Abstract
This paper deals with investigation and characterization of weld circumferential thin cracks in austenitic stainless steel (AISI 304) pipe with eddy current nondestructive testing technique (EC-NDT). During welding process, the heat source applied to the AISI 304 was not uniform, accompanied by a change of the physical property. To take into consideration this change, the relative magnetic permeability was considered as a gradiently changed variable in the weld and the heat affected zone (HAZ), which was generated by the Monte Carlo Method based on pseudo random number generation (PRNG). Numerical simulations were performed by means of MATLAB software using 2D finite element method to solve the problem. To verify, results from the modeling works were conducted and contrasted with findings from experimental ones. Indeed, the results of comparison agreed well. In addition, they show that considering this changing of this magnetic property allows distinguishing the thin cracks in the weld area.
Highlights
The austenitic stainless steel 304 is suitable for large field applications, such as heat exchangers, power plants, oil and gas industry, chemical engineering and especially in nuclear power plants, because of its useful characteristics, such as high temperature service and environment, corrosion resistance, weldability, formability and mechanical properties [1,2]
[26,27]—in ulation, statistics, machine learning, sampling and in other areas [26,27]—inthis this section according to the experimental measurement of the relative magnetic permeability, which which is according ofof thethe relative magnetic permeability, accordingtotothe theexperimental experimentalmeasurement measurement relative magnetic permeability, which is gradiently distributed in theinheat affected zonezone (HAZ)
The governing equations of the numerical model used in this paper are obtained with the consideration of assumptions that the conduction current is dominated, to describe electromagnetic eddy-current problems extracted from Maxwell’s equations, which describe the basics of electromagnetic theory given as follows [33,34]:
Summary
The austenitic stainless steel 304 is suitable for large field applications, such as heat exchangers, power plants, oil and gas industry, chemical engineering and especially in nuclear power plants, because of its useful characteristics, such as high temperature service and environment, corrosion resistance, weldability, formability and mechanical properties [1,2]. Hu et al [21] studied microstructure residual stress and corrosion cracking of repair welding on 304 AISI by experiment and simulation, and found that repair welding in 304 stainless steel is recommended no more than two times All these studies are related to the evaluation of defects in using different methods. It can be considered that the assembled pipe has three regions with three magnetic permeabilities Modeling this change on this input parameter and characterizing its consequence on the output response under MATLAB, in order to be able to both reproduce the distribution of this parameter and to compare this response with experimental, is an important step of this work. A comparison against constant relative permeability and experimental ones was done, and the results show that it is important to consider this change in magnetic property of the material
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