A digital image correlation method for detection of fatigue cracks in non-load carrying T-joints

Sammanfattning: In dynamical loaded welded structures fatigue life is often a limiting factor. Common practise is to reduce nominal stress by increased material thickness which leads to oversized, heavy structures. Those practises are replaced by improvement of production and designingtechniques to utilize better properties of high strength steels.When improving for example quality of welds, issues can occur that standards today did not consider and new test methods can be valuable.In this thesis a method for crack detection in non-load carrying T-joints have been tested. Specimens are made from 6mm Strenx 960MC high strength steel. DIC-analyses is made on frames captured be a high-speed camera during fatigue testing. Hypothesis is that crackpropagation starts when relative strain is higher than 10% per 10 000 cycles.Validation of the method is done by beachmarks from variable stress range during the fatigue test. With the same occurrence as framesets for DIC-analyse. Number of beachmarks agree well with the segment when relative strain indicates crackpropagation in a point at the weld toe.