Finite element investigation of speed dependent dynamic fracture toughness of X80 line pipe steel

摘要

Recent drop weight tear test (DWTT) showed that two measures of fracture toughness ofline pipe steels depend on fracture speed. Based on a properly designed separation-traction law,standard and modified DWTT of API X80 line pipe steel are simulated by Cohesive Zone ModelCZM) based FEA (finite element analysis). The loading-displacement curve, fracture speed, andcrack tip opening angle (CTOA) in FEA simulations are compared with experimental results. Theagreement between the present FEA and experimental results shows that the present FEA canwell describe high-speed fracture of API X80 line pipe steel. The relation between CZM fractureenergy, steady-state CTOA and steady-state fracture speed are investigated through two groupsof FEA simulations designed for standard and modified DWTT. Our FEA results show that bothCZM fracture energy and steady-state CTOA decrease with steady-state fracture speed, and twoempirical relations are suggested to describe the dependence of the two toughness measures onsteady-state fracture speed.