A Strain Gauge Method for Spot Weld Testing

Local stress parameters (hot-spot structural stress, notch stress, stress intensity factors and J-integral) at spot welds are preferred in fatigue assessments of spot-welded structures because these parameters better correlate fatigue test data across different weld sizes and different specimens. However, there is still a lack of measuring method to determine these parameters. The main difficulty in developing such measuring method is the poor accessibility to the inside of the overlap sheets near a spot weld. A strain gauge method is developed here for spot-welded joints under typical loads of coach-peel and cross-tension. All local stress parameters at the spot weld are determined by two neighboring strain gauges attached to the outer surface of the overlap sheet near the spot weld. The method is non-destructive and validated by finite element simulations.