Influence of Plastic Deformation Capacity on Failure Behaviour of Pipelines

摘要

Plastic deformation capacity parameters affect the deformability of steel in the plastic stage, and then affect the limit pressure of pipelines. This paper investigates the influence of plastic deformation capacity parameters on the limit bearing capacity of pipelines. These parameters include yield to tensile ratio (σ_y/σ_u), percentage uniform elongation (6) and strain hardening exponent (n). Based on the Swift strain hardening model, the relational expression of the plastic deformation capacity parameters is theoretically deduced. 95 groups of material tensile test datum have been collected. Based on these test data, the variation tendency of the plastic deformation capacity parameters have been analyzed statistically, and the empirical formula of the key parameters have been fitted numerically. 20 groups of finite element examples are designed to analysis the influence of yield to tensile ratio and uniform elongation to limit pressure of pipeline. Results show that, with the improvement of strength grade of steel, the plastic deformability of steel decreases;; the recommended of critical plastic deformation capacity indexes arc: pipeline steel below X65, σ_y/σ_u<0.85 and δ ≥10%;; ? pipeline steel for X70-X80, σ_y/σ_u<0.93 and 6>8%.