Abstract
The cladded conductor is broadly utilized in engineering fields, such as aerospace, energy, and petrochemical; however, it is vulnerable to thickness loss occurring in the clad layer and nonconductive protection coating due to abrasive and corrosive environments. Such a flaw severely undermines the integrity and safety of the mechanical structures. Therefore, evaluating the thickness loss hidden inside cladded conductors via reliable nondestructive evaluation techniques is imperative. This paper intensively investigates the pulse-modulation eddy current technique (PMEC) for the assessment of thickness loss in a cladded conductor. An analytical model of the ferrite-cored probe is established for analyzing PMEC signals and characteristics of lift-off intersection (LOI) in testing signals. Experiments are conducted for evaluation of the thickness loss in cladded conductors. An inverse scheme based on LOI for estimation of the thickness-loss depth is proposed and further verified. Through simulations and experiments, it is found that the influences of the thickness loss in the clad layer and protective coating on the PMEC signals can be decoupled in virtue of the LOI characteristics. Based on LOI, the hidden thickness loss can be efficiently evaluated without much of a reduction in accuracy by using the PMEC probe for dedicated inspection of the cladded conductor.
Highlights
In an effort to enhance resistance to corrosion and abrasion, the critical conductive components of nonferromagnetic materials in engineering structures employed in fields such as energy, aerospace, and petrochemical, are cladded with a layer of distinct/premium nonferromagnetic materials, including the copper alloy [1,2]
A featured example is a planar cladded conductor employed in aerospace engineering structures such as the unmanned aerial vehicle (UAV), which consists of a substrate of aluminum alloy, clad layer of copper alloy, and nonconductive protection coating over the clad layer
It is noted that in an effort to facilitate the analysis of lift-off intersection (LOI), every pulse-modulation eddy current technique (PMEC) signal is preprocessed by taking the absolute value of its amplitude, which gives |Bz |
Summary
In an effort to enhance resistance to corrosion and abrasion, the critical conductive components of nonferromagnetic materials in engineering structures employed in fields such as energy, aerospace, and petrochemical, are cladded with a layer of distinct/premium nonferromagnetic materials, including the copper alloy [1,2]. In this paper the characteristics of LOI in PMEC signals for quantification of the thickness loss in the cladded conductor, whose structure includes a nonconductive protection coating, nonferromagnetic clad layer, and substrate were intensively explored. The rest of the paper is together with the LOI-based inversion for simultaneous evaluation of the thickness loss in the clad organized as follows: Section 2 elaborates the formulation of closed-form expressions of PMEC layer and protective coating was further identified. It is followed by an experimental study probe to the cladded conductor. It is noteworthy that Equation (13) facilitates the prediction of the PMEC response from the probe to a cladded conductor with the thickness loss in the clad layer and protective coating
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