PRINCIPLES OF CALCULATING SAFE SERVICE LIFE OF OIL PIPELINES LAID IN ROCKY GROUND
<i>Background The article describes theoretical principles of methods developed to calculate oil pipeline safe service life in complicated conditions of construction and operation. Aims and Objectives Offered and justified are the improved phenomenological models of low-cycle damageability of pipe metal. Method of calculating pipeline safe life by the criteria of low-cycle crack resistance is developed. Generalized parameter of steel mechanical characteristics, which predetermines pipeline safe life under complicated operation conditions, is substantiated. Methods Basing on the principles of failure mechanics and the fatigue theory parameters of low-cycle crack resistance were quantified in the coordinates «crack growth rate - range of deformation intensity factor», depending on the known deformation characteristics of steel (δ</i><sub><i>5</i></sub><i> и ψ). Results Basing on performed complex testing of steel samples the damageability mechanisms of pipeline basic elements are determined. Offered and substantiated is the method of determining pipe durability under cyclic pressures, considering the dynamics of changes in deformation characteristics and damage. Generalized parameter (K</i><sub><i>тв</i></sub><i>) for assessment of steel quality and oil pipeline safety is offered and reasoned.</i>