SUS631ステンレス鋼はくの疲労き裂進展挙動

概要

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The fatigue crack growth tests of the SUS 631 stainless steel foil (thickness : 0.05 mm) were carried out in a wide range of fatigue crack growth rate covering the threshold stress intensity factor range ⊿K_<th>. The effects of aging hardening treatment and the stress ratio on the fatigue crack growth characteristics were investigated on the basis of fracture mechanics. The crack growth rate was measured using the center notched specimens of solution heat treatment (1313K, 2s) foil (STF) and two kinds of aging treatment (703 K, 1 h and 753 K, 1 h) foils. Crack growth tests were conducted at 10 Hz and the stress ratio R=0.1 and R=0.5. The main results obtained are as follows ; (1) The Paris'law could also be applied between da/dN and ⊿K to the SUS 631 stainless steel foil in a special region of da/dN and it was shown to be da/dN=C (⊿K)^m. (2) In a low-⊿K region the crack growth rate da/dN of aging treatment foil was higher than that of the STF and was accompanied by a small threshold value ⊿K_<th>. On the other hand, in a high-⊿K region da/dN of ageing treatment foils was lower than that of STF. (3) Fatigue crack growth resistance of a higher temperature aging material was higher than that of a lower temperature aging material with a higher tensile strength. (4) Crack closure level (K_<op>/K_<max>) was rapidly increased as the maximum stress intensity factor K_<max> decrease for each material at R=0.1 and R=0.5.
1999-03-25