Fatigue testing and analysis using the hot spot method

The structural stress or hot spot method of fatigue analysis draws its origins from the offshore industry where it has been used for many years as an accurate means of performing fatigue assessments of welded structures. Today the method is increasingly finding use for more common plate welded structures like ship hulls and land vehicle chassis. The design curves for the hot spot method, however, are still a problem due to the lack of test data needed to establish reliable life curves. This publication presents an overview of the hot spot method including the hot spot stress concept and a comparison of the reference curves used for fatigue life estimation found in several design codes or non-standard documents. Four of the six curves considered give approximately the same life estimate for a given stress, but the remaining two are significantly different. Experimental hot spot stress measurements for one relatively simple test specimen geometry and one larger more complex component are presented together with a fatigue test data. Fatigue data are compared with existing reference curves.