Robustness of post-weld treatment HFMI to increase the fatigue strength of welded structures (ROMI)

Project time: 2018 – 2018

Budget: 1 020 000 kronor

Funding: Fordonsteknisk forskning och innovation, FFI

Study the robustness of the post-weld treatment process HFMI with regard to weld quality and fatigue strength.

Post weld treating techniques such as TIG dressing, grinding or HFMI (High Frequency Mechanical Impact) are increasingly used to increase the fatigue strength of welded structures. The beneficial effect of HFMI is caused of impact energy that plastically deforms the material and causes changes in the microstructure, the local geometry and the residual stress state in the region of impact.

The IIW published recommendations for HFMI suggest that the weld before HFMI treatment should fulfil the acceptance limits of quality B in ISO 5817 (highest level) for a fully successful result. In production, the weld may not always reach this due to variations in the welding process. Assuming this area with lower weld quality is HFMI treated anyway, will this result in a reduction of fatigue strength or are the HFMI processes now so robust that weld variations can be tolerated? PhD and Master´s thesis students will be included and results published in scientific and popular papers.

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