC20 within two round-robins carried out on an automotive steel and a bearing steel. Results show the need for correct assessment of multiple types of particles. We present here a new method of analysis based on a “competing risks” model together with some practical exploitation in terms of: (i) evaluation of the minimum control area to be inspected by “block maxima” sampling; (ii) new implications for data collection based on image analysis; (iii) assessment of sensitivity to the distribution of different particles.