FAT-LW

The aim of the present project is to, in a critical manner, study the two improvement techniques, in order to increase understanding of the factors that control fatigue life of welded high strength steels and to help industry in selecting the most optimal procedure. To achieve this, cruciform welded samples will be produced using LTT and conventional welding consumables in 1100 MPa and 1300 MPa yield strength steels with a plate thickness of 15 mm. Some of the welded samples will then be HFMI treated. Residual stresses in as-welded condition and after application of HFMI will be evaluated using X-ray diffraction. Fatigue testing under constant and variable amplitude loading will be performed under stress ratio of 0.5. It is expected that the results will have a large interest among manufactures of equipment subjected to fatigue loading. For example, Volvo Trucks and Volvo Construction Equipment, manufacturing many types of heavy vehicles, can see some significant advantages of increasing the strength of the steel in their vehicles, since this could save weight and thus increase the payload. The results will be very interesting and useful to welding consumable producing companies as fatigue is a concern when dealing with welded HSS. The results of the investigations will also be important for the future use of high strength steels. The possibility to use HSS more than today is a significant step towards saving energy and a more sustainable future. The project aims is in line with 17 goals for a better world by 2030 where the goals have the power to end poverty and stop climate change. 

Project deliverables: The industrial deliverables and anticipated outcomes of this project are:

• Solid results as a basis for communication with customers
• A fundamental understanding of how fatigue life can be improved for high strength steels
• Possibility to use higher strength steels and consumables for fatigue loaded structures
• Development of a reliable database for selecting suitable improvement methods
• Possibilities to select the method giving best results to lowest cost
• A solid background for selecting a relevant implementation strategy