Numerical model of corrosion influence on mechanical behavior of steel AH36

Abstract

Mechanical behaviour of butt-welded joint specimens made of AH36 shipbuilding steel exposed to real marine environment for prolonged periods is analyzed experimentally and numerically in this paper. After the specimens were extracted from experiment site, standardized tensile tests have been performed along with the Charpy impact and hardness tests. In addition, the corroded surface was examined using optical and scanning electron microscopy. The most significant deterioration is noticed on the specimens exposed to continuous influence of the sea waves. The experimental results were base for development of the numerical model of the corroded surfaces. The corrosion pits for base metal, heat-affected zone and weld metal were modelled using Poisson process and gamma process (i.e. normal distribution) for the pit depth progress. The finite element model of the butt-welded steel specimen was developed in order to perform simulated tensile test using stress modified critical strain, ductile fracture criterion with different α parameters and hardening models for each zone. It is shown that with the increase of the stress triaxiality, which depends of the pit size and distribution, critical plastic strain decreases. Consequently, this leads to the earlier ductile fracture initiation and degradation of the mechanical properties.