Influence of Ultrasonic Testing Sensitivity Adjusting Method on Its Distribution over the Welded Joints Thickness of Building Structures

Welding is one of the most commonly used methods of manufacturing critical steel structures: beams and supports of buildings and bridges, frames and bodies of rolling stock. At the same time, the manufacturing quality of welded joints directly affects the strength and durability of structures. Currently used weld manufacturing technologies include ultrasonic testing in order to increase the reliability and failure-free operation of welded structures. The methods of ultrasound control are regulated by several standards: GOST R ISO 17640, STO-GC Transstroy-005-2007 and GOST R 55724, each of which defines different ways to adjust sensitivity. In these conditions, the issue of analyzing the ultrasound control results performed in accordance with various regulatory documents is relevant. A comparative analysis of the ultrasonic inspection sensitivity distribution over the weld thickness was carried out using two cylindrical control reflectors and tuning samples with reflectors of the lateral cylindrical hole and notch types. A sample with cylindrical reflectors with diameters of 2 mm and 3 mm was developed and manufactured to adjust the sensitivity of welded joint ultrasonic inspection by the DAC method according to ISO 17640 and two-zone control by direct and single-reflected beams according to STO-GC “Transstroy”-005-2007. The regularities of amplitude changes and detection coefficient of reflector signals located at different depths with different methods of sensitivity adjustment at a frequency of 5 MHz have been experimentally established. It has been experimentally shown that the use of cylindrical reflectors and notches for leveling sensitivity in the depth of the welded joint with a product thickness of up to 15 mm is equivalent with an unevenness of no more than 1.5 dB. To ensure uniform sensitivity with an uncertainty of no more than 2 dB, a two-parameter RF can be used, adjusted by three reflectors located at the boundaries of the control zone and at the midpoint.