Mehmet EFENDİ, A. Alper ÖZALP
In automotive industry, laser welding process is widely used in joining subcomponents. Welding seams are not only to join the parts, in some specific parts, they can play a very important role in prevention of leakage, for example in high pressure gasoline injectors. At injectors, fatigue strength of the welding seams are very important and must endure entire life time without failure. Fatigue strength of welding seams are obtained with hydropulsation test, 1 ppm pressure value is calculated statistically and working pressures must be below 1 ppm values. There are some approaches for simulations defined in IIW (International Institute of Welding) documents for modelling of welding seam geometry with linear mechanical properties. In this study, a new elastoplastic approach will be presented for finding fatigue strength of the welding seams. For mechanical properties characterization, welding seam locations roughly divided into different hardness zones and performed nanoindentation tests. Nanoindentation test has provided hardness information and force displacement curves. For each zone, average hardness value is calculated and corresponding force displacement curve is obtained as an output from the relevant hardness zone. Using hardness information, reference same material at different hardness value is linearly scaled to measured average hardness value at the relevant zone. Nanoindentation test was simulated with Ansys 2020R2. Force displacement curve from simulation is plotted and compared with relevant curve from nanoindentation test. Using mechanical properties and Wöhler curves of related welding seam, limit 1 ppm pressure value is converted to stress and accepted as fatigue strength.

Anahtar Kelimeler: Fatigue, Local Stress Concept, Laser Welding Seam