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A calculational model to solve the problems about welded joints life has beenformulated in this paper. A welded joint in this model is considered to be aninhomogeneous as to its physical-mechanical properties deformed solid with a lack offusion, which develops under cyclic loading. An equation for determining the fatigue crackgrowth rate was obtained from the energy balance of fatigue fracture of a jointinhomogeneous material and reversible elastic-plastic fracture of the process zone at thisdefect tip.A direction of crack propagation with respect to the initial defect location plane isdetermined from the condition that this direction provides the maximum crack growth rate.The proposed model has been used to evaluate the residual life of butt- and T-joints anda good agreement of the calculation and experimental data has been shown.