基于数字图像相关方法微裂纹萌生试验研究

To further study the behavior of crack in initiation stage, an in-situ observation system based on digital image correlation (DIC) method and the hydraulic fatigue test machine loading system was proposed. Meanwhile, the key techniques in DIC measurement were studied and a micro speckle preparation technique suitable for 2mm-width-vision field DIC calculation and spatial adjustment technique were proposed respectively to improve the experiment reliability. Finally, this system was applied for the micro crack natural initiation test for the GH536 which was applied in flame tube of combustion chamber of aero-engine. By adapting two different analysis strategies, the evolution of total strain amplitude and the maximum accumulated plasticity strain can be obtained respectively. The results indicate that the total strain amplitude can locate the natural crack initiation and identify minimum 50 micro meter crack while the maximum accumulated plasticity strain analysis suggests that initiation life accounts for 85% and the accumulated plasticity strain increases significantly once the crack appears.