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Towards Automation of Non-Destructive Testing of Welds
University West, Department of Engineering Science, Division of Process and Product Development.ORCID iD: 0000-0001-7748-0565
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

All welding processes can give rise to defects that will weaken the joint and can lead to failure of the welded structure. Because of this, non-destructive testing (NDT) of welds have become increasingly important to ensure the structural integrity when the material becomes thinner and stronger and welds become smaller; all to reduce weight in order to save material and reduce emissions due to lighter constructions.

Several NDT methods exists for testing welds and they all have their advantages and disadvantages when it comes to the types and sizes of defects that are detectable, but also in the ability to automate the method. Several methods were compared using common weld defects to determine which method or methods were best suited for automated NDT of welds. The methods compared were radiography, phased array ultrasound, eddy current, thermography and shearography. Phased array ultrasound was deemed most suitable for detecting the weld defects used in the comparison and for automation and was therefore chosen to be used in the continuation of this work. Thermography was shown to be useful for detecting surface defects; something not easily detected using ultrasound. A combination of these techniques will be able to find most weld defects of interest.

Automation of NDT can be split into two separate areas; mechanisation of the testing and automation of the analysis, both presenting their own difficulties. The problem of mechanising the testing has been solved for simple geometries but for more general welds it will require a more advance system using an industrial robot or similar. Automation of the analysis of phased array ultrasound data consists of detection, sizing, positioning and classification of defects. There are several problems to solve before a completely automatic analysis can be made, including positioning of the data, improving signal quality, segmenting the images and classifying the defects. As a step on the way towards positioning of the data, and thereby easing the analysis, the phase of the signal was studied. It was shown that the phase can be used for finding corners in the image and will also improve the ability to position the corner as compared to using the amplitude of the signal. Further work will have to be done to improve the signal in order to reliably analyse the data automatically.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2011. , p. 42
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords [en]
Welding, non-destructive testing, NDT
National Category
Computer Vision and Robotics (Autonomous Systems) Fluid Mechanics and Acoustics Applied Mechanics
Research subject
ENGINEERING, Industrial engineering
Identifiers
URN: urn:nbn:se:hv:diva-4122ISBN: 978-91-7439-352-1 (print)OAI: oai:DiVA.org:hv-4122DiVA, id: diva2:489016
Presentation
2011-12-19, E246, Luleå tekniska universitet, Luleå, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2012-02-08 Created: 2012-02-02 Last updated: 2018-01-12Bibliographically approved
List of papers
1. Comparison of NDT-methods for automatic inspection of weld defects
Open this publication in new window or tab >>Comparison of NDT-methods for automatic inspection of weld defects
2015 (English)In: International journal of materials & product technology, ISSN 0268-1900, E-ISSN 1741-5209, Vol. 50, no 1, p. 1-21Article in journal (Refereed) Published
Abstract [en]

The purpose of this study is to investigate different NDT-methods for weld inspection in an objective manner. Test objects are produced with known variation of flaws: internal pores, surface and internal cracks, toe radius and weld depth. The NDT-methods compared are: phased array ultrasound, radiography, eddy current, thermography and shearography. The results show that radiography is the better method for volumetric defects in thin plates while ultrasound is better for flat defects and thicker, non-flat plates. Thermography was shown to have a good ability of detecting surface defects. A combination of ultrasound and thermography results in a detection of all the non-geometrical defects investigated in this study.

Keywords
non-destructive testing, NDT, weld defects, automatic inspection
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-3113 (URN)10.1504/IJMPT.2015.066863 (DOI)000352133300001 ()2-s2.0-84921311226 (Scopus ID)
Projects
ANDTE
Available from: 2011-01-27 Created: 2011-01-27 Last updated: 2017-12-11Bibliographically approved
2. Improved Corner Detection by Ultrasonic Testing using Phase Analysis
Open this publication in new window or tab >>Improved Corner Detection by Ultrasonic Testing using Phase Analysis
2013 (English)In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 53, no 2, p. 630-634Article in journal (Refereed) Published
Abstract [en]

In ultrasonic testing, corners are used for sensitivity calibration in the form of notches, for measuring the sound velocity in the material, and as known reference points during testing. A 90° corner will always reflect incoming waves in the opposite direction due to a double reflection and therefore give a strong echo. This article presents a method for separating the echo from a corner from other echoes and more accurately find the position of the corner. The method is based on analysing the phase of the reflected signal. The proposed method was tested on a steel calibration block and the width of the indication was reduced by up to 50% compared to the amplitude signal. This results in a more accurate positioning of the corner. Using the phase instead of the amplitude will also improve the reliability, since reflections other than from corners will disappear.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
phase, ultrasound, non-destructive testing, corner, calibration, WIL, Work-integrated Learning, AIL
National Category
Signal Processing
Research subject
ENGINEERING, Physics; Work Integrated Learning
Identifiers
urn:nbn:se:hv:diva-4112 (URN)10.1016/j.ultras.2012.10.015 (DOI)000311488800039 ()2-s2.0-84870250647 (Scopus ID)
Projects
ANDTE
Available from: 2012-01-26 Created: 2012-01-26 Last updated: 2017-12-08Bibliographically approved

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