A Study on the Shape Selection of Mechanical Fastening for the Repair of Fighter Wing

A study on optimal shape selection of a mechanical fastening for the repair of crack defect of ROK Air Force F-5 fighter wing was conducted. The crack defect occurred in the spar of the wing, and the technical manual does not specify the repair method. However, ROK Air Force decided to develop a repair technology for this defect in consideration of various logistic conditions. Three repair shapes for the proper repair were devised and the finite element analysis was performed to examine the structural safety of these three connection members. As a result of the structural safety review, two connection members except one were structurally safe with safety margins over zero because the calculated stress values were at or below the yield strength level. Therefore, two connection members were determined to be able to use for repair under the condition that the aircraft operated within the design limit load. The results of this study would be very useful if the same defect occurs in long-term aircraft operated by the ROK Air Force.

Crack Detection and Geometry Measurements using Digital Image Processing

Digital image processing (DIP), is the use of a digital computer to process digital images through an algorithm. In this work DIP used to perform crack/defect Detection and geometry measurements in terms of angle, length, and width by building a MATLAB code. In this research, the test of tensile were applied on two flat samples, the two flat samples are painted in a speckle pattern on the tested surface to use DIP features. The DIP gives a low-cost optical, and an appropriate technique to detect crack/defect as well as geometry measurements with the load increment in terms of angle, length and width without any contact with the tested surfaces. The tests directed for both of flat Aluminum alloy and Copper alloy specimens. In order to guarantee the efficiency of the planned DIP systems, the comparison is considered between the test results of this technique with the measurements gained by actual physical by using calibrated digital vernier calliper (IP 54) to measure the length of the crack with 0-300 mm range and 0.01 mm resolution. The DIP obtained percentage of accuracy varies from (97) % to (99) % by comparison with the measurements gained by actual physical way.