Human Factors in Non-Destructive Testing (NDT): Risks and Challenges of Mechanised NDT Vorgelegt von Dipl. -Psych. Marija Bertovic geb. in Ogulin, Kroatien von der Fakultät V – Verkehrs- und Maschinensysteme der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktorin der Philosophie -Dr. phil.- genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. phil. Manfred Thüring Gutachter: Prof. Dr. phil. Dietrich Manzey Gutachter: Dr. rer. nat. et Ing. habil. Gerd-Rüdiger Jaenisch Tag der wissenschaftlichen Aussprache: 1 September 2015 Berlin 2015 D83 Acknowledgements I would like to use this opportunity to thank all those who have supported me throughout working on this dissertation. First, I would like to thank Prof. Dietrich Manzey for his openness and kindness, for the empowerment and support, and for guiding me scientifically and morally through this work. I extend this gratitude to the second advisor, Dr. Gerd-Rüdiger Jaenisch, for his most insightful comments, valuable discussions, and his constructive guidance. I would also like to remember my first advisor, the deceased Prof. Bernhard Wilpert, who introduced me to the field of human factors with such style, friendliness, and charm. My highest gratitude goes to Dr. Christina Müller, who set me on this path, guided, and supported me in every possible way—morally, spiritually, and professionally. I thank her for the strength she gave me, for the ways she has shown me, for her patience and understanding, and for giving me the opportunity to do this work. My further gratitude goes to Dr. Babette Fahlbruch, for her scientific guidance, relentless support, and continuous motivation—as a mentor and as a friend. This work was carried out during my employment at the Federal Institute for Materials Research and Testing (BAM), which funded my work and provided the resources necessary for its completion. The work presented in this dissertation is a result of a yearlong scientific cooperation between BAM, Swedish Nuclear Fuel and Waste Management Co (SKB), and the Finnish Posiva Oy. I feel privileged for being able to work on these projects and learn so much from my project partners. Their vision, interest, and openness to new challenges laid the foundations upon which this work was built. On that note, I would like to thank Ulf Ronneteg from SKB not only for his professional guidance, but moreover for his friendship and unlimited support. My gratitude extends to the recently deceased Jorma Pitkänen from Posiva, whose too early departure has left us saddened and whose absence is felt in more than one way. I would like to use this opportunity to thank him for his wondering mind and for all the valuable lessons on how NDT is carried out. Furthermore, I would like to thank my colleagues from BAM for their support, time, for their help when needed, for the preparation of the studies, and for the participation in the studies. Foremost, I thank Daniel Kanzler for the help in the preparation and execution of the studies, for his consult, and for the continuous moral support. Furthermore, I thank Martina Rosenthal and Steffen Milsch for aiding in the preparation of the data for the study. I also thank Matthäus Stöhr, I Julia Lakämper, and Christopher Borko for aiding in the preparation for the statistical analyses, and Dr. Inga Meyer for statistical consult. A special gratitude goes to Dr. Ralf Holstein and the DGZfP, for providing with solutions when they were most needed and appreciated. The studies presented in this work owe gratitude to all the participants from DGZfP, BAM, Siemens, Lise-Meitner School of Science, W. S. Werkstoff Service, and foremost, to the NDT experts from Sweden and Finland for their participation in the FMEA: Thomas Grybäck, Barend van den Bos, Johan Persson, Robert Risberg, David Åkerman, Matti Sarkimo, Aarne Lipponen, Raimo Paussu, Tommi Saastamoinen, and Petteri Raak. I am also extremely grateful to Dr. Katja Krol and Claudia Möhring for proofreading the thesis and to all my friends for their continuous support. Finally, I would like to express gratitude to my family. Without their love, support, and sacrifice, I would never have gotten to where I am now. II Glossary A-scan presentation Display of the ultrasonic signal in which the X-axis represents the time and the y-axis the amplitude Acceptance level Prescribed limits, below which a component is accepted Amplitude (UT) Absolute or relative measure of a sound wave’s magnitude Automated UT A method by which an object is tested ultrasonically and the results are analysed without human intervention Automatic scanning Automatic displacement of the probe B-scan presentation Image of the results of UT showing a cross section of the test object perpendicular to the scanning surface and parallel to the reference direction C-scan presentation Image of the results of UT showing a cross section of the test object parallel to the scanning surface Calibration A process of establishing the sensitivity of the measurement system Characterisation Classifying the size and shape of an indication so it may be identified Couplant (UT) A medium interposed between the probe and the object under examination to enable the passage of ultrasonic waves between them Critical defect Discontinuity in the material large enough to cause concern of structural failure Decision (or sizing) A threshold above which all pixels in the direct contact with the pixel threshold exceeding the reporting level are judged as belonging to the indication D-scan presentation Image of the results of UT showing a cross section of the test object perpendicular to the scanning surface and perpendicular to the projection of the beam axis on the scanning surface (D-scan is typically perpendicular to B-scan) Defect A component discontinuity that has shape, size, orientation, or location, such that it is detrimental to the useful service of the part Detection Establishment of the presence of a discontinuity Discontinuity Detectable change in the material (also known as inhomogeneity) III Echo (UT) Ultrasonic pulse reflected to the probe Evaluation Assessment of indications revealed by NDT against a predefined level Failure (FMEA) The failure of an item, which would result in failure of the system and is not compensated for by redundancy or alternative operational procedure Failure cause (FMEA) The physical or chemical processes, design defects, quality defects, part misapplication, or other processes which are the basic reason for failure or which initiate the physical process by which deterioration proceeds to failure Failure mode (FMEA) The manner by which a failure is observed (Generally, it describes the way the failure occurs and its impact on equipment operation) Failure effect (FMEA) The consequence a failure mode has on the operation, function, or status of an item Indication Representation or a signal from a discontinuity in the format typical for the method used Geometrical A non-relevant indication of a signal arising from an interaction of the indication energy sent through the material (e.g. ultrasonic beam) and the component geometry (e.g. edges). Kurtosis Pointyness of the distribution Localization Determining the location of an indication in the component Manual scanning Manual displacement of the probe NDT instruction Written description of the precise steps to be followed in testing to an established standard, code, specification or NDT procedure NDT method Discipline applying a physical principle in non-destructive testing, e.g., ultrasonic testing NDT procedure Written description of all essential parameters and precautions to be applied when non-destructively testing products in accordance with standard(s), code(s), or specification(s) NDT technique Special way of utilising an NDT method NDT training Process of instruction in theory and practice in the NDT method in which certification is sought, taking the form of training courses to a syllabus approved by the certification body NDT reliability The degree that an NDT system is capable of achieving its purpose regarding detection, characterisation, and false calls Noise (signal) Randomly distributed signals in the screen image, due to reflections from the structure of the material or the equipment Probe (UT) Electro-acoustical device, usually incorporating one or more transducers intended for transmission and/or reception of the ultrasonic waves Qualification Demonstration of physical attributes, knowledge, skill, training, and experience required to perform NDT tasks properly IV Reporting Amplitude of the echo above (or below) which every echo is reported or threshold/level (UT) recorded Sensitivity (UT) A measure of the smallest ultrasonic signal, which will produce a discernible indication on the display of an ultrasonic system Signal-to-noise ratio, Ratio of the amplitude of the signal arising from a discontinuity in a SNR (UT) material to the amplitude of the average background noise Sizing Determination of the dimensions of discontinuities or indications for evaluation Skewness Lack of symmetry of the distribution Winzorising A procedure of exclusion of outliers by replacing the outliers with the last value that is not an outlier _____________________________________________________ Note: The definitions were quoted from: Ali, Balint, Temple, & Leevers, 2012; DIN EN 1330-4, 2010; DIN EN ISO 9712, 2012; Field, 2013; Hellier, 2013; ISO 31000, 2009; MIL-STD 1629A, 1980; Nockemann & Fortunko, 1997; and Schmitz & Mißmann, 2009. V Abbreviations ET Eddy Current