Statistical analysis and correlation of Small Punch Test

Structural Health Monitoring methods are in general based on material testing during operation of structures under monitoring. Small Punch Test method is a new approach that allows for material sampling on metal structures without the need to repair the damage due to the size and shape of material volume taken from the structure. The way of material sampling for SPT makes it a non-destructive testing method thus allowing material condition assessment at any stage of machine life without the need to exclude it from usage and cause production downtime. Small Punch Test results provide Yield Stress and Ultimate Strength. In this work we investigate the accuracy of the SPT method in comparison with standard, widely used in industry Uniaxial Tensile Test that is destructive but regarded as a default source of precise mechanical properties data. Materials used for this research are boiler steels in various conditions starting at unused materials and ending on heavily fatigued samples from retired pressure tanks. The goal of this study is to establish a direct correlation between SPT and UTT for investigated materials by the means of statistical analysis of the results. Cluster analysis has been used to investigate the influence of small thickness differences between samples on final results in comparison to the data obtained from standard material testing methods by mixing the data together.