Technical condition of welded load-bearing metal structures of operated agricultural hoisting cranes

Abstract

The paper considers the methodology for assessing the technical condition of welded load-bearing metal structures of operated agricultural hoisting cranes. In the course of the study, the relationship between structural, mechanical and magnetic parameters was established during cyclic elastic-plastic deformation of low-carbon and low alloy steels. Based on the analysis, it was concluded that the dependence of the minimum values of the magnetic parameter on the acting stresses Нр(σ) is influenced by the metal structure and its chemical composition. It has been established that the coarser-grained structure of the studied steels under elastic-plastic deformation contributes to a shift in the minimum values of Нр towards lower acting stresses; an increase in the strength characteristics of steels shifts the minimum of Нр toward large values of s, which must be taken into account when conducting technical diagnostics of the elements of the operating metal structures of hoisting cranes. Based on the results of the study, a method for determining the acting stresses in the elements of the metal structures of hoisting cranes was developed, which, by the nature and magnitude of the change in the residual magnetization of the scattering field during their stepwise loading (unloading), allows judging the magnitude of the acting stresses. The work also presents a methodology for assessing the technical condition of welded load-bearing metal structures of hoisting cranes based on the integrated use of passive flux-gate and other control methods, which allows determining the acting stresses used in strength calculations in the identified hazardous zones of concentration of stresses in the elements of metal structures.