Substitution of the time-of-flight diffraction technique for nondestructive testing of welds and thick layers of steel: A comparative investigation

Abstract

Prevention of industrial disasters is a major concern. Nondestructive testing as a reliable tool has played an effective role in this regard. Ultrasonic testing of heavy press-sure vessels is a common practice. Particularly, a more customary procedure known as pulse-echo has become a standard in and of itself. In light of the increasing demand for more thorough inspection of pressure vessels, researchers have begun looking into more innovative means of defect measurement. Fundamentally, the time-of-flight diffraction (TOFD) flaw-detection procedure is based on the time measured for diffracted waves to travel from the two ends of a defect, and it is shown to be an effective procedure for size and location determination of a defect [1]. Specifically, it is demonstrated that this technique is more suitable for thick structures (above 10 mm). Today, the TOFD procedure is used for operational inspections or quality control of structures during production instead of routine radiography and ultrasonic NDT procedures [1]. Although TOFD is more often utilized for inspecting welds with simple geometry and small grain steels, such as face welds with thicknesses from 6 mm to 300 mm, it is useful in inspecting more complex geometries. Such defects as cracks, lack of penetration, lack of fusion, porosity, and slag in welds and pressure vessels could be diagnosed via this technique. In this investigation, on the basis of the review of related literature, the principal theory governing TOFD is discussed. A mathematical model is developed and different aspects have been compared. Advantages and disadvantages of its utilization are enumerated and specific applications are outlined. Recommendations and suggestions are made for future investigations and betterment of the procedure.