| Autor: |
C. S. Wiesner, André Pineau, P. Joly, E. Bouyne, B. Houssin |
| Rok vydání: |
2001 |
| Předmět: |
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| Zdroj: |
Fatigue & Fracture of Engineering Materials & Structures. 24:105-116 |
| ISSN: |
8756-758X |
| DOI: |
10.1046/j.1460-2695.2001.00363.x |
| Popis: |
Tests were performed on a 21/4 Cr-1 Mo steel to measure the fracture toughness at initiation, K Ic and at arrest, K Ia . The results were compared with those obtained on another pressure vessel steel (A508) of similar strength. Two techniques were used to measure K Ia : (i) isothermal compact crack arrest (CCA) tests, and (ii) specially designed thermal shock experiments using an externally notched ring. These specimens were cooled to -196°C and then heated by induction in the centre of the ring to produce very steep thermal gradients. This caused crack initiation from the notch. The crack propagates very rapidly (∼ 500 m s -1 ) and stopped when it reached the warmer region of the specimen. The specimens were analysed using an elastic-plastic finite element method to determine K Ia values. These tests reveal a greater temperature shift (∼ 100 °C) between K Ic and K Ia in 21/4 Cr-1 Mo steel than in A508 steel. Detailed metallographical examinations of the micromechanisms of crack propagation and arrest in the 21/4 Cr-1 Mo steel showed that this involves the nucleation of a three-dimensional network of cleavage microcracks which change their direction at bainitic packet boundaries. The remaining uncracked ligaments between the cleavage microcracks break by ductile rupture mechanism. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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