Automated ultrasonic system residual stresses in the welded joints of the circulation pipe NPP
Improving the reliability of welded structures is one of the important problems of NPP safety. The performance of welded structures is determined by the performance of the welded connection, the bearing capacity is significantly inferior to the load-bearing capacity of the base metal. This is due to thermal deformation processes, as well as phase and structural transformations in welding, including welds, residual stresses are formed. They are combined with stresses from external loads and are a major cause of destruction of welded constructions.
At the Department «Automation, control and diagnostics» of Obninsk Institute for Nuclear Power Engineering National Research Nuclear University «MEPhI» proposed and developed an ultrasonic method of relieving residual stresses in welded joints of metals and alloys. The prototype automated device for removing residual stresses. Currently a prototype automated system for removing the residual stress is applied in welding of circulation pipes at Kursk NPP. As a result of ultrasonic treatment of welded joints automated system of removing residual stresses are significantly reduced residual welding stresses, increase the mechanical strength properties of welded connections of circulating pipelines of NPP.
To ensure effective removal of residual stresses must be continuous the effect of ultrasound on the sample, so it uses 2 (~ 3kW) of an ultrasound generator with water cooling. The control unit controls the stepper drives moving the transducers along the pipeline. The control unit controls the electric brakes to hold the transducers on the pipe between movements; determines the position of the welding electrode relative to the converters by means of optical sensors and reports this information to the microcontroller of the control unit 1 via the RS485 interface. In addition, there is a system of visual control of the position of the welding device relative to the ultrasonic transducers.
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