No description available.

In this master thesis, the accuracy of the crack depth meter RMG 4015 was evaluated for different types of cracks with various damage mechanisms. In total, 61 crack depth measurements were conducted with the crack depth meter on 56 cracks which were located in the 23 different test pieces supplied by Kiwa. The measured crack depths were then compared to the true crack depths, which were determined by cutting the test pieces and measuring directly on the cross-sections of the cracks using a light optical microscope. The results of the comparison showed that the RMG 4015, which uses potential drop techniques, was very accurate at measuring both strain induced and alkaline stress corrosion cracks. However, the results also showed that the crack depth meter underestimates chloride induced stress corrosion cracks, corrosion fatigue cracks and stress corrosion cracks/hydrogen embrittlement cracks at varying degrees. Therefore, the main recommendation for Kiwa is to switch the RMG 4015 to a crack depth meter that uses ultrasonic techniques instead. The master thesis also explored the possibilities to improve an FE model produced by Kiwa in a previous project which involved an analysis of a cracked component. The present crack depth measure program included a test piece from this component. The stress distribution in the original model did not represent the cracks found in the real structure and it was suspected to be the result of some boundary conditions not corresponding to those acting in the actual pipe system. Some adjustments to the boundary conditions and contact regions were made and a new improved model with a better representing stress distribution was found. / I detta examensarbete utvärderades noggrannheten hos sprickdjupsmätaren RMG 4015 för olika typer av sprickor med olika skademekanismer. Totalt utfördes 61 sprickdjupsmätningar med sprickdjupsmätaren på 56 sprickor i 23 olika provbitar som tillhandahölls av Kiwa. De uppmätta sprickdjupen jämfördes sedan med de verkliga sprickdjupen, som bestämdes genom att provbitarna skars upp och mätningarna utfördes direkt på sprickornas tvärsnitt med hjälp av ett optiskt ljusmikroskop. Resultaten av jämförelsen visade att RMG 4015, som använder sig av potentialfallstekniker, var mycket noggrann vid mätning av både töjningsinducerade och alkaliska spänningskorrosionssprickor. Resultaten visade dock också att sprickdjupsmätaren underskattar kloridinducerade spänningskorrosionssprickor, korrosionsutmattningssprickor och spänningskorrosionssprickor/väteförsprödningssprickor i varierande grad. Den viktigaste rekommendationen till Kiwa är därför att ersätta RMG 4015 med en sprickdjupsmätare som istället använder ultraljudsteknik. I examensarbetet undersöktes också möjligheterna att förbättra en FE-modell som Kiwa tagit fram i ett tidigare projekt som omfattade en analys av en sprucken komponent. En provbit från denna komponent ingick i det nuvarande programmet för sprickdjupsmätning. Spänningsfördelningen i den ursprungliga modellen representerade inte de sprickor som fanns i den verkliga strukturen och det misstänktes vara resultatet av vissa randvillkor som inte motsvarade de som verkar i det verkliga rörsystemet. Vissa justeringar av randvillkoren och kontaktytorna gjordes, och en ny förbättrad modell med en bättre representativ spänningsfördelning hittades.

E. Lilly, S.A.; DGICYT (proyecto n. PB94-1515)

No description available.

The main goal of this thesis is to get an insight into a field of non-destructive testing using potential drop techniques that have nowadays become the standard not only in the fatigue and loading tests but also in the industry. These methods can serve to non-destructively and continuously measure material specimens, thickness, corrosion losses, deformations, spectroscopy and detection and analysis of crack geometry. They can help to identify materials and measure material changes over time. The second part of this thesis deals with designing the aperture for detection of cracks in steam and product piping using potential drop technique modified by Ing. Ladislav Korec, CSc. Last part deals with extensive testing, experimenting and evaluation of the aperture.