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Fatigue damage accumulation around notches

Through-thickness low cycle fatigue damage accumulation around notch and crack initiation of type 304 stainless steel
  • Yutaka Iino and Hideo Yano
Published/Copyright: May 26, 2013
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Materials Testing
From the journal Materials Testing Volume 46 Issue 6

Abstract

Notched compact tension specimens of type 304 stainless steel (notch tip radius of 1 mm and 4 mm) were low-cycle-fatigued at stress ratio R = −1 and 0.05 in order to investigate the through-thickness fatigue damage accumulation around the notch. The recrystallization-thermal etching technique was used to observe the accumulated plastic zone APZ with the accumulated plastic strain ∊ac above 0.12(APZ0.12) and APZ with ∊ac above 0.02 (APZ0.02) at midthickness, quarter thickness and surface. Both APZ0.12 and APZ0.02 are formed early during the fatigue (before crack initiation) near midthickness and not at less thickness or at the surface. The reason why the fatigue crack initiates near the midthickness of the notch root surface was found to be due to more fatigue damage near midthickness than at the surface. Magnetic permeability(degree of the martensite formation) at midthickness was also higher than at the surface, supporting the above result.

Kurzfassung

Im vorliegenden Beitrag wird über Low Cycle Fatigue Untersuchungen eines austenitischen Stahles des Typs 304 mit gekerbten CT-Proben mit einem Kerbradius von 1 mm und 4 mm berichtet. Das Spannungsverhältnis betrug R = −1 sowie R = 0,05 um die durchgängige Schädigung, die sich an der Kerbe akkumuliert, zu untersuchen. Um die akkumulierte plastische Zone (APZ) bei einer akkumulierten plastischen Dehnung von ∊ac über 0,12 (APZ0,12) und die APZ bei ∊ac über 0.02 (APZ0,02) an der Oberfläche sowie auf einem Viertel und der Hälfte der Dicke sichtbar zu machen, wurde ein thermisches Rekristallisationsätzverfahren eingesetzt. Beide Zonen, APZ0,12 und APZ0,02, bilden sich bereits in einem frühen Stadium der Schwingbeanspruchung vor der eigentlichen Rissinitiierung aus. Der Grund für den Rissbeginn auf der Hälfte der Dicke an der Wurzel des Kerbes besteht darin, dass der überwiegende Teil der Werkstoffschädigung im mittleren Dickenbereich liegt und nicht an der Oberfläche. Diese Annahme wird dadurch unterstützt, dass die magnetische Permeabilität als ein Maßstab für die Martensitbildung in diesem Bereich ebenfalls größer als an der Blechoberfläche war.

Dr.-Eng. Yutaka Iino, born in 1942, studied mechanical engineering at the Tohoku University. Afterwards he worked at the Faculty of Engineering of the Tohoku University and received his doctorate in 1977. Since 1981, he has been working at the Toyota Technological Institute (Strength and Fracture of Materials Laboratory).

Ms.-Eng. Hideo Yano, born in 1973, studied materials science at the Shizuoka Institute of Science and Technology. Afterwards he worked at the NSK-Warner Co. Ltd. From April 1999 to March 2001, he studied mechanical engineering (masters program) at the Toyota Technological Institute and received his masters degree in 2001.

References

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Published Online: 2013-05-26
Published in Print: 2004-06-01

© 2004, Carl Hanser Verlag, München

Articles in the same Issue

  1. Inhalt/Contents
  2. Inhalt
  3. Fachbeiträge/Technical Contributions
  4. The effect of microstructure
  5. Fatigue of anisotropic materials
  6. The influence of stress
  7. Fatigue damage accumulation around notches
  8. Refraction computed tomography
  9. Sensitivity of penetrant and magnetic particle testing
  10. Oberflächenprüfungen automatisieren
  11. Vorschau/Preview
  12. Vorschau
https://doi.org/10.3139/120.100590

Articles in the same Issue

  1. Inhalt/Contents
  2. Inhalt
  3. Fachbeiträge/Technical Contributions
  4. The effect of microstructure
  5. Fatigue of anisotropic materials
  6. The influence of stress
  7. Fatigue damage accumulation around notches
  8. Refraction computed tomography
  9. Sensitivity of penetrant and magnetic particle testing
  10. Oberflächenprüfungen automatisieren
  11. Vorschau/Preview
  12. Vorschau
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