The aim of the present investigation was to find techniques for improving the fatigue resistance of spot welds. Various mechanical treatments were performed with the StressWave process to introduce various levels of hardening and compressive residual stresses on the spot weld. The StressWave treatment consists a pair of opposing, specially shaped indenters squeezes the sheet to cause radial plastic flow of the material. This results in a zone of beneficial residual stress, which significantly improves fatigue behaviour. To understand the fatigue behaviour of spot welds with and without the StressWave treatment, an electrical method was used to detect fatigue crack initiation and to monitor the crack as it propagated across the thickness of the sheet during the fatigue tests. Results, based on a cold rolled TRIP 800 grade, show that an increase of fatigue resistance of more than 150 % can be expected using this treatment. Despite the pre-existing crack at the notch root for the StressWave spot welds, the improvement of fatigue resistance with the StressWave treatment is due to the reduced fatigue crack propagation in the area hardened by the mechanical treatment. As a next step this technique is thought to be applied on the weakest spot welds of a real structural part in order to highlight the possible weight saving.
Improvement of fatigue strength of spot welds using the stresswave technique
Welding in the World ; 52 , 1/2 ; 47-55
2008
9 Seiten, 13 Bilder, 4 Tabellen, 12 Quellen
Article (Journal)
English
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