The article deals with the issues of increasing the fatigue strength of critical parts and components of construction machines and equipment, which are more often subjected to fatigue failure under the influence of variable complex loading. A quantitative estimate of the size of the fatigue fracture zones in the parts and joints installed in the building structures and power circuits of this construction equipment has been made. A new technique for technical diagnostics of the causes of fatigue destruction of knots of construction machines and structures is considered, revealing regularities of changes in microhardness in various zones of fatigue fractures. The results of measurements of microhardness in the zones of fatigue fractures are obtained. The systems of standard regression equations are obtained that allow one to quantify the parameters of the loading regime that led to destruction. A computational subroutine has been created that allows us to obtain analogous equations by processing the microhardness measurements of the fracture under study, and comparing them with the reference equations, give a reasonable quantitative conclusion on the causes of failure.