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INSPECTION SYSTEM FOR FATIGUE CRACK DETECTION IN WELDED
JOINTS OF METALLURGICALLY CLAD PIPES
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Summary
The potential for fatigue cracks to occur in pipeline structures due to cycling
loads inherent of offshore oil production, makes necessary have an inspection tool to
carry out periodic non destructive inspection in the inner pipe surface. The most critical
point of pipeline structures is the circumferential weld and demands special attention
during inspection. The results achieved demonstrate the feasibility to apply eddy current
technology to detect fatigue cracks in welded joints of clad pipes. |
Literature Review
Yusa et. al. [28] |
Purpose |
Application of the eddy current technique for detection of fatigue cracks |
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Material |
Nickel 600 (Incoloy Alloy) plate |
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Artificial Defects |
The cracks were fabricated on a three-point support fatigue machine. |
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Image |
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Huang et.al. [30] |
Purpose |
In addition to detection, the sizing of cracks of fatigue |
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Material |
316 Stainless Steel plate |
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Artificial Defects |
The cracks were fabricated on a four-point support fatigue machine. |
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Image |
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Nakagawa et.al. [31] |
Purpose |
In addition to the detection reliability of the eddy current technique, the effects of using EDM notches to represent fatigue cracks. |
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Material |
Titanium Alloy (Ti-6246) e Nickel (IN-100) |
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Artificial Defects |
Electrical Erosion notches |
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Image |
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Final results |
From the results achieved with the fabricated notches, a linear function was fitted to the data, extrapolating them to opening values that the authors named “zero” opening. |
Larson et.al. [32] |
Purpose |
Similar Nakagawa et.al. [31] |
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Material |
Titanium Alloy and aluminium |
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Artificial Defects |
The notches studied in the work were superficial and shallow, with depth ranging between 25.4 µm and 0.4 mm, and openings ranging from 30 µm and 0.12 mm, and the interaction between the opening and the depth of the defects was mainly analyzed. |
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Image |
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Final results |
The results achieved by the author indicated that the amplitude attenuation factor, so that signals from EDM notches are representative for fatigue cracks, is between 10 and 30%. |
Difficulties to be considered in Crack detection
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