Validation of Acoustic Emission Waveform Entropy as a Damage Identification Feature

Farhan Tanvir Santo,Graham Edwards,Tariq Pervez Sattar

doi:10.3390/app9194070

Farhan Tanvir Santo, Graham Edwards + Show 1 more

Open Access

https://doi.org/10.3390/app9194070

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Abstract

The increase in the market for supersized LNG (liquefied natural gas) vessels, with double wall cargo tanks, has led to concerns regarding their safe operation. If both the primary and secondary wall of the cargo tank fail simultaneously, the hull of the vessel can be exposed to the LNG. This has the potential to cause brittle failure of the hull structure. This study presents a new acoustic emission (AE) technique approach that can be implemented for monitoring the structural condition of the cargo containment. The new technique approach is based on a feature of the AE waveform, calculated using quadratic Renyi’s entropy. The presented technique is capable of providing information regarding critical damage so that appropriate maintenance can be carried out to avoid failure. The new AE technique is based on an AE feature that is independent of acquisition settings (e.g., threshold and timing), unlike many traditional AE features. The effectiveness of the proposed feature was evaluated by comparison with traditional AE features under ideal conditions for a range of varying acquisition settings. Unlike the traditional feature, the new feature demonstrated no variance with variation of the acquisition settings and was effective in capturing the collective information in the waveform. The proposed AE feature was validated through tensile and fatigue testing on standard specimens of austenitic stainless steel (material of the primary wall). The results suggest that the proposed AE feature is sensitive in identifying the critical damages irrespective of some data acquisition settings.

Highlights

Liquefied natural gas (LNG) carriers are ships used for long distance transportation of LNG
The use of an extensometer is a traditional method to extract the strain in the material during tensile deformation
Each channel captured the elastic wave as a waveform with a different extensometer is adeformation traditional method to extract thequite strain in the material during tensile

Summary

Introduction

Liquefied natural gas (LNG) carriers are ships used for long distance transportation of LNG. According to the World LNG report [1], the primary wall of 74% of LNG carriers is constructed from austenitic stainless steel because its construction is cheaper and requires less engineering maintenance work [2]. If there is a leak of more than 5 mm in the secondary wall, the cryogenic fluid could potentially reach the hull of the ship, causing brittle failure [8,9]. Both leakage of LNG and failure of the hull can increase the risk to the safety of life and property.

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