Crack Detection and Geometry Measurements using Digital Image Processing

Abstract

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.

Conclusions

1. Tensile tests have been carried out for two cracked/defected specimens. The tests applied for both flat Aluminum alloy and Copper alloy plates. The DIP percentage of accuracy differs from (97) % to (99) % by comparing with the actual physical measurements.
2. The DIP technique can be developed in Structural Research laboratories, and make it possible to perform and work with the fatigue testing and/or crack propagation without human surveillance.
3. The measuring of crack geometry can be easily used by the developed program, it just needs an operator who is familiar with this kind of testing.
4. DIP had successfully used in the determination of the actual crack position, and it allows us to measure the actual length, width, and angle of the crack/defect.
5. For quick and reliable surface defect inspection, the DIP program for crack detection is effective technique using instead of the slower traditional human inspection method. Automatic crack detection is very useful for Non-destructive testing (NDT). By manual investigation, it is hard to evaluate deterioration accurately [24]. The automatic crack detection can be implemented using some of the NDT procedures like (i) Radiographic, (ii) Ultrasonic (UT), (iii) Laser, and (iv) Infrared and thermal.