A digital image correlation method for fatigue test experiments

In this paper, a method based on the digital image correlation (DIC) technique is proposed to monitor the crack growth process during a cyclic fatigue test. Stroboscopic illumination is used to acquire DIC speckle pattern images while the test sample is dynamically loaded. The proposed DIC algorithm uses the fact that the load is periodic to increase the accuracy of the displacement field estimates (a sinusoidal fitting method is introduced for this purpose). Using the appropriate post-processing both the crack lengths and the stress intensity factors can be estimated in function of the number of fatigue cycles. A validation test case on an aluminum U-profile will be presented in the paper.