Comparison of influence of pulsed effects of magnetic and electric fields on stressed state of welded joints of aluminium alloy AMG6

Abstract

The residual welding stresses negatively affect the fatigue limit of welded joint, being the main cause for brittle fracture of metal, i.e. corrosion cracking. Therefore, the development of effective methods for control of welding stresses, characterized by low energy consumption and relatively simple realization, is traditionally an urgent problem for modern production. At the present time the methods for reducing welding stresses became widespread, based on the influence of pulses of electric current and magnetic field. Moreover, each of the methods has its advantages and disadvantages, and evaluation of their efficiency in the control of residual welding stresses represents an urgent problem. In the work the comparative evaluation of efficiency of control of residual stresses of AMg6 alloy of welded plates was carried out at treatments by pulsed electromagnetic field (TPEMF) and pulsed current (EDT), applying planar inductors. Using the method of electron speckle interferometry it was revealed that TPEMF and EDT reduce the initial level of welding stresses in the zone of pulsed effects to 100 %. 16 Ref., 1 Table, 4 Figures. K e y w o r d s : electrodynamic and magnetic pulse treatment, aluminium alloy, welded joint, electron speckle interferometry, efficiency of treatment, residual stresses, electroplastic effect, current density, planar inductorThe investigations of influence of residual welding stresses on strength of welded joints, especially at cyclic loading are traditionally relevant in engineering practice of service of metallic structures. It is connected with the fact that welding stresses negatively affect the fatigue limit of welded joint, increasing the rates of fatigue crack propagation [1,2]. In this case the tensile welding stresses at their interaction with corrosive-active environment are the main cause for brittle fracture of metal, i.e. corrosion cracking [3].Traditionally, technological operations on reduction of welding stresses are sufficiently labor-intensive and are restricted by thermal or mechanical effect on the metal of welded joint. The development of efficient methods for control of welded stresses, characterized by low power consumption and relatively simple realization, is urgent for modern production.In scientific and technical publications the results of investigations of influence of pulses of electric current (PEC) and magnetic field (PEMF) on relaxation of technological stresses [4][5][6], including residual welding stresses, are presented [7,8]. Each of the effects mentioned above, has its advantages and disadvantages and the evaluation of efficiency of control of residual stresses is a relevant problem.The aim of the present work was the comparative evaluation of parameters of treatment using pulsed electromagnetic field (TPEMF) and pulsed current (EDT) on reduction of residual stresses in welded joints of aluminium alloy. methods of investigations. To carry out investigations the specimens of welded joint and base metal of annealed aluminium alloy AMg6 were used. The mo...