Steel plates are widely used in various structures, including building structures, bridges, ocean platforms, and industrial equipment. Such steel structures inevitably suffer from corrosion, the most common of which is pitting corrosion. Pitting corrosion greatly affects the tensile strength of steel. Hence, revealing the influence of pitting corrosion on steel strength is necessary. The influence of predefined pitting corrosion with different shapes on the tensile behavior of steel was investigated in this work. Then, the influence of the layout of corrosion pits was studied. A finite element model of coupons with random pitting corrosion was also established to extend the work to actual conditions. Stochastic numerical analysis was conducted to reveal the relationship between nominal yield and ultimate strength given the mass loss ratio of Q345 steel. A highly accurate method for predicting the nominal tensile strength of Q345 steel was proposed. The proposed method can also be adopted for pitting corrosion with random depths.

Tensile strength of Q345 steel with random pitting corrosion based on numerical analysis

A critical review of corrosion development and rust removal techniques on the structural/environmental performance of corroded steel bridges

Development of erosion equation and numerical simulation methods with the consideration of applied stress

Collapse of thick-walled subsea pipelines with imperfections subjected to external pressure

Effect of pitting defects on the buckling strength of thick-wall cylinder under axial compression

In the second part of this investigation, a 3D nonlinear (Finite Element) FE models was established to systematically study the collapse pressure of random corroded pipe. The models are developed within the framework of the nonlinear finite element ABAQUS in combination with a user defined Python program. Two constraints technique including surface-based tie constrain (SBTC) and shell-to-solid coupling (SSC) were implemented to take the complex geometry into account without the sacrifice of model accuracy while minimizing the computational cost. It was found that SBTC is more robust to simulate the locally random corroded pipe (external corrosion) than SSC. After validation models, a parametric investigation is performed to study the influence of wave number and amplitude of out-of-roundness, random pitting factors (pitting shape, pitting density and the length of pitting affect zone (LC)). It was revealed that the amplitude (wmax) and wave number (n) of out-of-roundness, pitting density and mass loss are the main factors that govern the collapse pressure (PCO) of 3D random corroded pipe whereas pitting shape has minor impact on PCO. Finally, a simplified pitting model was proposed, it was found that the circumferential and axial bending rigidity are key parameters that govern the PCO of pipe, which is mainly determined by the minimum remaining area in circumferential and axial direction.

Yan Zhao

Papers

Effect of 3D random pitting defects on the collapse pressure of pipe — Part II: Numerical analysis