Bondarenko A. Magnetic coercive control of technical condition of welded joints

Dissertational work is devoted to the question of development of magnetic coercimetric method of an estimation of a technical condition of welded joints of pipelines and forecasting of a residual life. Methods of nondestructive testing of welded designs are analyzed and the choice magnetic coercimetric method for an estimation of a technical condition and forecasting of a residual life of welded joints is proved. The mathematical model establishing communication between the geometrical sizes and coercive force of a welded seam, zone of thermal influence, the basic metal and welded joint that enables a local estimation of damaging of welded designs is offered and theoretically proved. For the first time the physical model of welded joint for revealing local features of distribution coercive forces in welded joint from the point of view of physics of the magnetic phenomena is constructed. Character of interrelations between metal fatigue, pressure, deformation of welded joint and informative parameter ofa magnetic method - coercive force is investigated. Influence of structural changes of metal of welded joints as a result of destruction on its magnetic properties is investigated and the reasons of change of coercive forces are certain. For the first time the technique of estimation and forecasting of a residual life of welded joints of pipelines with application magnetic coercimetric method of nondestructive testing is developed. Influence of real conditions of operation of a gas main on change of coercive forces in welded joints is investigated.