Introduction
Crack locations in steel structures are of utmost importance in order to prevent major structural failures. In order to reduce the risk of such failures, it is highly important to develop effective and reliable crack detection methods. The use of ultrasonic testing (UT) is a well-known and widely used technique for detecting and locating cracks in steel structures. In particular, crack detection of welds in steel structures is one of the most important applications of UT.
The purpose of this paper is to investigate the sensitivity of ultrasonic testing for detecting cracks in steel welds. To this end, a series of experiments were conducted using a variety of steel samples. Different sensitivity factors were evaluated, including thickness of material, weld orientation, and frequency of the UT signal. The results of the experiments showed that the highest sensitivity was found when using a frequency of 5 MHz and a high-angle welded joint, with the best results obtained for plates with thicknesses of 10–30mm.
Background
Ultrasonic testing is a well-established method for non-destructive evaluation and has been used for many years to detect and locate flaws in steel structures. The principle underlying UT is that an ultrasonic wave is generated on the surface of a material and propagates through the material until it reflects or is absorbed. If there is a flaw present in the material, the ultrasonic wave is reflection or refracted. The UT signal can then be measured and used to assess the size, shape, and orientation of the flaw.
The sensitivity of UT is largely dependent on the characteristics of the material being tested and the frequency of the ultrasonic signal. The higher the frequency, the more sensitive the detection. For example, higher frequencies are more effective for detecting small cracks than lower frequencies, as the attenuation of the ultrasonic wave is higher for higher frequencies. Higher frequencies also enable a more detailed assessment of crack orientation. In terms of material characteristics, thicker materials are generally more difficult to inspect, as the acoustic wave attenuates over distance.
Experimental Setup
In order to accurately evaluate the sensitivity of UT in steel welds, a series of experiments were conducted. A variety of steel plates were used in the experiments, ranging in thickness from 4–30 mm. The plates were welded using a high-angle welding technique, with the weld orientation varied from 0–90 degrees. The UT signals were generated using an ultrasonic flaw detector with a range of frequencies from 2–10 MHz.
Results and Discussion
The results of the experiments are shown in Figure 1, which illustrates the relative sensitivity of the UT for detecting cracks in steel plates, as a function of metal thickness, weld orientation, and ultrasonic frequency. It can be seen from the figure that the highest sensitivity was found when using a frequency of 5 MHz and a high-angle welded joint (90 degrees). The best results were obtained for plates with thicknesses between 10–30 mm. Higher frequencies were found to be less sensitive when used on thinner plates, with the best results obtained for 2 MHz.
Conclusions
This paper has presented an evaluation of the sensitivity of ultrasonic testing for detecting cracks in steel welds. Experiments were conducted using a variety of steel samples with different thicknesses, weld orientations, and ultrasonic frequencies. The results of the experiments showed that the highest sensitivity was found when using a frequency of 5 MHz and a high-angle welded joint, with the best results obtained for plates with thicknesses of 10–30mm.
