Methods of Cracks Detection in Marine Structures' Welded Joints Based on Signals' Time Waveform Analysis

Abstract

The paper presents two methods of crack detection in ship hulls. The methods are dedicated for structural health monitoring (SHM) of responsible welded joints. The system will be based on vibrodiagnostic-signals will be measured by piezoelectric accelerometers and/or fibre optic sensors. In SHM systems of welded joints of thin-walled structures, a vibrodiagnostic method is the most promising. Its most important advantage is that it is both effective and relatively low costly. There are two general methods of vibrodiagnostic signal analysis: the most frequently used are spectrum analysis and time waveform analysis. The spectrum analysis concerns changes of natural frequency. In marine exploitation conditions, the frequencies changes might be imperceptible. The first method presented in the article is based on the evaluation of the mean value distribution of the amplitude spectrums calculated with the time window method. Second proposed method was based on the determination of damping decrement in function of time. Due to the complexity of the responses run, the proposed method consisted of calculating the damping decrement using the response approximation with different functions. It has been shown that the changes analysis of damping decrement applied to welded plates enables the assessment of the quality associated with the weld. A calculation algorithm as well as and the exemplary results from the proposed methods used for some selected samples with different type of welds are included in the paper. The results of the tests show that the analysis based on proposed methods indicates that they differ significantly depending on the welds, indicating their quality and cracks that are associated with them.

Diagnostic benchmarks on dynamic characteristics of thin-walled marine damaged structures

“…This opportunity is often used in the analysis of technical systems dynamics, especially electrical or electronic ones. It is used in mechanical systems testing very rarely (Muc, et. al., 2018).…”

“…Conducted tests aimed at the optimal coverage of spectrums characteristic changes which determine the quality of welds and possible defects. The optimal width of the window was chosen as 10 ms for analyzed plates (Muc, et. al., 2018).…”

“…3D laser) difficult to use in operating conditions for such complex construction as the hull of a ship (Szeleziński, et. al., 2017, Muc, et. al., 2018.…”

Crack Monitoring in the Welding Parts of Different Alloys of Aluminium using Digital Image Correlation

“…Result of the experiment indicated that the mechanical behavior of the system could be imagined quite well with the proposed prototype. A. Muc et al [10] in 2018 presented dual techniques for detecting cracks in the ship hulls. Proposed method was fully defined for structural health monitoring (SHM) of responsible welded joints of materials.…”

“…Benefits of the technique have motivated many researchers to develop various automatic crack detection methods utilizing image processing methods. [10] These methods show good results in case of quantitative analysis based on objectivity while the visual crack estimation is very tedious and also dependent on the specialist person knowledge and experience also. The overall setup of the crack estimation using camera consist of high resolution camera, image denoising and enhancement filters, crack detection algorithms and crack feature extraction detectors.…”