Comparing profile monitoring procedures of metal foams

Density profiles can be used to analyze the homogeneity of metallurgically manufactured metal foams. In this work the density profiles are experimentally measured using a gamma ray technique, then regularized by a Support Vector Regression model to propose two alternative procedures controlling the average behavior of a profile. The first procedure calculates two limits from the shape of the profiles, the second one uses an EWMA chart. Both proposals are compared with a more classical method which extracts indicators related to the shape of the profile, then used to design a Hotteling T 2 control chart. The performance of the three methods is measured by the ARL. The three profile monitoring procedures can be used in Phase I to monitor the internal structure of a closed-cell metal foam. The highest performance is given by the first procedure which is also faster to warn that some density profiles are outside the established control criteria.