Surface Defect Inspection of Pressure Equipment Based on Indentation and Numerical Simulation

Abstract

Surface defects caused by damage or corrosion are major factor in petrochemical pressure vessels and line pipes failure. The characteristic size of typical surface defect is from micron to submillimeter which belongs to mesoscopic scale, leading to difficulties for inspection and evaluation. The instrumented indentation method has widely used in the characterization of micro-zone mechanical behavior which could be effective in surface defects analysis. This paper aims at investigating the correspondence between indentation experimental results and distribution characteristics of surface defects. Mechanical properties of pressure vessel steel with surface defects are measured by indentation, and corresponding finite element models are established. Finite element simulation results of equivalent mechanical properties under indentation and three dimensional deformations are compared, and the applicability of finite element models for indentation test of steel with surface defects is analyzed. The effect of randomized surface defects on measuring result is studied subsequently using stochastic finite element models. The relation of equivalent mechanical properties and description of surface defects is proposed. The achievement could used to estimate the degree of damage or corrosion by miniature indentation testing techniques for safety assessment.