Experimental and Numerical Investigation on Geometric Parameters of Aluminum Patches for Repairing Cracked Parts by Diffusion Method

Repairing cracked aerial structures using patches is a common way to restore mechanical properties, strength and extend fatigue life. The performance of such patches can be obtained by comparing the maximum amount of force tolerated by the repaired piece with the unrepaired piece. The shape and dimensions of the patch used to repair the crack and the way the patch is bonded affect the repair quality which are of great importance. Therefore, in this paper, we investigate the factors affecting the diffusion bonding between the patch and the piece. The impact of the shape of the aluminum patch attached on a 10 mm central crack piece and perpendicular to the loading direction (mode I) is studied experimentally and numerically. The optimum conditions for the diffusion connection including the pressure, time and temperature of the connection were obtained experimentally using a composite rotatable centered design and in the connection made under these conditions, the patch shape and aspect ratio was considered as variables of design, and the results were obtained for square, rectangular, circular and elliptical patches. At the end, it was found that the best connection under the pressure conditions of 570 °C, 70 bar and 100 min was formed and the rectangular patch efficiency was greater whereas its extent is more in line with crack than the other modes. At a fixed area, the different patch geometries investigated in this study were able to influence up to 80% of the maximum force tolerated by the repaired parts. Also, there is an acceptable convergence between experimental and numerical results.