The article considers the influence of mechanical inhomogeneity and crack-like defects on the stress state of welded joints (on the example of welded joints of trunk pipelines made of low-alloy steels). Analysis of the results of previously performed studies and existing calculation methods shows that taking into account the features of zones of mechanical inhomogeneity when assessing the bearing capacity of welded joints requires further study. The development of approaches to take into account the geometry of mechanical inhomogeneity will make it possible to assess more reasonably the degree of danger of crack-like defects depending on their location in the welded joint. The determination of the geometry of mechanical inhomogeneous zones was carried out by measuring the hardness indicators. The presented results of experimental studies show the distribution of mechanical characteristics in welded joints. The results of tensile tests of specimens with an applied surface crack-like defect in mechanical inhomogeneous zones of welded joints are presented. It is shown that the difference in the values of the strength parameters of welded joints with different defect locations reaches 10%.The obtained experimental data made it possible to create a mathematical model for determining the values of the critical stresses of welded joints, taking into account the geometry of the zones of mechanical inhomogeneity. The mathematical model is based on a combination of Prandtl's solution on the constancy of tangential stresses along the plastic strip together with the method for finding the stress discontinuity, which makes it possible to take into account edge effects at free boundaries and boundaries of zones of mechanical inhomogeneity. Comparison of the results of the calculated assessment of the strength of mechanically inhomogeneous welded joints with a crest-like defect and experimental data showed their high convergence and confirmed the reliability of the proposed model.
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